EFFECTS OF STIMULUS ALTERNATION, REPETITION AND RESPONSE REQUIREMENTSON EVENT-RELATED POTENTIALS TO PATTERNED VISUAL-STIMULI

Event-related potentials (ERPs) were recorded to square-pattern stimul i presented either to the upper or the lower half of the visual field. in the Same task the subjects had to respond to the fifth stimulus of a microsequence of stimuli that appeared on the same half field, wher eas in the Different task the target stimulus was the alternation of s timulus location after a microsequence of four stimuli to the same hal f field. The pattern-specific CII component (a negative wave to lower half-field stimulation with 100 ms latency) appeared to be insensitive to task variables. N1 increased to the uncertain alternations of stim ulus location. An N2 component with temporal maximum emerged to Nogo s timuli (to the fifth stimulus in the same location in the Different ta sk and the alternation after four identical stimuli in the Same task). An anterior N2 was characteristic to the Nogo stimuli of the Differen t task. P3 latency was longer, and it had more anterior distribution t o the Nogo stimuli.