5/26/2006

Conceptual Thinking: Just Out of Touch

Virtually anyone who reads the mainstream science press will have heard of mirror neurons - the nerve cells located in your frontal cortex that fire both when you perform a particular action action and when someone else performs that same action. The relatively recent discovery of these neurons lead to an explosion of theorizing about everything from the origins of theory of mind to autism. Interestingly, the same region of frontal cortex (premotor and inferior ventrolateral PFC) which contains mirror neurons has also been implicated in the encoding of abstract rules.

A recent review paper by Adele Diamond suggests that research on mirror neurons and research on the developmental time course of abstract thinking may be "missing the forest for the trees." In other words, the important feature of premotor and iVLPFC is not that they contain mirror neurons, or that fMRI shows them to be active during generalization tasks. Instead, the important feature of this region is that it is fundamentally responsible for associating things that are not physically connected.

This hypothesis is particularly tantalizing because we know that representations become progressively more abstract as you go from posterior to anterior frontal cortex. Intuitively, it makes sense that the area just anterior to motor cortex would contain mirror neurons.

A variety of behavioral results suggest that rudimentary forms of abstract thinking can be "bootstrapped" by physically connecting the relevant stimuli. For example, in the Delayed Non-Match to Sample (DNMS) task, children are presented with two stimuli and must pick the novel object in order to receive a small reward. Children normally are not able to succeed in this task until they are 21 months old, unless a surprisingly minor change is made: if the reward is physically attached to the underside of the novel object, children can learn this task as early as 9 months of age. To quote Diamond, "this result falsifies the previously held notion that the ability to dedduce abstract rules (such as 'Choose the item that does not match the sample') is beyond the ability of infants less than one year old."

Another example: it takes adult monkeys hundreds of trials to learn that the reward is always underneath the red cover, when the monkeys are presented with red and blue covers in varying locations. However, if the reward is physically attached to the red cover, they learn in just a single trial.

Diamond goes on to present many more examples of how the presence of a physical connection facilitates the learning of abstract relationships. She further argues that the critical region of frontal cortex is not premotor or even inferior ventrolateral PFC, but rather the inferior frontal junction (periarcuate in monkeys). A series of lesion studies indicates that monkeys with a damaged periarcuate fail the DNMS in the same way that human infants do when the task does not involve physical connection between stimuli and reward.

In summary, it appears that this region is involved in abstract rule learning, the learning of conditional associations, imitation, and even empathy (neural activity here is increased during observation of emotions) precisely because it is the first region of cortex where the representations are completely dissociated from physical connections in the real world. This research has profound implications for education - and perhaps even therapy for autistics - because it suggests that activity in this region can be facilitated by making connections between abstract ideas physically explicit.

1 Comments:

Blogger Dan Dright said...

Great post. I have loads to say on this subject. I was actually thinking about this, but from a different point of view, the other day. Suffice it to say that I am now questioning the entire concept of mirror neurons as a separate class at all.

More later.

5/28/2006 10:21:00 PM  

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