Neural activation differences in a model of cognitive control
Valtcheva, Manouela Vesselinova
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Cognitive control is responsible for planning, cognitive flexibility, working memory, and inhibition. The antisaccade task is a good measure of inhibition as it requires the subject to inhibit looking at a peripheral target, and to generate a saccade (a quick eye movement) to the mirror image location of the stimulus. People with schizophrenia perform normally on simple refixation tasks (prosaccades) but make more antisaccade errors than control subjects. Imaging studies indicate reduced prefrontal cortex (PFC) and related circuitry activation during antisaccades in schizophrenia. Such dysfunction may be associated with poor performance on tasks requiring inhibition and working memory, generally, not just among people with schizophrenia. This study investigated differences in neural activation patterns between good and poor performers of the antisaccade task. Subjects were placed in a 1.5 T MR scanner while performing three tasks: antisaccade-fixation, prosaccade-fixation, and antisaccade-prosaccade. Functional MRI data were obtained for 30 subjects (69% female, M=19.6 (SD=2.1) years, 100% right handed), representing the top and bottom third of an antisaccade proportion correct distribution (N=114). Data were assessed using whole brain and region of interest (ROI) analyses. Good performers demonstrated robust anti- and prosaccade-related activation during antisaccade-fixation and prosaccade-fixation, respectively, while poor performers displayed reduced activation during both. ROI analyses demonstrated significant differences between the two groups during antisaccades but not during prosaccades. Neither group demonstrated significant percent signal change during the antisaccade-prosaccade task. Reduced activation in poor performers may be associated with more antisaccade errors and may be due to a reduced signal to noise ratio.