Monday, December 6, 2010

Journal Club presentation (11/29/2010)

I presented the article: The Architecture of Reward Value Coding in the Human Orbitofrontal Cortex by Sescousse et al, 2010, JNeurosci. in our weekly journal club last week and will discuss a brief summary of it below.

Firstly, the reason I chose this particular article is due to the similarity in design to the experiment I'm in the midst of creating for my Ontario Problem Gambling Research Centre funded project.

This study aims to parse the orbitofrontal cortex (OFC) into different functional regions based on the phylogeny of each part of this structure: the anterior lateral OFC is phylogentically the most recent whereas the posterior lateral OFC is older. They hypothesize that the more recent region (anterior OFC) will be involved in encoding monetary rewards which are considered secondary reinforcements whereas the older region of posterior OFC will process erotic rewards which are considered primary reinforcements as they satisfy biological needs (i.e. reproduction).

So the main idea that is the make it or break it basis for this study is:
The dissociation between the so-called "primary" gratifications such as food or sex, which satisfy basic vital needs and have an innate value, and more "secondary" rewards such as money or power, which are not essential for survival and whose value is assessed by association with primary gratifications.
There is no doubt that such dissociation exists BUT whether the researchers are able to assess this using their experimental stimuli remains to be decided through their results.

Their results did indeed confirm their hypothesis and they were able to provide the first evidence of a dissocation in the brain, particualry the OFC between two different types of rewards. Whether its the more primitative nature of erotic images or the more concrete nature of the stimuli used, they are processed by the posterior region of OFC. Similarly, the abstract and complex nature of monetary gains (a secondary reward) activate the anterior region of OFC.

Such postero-anterior axis has already been suggested to exist in the lateral prefrontal cortex (PFC), and some have also proposed that a hierarchical organization exists, whereby anterior frontal regions influence processing by posterior frontal regions during the realization of abstract action goals as motor acts (see review by: Badre & D'Esposito, 2009).

Overall, this is a very interesting study which could aid in better understanding of certain psychiatric disorders, including gambling addiction which are known to effect the OFC.
I will be designing a similar study in order to evaluate the effects of rewards in a gambling task requiring the suppression of an innate ability (the anti-saccade task).

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