PREPARING THE HEART, EYE, AND BRAIN - FOREPERIOD LENGTH EFFECTS IN A NONAGING PARADIGM

Psychophysiological ''preparatory'' responses may or may not depend on a focused expectation of when a stimulus will occur. Changes in heart rate, pupillary diameter, and brain potentials were examined during t rials in which foreperiod of a simple reaction time (RT) task was fixe d or unpredictable. Trials were also included in which stimuli for the speeded motor reaction were triggered by psychophysiological changes occurring spontaneously in the foreperiod. Thirty-two college-aged vol unteers equally divided by gender participated in the experiment. Redu cing expectancy, by using nonaging foreperiods, eliminated transient p restimulus psychophysiological responses but failed to eliminate slow changes over the foreperiod-slowing of heart rate, dilation of the pup il, and cortical surface negativity. Triggering the reaction stimulus by physiological changes did not influence RT. Correlations between ps ychophysiological changes in the foreperiod and between these changes and RT were generally low. The results were consistent with a multipro cess view of preparation.