6/15/2006

The Rules in the Brain

Much of cognitive psychology has undergone a profound shift in emphasis during the last decade or so, moving from theoretical information processing accounts of cognition towards a more embodied view of cognition. This embodied view seeks to identify the brain regions that implement the cognitive processes studied for decades previously in cognitive science.

One cognitive process (or set of processes?) that has been particularly elusive is executive function: this "catch-all" phrase has been difficult to pin down either in information processing terms, or in terms of which brain regions implement it. Notable exceptions include some fascinating factor analyses that identify likely executive subfunctions, and a new paper by Bunge and Zelazo in a recent issue of Current Directions in Psychological Science.

In this paper, the authors argue that orbitofrontal cortex is responsible for the control of simple stimulus-reward rules, as might be required when the reward value of a stimulus undergoes rapid reversal. Accordingly, damage to oPFC results in impaired learning of reversed stimulus-reward associations.

In contrast, ventrolateral and dorsolateral PFC seem to represent "univalent conditional" rules, or rules in which each stimulus is associated with a different response (neither of which is intrinsically rewarding or unrewarding). Alternately, dlPFC may also be involved in representing bivalent rules, in which a single stimulus is associated with multiple different responses. These regions appear to be more highly activated for bivalent than univalent rules.

Finally, rostrolateral PFC seems to be involved in resolving interference between multiple different rules, and thus choosing between them. According to these authors, rlPFC thus manages hierarchical rules.

Several structural and functional imaging studies loosely support the accounts provided here, namely that oPFC develops first, with dlPFC and rlPFC following much later afterwards. Furthermore, activity in child oPFC becomes similar to that seen in adult oPFC before this happens in dlPFC and rlPFC, though this is not surprising given that the structure of these regions takes longer to reach and adultlike state.

What is truly interesting about this paper, however, is that it is an extension of earlier work by Zelazo on the development of executive function. Specifically, his perspective has always focused on the importance of rules and rule structure to success in tasks like the Dimensional Change Card Sort, or the Tower of Hanoi. This paper can be viewed as an attempt to firmly bind these abstract information processing theories to the brain regions responsible for implementing them.

However, it is not clear that rule use is the essential function of these regions. For instance, it is possible that these regions are merely responsible for maintaining information, and biasing more downstream regions. One need not posit that these areas are intrinsically specialized for rule representation, but merely that complex rule use requires that these regions be active. In this alternative account, the most important function of prefrontal activity is active maintenance. This is the critical function that subserves rule use, merely because complex rules are too quickly forgotten unless the "prefrontal machinery" is fully developed.

Related Posts:
Task Switching in Prefrontal Cortex
Under The Rug: Executive Functioning
The Transience of Memory
Models of Active Maintenance as Oscillation

7 Comments:

Anonymous benp said...

the most important function of prefrontal activity is active maintenance. Is active maintenance and working memory is a synonyme for you ?

6/15/2006 05:00:00 PM  
Blogger Chris Chatham said...

This comment has been removed by a blog administrator.

6/15/2006 05:08:00 PM  
Anonymous The neurophilosopher said...

I regard cognitive functions as an product of multiple brain modules or circuits acting in parallel.

The recent paper by Peterson, et al implicated Broca's area as one of these 'executive' areas.

If Broca's area is indeed involved in executing cognitive tasks, this takes things to an even more complex level - parallel processing in multiple modules or circuits, each with an involvement in multiple tasks.

By the way, I'm starting a neuroscience carnival and would value your contribution. Visit the homepage for more info.

6/19/2006 05:42:00 AM  
Anonymous The neurophilosopher said...

A recent paper by Peterson, et al implicated Broca's area in executive function.

If Broca's area is indeed involved in executing cognitive tasks, then we have to add an additional layer of complexity, and think of cognition as the product of parallel processing in multiple brain modules/ circuits, each with an involvement in multiple tasks.

By the way, I'm starting a neuroscince carnival and would value your contribution. Please visit the carnival homepage for more info.

6/19/2006 05:49:00 AM  
Blogger Chris Chatham said...

alas I am going on a two week vacation starting tomorrow. DevelIntel will be on hiatus until I get back (and afterwards will hopefully resume to a far more normal schedule than before). Thanks for stopping in though!

6/19/2006 07:59:00 AM  
Anonymous sosaystherobot said...

i've never commented before, but i enjoy reading your blog too.

7/04/2006 05:37:00 PM  
Blogger Chris Chatham said...

thanks sosays... i'm headed back home today, so blog postings will resume shortly. thanks for stopping in!

7/05/2006 07:48:00 AM  

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