Activation patterns to aversive stimulation in man: passive exposure versus effort to control.

The present study contrasted physiological response patterns occurring when subjects coped passively and actively with aversive stimuli. In one condition, 29 healthy young men were exposed to unpredictable noise (115BA) and shock (3.5 mA) with no means of control, and in the other they attempted to avoid the noise and shock with rapid keypresses. Both tasks were characterized by maximal uncertainty as to locus of presentation, chance of occurrence, and type of stimulus to occur next in sequence. Dependent variables included: reports of moods, reaction times, muscle tension, plasma concentrations of free fatty acids, cortisol and catecholamines, heart rate, blood pressures, systolic time intervals, cardiac output, systemic vascular resistance, and an index of myocardial contractility. Both experimental conditions produced significant neuroendocrine, lipid, and cardiovascular changes from baseline. The active avoidance procedure produced further increases in cardiac function which were related to control efforts as indexed by muscle tension and task performance. The results point toward the effects of effort in the face of uncertainty in determining the patterns of response to aversive stimulation.