Abstract
The cortical sources of event-related-potentials (ERP) using realistic source models were examined in a prosaccade and antisaccade procedure. College-age participants were presented with a preparatory interval and a target that indicated the direction of the eye movement that was to be made. In some blocks a cue was given in the peripheral location where the target was to be presented and in other blocks no cue was given. In Experiment 1 the prosaccade and antisaccade trials were presented randomly within a block; in Experiment 2 procedures were compared in which either prosaccade and antisaccade trials were mixed in the same block, or trials were presented in separate blocks with only one type of eye movement. There was a central negative slow wave occurring prior to the target, a slow positive wave over the parietal scalp prior to the saccade, and a parietal spike potential immediately prior to saccade onset. Cortical source analysis of these ERP components showed a common set of sources in the ventral anterior cingulate and orbital frontal gyrus for the presaccadic positive slow wave and the spike potential. In Experiment 2 the same cued- and non-cued blocks were used, but prosaccade and antisaccade trials were presented in separate blocks. This resulted in a smaller difference in reaction time between prosaccade and antisaccade trials. Unlike the first experiment, the central negative slow wave was larger on antisaccade than on prosaccade trials, and this effect on the ERP component had its cortical source primarily in the parietal and mid-central cortical areas contralateral to the direction of the eye movement. These results suggest that blocked prosaccade and antisaccade trials results in preparatory or set effects that decreases reaction time, eliminates some cueing effects, and is based on contralateral parietal-central brain areas.
Highlights
The prosaccade and antisaccade procedure has been useful in the study of the brain control of eye movements
Several studies with non-human animals have shown that areas of the frontal cortex, such as the frontal eye fields (FEF), supplementary eye fields (SEF), dorsolateral prefrontal cortex (DPC), and prefrontal cortex are involved in the generation of eye movements and differ for prosaccade and antisaccade eye movements
Several studies using event-related fMRI showed that activity in the areas of the brain that differentiate antisaccade from prosaccade eye movements (e.g., FEF) have substantial preparatory BOLD activity (Cornelissen et al, 2002; Curtis and D’Esposito, 2003; Desouza et al, 2003; Ford et al, 2005; Ettinger et al, 2008)
Summary
The prosaccade and antisaccade procedure has been useful in the study of the brain control of eye movements. An eye movement is made either to the target (“prosaccade”) or away from the target to the opposite location (“antisaccade”) This procedure has been used in a wide variety of studies to examine visual attention and eye movement control (Everling and Fischer, 1998; Munoz and Everling, 2004) and may be useful for examining neuropsychological status (i.e., schizophrenia, McDowell and Clementz, 2001; ADHD, Klein et al, 2003). Neuroimaging studies using PET, block-design fMRI, and event-related fMRI have examined these eye movements in human participants and have found activity in several of these brain areas (see review by McDowell et al, 2008). The cortical sources of the ERP activity were studied with realistic source models based on individual MRIs, and the effect of mixed-choice trials and blocked trials on ERP components was studied
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