Cognitive control of simple and complex saccade tasks in varying contexts assessed with functional MRI
Pierce, Jordan Elisabeth
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The context of a cognitive task influences an individual’s ability to perform the task efficiently, with cognitive control adapting behavior to satisfy current goals. Saccade tasks provide an excellent model of cognitive control with simple prosaccades (rapid eye movements towards a stimulus) and complex antisaccades (movements to the mirror image location) representing lower and higher levels of cognitive control, respectively. In the first of three studies, saccades were presented in two mixed functional MRI tasks with either alternating blocks or randomly interleaved prosaccade and antisaccade trials. The second and third studies manipulated the cognitive demands of saccade tasks by presenting interleaved runs with a varying probability of antisaccade versus prosaccade trials (0, 25, 50, 75, or 100%) at baseline and post-test MRI sessions. Between the scans, participants practiced either the specific probability blocks used during testing or only a general 100% antisaccade block. The results from the first study suggested that the more cognitively demanding interleaved context fostered transient responses in cognitive control circuitry for high conflict trials compared to sustained activation over single-trial-type blocks. Results from the second and third studies showed slower responses and fewer antisaccade errors in runs with a high antisaccade probability. In the mixed probability runs, improbable performance of one trial type led to an augmented BOLD signal. Following practice, there was an overall reduction in BOLD signal within cognitive control and saccade circuitry, with the specific practice group showing additional regions with a strong signal decrease. These findings imply that with extended saccade practice the appropriate task set was selected in a more automatic manner with less top-down control, especially with exposure to mixed task contexts. Overall, cognitive control of behavior and brain activation supporting simple and complex saccade trial types is sensitive to the context in which the task is performed and more effort must be exerted to support a weak or unfamiliar task set.