Self-conscious emotion deficits in frontotemporal lobar degeneration.
Frontotemporal lobar degeneration (FTLD) is a neurodegenerative disease associated with dramatic changes in emotion. The precise nature of these changes is not fully understood; however, we believe that the most salient losses relate to self-relevant processing. Thus, FTLD patients exhibit emotional changes that are consistent with a reduction in self-monitoring, self-awareness and the ability to place the self in a social context. In contrast, other more primitive aspects of the emotional system may remain relatively intact. The startle response is a useful way to examine the precise nature of emotional deficits in neurological patients. In addition to a stereotyped defensive response (characterized by negative emotional facial behaviour and physiological activation), in many individuals it also evokes embarrassment, a self-conscious emotional response. Embarrassment seems to occur as the person becomes aware that the reaction to the startle was excessive and was observed by others. Because the self-conscious response depends on certain regions in frontal cortex, we expected that FTLD patients would have specific deficits in their self-conscious response. To test this notion, we examined the response of 30 FTLD patients and 23 cognitively normal controls to a loud, unexpected acoustic startle stimulus (115-dB burst of white noise). Emotional behaviours were measured along with an assessment of somatic, electrodermal, cardiovascular and respiratory responses. Results indicated that FTLD patients and controls were similar in terms of physiological responses and negative emotional facial behaviour to the startle, indicating that the defensive aspect of the startle was preserved. However, there were profound differences in the self-conscious response. FTLD patients showed significantly fewer facial signs of embarrassment than controls. This deficit in self-conscious response could not be explained by sex, cognitive status, age, education, medication, or differences in the negative emotional behaviour or physiological response. Thus, the emotional deficit in FTLD patients' response to the startle suggests a reduction in self-consciousness. These findings suggest that the emotional deficit in FTLD may be most profound in higher-order processes akin to those involved in the generation of embarrassment. These deficits are consistent with neural loss in the medial prefrontal cortex, which may play an important role in the production of self-conscious emotions. Disrupted self-conscious emotions in FTLD patients may have clinical importance because these deficits may underlie some of the socially inappropriate behaviours that are common in these patients.