Hemispheric Asymmetry and the Diversity of Emotional Experience in Anosognosia

Abstract

A long-standing question in neuropsychology has been whether basic emotions are lateralized in one hemisphere in the brain. A more recent, controversial, conceptualization has been that both hemispheres process emotion, but the left is specialized for positive emotions and the right for negative emotions. This claim has been partially bolstered by the claim that denial of deficit (anosognosia) results from a loss of negative emotions after right-sided lesions. A range of objections have been raised to this account. These include the analytically inspired suggestion that anosognosia might result from an emotion-regulation deficit, associated with changes in body image, producing ill-maintained defenses against aspects of reality that are difficult to tolerate. The present study involved presenting emotion-related stimuli to each hemispace of anosognosic patients and measuring emotional experience. Across three different assessment methods, the anosognosic patients were able to experience the full range of emotions, independent of location. In addition, the magnitude of the anosognosia was not obviously related to lesion size and location and may reflect differences in premorbid personality. These findings run counter to the claim of a hemispheric asymmetry in positive vs. negative emotion and are consistent with the psychoanalytically inspired claim that the right hemisphere plays a substantial role in emotion regulation, rather than in the experience of a single class of emotion.