Sunday, December 23, 2007

Happy Holidays :-)

A Merry Christmas and an enjoyable New Years celebration to you all. I'm off on holiday, so will next post in the new year.

Friday, December 21, 2007

Embodiment and the Mind

Taken from the introduction to the seminal work "Descartes' Error", in the following extract, Damasio describes the often unmentioned link between the brain (and the mind) and the body: generally assumed, but rarely stated - although this emphasis on the role of the body in the proceedings is of course more central in embodied cognition, cognitive robotics, and the like.

"Surprising as it may sound, the mind exists in and for an integrated organism; our minds would not be the way they are if it were not for the interplay of body and brain during evolution, during individual development, and at the current moment. The mind had to be first about the body, or it could not have been. On the basis of the ground reference that the body continuously provides, the mind can then be about many other things, real and imaginary.


This idea is anchored in the following statements: (1) the human brain and the rest of the body constitute an indissociable organism, integrated by means of mutually interactive biochemical and neural regulatory circuits (including endocrine, immune, and autonomic neural components); (2) the organism interacts with the environment as an ensemble: the interaction is neither of the body alone nor of the brain alone; (3) the physiological operations that we call mind are derived from the structural and functional ensemble rather than from the brain alone: mental phenomena can be fully understood only in the context of an organism's interacting in an environment. That the environment is, in part, a product of the organism's activity itself, merely underscores the complexity of interactions we must take into account."


The central thesis of the rest of the book is well known: that 'logical' reasoning and decision making does not, indeed cannot, exist without the central role of emotion processes. This directly contradicted the traditional view of emotion clouding the 'cold', logical reasoning processes - a premise also used by 'traditional' AI (i.e. that not based on environmental situatedness, or some other form of grounding).

Antonio Damasio, "Descartes' Error: emotion, reason and the human brain", 1994, New York: Grosset/Putnam

Thursday, December 20, 2007

Encephalon #38

The 38th edition of Encephalon was put at Not Exactly Rocket Science on Monday/Tuesday. Another excellent instalment of the brain sciences blog carnival, with the following contributions being (for me) particularly interesting:

- Firstly, two posts on Mirror Neurons, and how they're not all they're cracked up to be: at Brians on Purpose comes a post on how the role of mirror neurons in every aspect of human cognition has been blown out of all proportion, and from The Neurocritic is a post questioning the 'specialness' of mirror neurons, and the difference between primary motor cortex activation, and action.

- Secondly, Cgnitive Daily reviews a study on attention and intention which concludes that our conscious intentions have a greater effect on perception (and the memory thereof) than priming.

Monday, December 10, 2007

The function of the Hippocampus

ResearchBlogging.orgIn a 2004 Neuron paper, Howard Eichenbaum describes the function of the hippocampus in terms of three cognitive processes:

"The hippocampus is envisioned as critically involved in the rapid encoding of events as associations among stimulus elements and context, in the encoding of episodes as sequences of events, and in linking episodes by common features into relational networks that support flexible inferential memory expression."
There is mounting evidence for the first of these cognitive functions that the hippocampus performs which is associative representation: the encoding of "...associations among stimuli, actions, and places that compose discreet events." Functional neuroimaging studies have provided some evidence for this, however, they have also shown activation of the surrounding cortical regions - indicating that the cortex is also involved in this process of associating stimuli, albeit (perhaps) in a different manner. There has also been increasing evidence for the role of the hippocampus in learning the context of events. For example, in fear conditioning, it has been found that damage to the hippocampus results in a lack of contextual fear conditioning, without affecting the conditioned response.

The second cognitive function proposed to be mediated by the hippocampus is sequential organisation, which is "...the organisation of an episode as a sequence of events that unfolds over time." This is evidenced by the fact that damage to the hippocampus impairs order memory, bu not recognition memory. Similarly, it has been shown that it is not the relative memory trace strengths which are use to determine temporal order - and it is suggested that sequence learning is "...mediated by declarative and non-declarative strategies involving distinct memory systems, and these forms of representation are independant."

The third cognitive function is the linking of common features of disparate memory episode to create flexible representations. This is the consolidation (abstraction) of common features of different episodes into representations in their own right - the creation of semantic information from episodic memory. Further functional neuroimaging studies have shown that extensive cortical networks are activated in addition to the hippocampus when factual information is acquired. There is however a proposed difference in processing method for the two regions which facilitate this linking process: "...the hippocampus rapidly learns about individual experiences and prevents interference by separating representations of those experiences, whereas the cortex gradually extracts regularities over many experiences." This suggests a uniform underlying representation - although there would be differences based on the manner in which the memories are formed. Furthermore, it has been found that the learning of hierarchical relationships in rats is impaired by hippocampal damage. In summary, the findings suggest that while the cortex can perform complex associations, the hippocampus is required to create linkages between related memories which support inferences.

In addition to the funtional neuroimaging and behavioural evidence in support of the proposal of these three cognitive functions, the paper also reviews neural firing pattern support for these proposals, which are presented below by means of quotes of the summarising sentences.

For associative representations:
"...a prevalent property of hippocampal firing patterns involves the representation of unique associations of stimuli, their significance, specific behaviours, and the places where these events occur."
For sequential organisation:
"...the hippocampal network encodes routes through space as a meaningful sequence of events that characterise a particular spatially extended experience."
For relational networking:
"...compelling evidence for the notion that some hippocampal cells represent common features among the various episodes that could serve to link memories obtained in separate experiences."
This paper has reviewed the evidence for the proposal that the hippocampus supports three major cognitive functions. However, with this comes the acknowledgement that numerous cortical regions are also involved in these processes. Perhaps these proposals, taken with a complementary theory of cortical cognitive functioning, may be able to address some more global cognitive issues.

Eichenbaum, H. (2004). Hippocampus: cognitive processes and neural representations that underlie declarative memory. Neuron, 44(-), 109-120.

Sunday, December 09, 2007

UK off-shore wind energy

Debate on wind energy on "The Politics Show" - BBC1 mid-day Sunday 9th December

I'm interested (like everyone else on the planet) in the renewable energy debate, so when I saw a special report on tomorrow's announcement on new planning laws to facilitate the implementation of off-shore wind farms around the coast of Great Britain, I was interested, and took a few (very brief) brief notes, which are reproduced below. Being "The Politics Show", all the arguments naturally revolved around political and public opinion issues, with no mention of technical issues - the closest they got to that was a (perfectly valid, in my view) question regarding an over-reliance of the national grid on wind-energy: what happens if the wind stops for a long period of time (e.g. a week)?? Interesting nonetheless...

Report on off-shore wind power:
- Expansion of offshore wind farms - new planning laws to be announced tomorrow.
- 20% EU target for renewable energy production by 2020.
- Significant obstacles to this happening.
- However, very expensive for the amount of energy produced.
- Consumers will pick up the tab for offshore wind for subsidies - in addition to the already existing subsidies for on-land wind farms.
- RSPB (Royal Society for the Protection of Birds) also has concerns regarding sea-birds and migration routes.

Interview with John Hutton (Government business minister):
- Must facilitate shift to low-carbon use, and ability for Britain to supply own energy (and in a clean way.
- How much will be generated: all electricity used by households in the UK if all of the resources round the coast is used.
- 1GW from offshore at moment => want 34GW in 12 years (!)
- No single technology will solve energy problems, but wind power will be a major part.
- The choices can't be postponed - decision must be made now.
- The planning laws are changed with announcement tomorrow- at end of day, it will be private companies who will actually build the turbines.
- There will mean increases in costs for the consumer.
- What about over-reliance on wind: stressed need for a balanced approach to energy production.
- Will 20% target be met? No - not by 2020.

Interview with Alan Duncan (Conservative energy brief):
- Largely agrees with announcement. The coastline should be used.
- Electricity prices will go up: yes, but stability of carbon based fuels not guaranteed in the future, and it the difference in cost between renewables and carbon-based energy production which is of importance.
- Both bottom-up and top-down energy policies needed: both - Nuclear energy needs to be part of the energy mixture - though without subsidies.

Wednesday, December 05, 2007

Encephalon #37

The 37th issue of Encephalon is now up (well, two days ago) at A blog around the clock. I've missed the last couple, so it's nice to catch up on some good blogging. Two particularly caught my eye this time around:

- From Brain in a vat comes a review on a paper on the perceived importance of paper authors, if there are more than one. As well as covering general trends, it looks at how the perceived importance of the author is if he/she is listed first, last or in the middle.

- From Neurophilosophy comes a series of four posts on axon guidance, with particular regard to growth cones (link to first part). The final part summarises nicely, and discusses some issues in need of clarification to further our understanding of axon guidance.

Tuesday, November 27, 2007

"Modelling natural action selection"

Introduction to the Special Issue "Modelling natural action selection"
Philosophical Transactions of the Royal Society London B
September 2007

A special issue containing fourteen papers on various aspects of modelling action selection in animals and humans. There are multiple methods in the study of biological action selection ("of deciding 'what to do next'"), each approaching the problem from different points of view: be it ethology or psychology studying the biological systems, or artificial intelligence or artificial life attempting to build artefacts based on the biological principles. These differing approaches may be characterised by distinguishing between the analytical and synthetic methods in the behavioural and brain sciences, as proposed by Braitenberg.

The analytical method seeks to describe transitions in behaviour (and to explain why they occur in any given context), either functionally through reference to some concept of utility, or mechanistically through reference to underlying neural systems. It is at the overlap between these two approaches that modelling (the "synthetic" approach - the creation of artificial systems which behave as natural ones) has an increasing influence: "what would it take to build a system that acts in this way?" It is not only formal mathematical models which are of interest, but also, and in cooperation, simulations for which mathematical solutions are intractable or unknown. This usually consists of extracting desired properties to be reproduced through observation, and their characterisation using tools from more traditional experimental sciences. In this way, novel hypotheses may be developed, and empirical data may be analysed from the perspective of the simulation model.

In creating models of action selection (and of other models of biological functioning), there are four important questions which need to be addressed and which should also be bourne in mind during development (quote from paper): "...is the model sufficiently constrained by biological data that its functioning can capture interesting properties of the natural system of interest? Do manipulations of the model, intended to mirror scientific procedures or observed natural processes, result in similar outcomes to those seen in real life? Does the model make predictions? Is the model more complex than it needs to be in order to describe a phenomenon, or is it too simple to engage with empirical data?" Concerning this last question, there is then a trade-off between simplicity for the purposes of analysis and adequate complexity for a sufficient model of the process(es) in question, neither extreme of which is suitable.

The introductory paper (by Prescott, Bryson and Seth) summarises the eight main areas covered by the special issue contributors (optimality of action selection, cortical-basal ganglia substrates, behavioural sequencing, subcortical substrates, disorders, perceptual selection, units of selection, and action selection in social contexts) and provides a discussion of modelling strategies and techniques in general. I hope to summarise a few of these papers in the coming weeks (particularly Botvinicks paper on a model of Fusters 'hierarchies').

Contents of special issue, here. Unfortunately, all of the papers are available by subscription only.

- Introduction. Modelling natural action selection TJ Prescott, JJ Bryson and AK Seth
- Do we expect natural selection to produce rational behaviour? AI Houston, JM McNamara and MD Steer
- The ecology of action selection: insights from artificial life AK Seth
- Compromise strategies for action selection FL Crabbe
- Action selection and refinement in subcortical loops through basal ganglia and cerebellum JC Houk, C Bastianen, D Fansler, A Fishbach, D Fraser, PJ Reber, SA Roy and LS Simo
- Cortical mechanisms of action selection: the affordance competition hypothesis P Cisek
- Towards an executive without a homunculus: computational models of the prefrontal cortex/basal ganglia system TE Hazy, MJ Frank and RC O'Reilly
- Multilevel structure in behaviour and in the brain: a model of Fuster's hierarchy MM Botvinick
- Is there a brainstem substrate for action selection? MD Humphries, K Gurney, and TJ Prescott
- Understanding decision-making deficits in neurological conditions: insights from models of natural action selection MJ Frank, A Scheres and SJ Sherman
- Extending a biologically inspired model of choice: multi-alternatives, nonlinearity and value-based multidimensional choice R Bogacz, M Usher, J Zhang and JL McClelland
- Biologically constrained action selection improves cognitive control in a model of the Stroop task T Stafford and KN Gurney
- Agent-based modelling as scientific method: a case study analysing primate social behaviour JJ Bryson, Y Ando and H Lehmann
- An agent-based model of group decision making in baboons WI Sellers, RA Hill and BS Logan
- Spatial models of political competition with endogenous political parties M Laver and M Schilperoord

10,000

A week or two ago now (I don't know exactly, since I've not been about much to check), this little blog received its 10,000th visitor - which is around 9,900 more than I was expecting when I started just over a year ago, since it was intended as a repository of my thoughts and notes. I hope that there has been something of interest and utility, and I would like to use this opportunity to thank all those who have linked here or left comments - many have led me in directions of research both interesting and useful to my own work.
Paul :-)

Tuesday, November 06, 2007

Behaviour-based robotics and artificial ethology

The following are quotes from the introductory paragraphs to chapter two of "Behaviour-based Robotics", Ronald C. Arkin, 1998 (MIT Press):

"The possibility of intelligent behaviour is indicated by its manifestation in biological systems. It seems logical then that a suitable starting point for the study of behaviour-based robotics should begin with an overview of biological behaviour. First, animal behaviour defines intelligence. Where intelligence begins and ends is an open-ended question, but we will concede in this text that intelligence can reside in subhuman animals. Our working definition will be that intelligence endows a system (biological or otherwise) with the ability to improve its likelihood of survival within the real world and where appropriate to compete or cooperate successfully with other agents to do so. Second, animal behaviour provides an existence proof that intelligence is achievable. It is not a mystical concept, it is a concrete reality, although a poorly understood phenomenon. Thirdly, the study of animal behaviour can provide models that a roboticist can operationalise within a robotic system. These models may be implemented with high fidelity to their animal couterparts or may serve only as an inspiration for the robotics researcher."

These three points provide the basis for the point of view that animal behaviour has a lot to offer the robotics community (behaviour-based robotics to be specific), and hints at the potential feedback that such work may offer the biologists. Without actually mentioning the term, this description could just as well be applied to artificial (or computational) ethology. The first point I think to be particularly interesting. In my opinion, the working definition of 'intelligence' it introduces is not particularly controversial - however, the implication of the the phrase '...improve its likelyhood of survival...' for cognitive/autonomous robotics is that without some form of actual physical dependancy on the environment (e.g. 'food' - and I hesitantly add, some form of concept of 'life and death' for the agent concerned), intelligence for an artificially created being means nothing (see a related concept in embodiment: organismic embodiment). The second point is one which is generally assumed, but not usually explicitly stated, and something which I think is useful to remind oneself of occasionally. The third point I think is self evident, stated many times, and with plenty of examples in the literature. In fact I think it is the basis for most cognitive robotics work.

The next part of the introduction to chapter two lists two reasons why the robotics community has traditionally resisted the use of the previously mentioned methods of creating artificial agents with 'useful' behaviours (e.g. perceiving and acting in an environment):

"First, the underlying hardware is fundamentally different. Biological systems bring a large amount of evolutionary baggage unnecessary to support intelligent behaviour in their silicon based counterparts. Second, our knowledge of the functioning of biological hardware is often inadequate to support its migration from one system to another. For these and other reasons, many roboticists ignore biological realities and seek purely engineering solutions."

The second point is, I feel, perfectly justified. One only has to consider, for example, the complexity of natural neurons and networks in comparison to the most advanced artificial neural networks which use population-based firing rates, to see that this is true. The first point however, I don't think is necessarily true, especially if one considers that the biological hardware which 'produces' the intelligent behaviour we seek holds many of answers. In this case, an understanding of the 'evolutionary baggage' which produces the biological hardware would be of importance when seeking to understand the intelligent behaviour itself. Or so I think, anyway.

Monday, November 05, 2007

Encephalon #35

I've been slacking recently when it comes to updating the blog... Anyways...

The 35th edition of Encephalon is now up at The Primate Diaries, with 17 of the best neuroscience (and related) posts from the last fortnight. I particularly liked the post from Pure Pedantry with some videos of synapse activation by insertion of AMPA-R into neurons (if I understand correctly, you're much better off reading it for yourself). Fascinating!

Monday, October 22, 2007

On Robots and Psychology

Valentino Braitenberg's Vehicles are often the first lesson in (cognitive) robotics courses as a prime example of the interaction between an agent and its environment, and how complex behaviour does not necissarily imply a complex control architecture (as well as Rodney Brooks' work of course). The fourteen vehicles (or agents) of increasing complexity demonstrate an 'evolution' of behaviours, dependant as much on the environment as on the morphologyand control architecture of the agents themselves. I think the following paragraphs, quoted from the introduction to the book (full reference at end) illustrates how this examination may lead to insight into the biological organisms from which they were inspired (whilst not claiming to 'solve' any of the problems):

I have been dealing for many years with certain structures within animal brains that seemed to be interpretable as pieces of computing machinery because of their simplicity and/or regularity. Much of this work is only interesting if you are yourself involved in it. At times, though, in the back of my mind, while I was counting fibres in the visual ganglia of the fly or synapses in the cerebral cortex of the mouse, I felt knots untie, distinctions dissolve, difficulties disappear, difficulties I had experienced much earlier when I still held my first naive philosophical approach to the problem of the mind. This process of purification has been, over the years, a delightful experience. The text I want you to read is designed to convey some of this to you, if you are prepared to follow me not through a world of real brains but through a toy world that we create together.

We will talk only about machines with very simple internal structures, too simple in fact to be interesting from the point of view of mechanical or electrical engineering. Interest arises, rather, when we look at these machines or vehicles as if they were animals in a natural environment. We will be tempted, then, to use psychological language in describing their behaviour. And yet we know very well that there is nothing in these vehicles that we have not put in ourselves. This will be an interesting educational game.

I like this, as I feel that it represents in some way (albeit more poetically than is generally stated) one of the aims of cognitive robotics as a field: elucidating issues in psychology/neuroscience, via a process (which I have vastly oversimplified here) of model creation on the basis of some biological system, implementation of said model (embodiment in the real world, or simulation thereof), and then evaluation of the resulting system against the original biological system. Hence the emphasis on behaviour - as a means of performing this comparison (since the 'computational substrate' is so obviously different) - which leads to the field of Artificial Ethology.

Ref: Valentino Braitenberg, "Vehicles: experiments in synthetic psychology", 1984

Monday, October 08, 2007

Hammers and Distributed Memory

In “The Feeling of what Happens” (1999), Antonio Damasio describes, among many other things, the distributed nature of memory. The following quote describes an example of how the concept of an object (in this case a hammer) may be represented in the brain (from page 220 of the book):

The brain forms memories in a highly distributed manner. Take, for instance, the memory of a hammer. There is no single place of our brain where we will find an entry with the word hammer followed by a neat dictionary definition of what a hammer is. Instead, as current evidence suggests, there are a number of records in our brain that correspond to different aspects of our past interaction with hammers: their shape, the typical movement with which we use them, the hand shape and the hand motion required to manipulate the hammer, the result of the action, the word that designates it in whatever many languages we know. These records are dormant, dispositional, and implicit, and they are based on separate neural sites located in separate high-order cortices. The separation is imposed by the design of the brain and by the physical nature of our environment. Appreciating the shape of a hammer visually is different from appreciating its shape by touch; the pattern we use to move the hammer cannot be stored in the same cortex that stores the pattern of its movement as we see it; the phonemes with which we make the word hammer cannot be stored in the same place, either. The spatial separation of the records poses no problem, as it turns out, because when all the records are made explicit in image form they are exhibited in only a few sites and are coordinated in time in such a fashion that all the recorded components appear seamlessly integrated.

If I give you the word hammer and ask you to tell me what hammer means, you come up with a workable definition of the thing, without any difficulty, in no time at all. One basis for the definition is the rapid deployment of a number of explicit mental patterns concerning these varied aspects. Although the memory of separate aspects of our interaction with hammers are kept in separate parts of the brain, in dormant fashion, those different parts are coordinated in terms of their circuitries such that the dormant and implicit records can be turned into explicit albeit sketchy images, rapidly and in close temporal proximity. The availability of all those images allows us, in turn, to create a verbal description of the entity and that serves as a base for the definition.

This 'story' of the recall of an abstract concept (by which I mean something which is not explicitly tied to a particular sensory experience) describes a situation where memory, as is generally thought of (recalling objects and events), is fully distributed throughout the brain, and can not be localised in a particular region. This concept has had much supporting empirical evidence found in recent years, including that I've reviewed in last weeks series of posts (which I believe was first proposed by Lashley in the early 20th century).

Saturday, October 06, 2007

Part 3 - Areal specificity in the PFC and temporal integration

In this third and final part of my review of this paper by Fuster (reference at the end of this post), the paper turns to look a little more closely at what neural mechanisms are at play in the performance of the central function it is proposed to carry out: temporal integration of information, and more generally, the temporal organisation of behaviour.

The paper then turns to the question of the supposed area specialisations in the cortex: the Network Memory theory predicts that functional subdivisions do not exist, but multiple lesion studies have suggested the opposite, to the extent that some cortical regions are generally accepted to be tied to a particular function. The PreFrontal Cortex (PFC) in particular has been subject to many proposed functional subdivisions, according to functions such as attention, working memory (visual, spatial and verbal), and involvement in episodic and semantic memory. The two points of views thus need to be reconciled.

Fuster addresses this problem by proposing that there is a common underlying process to all of the previously mentioned functions. As has been mentioned, this common process is proposed to be temporal integration. An example of this process in the PFC is given by cells which respond specifically to two temporally separate stimuli which have been associated through experience. These neurons have been demonstrated in monkey studies where the presented stimuli consisted of colours and sounds, so that for a given behavioural goal (which for the monkeys was learning and remembering associations between a colour and a sound, for some reward) cells "...seemed to belong to executive networks that, ..., integrated sounds with colours over time." This example demonstrates a principle with important implications for the concept of working memory, particularly the view of executive functions. Instead of dedicated neural circuitry for executive processes as has been proposed by most psychologically based working memory theories, this example (and other converging evidence) indicates that "...executive working memory seems to be essentially based on the ad hoc activation of executive networks of long-term memory."

From this proposal, it becomes necessary to answer two questions: (1) how are these executive networks activated in a timely fashion for the task at hand; and (2) how is this network (or networks) maintained active for the temporal bridging of separate components?

In order to process perceptual information, some form of modulation is required from the PFC – this being necessary for the context dependant retrieval of information from the posterior cortex (i.e. The perceptual hierarchy of the Network Memory theory). Feedback from these regions would then activate executive representations in the PFC. Together with the influences from sub-cortical regions, and the obvious effect of the external environment on the activation of perceptual and motor memories, this loop may be held responsible for the so called 'monitoring' function of the PFC, where relevant information is activated and made available as and when required. It also addresses the question of 'implementation' of working memory: this mechanism strongly indicates that "[it] is as widely distributed as the long-term memory that supports it." Furthermore, the cooling (known to inhibit brain function in a relatively tightly specified region) of any of these implicated regions in monkeys when performing a behavioural task produces deficits in performance indicative of working memory deficit. This may be explained by viewing such an inhibition as interrupting the 'loops' of recurring activity just mentioned, and thus impairing the monitoring function. In summary then: "Working memory is emerging as a mechanism of temporal integration essentially based on the concurrent and recurrent activation of cell assemblies in long-term memory networks of frontal and posterior cortex."

In the paper conclusion, we are reminded of the evidence from a wide range of disciplines in support of the proposed cardinal function of the PFC being the temporal organisation of behaviour, and temporal integration: anatomical interconnections, and developmental evidence (both in the individual and in evolutionary history). The PFC operates as part of the perception-action cycle, which links the actions of the animal with the environment and its internal neural dynamics.

REF: Fuster (2001), "The Prefrontal Cortex – An update: Time is of the essence", Neuron, vol. 30, pp319-333

Thursday, October 04, 2007

Part 2 - The PFC: a temporal organiser

There have been a number of studies in the past (including Endel Tulving, who proposed the view of separate semantic and episodic memory, and the associated HERA model), particularly neuroimaging based, which have observed two things in particular: firstly that the encoding of new memories activates the left PFC more than the right PFC, and secondly that the reverse activation profile is seen when memory is retrieved. This indicates the sort of specialisation that Fuster moves away from. An argument is thus provided to counter this: "...it is not altogether clear that the asymmetric activations of the two prefrontal cortices in encoding and retrieval are attributable to their differential involvement in these two cognitive operations. The apparent functional dissociation of right and left PFC may be a product of the subtractive method if the material utilized to test the two operations carries a different semantic load... in both encoding and retrieval tasks, the executive memory networks of lateral PFC may be activated inasmuch as the tasks consist of temporally integrative acts based on internal or external contingencies." In summary, the lateral PFC's most important function is the temporal organisation of behaviour.

Whereas routine behaviours sequences may be made up of chained behaviours, where one action leads to the next, there is no temporal contingency required - i.e. no planning. However, when ambiguity or uncertainty is introduced, such temporal planning ("cross-temporal contingencies") is required. Hence the role of the PFC (in delay tasks, for example, where there is at least one ambiguity that needs to be resolved) in temporal integration. The figure below, taken directly from the paper (figure 4 in paper), gives examples of these two events: in the top case, a routine sequence of behaviours occurs, and in the bottom, a complex or novel sequence. In this latter case, any given act is contingent on the goal, the plan, and other acts - this is the hypothesised role of the lateral PFC: the temporal organisation of behaviour.


Given this role for the lateral PFC, working memory is proposed as the first "temporal integrative function" of the PFC which has been verified in primates using electrophysiology. These experiments, which used delayed response tasks (and occurred in the early '70s), have identified four properties of neural firing related to spatial memory (thus also working memory):
(1) it was absent after stimuli that did not call for prospective action;
(2) it was absent in the mere expectation of reward;
(3) it was correlated with the accuracy of the animal's performance; and
(4) it could be diminished or aborted by distracting stimuli occurring in the delay period.

These properties strongly indicate "retention of the memorandum" (that which is to be remembered), which is dependant on the future need for action. "In sum, considerable evidence from several methodologies supports a prospective role of the PFC, in addition to its retrospective role of working memory. Ingvar (1985) dubbed that prospective role the 'memory of the future'". The retention of the memorandum could then allow the activation of the necessary motor functions (so called motor attention or preparatory set), thus priming the system as a whole for the execution of the required actions: “A temporally symmetric and complementary function of preparatory set, or 'motor attention' would activate the network's motor components and thus prime executive systems for the anticipated action.”

The final part of this paper review will be posted tomorrow, on more specific cortical mechanisms involved in this proposed function of the PFC...

REF: Fuster (2001), “The Prefrontal Cortex – An update: Time is of the essence”, Neuron, vol. 30, pp319-333

Wednesday, October 03, 2007

Part 1 - The PFC: anatomy and the network memory theory

The PreFrontal Cortex (PFC) is widely implicated in many 'high-level' cognitive functions, from working memory to planning, and others. It is frequently decomposed into a number of subregions, each supposedly specialised in some way or another for particular tasks. It is however difficult to establish these claims for certain given that current neuroimaging techniques do not have adequate spatial and temporal resolution to examine the real-time workings of these very small subregions of the PFC. All that can be done is to collect a wide variety of evidence from various methodologies in support of the theory. This is what Fuster does in this paper (ref at end): neuroanatomical, neuroimaging, single-cell recordings and behavioural studies are all reviewed in support of his theory of PFC functioning. His view is that the PFC essentially performs the function of temporally integrating information in order to achieve behavioural goals. This view was covered briefly covered in a previous post, but a number of details were missing from that short paper, which this paper attempts to address.

Fuster considers the PFC as being at the apex of the motor hierarchy in the Network Memory theory. As such, the supposed widely distributed network nature of the cortex in general is of great importance (quote "Any hypothetical modularity of the PFC is functionally meaningless if taken out of wide-ranging networks that extend far beyond the confines of any given prefrontal area."), and that is where the paper starts - the placement of the PFC in the cortex, with regard to neural connectivity. A summary of these connections by means of a quote (text in italics added): "The PFC is connected with the brainstem, the thalamus, the basal ganglia, and the limbic system (hypothalamus in particular). Much of that connectivity with subcortical structures is reciprocal. Especially well organized topologically are the connections between the PFC and the thalamus. The prefrontal connections with the mediodorsal thalamic nucleus have been used as a criterion for identifying the PFC in a wide variety of species." In terms of cortical connectivity, the PFC has connections to the cortices of association, but not with the primary sensory or motor cortices - which given the Network Memory theory's placement of the PFC at the top of a hierarchy, makes sense.

The PFC may be divisible into three main sub-regions: medial, orbital, and lateral. Each of these is 'connected' to itself and to each other. Damage to each of these three sub-regions typically produce distinct behavioural deficits. Damage to the orbital PFC (such as that sustained by the famous Phineas Gage) results in behaviour which is impulsive, an inability to inhibit instinctual behaviours, and typically exhibit a severe attention disorder (inability to withstand distraction). Damage to the medial part of the PFC generally result loss of spontaneity, and difficulty in the initiation of movements and speech. However, it is damage to the lateral PFC which produce the most characteristic cognitive deficit (according to Fuster). For humans, the most notable deficit is in the ability to plan and carry out sequences of actions which manifests itself in a difficulty in both speech and behaviour, and the difficulty to initiate and perform sequences in an orderly manner. Fuster points to this in particular to be a strong indication that the lateral PFC "plays a crucial role in the organization and execution of behavior, speech, and reasoning."

After reviewing the basics of the Network Memory theory (which may be seen in this post), the paper then goes on to describe in broad terms how the PFC fits in, and what more precisely its role is. The low levels of the motor hierarchy are located in the primary motor cortex, the so-called phyletic motor memory, which defines movements by muscle actions. Higher up in the motor hierarchy, these may be grouped, such that movements are defined by goals and/or trajectories. These higher levels are located in the PFC, and include, for instance, "elementary linguistic structures". The lateral PFC in particular "appears to harbour networks representing schemas, plans, and concepts of action." However, as sequences become over-learned and automatic, their representations 'move' towards lower executive levels: i.e. as the 'novelty' of an action decreases (or becomes more routine), less planning is required, and so the representation may 'drop down the hierarchy' (Fuster mentions that they may be organised entirely in sub-cortical structures). Despite this, if ambiguities in the action remains, then the involvement of the PFC remains necessary, in order to "integrate events in the temporal domain". A note is made that despite these functions being at the top of the hierarchy, they are not necessarily organised hierarchically: they are to some extent at least organised heterarchically. This is an important point, as it is an effort to acknowledge that the PFC does not perform top-down serial processing, as is often implied by a strict hierarchical structure.

This paper review continues tomorrow with a closer look at the function of the PFC...

REF: Fuster (2001), "The Prefrontal Cortex – An update: Time is of the essence", Neuron, vol. 30, pp319-333

The Prefrontal Cortex: Time is of the Essence

In this paper, Prof. Joaquin Fuster details the evidence he has from a wide range of disciplines in support of his proposed function for the prefrontal cortex. Since my review of the paper is itself quite lengthy, I have split it up into three parts, which will be posted here over the next three days. These three parts are as follows:

(1) The PFC: anatomy and the network memory theory

(2) The PFC: a temporal organiser

(3) Areal specificity in the PFC and mechanisms involved in temporal integration

Reference: Fuster (2001), “The Prefrontal Cortex – An update: Time is of the essence”, Neuron, vol. 30, pp319-333

Thursday, September 20, 2007

Silence on the posting front...

I have not managed to post much recently due to other commitments, but hope to resume posting on something a little more substantial than pointers to other people's blogging (as good as they are...) in the middle of next week.

For now: see a great post on "Neuroarchitecture", over at Mind Hacks

Wednesday, September 12, 2007

What is an emotion?

"And yet it is even now certain that of two things concerning the emotions, one must be true. Either separate and special centres, affected to them alone, are their brain-seat, or else they correspond to processes occurring in the motor and sensory centres, already assigned, or in others like them, not yet mapped out. If the former be the case we must deny the current view, and hold the cortex to be something more than the surface of "projection" for every sensitive spot and every muscle in the body. If the latter be the case, we must ask whether the emotional "process" in the sensory or motor centre be an altogether peculiar one, or whether it resembles the ordinary perceptive processes of which those centres are already recognised to be the seat. The purpose of the following pages is to show that the last alternative comes nearest to the truth, and that the emotional brain-processes no only resemble the ordinary sensorial brain-processes, but in very truth are nothing but such processes variously combined."

Quote from William James in "What is an Emotion?", first published in Mind 9, pp 188-205

Encephalon #31

The thirty-first edition of Encephalon is up at Dr. Deb. It has been since Monday, but I've only just got round to reading it. A good one as usual, and this one even starts with a picture of Spock... :-) There are three contributions to this edition which I found particularly interesting:

- Vaughan at Mind Hacks brings us a look at the psychology of believing news reports. Case studies are reviewed in support of the view that if false information is presented first it is likely to be believed, even in the face of subsequent corrections - indeed, these corrections may even embed the incorrect initially provided information (perhaps through the effect by which repeated information is more likely to be believed). The implications of this effect is quite wide ranging as pointed out by Vaughan: "As I'm sure these principles are already widely known among government and commercial PR departments, bear them in mind when evaluating public information."

- From Neurobiotaxis comes a review of the "Triune brain" theory, espoused by Paul MacLean. This theory of brain evolution proposes the well known three "layers" (for want of a better word on my part) of brain organisation, from the evolutionary primitive structures of the spinal cord and brain stem, through the midbrain structures of the limbic system, to the cerebral cortex, which is proposed as the most advanced structure in evolutionary terms. The post deals with it in terms of affective neuroscience, and asks the question whether the "triune brain" view is appropriate and relevant as a major theory. The conclusion after very detailed discussion (it took me a while to take in all the information) is essentially no, but it is noted that in the area of emotional behaviour, it is still defended by some (though at times as a useful conceptualisation rather than a prediction-producing model). A good read.

- Finally, a post on Synaesthesia by Mo at Neurophilosophy, particularly the recently discovered mirror-touch synaesthesia. After a review of the neuropsychological basis of synaesthesia (possibly by excess cross-modal neural connectivity, or by impaired inhibition across regions), MTS is introduced as a condition whose 'carriers' experience tactile information when they see another person being touched. Synaesthesia has long been something I have been interested in, partly as an example of how (if one ascribes to the cross-modal connections view) an 'error' in the development of the brain doesn't lead to impaired performance of any sort, and in some cases quite the opposite - demonstrating the amazing flexibility of the system that is the brain.

Friday, September 07, 2007

Mind Games

A story on the BBC appeared yesterday discussing the rise of the "brain training" computer game. I'm sure that everyone by now has seen those Nintendo DS adverts for that brain training game with Nicole Kidman in it that seems to be absolutely everywhere. They have been around for a while - although it seems as though only recently has it turned into a "fad". I particularly like the following sentence in the BBC article, which I think sums up this sentiment nicely:

"As if the gym was not tyranny enough, now there's another fitness routine
that's playing on the insecurities of the masses - the brain workout."
You would expect games companies to take whichever angle they can in order to sell more games, by using emotional blackmail perhaps by saying its for your (and your childrens...) wellbeing. But now Baroness Susan Greenfield, an eminant member of the Royal Society (if my memory serves me correctly), is fronting the MindFit family of mental games/exercises. I can't comment on the cognitive benefits of such software because I don't know enough about it, but I would have thought that if it were that genuinely good for your mental health, it would be freeware. But it's not (allthough of course I can see many reasons why it isn't).

Anyways, SharpBrains might be an interesting place to look for further information on "brain exercises" in general.

Monday, September 03, 2007

The biochemistry of memory

From a post at Neurophilosophy:

Found a series of links over at Neurophilosophy to five articles written on the subject of memory (at Chemical and Engineering News), particularly the biochemistry aspects. Not read the articles fully myself yet (just a quick skim so far), but look very interesting at the very least:

- Hold that thought
- Molecules for memory
- The well-endowed mind
- Memory at its worst
- Sleep anchors memory

Defending oneself against misuse of statistics

A little while ago, I came across a review of the five questions that Darryl Huff ("How to lie with statistics") suggested one should use to defend oneself "against statistics", via Mind Hacks. In addition to reviewing the five points, Tom at idiolect provides a commentary which provides some interesting and relevant additional points. The five questions I quote below, you can find the commentary here:
1. Who says so? Can we suspect deliberate or unconscious bias in the originator of the statistic? Huff recommends looking for an “O.K Name” - e.g. a university - as some slim promise of reliability. Second to this he recommends being careful to distinguish the originator of the ‘data’ from the originator of the conclusion or intepretation.
2. How Does He Know? Is the sample biased? representative? large enough?
3. What’s Missing? Statistics given without a measure of realiability are ‘not to be taken very seriously’. What is the relevant base rates / appropriate comparison figure? Do averages disguide important variations?
4. Did somebody change the subject? E.g. More reported cases are not the same as more cases, what people say they do (or will do) is not the same as what they actually do (or will do), association (correlation) is not causation.
5. Does it make sense? Is the figure spuriously accuracy? Convert percentages to real numbers and convert real numbers to percentages, compare both with your intuitions.

For me, one of the most interesting observations (and ensuing comment) made is concerned with credibility of the author who uses statistics (point one above). But I'm not going to recreate the discussion here (especially given some of the posts in the current Encephalon), read the post at idiolect.

Wednesday, August 29, 2007

Encephalon #30

The 30th edition of Encephalon is up at Neurofuture (which is unfortunately also the last post post there). An excellent installment as usual. A couple of my fovorites:

- A critique of science reporting in the media from Pure Pedantry: a look at the reporting of a study on the links between exercise and cognition. Particularly, I agree with all the general points made in the last few paragraphs on the interpretation of facts.

- Somewhat related to this is a post at Brains on Purpose, which looks at the (possibly unintentional) warping of information when reviewed second or third hand by analogy to the telephone game (which I know as the possibly politically incorrect chinese whispers...). The solution to avoiding the problem? (quote from post...) " First, be careful about the conclusions we draw from studies. Second, related to the process of conflict resolution, remember the tricky telephone-game effect. "

- And finally, a critique at Mind Hacks of the behaviour detection officers proposed for use at US airports, based on work by Paul Ekman on subtleties of facial expression.

The next edition of Encephalon is due at Dr. Deb on the 10th of September.

Friday, August 17, 2007

Crows and Tools

The BBC News website has reported on another study involving the New Caledonian crows originating from a few small islands in the Pacific ocean (picture above from BBC news story). This species came to light with the famous experiments at Oxford University (by Kacelnik and associates) on Betty and Abel, which showed their ability not only to use tools, but also to fashion them from non-tool and non-naturally occurring materials. These abilities had previously only been observed in humans and some primates.

The present study looked at 'meta-tool use' by this species. Meta-tool use is the ability to use one tool on another to achieve the desired state/goal. Seven wild crows were used in the experiment, with the following setup: a crow was presented with a box in which there was food. It was also provided with a stick, which by itself was not long enough to get the food. Another box was also present, in which there was a longer stick. The solution to getting the food is then to use the short stick to get the long stick, and the long stick to get the food from the first box: meta-tool use. The results showed not only that the crows were able to to this, but that this performance was achieved in the first trial (in 6 out of 7 subjects) – see the paper abstract below. As suggested by the paper, this indicates that the crows abstracted from, or used in some other way, information that had been previously learned to a novel situation – an not merely through trial and error.

This being a domain traditionally the preserve of humans, if found to be verifiable/replicable (from my understanding, this is the only study conducted of its type), the results could have a wide variety of implications in a number of fields. As I understand it, the learning and abstraction capabilities of the higher primates are explained by the 'closeness' in brain structure between humans and these animals: that it is the human brain that is capable of these feats, and that primates have limited capabilities due to similarities. The brain of the bird, in this case New Caledonian crow, however I assume to bear very little similarity by comparison. In this case, it would not be the structure which is important (not necessarily anyway), but some other property. I'm hardly intimate with the details of the study (or indeed the neuroanatomy of these crows), but I view it as an interesting issue: I'm thinking here of Fuster's Network Memory theory, of which, while being a model of the human information processing system, the underlying principles I assume may be equally applied to any neurally-based nervous system, including that of the crow (the detailed accounts of the specific brain regions in the Network Memory theory, particularly the prefrontal cortex, would naturally not apply – but perhaps this functionality may be physically represented in some other, limited, way?). Of course, these last thoughts are pure speculation on my part – perhaps some of your comments could help me untangle my thoughts?...



A crucial stage in hominin evolution was the development of metatool use—the ability to use one tool on another [1] and [2]. Although the great apes can solve metatool tasks [3] and [4], monkeys have been less successful [5], [6] and [7]. Here we provide experimental evidence that New Caledonian crows can spontaneously solve a demanding metatool task in which a short tool is used to extract a longer tool that can then be used to obtain meat. Six out of the seven crows initially attempted to extract the long tool with the short tool. Four successfully obtained meat on the first trial. The experiments revealed that the crows did not solve the metatool task by trial-and-error learning during the task or through a previously learned rule. The sophisticated physical cognition shown appears to have been based on analogical reasoning. The ability to reason analogically may explain the exceptional tool-manufacturing skills of New Caledonian crows.

Thursday, August 16, 2007

Hemispheric Specialisation

Being a subject I am interested in but know little about, a little while ago I made some notes on hemispheric specialisation. It's by no means a comprehensive overview, but I think there are some intriguing points, so I post it here in the hope that it interests someone else.

That hemispheric specialization exists to some extent is widely accepted: there are two theories regarding the reasons why this emerged [1]. First is the theory that over the course of evolution, nervous system sizes increased. This led to the need for more efficient use of the intracranial space, which led to the folding of the cerebral cortex, and, it is hypothesized, hemispheric specialization. Second is the theory that with increases in brain sizes came increased distances over which neural signals had to travel, leading to an increased amount of time required for transmission. As there is no evidence for the increase in speed of transmission, the net logical step is the shortening of the distances involved. This is proposed to be the driving force behind hemispheric specialization: the need for reduction in distance of transmission. In apparent support for this view is the observation that larger brains have, proportionally speaking, a smaller corpus callosum, resulting in fewer trans-hemispheric connections and thus increased specialization.

With regard to the nature of the hemispheric specialization itself, there seem to be two competing views: material-specific and process-specific specialization. The material-specific view is that each cerebral cortex hemisphere is specialized for a particular type of information [2]. For example, a study by Kelley et al on the dorsal frontal cortex found left sided activation for word encoding (verbal), right sided activation for face encoding (non-verbal), and bilateral activation for object encoding (both verbal and non-verbal) [3]. Similar results found for the medial temporal lobe. This was replicated by [4], who found that interference with the right dorsolateral prefrontal cortex caused disruption to the encoding of patterned stimuli (hence non-verbal). A possible explanation for this type of specialization comes from Josse and Tzourio-Mazoyer [1]. It is asserted that the left auditory cortex is specialized for temporal (i.e. time based) analysis, whilst the right auditory cortex is specialized for spectral (i.e. frequency based) analysis, which it is argued could explain the specialization of the left hemisphere for language, where the temporal content of speech is more important, and the specialization of the right hemisphere for music, where the spectral nature of the auditory information is more important.

This last point, concerning the specialization of the right hemisphere for music, has been contested by [4] for example, who emphasized the bilateral nature of activations due to various musical semantic and episodic tasks. More importantly here however, is their overall finding that there is generally a functional specialization of the left hemisphere for semantic memory tasks, and of the right hemisphere for episodic memory tasks. These findings were consistent with the HERA model of frontal cortex lateralization developed by Tulving et al in 1994 [5]. This model is a process-specific specialization view with the same views as those expressed by [4] with regard to hemispheric specialization.

As I said, a very brief overview. Hopefully, people who know more can fill in some of the gaps by leaving some comments. Thanks!

References:
[1] Josse, G.; Tzourio-Mazoyer, N. (2004), Hemispheric specialization for language, Brain Research Reviews, 44, pp1-12
[2] Glosser, G. et al (1998), Differential lateralization of memory discrimination and response bias in temporal lobe epilepsy patients, Journal of the International Neuropsychological Society, 4, pp502-511 (Abstract)
[3] Kelley, W.M. et al (1998), Hemispheric specialization in human dorsal frontal cortex and medial temporal lobe for verbal and nonverbal memory encoding, Neuron, 20, pp927-936
[4] Epstein, C. et al (2002), Asymmetries of prefrontal cortex in human episodic memory: effects of transcranial magnetic stimulation on learning abstract patterns, Neuroscience Letters, 30, pp5-8
[5] Tulving, E. et al (1994), Hemispheric encoding/retrieval asymmetry in episodic memory: positron emission tomography findings, Proceedings of the National Academy of Science USA, 91, pp2016-2020

Monday, August 13, 2007

Encephalon #29


Welcome to the 29th edition of Encephalon, the (loosely) neuroscience based blog carnival, featuring some of the best blogging in this area from the past two weeks. As per usual, there are a wide range of subjects in this issue; from caffeine to steroids, and from cosmetics to infidelity...

History

Since the past has led to where we are today, we'll start with a history lesson from Neurophilosophy on the rise and fall of the lobotomy. In this post, we are guided through the development of the lobotomy procedure into a widespread and somewhat popular treatment for a wide range of psychiatric disorders, to its ultimate demise due to misuse and the rise of drugs. The picture (taken from the post at Neurophilosophy) gives an idea as to the sometimes graphic detail that is given.

Cognitive enhancement

From the removal of large parts of the brain, we move to how we can enhance it without scalpel or capsule. First off we have SharpBrains who review an interview with Dr. Elkhonon Goldberg on cognitive enhancement and brain exercise. After an introduction to the history of neuropsychology, it moves on to discuss lifelong learning and the impact it can have on cognitive ability. In particular, challenging oneself with novel tasks is deemed to be vital, as the process of learning the piano for example has a good effect whether you are eighteen or eighty. Secondly, FitBuff looks at the 'Mozart effect' (picture taken from post), which supposedly increases cognitive ability and learning through listening to music in the baroque style. After looking at possible reasons why this effect could work, the conclusion is essentially that the effect is largely over-hyped, but that the effect of relaxation upon hearing the music should not be discounted.

Brain growth and memory formation

Now, improving cognitive ability non-invasively is of course to be desired, but at some point, a physical intervention is necessary. More specifically, an understanding of the structural and chemical factors in the development of the brain is important. From this perspective, we have GrrlScientists' entry on the influence of steroids on brain growth. It reviews a study on the development of song-control brain regions in song birds – in particular to test the prevailing view that this seasonal growth is dependent on hearing other song birds sing. However, through some manipulation, it was found that this is not the case: rather it is the production of steroids which drove the brain region growth, not environmental stimuli. The consequences for humans are interesting. Instead of stroke patients speech rehabilitation involving listening to tapes, perhaps it would be more effective to use growth stimulating hormones in the effected brain regions? Following on in a similar theme, The Neurocritic brings us a two-parter which reviews papers challenging the view that protein synthesis is necessary for memory formation. In the first part (Everything is wrong) it is suggested that rather than inhibiting the creation of proteins, drugs such as anisomycin actually cause massive fluctuations in neurotransmitter levels, which is proposed as the real cause of the observed memory impairment. In the second part (Anisomycin is strong), the mechanisms causing this are more closely examined, and the evidence against the prevailing view is reviewed.

Looking towards old age

As the baby-boomers are due to retire at the end of the decade, SharpBrains brings us a look at the consequences, emphasising the role for continuing training in allowing those who wish to continue working through retirement to actually do so. Somewhat related to this, GrrlScientist reviews a paper in Neurology on the effect of coffee in elderly women (picture taken from post). The results were very interesting: it found that for women aged 65 and over, drinking three or more cups of coffee (or the equivalent caffeine intake in tea for example) a day aided in preventing some age-related memory declines. Furthermore, this effect was more pronounced the older the women were. Unfortunately, there was no observed effect in men. Finally in this section, since Alzheimer's is a disease affecting the elderly, we have a post from Brain Blogger on the possible presence of an Alzheimer related gene. Coming in three types, each type of this particular gene is responsible for the development of three thicknesses of the entorhinal cortex – and a thinning of this cortex is linked to the onset of Alzheimer's in later life.
Altruism

Next we have three related posts from Natural Rationality on altruism, morality and generosity, each looking at a number of papers and providing a discussion of the major views and research methodologies involved in each. Firstly, the post on altruism. Starting with an apt quote from Friends, this excellent overview goes on to describe the seeming incompatibility between altruism and an individuals 'genetic fitness' and how this is not actually the case. The differing altruism theories in humans and other animals are discussed, before a suggestion is made that actually, there should be no such divide made. Secondly is a post on morality and the brain, in which papers are reviewed in support of the two competing views: is morality emotion- or reason-based? The conclusion is that the issue has yet to be resolved, but that cognitive science has the tools to enable an empirical examination of the problem. Finally, we have a review of a paper presented at the economic science association conference which found that subjects in a game-playing scenario who were given oxytocin exhibited greater generosity tendencies. The suggestion is made that generosity is based on empathy, and that oxytocin 'boosts' empathy.

Beauty and relationships

For the beauty part: from The Neurocritic we have a post reviewing a recent study in Nature Medicine which announces the discovery of the use of non-toxic injections which allow the targeted reduction of fat deposits. Conducted in mice, the work described the stress related neural pathways supposedly responsible for excessive weight gain when stressed, and how the introduction of blockers in the areas prevented this increase in fat due to stress. The researchers were hopeful of the applications of his research to cosmetics and the control of metabolic syndrome. For the relationship part: building on previous research which has shown that women alter their sexual preferences based on where they are in their menstrual cycle, The Primate Diaries reports on a study which has shown that this information can be determined simply by looking into the womans eyes. Pupil dilation in response to looking at pictures of desirable men (including the womans partner and favorite film star for example) gave an indication of their sexual preferences at that particular time. The authors of the paper use a "dad versus cad" theory to explain this change in behaviour.

And that's it...

That's all for this issue of Encephalon, I hope it's been a decent one. Next host is due to be Neurofuture on the 27th of August. Entries can be made through the usual channels: the online form here, or send to encephalon{dot}host{at}gmail{dot}com. Until then!

Thursday, August 09, 2007

Upcoming Encephalon #29

Following on from issue 28 at Bohemian Scientist, on Monday the 13th of August (next Monday), the 29th edition of the blog carnival Encephalon will be hosted here. Founded on the field of Neuroscience, it encompasses many fields, including AI, philosophy (of the mind-brain variety), psychology and cognitive science. If you wish to submit up to three blog posts to this issues, submissions can either be sent to encephalon{dot}host{at}gmail{dot}com, or can be submitted through the blog carnival subission form, here. I look forward to receiving them, and hope that issue 29 meets the high standards we have come to expect from Encephalon.

Wednesday, August 08, 2007

Emotion understanding from the perspective of autonomous robots research

The following bullet points are the outline of a paper review I gave at the Neuro-IT summer school which I was recently fortunate enough to have attended. It was given in a workshop led by Tom Ziemke on whether robots need emotions. This review paper was one of three covered during the workshop. Written by Lola Canamero, currently at the University of Hertfordshire, it essentially looks at how emotion research in robotics can aid in the understanding of emotions, whilst also aiding in the development of more 'intelligent' robots, by reviewing work that has occured in the field. Hope it's of interest, reference at end as usual.

Overview
• The contribution of emotion modelling in autonomous robots to emotion research
– The Questions that need answering (‘Bottlenecks’)
– Current/past approaches
– Interdisciplinary issues
– Challenges and goals for the future

Introduction
• Advantages of affective features in robots:
– human-robot interaction
– improved performance and adaptation in the ‘real world’
• How are these features related to emotions in biology?
• Focus on physical robots - not simulation
• The contributions that modelled emotions can make to emotion research:
– Human perception of emotions
– ‘Virtual Laboratories’
– Understand by building (the synthetic approach)
– The value of simplification (although the risk of oversimplification must be kept in mind)
• Contribution to emotion research in general, not just to human emotion research

Interdisciplinary action and Aims
• The necessity of long-term interdisciplinary efforts to achieve “principled emotion-based architectures”
• Two additional aims:
– finding solutions to problems arising in autonomous robots research
– production of tools to test emotion theories and gain insight

Questions
• Regarding models:
– scope and limitations of emotion theories?
– is a general definition of emotion required?
• Regarding mechanisms:
– plausible underlying emotion mechanisms?
– How can the different postulated mechanisms be reconciled and integrated?
• Applications:
– what emotions can be implemented in autonomous and interactive robots?
– are different models suitable for different tasks?
• Assessment:
– how can emotional states/processes be quantified?
– does observed behaviour aid understanding?

Current and past approaches
• Adaptation to environment - two time scales for autonomous robots:
– Emotion in Action selection
• behaviour control
• emergent emotions
– Learning, and,
– Memory
Emotion in Action Selection
• Behavioural control:
– emotions grounded in an internal value system: at the heart of autonomous behaviour (survival)
– motivations may be used to drive behaviour selection
• Emergent emotions:
– emotions in the eye of the beholder
– emergent from interaction with environment and dependant on morphology (Braitenberg)
Emotion and Learning
• Typically follows association or reinforcement learning models
– typically uses external reward signals
– how to make these signals ‘meaningful’?
• A more biologically plausible approach: an internal ‘value system’
– the learning of responses to reward and punishment as indicated by the value system
Emotion and Memory
• Memory management: must be both timely and accurate
• Using emotion:
– ‘mood congruent recall’ in humans
– the priming of memories relevant to the current emotional state

Interdisciplinary Issues
• Many parallels between autonomous robot emotion research, and emotion theories:
– Mechanisms underlying involvement of emotions in cognition and action
– Emotion elicitors
– Emotions as cognitive modes
– Emotions, value systems and motivation
Emotions in cognition and action
• How does emotion influence cognition and behaviour?
• ‘Circuit Models’:
– postulate set of neural mechanisms - promising for study of specific neural circuits, but difficulty in integrating at a global scale
• ‘Adaptational Models’:
– emotions as dynamic patterns of neuromodulations - can’t make contributions to human neural process examination, but allows study of the ‘global picture’
Emotion Elicitors
• What mechanisms are in place to allow influences to cause emotions?
– Establishing causal relations and possible implementation approaches a problem
– similar problem with Appraisal theories
• Gap between level of abstraction and implementation details too large
• Neuroscience feedback required concerning ‘valence’
Emotions as Cognitive modes
• The view that emotions have a global and and synchronised influence on the relation with the world
• Issues in implementing this view:
– The aspect and mechanism of emotion required
– How to account for cultural and individual differences?
– How to model relation between cognitive modes and action tendencies?
Emotions, value systems and motivation
• The role emotion plays in the production of action in autonomous robots:
– emotions allow more varied and flexible behaviour (related to goals)
– emotions as second-order control systems
– motivation factors and value systems
• Many different architectural implementations
• A quantitative assessment of utility of emotions?

Challenges and goals for the future
• The authors identified research directions, or challenges to be overcome:
– the grounding problem of artificial emotions
– dissolving the ‘mind-body’ problem
– linking emotion and intelligence
– how to measure progress?
Grounding emotions
• The drawbacks of a priori design of emotion constructs/mechanisms:
– over-attribution (over-design)
– lack of grounding (no ‘meaning’ for the robot)
• The emergent approach is promising
– counters over-attribution
• Computational models incorporating developmental and/or evolutionary perspectives:
– helps overcome the grounding problem
Dissolving the mind-body problem
• Investigating the links between ‘higher’ and ‘lower’ levels of cognition and action, and the influence of emotion
– “Symbolic AI” and “Embodied AI”
– The need for overlap between the two
• Problems that need to be addressed:
– role that emotion plays in synchronisation
– mechanisms for bridging the gap between internal and external aspects of emotion
– the integration of multiple levels of emotion generation
Linking emotion and intelligence
• Emotions are now considered pervasive in cognition and action, and an essential element of intelligence
– should not become an unquestioned assumption
• The modelling and study of individual cognitive and emotional systems necessary but not sufficient to understanding both:
– they are deeply intertwined, and should also be studied as such - in parallel
Measuring Progress
• What are the contributions of emotions, and how can this be quantified?
• “An obvious way of doing this is by running control expt’s in which the robot performs the same task ‘with’ and ‘without’ emotions and comparing the results.”
• Quantitative evaluations necessary in addition to qualitative ones

Summary
• The dual potential:
– The use of these robotic models as tools and ‘virtual laboratories’
– A modelling approach that “fosters conceptual clarification”
• The field is in its infancy; but progress is evident
• Necessity for interdisciplinary effort for understanding emotions in general

Reference: "Emotion understanding from the perspective of autonomous robots research", Lola CaƱamero, Neural Networks 18 (2005) 445-455

Tuesday, August 07, 2007

New Blog: Issues in the philosophy of mind and cogsci

A few days ago I came across a recently started blog called "Issues in the Philosophy of Mind and Cognitive Science". Written by a final year Philosophy and Cognitive Science student, Jack Josephy (see here for some other articles he's written), at the University of Sussex, it currently only has a few posts, but each looks at some of the philosophical issues involved in each of the post topics. So far, there are posts on intelligence, the nature/nurture debate, and machine consciousness. I particularly like the central emphasis he places on embodiment, something which I place great importance on.

Thursday, August 02, 2007

Life, Consciousness, and Brain Evolution

The February issue of Discover Magazine (07/03/07) carries an interview with Gerald Edelman, Nobel prize winner (for work on the structure of antibodies), and founder/director of the Neurosciences Institute. In this interview, conducted by Susan Kruglinski, he discusses his views on consciousness and the work he, and collaborators, are conducting with robots to shed more light on its mysteries. In doing so, the concept of life and the evolution of the brain is also briefly discussed.

From the outset of the interview, Edelman states his belief that consciousess can be created in artificial systems. He does, however, make a distinction between living conscious artefacts and non-living conscious artefacts. He takes 'living' to be "the process of copying DNA, self-replication, under natural selection". Anything with these properties is a living system - all else is not. Consciousness created in an artificial system would then be fundamentally different from our own (human) consciousness - although he does say that he would personally treat is as though it were alive: accord it the same basic respect ("...I'd feel bad about unplugging it.").

When it comes to giving a definition of what consciousness is, Edelman starts by turning to proprties described by the psychologist and philosopher William James: (1) its the thing you lose when you fall into a deep dreamless sleep, which you regain when you wake up, (2) it's continuous and changing, and (3) it's modulated or modified by attention, and so not exhaustive. From this, Edelman describes two states of consciousness. The first is primary consciousness. This supposedly arose with the evolution of a neuronal structure which allowed an interaction between perceptual categorisation and memory. In this way an internal scene could be created which could be linked to past scenes (i.e. memory). Built on this is secondary consciousness - resulting from the development of another neural structure (or structures, which is apparent in humans, and to a certain extent in chimps), which enabled conceptual systems to be connected: enabling the development of semantics and "true language", resulting in higher-order consciousness. A more simplified view of this consciousness is that it requires the inernalistion of stimuli, the remembering of them, and the interactions of these processes (not only perception and memory, but also things such as emotion). From this theory of consciousness, Edelman says that its further understanding would allow a clearer picture of how knowledge is acquired, which has importance in many diffenent respects.

It is based on this view of consciousness that he describes the Neuroscience Institute's approach to understanding consciousness. They construct what are described as Brain Based Devices (BBD's), which are essentially robots with simulated nervous systems. This artificial nervous system is modelled on that of a vertebrate or mammalian brain - although of course the number of neurons and synaptic connections in the simulated are many orders of magnitude smaller than in their natural counterparts. Nonetheless, one of their BBD's, called Darwin VII, is capable of undergoing conditioning: learning to associate objects in its environment with 'good' or 'bad' taste (where these 'tastes' have been defined a priori as fundamental properties of the environment). An important point regarding this experimentation is that it was conducted using real physical robots in the 'real world' (albeit simplified for the purpose of the task, it wasn't a simulation environment). Edeleman points out that a big problem with simulated environments is the difficulty of replicating reality, or in his words: "...you can't trace a complete picture of the environment." As demonstrated by the conditioning experiment, these BBD's are capable of learning: an example given in the interview of a segway-football match between a BBD-segway, and one programmed using 'traditional' AI techniques. Five matches were played, and the BBD-based device won each time. Edelman puts this down to the learning capabilities, and behavioural flexibility, from the fact that it learned all actions, rather than merely implement a set of algorithms (as a 'traditional AI' system does).

The BBD's being controlled by artificial nervous systems leads to questions regarding specifics of implementation. Instead of individually simulating the million or so neurons that make up the simulated nervous system, it is actually groups of around 100 neurons being simulated together, with the mean firing rate for this sub-populaion being taken (mean firing-rate models). This average firing rate is a reflection of synaptic change. According to Edelman, this sort of response is not just biologically plausible, it is identical: "The responses are exactly like those of [biological] neurons" (square brackets added).

The final part of the interview looks at other work going on at the institute. Currently, work is progressing on Darwin 12, the latest incarnation of the BBD's. This version is new as it intends to look at how embodiment affects the development of learning in the artificial nervous system, and its general functionality. It has both wheels and legs, and nearly 100 sensors in each of its legs. Mention is also made of other work concerning rhythm and melody as intrinsic human capabilities, more so than any other animal, and how this may have led to the development of language. This aspect of work seems to be only loosely brushed-over, so I do likewise.
I think that this interview, albeit reasonably short, covered a number of very interesting concepts on a wide range of subjects. However, I feel that it doesn't entirely succeed in bringing all of these elements together. An interesting read nonetheless.

Wednesday, August 01, 2007

Encephalon #28

The 28th edition of Encephalon is now up at Bohemian Scientist. This issue covers a wide range of subjects as usual; from biology and neuroscience, to psychology and neuroscience, and reviews of books and lives. The articles I most enjoyed from this edition are the following:

- From the Neurocritic comes a review of a study which looked to see if there were differences between the neural activities of children looking at angry faces, and whether it differed between those who were ajudged more or less susceptible to peer pressure. The post has more of the details from the paper, but just to summarise the conclusions: children better able to resist peer pressure showed better executive control functions.

- From the Thinking Meat Project, we have a review of two books described as being "informative and worth reading". Both are concerned with various aspects of neuroplasticity (find the references to these books in the post) - a subject I find fascinating. In the first book (by Doidge), presents a case study of patient which displayed dramatic examples of neuroplasticity as a lead into discussing the neuroscience issues. The second book (by Begley) prsents an ordered discussion of neuroplasticity from animals, to children, and through into adults. I like the review, and have the books to my ever-growing to-read pile (which I already can't keep up with).

- Finally, from The Third Culture comes a post entitled "Art, Context and the Brain" - a look at neuroaesthetics. This field aims to look at the neural processes underlying human behaviour in order to aid in aesthetic design and the understanding of art. After reviewing the problems with this approach (and this approach in general too, such as neuroethics and neuroeconomics), it goes on to give some examples of where this approach may be justified - the 'neural correlates of gambling' study. It even looks at the Ramachandran ethology example, which I personally like on a conceptual level at least, as a means of demonstrating the importance of context. If I might quote a part of the conclusion: "As the fields making up applied neuroscience explode in every direction, it is crucial that we keep two things in mind. First, we must not overstate what the findings can actually say, ... Second, and more central here, is that we must always be cognizant of the effect of context on any life experience." A good read.

All round a good issue of Encephalon. Finally, I'm pleased to announce that the next issue of Encephalon will be hosted here, at Memoirs of a Postgrad, on Monday th 13th of August. Submissions can be made through the usual channels. The more the merrier!

Wednesday, July 25, 2007

Cronos and Cognitive Reserve

Over the past couple of days, I've come across two very interesting posts which I thought I'd share: the first is the concept of "Cognitive Reserve", by way of an interview with one of its main proponents, and the second is an interesting look at robot ethics and machine consciousness, with some nice links to some very interesting people.

Cognitive Reserve: SharpBrains has an interview with Yaakov Stern (Division Leader of the Cognitive Neuroscience Division of the Sergievsky Center, and Professor of Clinical Neuropsychology, at the College of Physicians and Surgeons of Columbia University, New York) on Cognitive Reserve. The idea is basically that some people who are better able to withstand the effects of Alzheimer's have a greater cognitive reserve, i.e. numbers of neurons, which make up for the deficit. Also central to the theory is that mental and physical training aids in the building up of this cognitive reserve in a cumulative way.

Robot Ethics: A nice post I came across a few days ago at Bloggetiblog - a discussion of robot ethics. It mentions the humanoid robot Cronos in relation to Owen Hollands machine consciousness project, a quote from Murray Shanahan, and a brief look at the ethical issues facing robots and their designers. Altogether a nice read.

Tuesday, July 24, 2007

Another week away - Summer School

For the past week, I was away in Germany at the 5th Neuro-IT summer school in Delmenhorst (near Bremen), hence no posts. I hope to post a few of my (bullet-pointed) notes on some of the talks over the next few days - the subjects were very varied and technical, and needless to say, extremely interesting. To my dissapointment, one of the people I went to see, Ezequiel di Paolo, wasn't able to attend, but the school was nevertheless excellent.