On the role of frontal eye field in guiding attention and saccades.

The neural bases of shifting attention and directing gaze were investigated in macaque monkeys performing a singleton search that required a prosaccade, antisaccade, or no saccade cued by the shape of the singleton. In prosaccade trials, most neurons in frontal eye field selected the location of the singleton that was also the end point of the saccade. In antisaccade trials, most neurons selected the singleton followed by selection of the endpoint of the saccade. Other neurons selected only the endpoint of the saccade in antisaccade trials. When no saccade was produced, many of the first type of neuron still selected the singleton, and many but not all of both types of neurons later selected the stimulus opposite the singleton even though no saccade was produced. These patterns of activity are consistent with the hypotheses that covert shifts of attention can occur without saccade production and that FEF contributes to covert as well as overt orienting.