When do neurons in visuomotor areas of the brain distinguish between saccades to a stimulus in their response field or to saccades made to stimuli outside this field? The upper figure shows the discharge of a visuomotor neuron in the superior colliculus (SC). The lower figure shows the activity of a neuron in the frontal eye field (FEF). Both cells prefer movements to the right. In each figure rasters of cell discharge constructed from individual search trials in which an array of four visual stimuli appear simultaneously. One is of an odd color. Data is aligned on array onset (light vertical line) for trials in which the animal saccades to the correct (odd) stimulus. Lower continuous traces show the average spike density records constructed from the rasters shown above. Times of saccade onset on individual trials shown by the light blue dots. In the lower plates the mean spike density traces are superimposed so the time of departure of the density function when the animal saccades to right departs from that when he saccades to the left (arrow). The dashed curve shows the mean plus the SEM for saccades out of the response field.

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