Normal cognition depends on interactions between the prefrontal cortex (RFC) and basal ganglia (BG). The cognitive impairments observed in a host of neuropsychiatric disorders including schizophrenia, Parkinson's disease, Huntington's disease, and ADHD have been linked to their dysfunction. Thus, understanding the respective contributions and collaborations between the PFC and BG will be critical to opening paths to treatment of these disorders. However, we understand little about the normal functioning of these areas because their neural activity has largely been studied separately, by different laboratories in different monkeys performing different tasks.
The aim of this proposal is to advance our understanding by recording from multiple electrodes simultaneously implanted in each region while monkeys perform a cognitively demanding task that will test the hypothesis that the basal ganglia is responsible for the acquisition and implementation of simple associations while the PFC pieces such information into a higher-level representation of the entire task structure. This project will test this hypothesis by extending investigations to a novel type of goal-directed behavior. Previous studies have employed rules with a strong motor component;in contrast, I will use categorical learning. It is fundamental to cognition and can be dissociated from motor responses. Neurophysiological studies in monkeys and fMRI studies in humans indicate involvement of both the PFC and BG in categorization, but they have never been directly compared.
Aim 1 of this proposal is to directly compare visual category information in PFC versus BG. This will allow us to compare the prevalence, strength, and latency of neural category information and to examine precise timing relationships within and between brain areas that can provide insight into their respective roles and how information is transferred between them. Prior studies also indicate that familiar, higher-order, motor-related rules are even more strongly represented and have a shorter latency in the premotor cortex (PMC) than the PFC. Thus, the PMC may function to consolidate information pertaining to frequently utilized tasks. But we do not know if this is only limited to rules with a motor component;non-motor rules such as visual categories have never been examined in the PMC. This is the goal of the second aim, to directly compare visual category information in premotor cortex, prefrontal cortex, and the BG. By directly comparing neural activity in these three structures, I hope to provide insight into their roles in a fundamental cognitive function - categorization. By understanding the normal functioning of these brain regions and their respective roles in cognition, we may better understand how to approach treatments for patients whose afflictions involve them.
|Cromer, Jason A; Roy, Jefferson E; Buschman, Timothy J et al. (2011) Comparison of primate prefrontal and premotor cortex neuronal activity during visual categorization. J Cogn Neurosci 23:3355-65|