Self-recognition in Alzheimer's disease: a mirror and video study.

Twenty-nine subjects with Senile Dementia of the Alzheimer Type (SDAT) were tested for self-recognition when confronted with their reflection in a mirror and with a noncontingent video image. All subjects at stage 5 (moderately severe cognitive decline) on the Global Deterioration Scale (GDS) showed self-recognition in the mirror condition, whereas 25% of GDS stage 6 subjects (severe cognitive decline) did not self-recognize. Only seven subjects showed signs of self-recognition on video (six at GDS 5, one at GDS 6). The results confirm two hypotheses: the first, based on studies with infants, is that contingency cues in the mirror condition facilitate self-recognition; the second is that SDAT patients may show "regression" of at least some cognitive functions.