Look and see: how the brain moves your eyes about.

Two major cortical streams are involved in the generation of visually guided saccadic eye movements: the anterior and the posterior. The anterior stream from the frontal and medial eye fields has direct access to brainstem oculomotor centers. The posterior stream from the occipital cortices reaches brainstem oculomotor centers through the superior colliculus. The parietal cortex interconnects with both streams. Our findings suggest that the posterior stream plays an unique role in the execution of rapid, short-latency eye movements called 'express saccades'. Both the anterior and posterior streams play a role in the selection of targets to which saccades are to be generated, but do so in different ways. Areas V1, V2 and LIP contribute to decisions involved in where to look as well as where not to look. In addition, area LIP is involved in decisions about how long to maintain fixation prior to the execution of a saccade. Area V4 does not appear to be directly involved in eye-movement generation. In the anterior stream, the frontal eye fields, and to a lesser extent the medial eye fields, are involved in the correct execution of saccades subsequent to decisions made about where to look and where not to look.