AUTONOMIC SPACE AND PSYCHOPHYSIOLOGICAL RESPONSE

Contemporary findings reveal that autonomic control of dually innervat ed target organs cannot adequately be viewed as a continuum extending from parasympathetic to sympathetic dominance. Rather, a two-dimension al autonomic space, bounded by sympathetic and parasympathetic axes, i s the minimal representation necessary to characterize the multiple mo des of autonomic control. We have previously considered the theoretica l implications of this view and have developed quantitative conceptual models of the formal properties of autonomic space and its translatio n into target organ effects. In the present paper, we further develop this perspective by an empirical instantiation of the quantitative aut onomic space model for the control of cardiac chronotropy in the rat. We show that this model (a) provides a more comprehensive characteriza tion of cardiac response than simple measures of end-organ state, (b) permits a parsing of the multiple transformations underlying psychophy siological responses, (c) illuminates and subsumes psychophysiological principles, such as the Law of Initial Values, (d) reveals an interpr etive advantage of expressing cardiac chronotropy in heart period rath er than heart rate, and (e) has fundamental implications for the direc tion and interpretation of a broad range of psychophysiological studie s.