Cognitive determinants of the postimperative negative variation.

This study examined cognitive determinants of the postimperative negative variation (PINV), a slow brain potential observable after the onset of an imperative stimulus in a forewarned reaction time task. Controllability of the aversive imperative stimulus by a motor reaction and predictability of the contingency were varied in a factorial design. The exogenous portion of the slow negative wave was assessed in a passive listening condition using tones of the same quality as the imperative stimuli, but presented without forewarning. Results show that PINV not only occurs when control is absent but also during unpredictably gained control. Similarly, unpredictable lack of control yields a more negative potential than continual helplessness. Negativity elicited by the aversive tone alone was not significantly different from PINV during predictable lack of control. The order of conditions, which was manipulated between groups, did not affect amplitudes. It was concluded that contingency change is a crucial cognitive determinant of the PINV, whereas the effect of lack of control is difficult to differentiate from the sensory influence of the acoustic stimulation.