Monthly Archives: November 2013

Place tagged memories

We have another paper from scientists using epilepsy patients with electrodes implanted in their brains during treatment. This method gives very clear results because it measures very small groups of neurons with very accurate time measurements while the patients are able to behave in normal ways. In this case the researchers looked at place cells while the patients played a video game. The places were stores in a virtual city, the patients made deliveries to these stores, each delivery was unique and finally the patients tried to recall the delivered items. The pattern of place cells was recorded for each store just before the delivery was made, then during the delivery when the item was revealed and finally when each item was recalled. When patients recalled a delivery to that store by recalling the item (an event), their place cells showed the store’s signature (the place tag). So something that has been thought to be likely has been demonstrated.

The hippocampus appears to have (at least) two roles: it tracks location for a spatial memory; and it records events for episodic memory. These are interwined. “Our finding that spontaneous recall of a memory activates its neural geotag suggests that spatial and episodic memory functions of the hippocampus are intimately related and may reflect a common functional architecture,” said Kahana, head of one of the groups involved.

The connection between a place and what has happened in that place would be very useful to survival. Deciding how to act in that place would that take into account what was known of the place.

It has seemed to me that memories may also be time-tagged in the sense that episodic events have a serial order for some time. This does not have as strong an involvement in recall but has some. When we remember one event we have a tendency to remember what happened before and after that.

Here is the abstract (Miller etal. Neural Activity in Human Hippocampal Formation Reveals the Spatial Context of Retrieved Memories. Science, 2013):

In many species, spatial navigation is supported by a network of place cells that exhibit increased firing whenever an animal is in a certain region of an environment. Does this neural representation of location form part of the spatiotemporal context into which episodic memories are encoded? We recorded medial temporal lobe neuronal activity as epilepsy patients performed a hybrid spatial and episodic memory task. We identified place-responsive cells active during virtual navigation and then asked whether the same cells activated during the subsequent recall of navigation-related memories without actual navigation. Place-responsive cell activity was reinstated during episodic memory retrieval. Neuronal firing during the retrieval of each memory was similar to the activity that represented the locations in the environment where the memory was initially encoded.

Willpower

The very word ‘willpower’ implies a metaphor: that actions (and inhibition of actions) are a matter of conscious will and that they require the use of a resource or source of power. What powers the will is willpower. This is a sort of folk psychology – it takes a special sort of effort to have self-control, make a decision, solve a problem or resolve conflict. People vary in how much of this special effort they can sustain and it is limited. Will is like a muscle and it can tire, but if ‘exercised’ it can become stronger. Baumeister and others investigated this view of willpower experimentally. This metaphor is supported by showing that different tasks that were thought to require willpower interfered with one another. This phenomenon was called “ego depletion”. (I find that name hints at a Freudian picture.) It also appeared that tasks associated with willpower required glucose and this might be the limited fuel. This was a nice clear picture – the metaphor was holding up. But - this is one of those metaphors that is true if you believe it. If you believe that willpower is required to do hard mental work, that it is limited and can be used up, then that is what you will find.

 

 

But then the doubts came. Job and others showed the ego depletion works only if the subject believes the theory and Clarkson and others showed that the subject had to believe that they were short of energy for sugar to be limiting. It seems that gargling sugar water is as effective swallowing it. Some people think that physical exercise depletes willpower and for them it does. Others believe that exercise is mentally invigorating and surprise, it is. This history is reviewed by Brass (see citation below).

 

 

Doubts have also been shown in the area of conscious will as opposed to decisions and other ‘will’-requiring tasks having to be conscious. So both the will and the power in willpower are now suspect.

 

 

Brass and others also outline another way to look at willpower. The brain compares the predicted reward of doing something with the predicted effort. This is what affects what people decide to do, manage to do, and manage not to do. So instead of calling it willpower, we now can call it self-control and leave the old baggage behind. People vary in what they bring to the table when making the comparison of reward to effort. That is really what is involved in some people being able to resist temptation and others not. They include different values in the assessment of reward versus effort. The interference between tasks is thought to be due to the tasks requiring the same set of brain regions, and those areas not being good at doing two things at the same time.

 

 

Interestingly, most of the tasks that are described as drawing on willpower are tasks that involve the mPFC (medial pre-frontal cortex), and in particular the ACC (anterior cingulate cortex) . … The research outlined here suggests that the mPFC, and in particular the ACC, might be a central node in the neural circuit related to willpower. From what we know about the ACC, however, it is not plausible to assume that it provides a common resource, but rather that it has a kind of regulatory function determining the level of effort that is invested in a task. In a recent position paper, Holroyd and Yeung argued that the ACC is involved in choosing between different behavioural options and determining the level of effort that is invested in executing the chosen behavioural option. This description is consistent with the idea that the ACC implements a regulatory mechanism that determines the intentional investment in a specific response option or task. Accordingly, there is strong evidence for construing willpower as a regulatory function that can be related to specific brain structures in the mPFC. While such a regulatory mechanism is evidently required in situations of self-control and complex choice, we argue that any kind of intentional decision draws to some degree on this mechanism.

 

 

I feel for the people who are gritting their teeth and trying to muster willpower as if by magic, when it is cultivating a fuller value system that might serve them better.

ResearchBlogging.org

Brass M, Lynn MT, Demanet J, & Rigoni D (2013). Imaging volition: what the brain can tell us about the will. Experimental brain research. Experimentelle Hirnforschung. Experimentation cerebrale, 229 (3), 301-12 PMID: 23515626

Watching hands

Think of a little baby trying to understand the world. One thing they need to be able to deal with is causal relationships. They seem to come with their visual systems able to identify some simple events, for example the ‘launching effect’ where one moving object contacts another stationary one and imparts its motion to the stationary object. Identifying objects that seem to control other objects is an important starting point for understanding events. I had presumed this is why infants notice hands and follow their movements. Hands, including their own, are movers of other things. Well, I still do assume this importance of hands to infants, but a recent paper by Yu and Smith adds more importance to hands (see citation below). They are useful in establishing joint attention.

 

 

Joint attention is a key to communication. Once two people are both attending to the same object/event and know it, they can communicate. Even without language - through gesture, posture, facial expression and little noises - they can ‘discuss’ the joint target of their attention. With language, words become the pointers to steer joint attention, not just to objects in sight but to objects and metaphors in the mind. Being able to establish and maintain joint attention is very important for infants to master in order to go on to master a number of skills including language.

 

 

Until recently it was thought that infants established joint attention by following the eye movements of their partner. But this is quite a difficult skill. The eye movements are small, not too accurate and limited in availability. On the other hand, hand movements are very clear and accurate. Most people move their eyes in the same direction as they move their hands when they are using their hands. It is more efficient for an infant to follow hand movement then eye movements.

 

 

Here is part of the Yu/Smith paper:

 

One-year-olds and their parents temporally coordinated their visual attention to objects and did so smoothly, consistently, and as equal partners without one partner dominating or leading the interaction. Further, the two partners often shifted attention to the same objects together in time. (One way) to coordinated visual attention: each partner looks to the other’s eyes and the seen direction of gaze of the partner influences the direction of the other partner’s gaze, leading to coupled looking behavior. (An other way) alternate pathway: Within individuals a tight coordination of hand and eye in goal-directed action means that hand and eye actions present spatially redundant signals but with the hand cue being more spatially precise and temporally stable. The results show that the hand actions of an actor have a direct effect on the partner’s looking, leading to coordinated visual attention without direct gaze following. This hand-eye pathway is used by one-year-olds and their parents, and supports a dynamic coordination of the partners’ fixations that is characterized by rapid socially coordinated adjustments of looking behavior. The documentation of a functional alternative to following the eye gaze of a social partner begins to fill the contemporary knowledge gap in understanding just how joint attention between infants and parents might work in cluttered and complex everyday contexts. Joint attention as a means of establishing common reference is essential to infant learning in many domains including language and the present results show how coordinated looking may be established and maintained in spatially and dynamically complex contexts that include manual actions on objects. Infant attention and sensitivity to hand actions demonstrated in the present results is also consistent with the large and growing literature on their ability to interpret the causal implications of hand movements and gestures .

 

Successful adult social interactions are known to depend on rapid (with fractions of a second) behavioral adjustments in response to and across a suite of sensory-motor behaviors that include eye, head, hand, mouth, and posture movements. The hand-eye pathway evident in one-year-olds and their parents shows this same character of well-coordinated rapid adjustment in response to the partner.

ResearchBlogging.org

Yu C, & Smith LB (2013). Joint Attention without Gaze Following: Human Infants and Their Parents Coordinate Visual Attention to Objects through Eye-Hand Coordination. PloS one, 8 (11) PMID: 24236151

Decision funnel - the Brass model

Marcel Brass’ group has published a very wide ranging and interesting article on volition (citation below). They look at what fMRI results have shown (and not shown) on a number of questions regarding how volition works in the brain. Near the end of the paper they outline their own model of the progression of stages from goals to actions.

Here is their figure 1: Brain regions in the medial frontal cortex that have been implicated in human volition. SMA supplementary motor area, preSMA pre-supplementary motor area, RCZ rostral cingulate zone, dmPFC dorsomedial prefrontal cortex, vmPFC ventromedial prefrontal cortex

And here is their section on the funnel model:

Based on the research outlined above, we propose an extension of the WWW model (whether, what, when) of intentional action. This extension assumes that intentional action follows a kind of funnel-like organization that is related to an anterior-posterior gradient within the medial frontal cortex. It is, however, crucial to note that while this model focuses on the role of the mPFC (medial prefrontal cortex) in intentional action, we assume that areas in the lateral pre-frontal cortex, subcortical regions, and parietal regions are involved in intentional control of action as well.

Our model assumes that early stages of intentional action are related to anterior prefrontal brain regions. These brain regions process complex and heterogeneous information that is only broadly determined by specific task instructions or goals. Processing in these brain regions provide a sort of

informational background, or intuition, and has a biasing function towards later processing stages. This complex set of information is funnelled when information travels more posteriorly and enters later stages of intentional action. Regions in the RCZ (rostral cingulate zone) are related to choices between different response options. Such choices are biased by bottom-up information but also by concrete instructions that operate as a top-down influence and thus are a result of the interplay between top-down and bottom-up processing. Furthermore, the RCZ determines the level of effort that is invested in pursuing a specific behaviour and thus regulates the ‘willpower’ that is invested in a specific choice. When a specific response option is selected, this information is transferred to brain areas more closely related to the motor system, namely SMA/PreSMA (supplementary motor area/pre-supplementary area). Here, the impulse to initiate a specific response is generated. At this point in the processing stream, it is still possible to disengage from the intention to act or to change the intended behaviour. Intentional inhibition is achieved by a signal from the dorso-medial prefrontal cortex that down-regulates activation in the SMA/preSMA. As a working hypothesis, we assume that the subjective experience of volition results from supra-threshold activation in brain circuits that are involved in the control of intentional action. Such subjective experiences are phenomenologically rich because they can be related to any level of the processing stream, ranging from intuitive feelings to concrete urges to act.

The funnel-like organization of human volition guarantees that choices are based on a broad scope of information. At the same time, it also ensures that we can choose very quickly and efficiently when necessary. Whether our choices are primarily determined by intuitions and introspective thoughts, or by explicit deliberation and task instructions, strongly depends on the specific task context and the time

frame of our choices.

ResearchBlogging.org

Brass M, Lynn MT, Demanet J, & Rigoni D (2013). Imaging volition: what the brain can tell us about the will. Experimental brain research. Experimentelle Hirnforschung. Experimentation cerebrale, 229 (3), 301-12 PMID: 23515626

Should science be dishonest to the public?

There is an idea floating about that people should be encouraged to believe in free-will even if it is not a sensible thing to believe. This is not the way science should work. Why upset people by telling them that the earth goes around the sun? How upsetting! Why tell them that they are descended by evolution from animals? They will act badly if they think they are animals. Why tell them that the world is billions of years old? That would only disturb their faith in the truth of the Bible. And here we go again. Why tell people how they make decisions with their brains? Why tell people that consciousness is not as it appears? Why not just lie about the impossibility of free-will? They may become criminals.

This is not how science is supposed to work. Science is about making our model of the world more and more correct and publishing the improvements. The task is to find a more and more clear picture of the workings of the brain, not to tell convenient lies.

So Vohs and Schooler (see citation) have published a paper that shows that being primed to think of determinism prompts people to cheat more. This one paper appears with no replication to date and yet there is discussion of abandoning scientific ideals. I have four reasons to suspect the paper but even if it turns out to be strong evidence, it does not justify telling people that free-will exists in the sense that they understand it. Libet’s experiments have been replicated and have stood up to attempts to disprove them for a few decades. His was a disproof of free-will as ordinary people used the term. We should not tell people otherwise.

The first thing that bothered me about the Vohs paper was the particular quotation they used to prime people towards determinism. It is about the most negative way to present the issue that can be imagined. What a depressing way to say that your brain makes decisions! There is nothing in this essay from the Astonishing Hypothesis that is not factual. But it is written in a way that makes one feel doomed. It starts: “You,” your joys and your sorrows, your memories and your ambitions, your sense of personal identity and free will, are in fact no more than the behavior of a vast assembly of nerve cells and their associated molecules. Who you are is nothing but a pack of neurons. I don’t know what was used for the free-will or neural primers but I assume that they were not depressing.

Then I noticed that there was all of 30 subjects and the results were not dealt with individually but as averaged results. That can hide a lot of outliers and data spreads much larger than the average effect. This is just not the sort of statistical analysis that gives me a lot of confidence. By that time I was setting aside the paper as something that needed corroboration by other experiments.

Finally I saw a posting in the Why Evolution is True blog (here) discussing some unpublished work by Rolf Zwaan (here) which failed to replicate the Vohs results and pointed out some flaws that were not obvious to me, such as the subjects being predominately Mormon.

The Vohs/Schooler paper seems to have been accepted without much criticism by many - so have papers by Baumeister, Stillman, Wegner. But there is some criticism. One paper by Miles (citation below) is particularly useful for its broad and deep treatment of the issues.

Here is the abstract and part of the conclusions:

Over the last few years, a number of works have been published asserting both the putative prosocial benefits of belief in free will and the possible dangers of disclosing doubts about the existence of free will. Although concerns have been raised over the disservice of keeping such doubts from the public, this does not highlight the full danger that is presented by social psychology’s newly found interest in the ‘hard problem’ of human free will. Almost all of the work on free will published to date by social psychologists appears methodologically flawed, misrepresents the state of academic knowledge, and risks linking social psychology with the irrational.

Of course, even if we were to begin to acknowledge the moral and intellectual downsides to the free will myth, this would not suggest that Vohs and Baumeister were right to claim that belief in free will may also have prosocial upsides. We have seen that Vohs and Baumeister appear as yet to have shown no such thing, because all they have been studying appears to have been the effect of an acceptance of fatalism, not disbelief in free will. Contrary to the claims made in social psychology journals, we appear to have seen no evidence to date that disabusing people of the myth of free choice encourages anti-social behaviour, yet significant evidence that the myth of free choice encourages immoral, unjust, prejudiced, and anti-intellectual behaviour. If nothing else, this paper should stand as an important corrective within the psychological literature on free will.

This seems to put the nature of this work in a nut shell. I am not surprised that Vohs has won a Templeton prize.

ResearchBlogging.org

Vohs KD, & Schooler JW (2008). The value of believing in free will: encouraging a belief in determinism increases cheating. Psychological science, 19 (1), 49-54 PMID: 18181791

Miles J.B. (2013). ‘Irresponsible and a Disservice’:The integrity of social psychology turns on the free will dilemma British Journal of Social Psychology, 52, 205-218 : 10.1111/j.2044-8309.2011.02077.x

An electronic synapse

It is a truism that simulation of the brain with ‘electronic neurons’ has been very approximate at best. One problem was simulating the behavior of synapses in software – and synapses are key to ‘biological neuron’ communication. But soon there may be a simulation of the synapse in hardware. This does not solve all the problems with simulating the brain but it will be a large step in that direction. This is somewhat like the brain’s architecture which is more physically based than algorithmically based. Of course, miniaturization is necessary as the number of synapses in any smallish part of the brain is astronomical.

 

The idea is to use a very thin sheet of samarium nickelate between two platinum terminals. The sheet can be changed from isolating to conducting by the concentration of oxygen ions in the sheet. The oxygen ions can be made to leak out or in - from a small reservoir of ionic liquid by applied voltages. The voltage is controlled by the strength and timing of spikes on the ‘dentrite’ and ‘axon’ terminals. The changes in conductivity are stable until forced to change by another voltage signal. The devices can therefore ‘learn’/’remember’.

 

They have the advantages that they: can be integrated into silicon-based circuits, are fast, can work at room temperature, are energy efficient, do not require continuous power to maintain their ‘learning’.

 

Here is the citation and abstract:

 

Jian Shi, Sieu D. Ha, You Zhou, Frank Schoofs, Shriram Ramanathan. A correlated nickelate synaptic transistor. Nature Communications, 2013

 

Inspired by biological neural systems, neuromorphic devices may open up new computing paradigms to explore cognition, learning and limits of parallel computation. Here we report the demonstration of a synaptic transistor with SmNiO3, a correlated electron system with insulator–metal transition temperature at 130°C in bulk form. Non-volatile resistance and synaptic multilevel analogue states are demonstrated by control over composition in ionic liquid-gated devices on silicon platforms. The extent of the resistance modulation can be dramatically controlled by the film microstructure. By simulating the time difference between postneuron and preneuron spikes as the input parameter of a gate bias voltage pulse, synaptic spike-timing-dependent plasticity learning behaviour is realized. The extreme sensitivity of electrical properties to defects in correlated oxides may make them a particularly suitable class of materials to realize artificial biological circuits that can be operated at and above room temperature and seamlessly integrated into conventional electronic circuits.