Affective facial and lexical expression in aprosodic versus aphasic stroke patients

Past research has shown that lesions in the left cerebral hemisphere often result in aphasia, while lesions in the right hemisphere frequently impair the production of emotional prosody and facial expression. At least 3 processing deficits might account for these affective symptoms: (1) failure to understand the conditions that evoke emotional response; (2) inability to experience emotions; (3) disruption in the capacity to encode non-verbal signals. To better understand these disorders and their underlying mechanisms, we investigated spontaneous affective communication in right hemisphere damaged (RHD) stroke patients with aprosody and left hemisphere damaged (LHD) stroke patients with aphasia. Nine aprosodic RHD patients and 14 aphasic LHD patients participated in a videotaped interview within a larger treatment protocol. Two naïve raters viewed segments of videotape and rated facial expressivity. Verbal affect production was tabulated using specialized software. Results indicated that RHD patients smiled and laughed significantly less than LHD patients. In contrast, RHD patients produced a greater percentage of emotion words relative to total words than did LHD patients. These findings suggest that impairments in emotional prosodic production and facial expressivity associated with RHD are not induced by affective-conceptual deficits or an inability to experience emotions. Rather, they likely represent channel-specific nonverbal encoding abnormalities.