On your mark, get set: Brainstem circuitry underlying saccadic initiation

Saccades are rapid eye movements that are used to move the visual axis towa rd targets of interest in the visual field. The time to initiate a saccade is dependent upon many factors. Here we review some of the recent advances in our understanding of the these processes in primates. Neurons in the sup erior colliculus and brainstem reticular formation are organised into a net work to control saccades. Some neurons are active during visual fixation, w hile others are active during the preparation and execution of saccades. Se veral factors can influence the excitability levels of these neurons prior to the appearance of a new saccadic target. These pre-target changes in exc itability are correlated to subsequent changes in behavioural performance. Our results show how neuronal signals in the superior colliculus and brains tem reticular formation can be shaped by contextual factors and demonstrate how situational experience can expedite motor behaviour via the advanced p reparation of motor programs.