ILLUSIONS, ARITHMETIC, AND THE BIDIRECTIONAL MODULATION OF VAGAL CONTROL OF THE HEART

Behavioral contexts can evoke a variety of autonomic modes of response , characterized by reciprocal, coactive, or independent changes in the autonomic divisions. The present study investigated the modes of auto nomic response to visual illusion and mental arithmetic tasks, by the use of noninvasive measures of sympathetic (pre-ejection period; PEP) and parasympathetic (respiratory sinus arrhythmia; RSA) cardiac contro l. As previously demonstrated, mental arithmetic was associated with a reciprocal pattern of sympathetic activation and vagal withdrawal. Th e illusion task, however, yielded a distinct mode of vagal activation in the absence of sympathetic change. Responses within tasks were reli able. In contrast to the general intertask consistency reported for st ress tasks that yield similar autonomic modes of response, however, ne ither PEP nor RSA responses were correlated across the illusion and ar ithmetic tasks. This may be attributable to the dissimilar modes of au tonomic control evoked by these tasks. The distinct modes of autonomic response to arithmetic; and illusions emphasize the importance of a b ivariate model of autonomic control, and may offer important experimen tal tools for psychophysiological studies of autonomic control.