| Summary: | This project aims to examine the dorsal anterior cingulate cortex (dACC) and the globus pallidus internal (GPi) within the context of their cognitive functions from patients that had undergone deep brain stimulation (DBS) surgery. Patients performed the intra-extra dimensional set shifting (IED) task that allowed neural activity from both the dACC and GPi to be recorded while participants got trials correct and incorrect. These trials were categorized beyond these two domains into five different types (expected correct, adjusted correct, guess correct, mistake, and unexpected incorrect) based on their level of surprisingness. Various analytical techniques including event-related spectral perturbation (ERSP), event related potential (ERP), linear regression, Fourier transform, and autoregression were used to examine the neural activity associated with the five conditions. ERSP analysis of the data highlighted that both the dACC and the GPi show differences in frequency power for correct vs incorrect trials and for types of incorrect trials but show no differences when comparing types of correct trials. The ERP analysis alongside linear regression highlighted trends when examining ERP parameters such as maximum ERP amplitude, minimum ERP amplitude, and the amplitude range. A positive correlation was seen as the level of surprise increased for both the maximum ERP amplitude and the ERP range and a negative correlation was seen as the level of surprise increased for the minimum ERP amplitude. A stronger correlation was seen in the dACC compared to the GPi. In addition to looking at the entire trial length of each trial in the IED task, three components of the trials were further examined independently including the decision-making phase, the learning phase, and the peri feedback phase of the trial. This allowed for more focused examination of these nuclei within three different cognitive domains. The Fourier transform and autoregression analyses were used to examine the spectral amplitude and post spectral density respectively of various cognitively significant frequency bands (theta, alpha, beta, gamma, and high gamma). Within the GPi significant differences were found in the gamma/high gamma frequencies during the peri feedback and learning phase of trials when comparing expected correct and unexpected incorrect trials. Within the dACC significant differences were found in the gamma/high gamma frequencies only during the peri feedback phase of the trial. Although greater gamma/high gamma amplitudes were found for the unexpected incorrect condition within the GPi, within the dACC, greater gamma/high gamma amplitudes were found for the expected correct condition. This reversal could indicate that the gamma/high gamma frequency may be one mechanism differentially guiding the learning and memory of correct and incorrect trials within the GPi and dACC. Overall, the results from this project provide evidence in supporting the hypothesis that the dACC and the GPi do serve cognitive functions and are not merely motor nuclei within the brain.
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