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B. K. Flatt, L. Lillakas, E. L. Irving; Context Effects in Saccade Performance. Invest. Ophthalmol. Vis. Sci. 2008;49(13):128.
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Inhibitory mechanisms are among the last saccadic parameters to develop and the first to deteriorate. In the antisaccade task, participants are required to inhibit the reflexive saccade toward a peripherally presented target and generate a voluntary saccade in the opposite direction. In the nogo task, the prosaccade must be inhibited and fixation held still. These tasks, combined with prosaccades, were used to study saccadic inhibitory mechanisms.
Eye movements of 21 participants (ages 19 to 35) were recorded in response to randomly presented dot targets requiring either a prosaccade, antisaccade, or nogo response. Stimuli were presented in blocks containing either a single stimulus type or a combination of two different stimulus types. In mixed blocks, the target color was the cue to the required response (pro, anti or nogo). Latency, gain, and error rates were calculated for each type of movement within each condition.
Mixed block tasks involving nogo trials showed the longest latencies. Nogo trials in mixed block tasks, specifically in combination with antisaccades, showed the highest error rates. A greater number of nogo errors in the antisaccade/nogo blocks were made away from the target rather than towards it. Nogo errors made away from the target showed a lower gain than correct movements made toward the target.
These results suggest that more than simple inhibition of the prosaccade is involved. Variation in error rates and latencies between experimental conditions show that the dynamics of the movements are influenced by the context in which they are being performed. A parallel signal mechanism is proposed. Working memory load and decision-making complexity are relevant factors in determining saccadic parameters, and must be taken into consideration when designing paradigms for detecting and monitoring disease using eye movements.
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