Archive for the ‘Scientific Article Review’ Category

The role of reward and cognitive control in decision making

Monday, September 24th, 2007

Here’s an exchange of emails between PL and MC on a recently published paper (Balleine et al., 2007).

Email 1 (from PL):
Have a look at this introductory paragraph from a recent (Aug 2007) J Neurosci article by Balleine, Delgado and Hikosaka. What do they mean by “cognition” here?

The Role of the Dorsal Striatum in Reward and Decision-Making
To choose appropriately between distinct courses of action requires the ability to integrate an estimate of the causal relationship between an action and its consequences, or outcome, with the value, or utility, of the outcome. Any attempt to base decision-making solely on cognition fails fully to determine action selection because any information, such as “action A leads to outcome O,” can be used both to perform A and to avoid performing A. It is interesting to note in this context that, although there is an extensive literature linking the cognitive control of executive functions specifically to the prefrontal cortex (Goldman-Rakic, 1995; Fuster, 2000), more recent studies suggest that these functions depend on reward-related circuitry linking prefrontal, premotor, and sensorimotor cortices with the striatum (Chang et al., 2002; Lauwereyns et al., 2002; Tanaka et al.,2006).


Email 2 (from MC):

It sounds like they are distinguishing cognition from reward processing. I’m not sure why, since ‘cognition’ typically encompasses reward processing now days.

The distinction I think they’re really trying to make is between cognitive control and reward processing. Given that, it’s still a ridiculous paragraph. Why must it be either cognitive control or reward processing? It’s likely (no, virtually certain!) that the two interact during reward-based decision making. For instance, O’Reilly’s stuff shows how this might happen.

Another problem with this paragraph: They equate causal knowledge with cognitive control. Well-known causal knowledge doesn’t involve cognitive control! For instance, routine decision making would involve lower perceptuo-motor circuits, and if it involved differential reward then reward circuits would be engaged as well. Cognitive control has little/no role here.

When cognitive control is involved it’s probably doing a lot more than just retrieving causal relations from semantic memory. For instance, perceptual decision making studies show that cognitive control is involved even in deciding what is being perceived when uncertainty arises.

I guess what they’re trying to do is show that cognitive control doesn’t explain all of decision making since there must be a reward component as well. Perhaps this is a good point to make; they just didn’t do it well.


Email 3 (from PL):

Ahhh, ok I think I see now what they’re trying to say.  It really just struck me as an excessively divisive statement to start out what appeared to be an interesting article.  Can you say “flamebait”?  Perhaps they’re trying to be provocative.

- PL & MC

The neural basis of preparation for willful action

Wednesday, February 7th, 2007

My latest scientific publication is entitled Selection and maintenance of stimulus–response rules during preparation and performance of a spatial choice-reaction task (authors: Schumacher, Cole, and D'Esposito). It is a study using functional MRI with humans to investigate how we prepare for and execute willful action.

In this post I'll attempt to translate the article's findings for both the layperson and the uninitiated scientist.

What is willful action?

Willful action is a set of processes in direct contrast to automatic, habitual, processes. We can say with certainty that you are using willful action minimally when you are resting, brushing your teeth, driving to work for the thousandth time, or while performing any task that is effortless.

Willful action is necessary during two types of situations.

First, when you are attempting to do something for the first time (i.e., when you've had little practice at it) these processes are necessary for accurate performance. Think of the immense amount of effort while learning to drive. At first willful action was necessary, but later this need subsided.

Second, when two potential actions conflict in the brain willful action is necessary to overcome the incorrect action. The conflicting action may originate in an inappropriate desire, a habitual action that is no longer appropriate, or a natural tendency to perform one action rather than another.

In this latest publication we have used this last case (conflict due to a natural tendency to respond in a certain way) to investigate willful action.
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Wandering Minds and the Default Brain Network

Friday, January 19th, 2007

Several news articles have come out today which seem to imply that a recent Science report's main finding is that the mind wanders for a purpose (see this Forbes article), and that "daydreaming improves thinking" (see this Cosmos article). These are typical of fabrications used by popular science journalists to pique the public's interest.

Mason, et al. 2007 (the Science article published today) did not say that the mind wanders for a purpose (though they speculated that there may be one), and specifically mentioned that "the mind may wander simply because it can". Also, I could not find anything about daydreaming improving thinking in the article, except a short sentence about daydreaming possibly improving arousal. (A slap to the face will probably improve arousal; will the next headline be "face slaps improve thinking"?)

The two popular news articles mentioned above present these very speculative statements from the article not only as fact but also as the main results of the research, which I find to be disingenuous.

As a researcher in the area, I would say these are the main points to take from Mason, et al. 2007:
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