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Differential Roles of Primary Motor Cortex and Dorsolateral Prefrontal Cortext in Probabilistic Category Learning


Devin Bageac Photo

Devin Bageac, Adam Steel, BA, Leonora Wilkinson, PhD, Eric Wassermann, MD

The dorsolateral prefrontal cortex (DLPFC) and primary motor cortex (M1)each play a key role during learning. Specifically, an excitatory brain stimulation procedure delivered over the DLPFC called transcranial magnet stimulation (TMS), which turns up the function of areas of the cortex,has been shown to improve implicit learning of the complex probabilistic rules in a card gameon a task called the weather prediction task (WPT). Furthermore, patients with damage to the basal ganglia and the motor circuit between the putamen, M1, and supplementary motor cortex (SMA) due to Parkinson’s disease are impaired on the standard version of the WPT. Using an inhibitory form of TMS, known as continuous theta burst stimulation (cTBS), which turns down the function of regions of the cortex, this experiment aims to determine the causal roles of both DLPC and M1 in implicit learning as measured by the WPT. 60 participants will be divided evenly into three groups that will receive inhibitory cTBS: over M1, DLPFC, or ‘sham’ (i.e. no TMS) stimulation. Each participant will complete two versions of the WPT, one with a response that requires the processing of corrective feedback and one witha paired associative mechanism. Participants will then be tested to gauge learning, and comparisons will be made both within and between groups in order to determine the effects that inhibition of these regions will have on each type of learning.  We expect that inhibition of DLPFC will impair learning in both forms of the task due to the fact that both involve executive functioning and working memory.  In contrast, inhibition of M1 will selectively impair learning on the form of the task that requires the processing of feedback.

Last updated November 26, 2013