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Joseph F.X DeSouza, Stefan Everling; Neural correlates for preparatory set associated with pro-saccades and anti-saccades in humans investigated with event-related fMRI. Journal of Vision 2002;2(7):578. doi: https://doi.org/10.1167/2.7.578.
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© ARVO (1962-2015); The Authors (2016-present)
We sought to discover exactly when does the fMRI signal differ as subjects are planning to execute a pro-saccade or an anti-saccade. Thus as subjects waited prolonged instruction periods (6, 10 or 14-seconds) prior to the onset of a peripheral visual cue to execute either the pro- or anti-saccade, we examined the fMRI signal in various areas along the saccade network. The cortical regions examined were visual cortex (V1/V2), intraparietal sulcus (IPS), frontal eye fields (FEF), supplementary eye fields (SEF), and dorsolateral prefrontal cortex (DLPFC). The instruction to plan either a pro- or anti-saccade was conveyed by changing the color of the fixation cross from white to green (pro) or red (anti). A simultaneous peripheral cue and offset of the central fixation cross cued the subject to execute the appropriate eye movement. The cortical areas were functionally mapped using the general linear model comparing pro- and anti-saccade blocks to fixation blocks (p(corrected) < 0.001). We used these maps to define the brain areas and then examined the single trial event-related signal from each subject's scans. When the single eye movements were aligned to the onset of the instruction cue, the signal for visual areas showed no differences during the instruction period across subjects. More importantly, bilateral FEF, SEF and right hemisphere DLPFC & IPS showed an increased signal during the instruction period planning an anti-saccade as compared to a pro-saccade (p <0.05). When data was aligned to the movement cue and the instruction period activity was removed, there were only signal differences between anti- and pro-saccades in bilateral SEF and left hemisphere FEF & V1/V2. This suggests that the larger signal for the preparatory set we have shown during anti-saccades preparation may have contributed to a larger baseline signals and thus greater activation patterns during the anti-saccade block designs that were found in many previous imaging studies. Supported by Canadian Institutes of Health Research & National Alliance for Research on Schizophrenia and Depression.
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