Two lines of inquiry were followed to determine how the cerebral cortex and its efferent regions control eye movements and visuospatial attention. In one, focal transcranial magnetic stimulation of the human frontal eye field activity can have on the generation of saccadic eye movements. Depending on the relationship of the exogenous stimulation to the ongoing processes of saccade initiation, such stimulation can facilitate or interfere with saccade generation. In the other, single neuron recording was used to probe the mechanisms whereby the parietal cortex of the monkey achieves spatial accuracy. Neuronal behavior in a double-step task is entirely predicted by presaccadic and predictive-shift activity in a single-step task. The activity of parietal neurons is most consistent with their specifying a shift of visual attention of particular amplitude and direction.
