ATTENTION AND OCULOMOTOR CONTROL - A HIGH-DENSITY ERP STUDY OF THE GAP EFFECT

In a gap paradigm, healthy adult subjects performed visually triggered saccades to peripheral targets either with the fixation stimulus rema ining on (overlap trials) or going off before target onset (gap trials ). All subjects showed faster reaction times in the gap trials (the ga p effect). High density scalp event-related potentials were recorded t ime-locked to both the target stimuli and the eve movement onset. We o bserved three neural correlates of the gap effect: (i) a prefrontal po sitivity that precedes the target presentation which may reflect speci fic preparatory processes, (ii) an enhancement of the early cortical v isual responses (P1) to the peripheral target in the gap trials, and ( iii) a prolongation of parietal activity in the overlap trials relativ e to the gap trials prior to the saccade execution. These results sugg est that several factors contribute to the gap effect, each having its own neural basis. (C) 1997 Elsevier Science Ltd.