CHANGES OF PRESACCADIC CORTICAL ACTIVITY WHEN PERFORMING HORIZONTAL, VISUALLY GUIDED SACCADES

When a visually guided saccade task is running, the presaccadic potent ial obtained in the initial period of the task differs from those obta ined later, while the subject's oculomotor performance remains unaffec ted. These time-related changes of cortical activity consist both of a n overall decreasing electrical activity as well as a selective one ov er certain cortical areas. The generalised reduced activity already de scribed in earlier studies is considered as an unspecified effect such as fatigue or decreased motivation. On the contrary, the pronounced s elective changes of cortical activity obtained over cortical areas suc h as the centro-parietal and frontal cortices, should be related with more specific, that is, visuomotor function. We assume that at the beg inning of the task the performance of the saccade needs the activation of several cortical areas but later on the same oculomotor plan runs sufficiently under subcortical control. (C) 1997 Elsevier Science Irel and Ltd.