In the past, two main theories of prefrontal function in animals have been proposed. The first implicates the prefrontal cortex in working memory, the second in the inhibitory control of behaviour. However, to date the organisation of the prefrontal cortex in the control of these functions is largely unknown. To address the issue of functional organisation within the prefrontal cortex of the marmoset, this thesis focused on the inhibitory control of behaviour. The initial study demonstrated that attentional set-shifting and visual discrimination reversal learning are sensitive to global prefrontal damage in the marmoset in a qualitatively similar manner to that observed previously in man and Old World monkeys respectively. The deficit was interpreted to be one of inhibitory control but, given the cognitive processing demands of these two tasks are different from one another, it is highly probable that the type of inhibitory control required is also different. Subsequently, the effects of discrete lesions specific to either the lateral or orbital regions of the prefrontal cortex on performance of attentional set-shifting and discrimination reversal learning were examined. Whereas the lateral, but not the orbital, prefrontal cortex was the critical locus in <I>shifting</I> an attentional set between perceptual dimensions; in contrast, the orbital, but not the lateral, prefrontal cortex was the critical locus in <I>reversing</I> a stimulus-reward association within a particular perceptual dimension. Both deficits were interpreted as constituting disinhibition or loss of inhibitory control, but a different levels. The inhibitory control required in attentional set-shifting appears to be at the level of attentional selection whereas the inhibitory control required in reversal learning is likely to be at the level of stimulus-reward associations or 'affective' processing.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:598525 |
| Date | January 1996 |
| Creators | Dias, R. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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