Psychophysiological correlates of emotion processing in Alzheimer's disease

Abstract

The main purpose of this study was to investigate whether emotion processing deficits previously reported in individuals with Alzheimer's disease (AD) represent a direct extension of their cognitive impairments or a specific emotion processing deficit, and whether affective information is available, but inaccessible to consciousness in AD. Another aim was to determine whether AD patients have the same emotional experiences to affective stimuli as do other healthy, but non-demented older individuals. An autonomic recognition paradigm was developed to compare overt (verbal report) and covert (electrodermal) facial affect recognition in 19 mildly to moderately demented AD patients and in 19 age- and education-matched cognitively-intact controls (NCs). Subjective reactions and physiological responses to emotionally-laden materials were also compared within and across groups. Contrary to expectation, the two groups did not significantly differ in their ability to correctly match an emotion name with an affective facial expression. As expected, both groups generated significantly more frequent event-related skin conductance responses (ER-SCRs) to congruent, as opposed to incongruent emotion name/facial expression stimulus pairs, and evidenced similar levels of electrodermal activity while viewing images which differed in emotional valence. There were no significant group differences in subjective reactions to emotional pictures; both AD patients and NCs rated positive, negative, and neutral slide images similarly across the dimensions of valence and arousal. AD patients did, however, have more difficulty discriminating facial identity and facial affect than did NCs. There was some indication that these relative impairments may have been related to the dual-task demands inherent in the tests employed. Performances on emotion processing tests used in this experiment did not significantly correlate with measures of orientation/mental status, dementia severity, or depression in either group. Taken together, the results of this study suggest that the difficulties AD patients have on emotion processing tasks are primarily related to specific cognitive demands of the tests employed and do not reflect a specific disruption in emotion processing systems.