The Mirror Sign: A Reflection of Cognitive Decline?

The Neurological Asymmetry of Self-Face Recognition

While the desire to uncover the neural correlates of consciousness has taken numerous directions, self-face recognition has been a constant in attempts to isolate aspects of self-awareness. The neuroimaging revolution of the 1990s brought about systematic attempts to isolate the underlying neural basis of self-face recognition. These studies, including some of the first fMRI (functional magnetic resonance imaging) examinations, revealed a right-hemisphere bias for self-face recognition in a diverse set of regions including the insula, the dorsal frontal lobe, the temporal parietal junction, and the medial temporal cortex. In this systematic review, we provide confirmation of these data (which are correlational) which were provided by TMS (transcranial magnetic stimulation) and patients in which direct inhibition or ablation of right-hemisphere regions leads to a disruption or absence of self-face recognition. These data are consistent with a number of theories including a right-hemisphere dominance for self-awareness and/or a right-hemisphere specialization for identifying significant social relationships, including to oneself.

Delusional Misidentification of the Mirror Image

PURPOSE OF REVIEW

Delusional misidentification syndromes (DMS) include conditions in which a false belief about the identity of a person, place, or object occurs in the context of psychiatric or neurological disorders. One form of DMS involves the delusion that the patient's mirror image is a separate individual. This review of reported cases characterizes the psychiatric, neuropathological, and neuropsychological aspects of DMS for the mirror image. An individual case presentation highlights the patient's subjective experience. Finally, the impact of this syndrome on the sense of self is considered.

RECENT FINDINGS

Mirror DMS is a persistent delusion that occurs in the context of neurological illness. It is associated with right hemisphere impairment and a variety of neuropsychological and neuroimaging abnormalities. This phenomenon contributes to our understanding of a range of neurobehavioral syndromes that can be classified as neuropathologies of the self (NPS). DMS for the mirror image is a neurobehavioral syndrome in which the inability to recognize oneself in the mirror entails neurological, neuropsychological, as well as psychiatric aspects of the sense of self.