Neural substrates of implicit and explicit emotional processes: a unifying framework for psychosomatic medicine

There are two broad themes in psychosomatic medicine research that relate emotions to physical disease outcomes. Theme 1 holds that self-reported negative affect has deleterious effects and self-reported positive affect has salubrious effects on health. Theme 2 holds that interference with the experience or expression of negative affect has adverse health consequences. From the perspective of self-report these two traditions appear contradictory. A key thesis of this paper is that the foundational distinction in cognitive neuroscience between explicit (conscious) and implicit (unconscious) processes, corresponding to Themes 1 and 2, respectively, provides a unifying framework that makes empirical research on unconscious emotional processes more tractable. A psychological model called "levels of emotional awareness" is presented first that places implicit and explicit emotional processes on a cognitive-developmental continuum. This model holds that the ability to become consciously aware of one's own feelings is a cognitive skill that goes through a developmental process similar to that which Piaget described for other cognitive functions. Empirical findings using the Levels of Emotional Awareness Scale are presented. A parallel hierarchical model of the neural substrates of emotional awareness is presented next supported by recent neuroimaging and lesion work. The evidence presented in this review suggests that the neural substrates of implicit and explicit emotional processes are distinct, that the latter have a modulatory effect on the former, and that at the neural level Theme 1 and Theme 2 phenomena share critical similarities. The implications of this psychobiological model for research in psychosomatic medicine are discussed.