Neural basis of executive control in prefrontal cortical networks.

University of Minnesota Ph.D. dissertatation. April 2012. Major: Biomedical Engineering. Advisors:Matthew V. Chafee and James Ashe. 1 computer file (PDF); viii, 136 pages.The goal of this research is to better understand how prefrontal cortical networks mediate executive control, the capacity to select and implement different information processing algorithms as a function of goals, rules, or other internal state variables. We trained two rhesus macaque monkeys to place visual stimuli into spatial categories according to a variable rule. We refer to the behavioral paradigm we developed for this purpose as the Dynamic Spatial Categorization (or DYSC) task, because the task requires the brain to classify each stimulus differently according the rule or grouping principle that is in force. Behavioral performance provided evidence that the monkey placed visual stimuli into spatial categories according to the variable rule. We then recorded neural activity from prefrontal and posterior parietal cortex simultaneously during task performance using dual, depth-adjustable 16 microelectrode arrays from ensembles of neurons. We found that the neural representation of the category and executive control of category as evidenced by the rule dependence of that representation were distributed in the network. The neural signal coding spatial category exhibited rule-dependence in prefrontal cortex first however, consistent with prefrontal cortex leading in the network implementation of executive control