Evidence of incomplete cortical modulation of autonomic responses in 11-to 16-year-old adolescents

This study examines response differentiation in the sympathetically innervated skin conductance response (SCR). Differentiation in such systems has been ascribed to cortical inhibitory control over subcortical autonomic centers. Developmental study of such differentiation thus provides information on cortical development and the maturation of cortical control over subcortical centers. Previous investigators have focused on the simple level of differentiation involved in discriminating response on one side the body from that on the other. In such studies several investigators reported more diffuse response among young children; some reported adultlike differentiation by approximately age 10. The present study examines a more complex instance of differentiation, the quantitative modulation of response from a given site in order to produce SCR amplitudes proportionate to the information value of the eliciting stimulus. Relatively large amplitude SCRs elicited by imperative PRESS-SIGNALS of varying information value were studied, together with smaller SCRs elicited by NONPRESS-SIGNALS also varying in information value, in two adolescent groups, aged 11-16 years, and in a young adult sample. In contrast to earlier work, the present study demonstrates a continuing difference between adolescents and adults. Adults showed consistent differentiation, with SCR amplitude reflecting changes in stimulus information values for both PRESS- and NONPRESS-SIGNALS. Adolescents displayed differentiation only for SCRs elicited by NONPRESS-SIGNALS: Response to PRESS-SIGNALS did not reflect stimulus information values, even though reaction time data demonstrated that PRESS-SIGNAL information was being registered cortically. The degree of cortical control present in these adolescents, enabling them to display differentiated SCRs to NONPRESS-SIGNALS, would likely be sufficient to allow simple left-right discrimination, perhaps accounting for the "adultlike" reactions previously reported for this age group. The inability of the adolescents to sustain SCR differentiation when large amplitude responses were elicited by the PRESS-SIGNALS might reflect the inability of still immature cortical controls to cope with sizable sympathetic output. A "critical level" of sympathetic "arousal" may exist for adolescents in this age range, above which cortical inhibitory controls may become ineffective.