[Saccadic eye movement related scalp potentials--scalp distribution of presaccadic slow negative potential]

We studied scalp distribution of presaccadic slow negative potential (PSN) among saccadic eye movement related scalp potentials in 17 normal subjects performing self-paced voluntary saccades in light (VS). There was a widespread PSN beginning at 1400 msec prior to saccades, maximum at the vertex. Amplitudes of PSN were greater over frontocentral electrodes contralateral to the direction of the saccades. These findings are consistent with reflection of activation of the supplementary motor area, and the frontal eye field contralateral to the direction of the saccades. On the other hand, amplitudes of PSN were relatively greater over occipital electrodes ipsilateral to the direction of the saccades. In addition, we studied PSN in 6 normal subjects performing self-paced voluntary saccades in darkness (VSD). PSN with VSD did not extend to occipital electrodes in comparison with PSN with VS. Occipital component of PSN with VS may reflect activation of other cerebral cortices which relate to visual inputs.