Behavioural Functions of the Frontal Cortex

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The primate frontal cortex comprises a large number of areas that have distinct cellular architecture and connectivity with other areas of the brain. These different areas form distinct functional frontal subsystems. In trying to understand the functional organization of the frontal cortex, the focus of my research has been to identify anatomically these different subsystems, to study the nature of the cognitive and behavioural impairments that follow damage to them, and to study the interactions between these functional subsystems in effecting the high-level control of behaviour and cognition that is the domain of frontal function. In my research, I have shown that patients with frontal cortical excisions exhibit specific impairments in monitoring processes within working memory, as well as impairments in selection between different actions based on learned conditional rules. In work with the monkey, I have shown that specific areas of the dorsolateral frontal cortex underlie these two classes of impairment: the mid-dorsolateral frontal cortex (areas 46 and 9) for the monitoring of information in working memory and the posterior dorsolateral frontal cortex (areas 8 and 6) for conditional rule-based choices between responses. In the work proposed in the present grant application, I shall explore the functional contribution of the ventrolateral frontal cortex in memory retrieval and the frontal polar cortex (area 10) which, in interaction with areas 46 and 9, may be involved in a hyper-monitoring function that would underlie our ability to multitask. These issues can now be approached in a powerful way because of: a) new experimental paradigms (appropriate for human and monkey studies alike) that we have recently developed, b) the availability of detailed knowledge of the anatomical connectivity of the various frontal cortical areas (to which we have contributed), and c) the results of our recent comparative anatomical studies of the human and the monkey frontal cortex. My research program utilizes behavioural analysis of lesion effects in monkey and human subjects and study of the connections of the prefrontal cortical areas in the monkey in an effort to elucidate the functions of this most complex part of the primate brain.