Brain Metabolic Dysfunction in Capgras Delusion During Alzheimer's Disease: A Positron Emission Tomography Study.

Capgras delusion is characterized by the misidentification of people and by the delusional belief that the misidentified persons have been replaced by impostors, generally perceived as persecutors. Since little is known regarding the neural correlates of Capgras syndrome, the cerebral metabolic pattern of a patient with probable Alzheimer's disease (AD) and Capgras syndrome was compared with those of 24-healthy elderly participants and 26 patients with AD without delusional syndrome. Comparing the healthy group with the AD group, the patient with AD had significant hypometabolism in frontal and posterior midline structures. In the light of current neural models of face perception, our patients with Capgras syndrome may be related to impaired recognition of a familiar face, subserved by the posterior cingulate/precuneus cortex, and impaired reflection about personally relevant knowledge related to a face, subserved by the dorsomedial prefrontal cortex.

[Brain imaging of reflection on self]. / Imagerie cérébrale de la réflexion sur soi.

Precise brain regions are activated when a subject gives a judgment on himself. Those are the medial parietal cortex, essentially related to episodic memory processing, and the ventromedial prefrontal cortex, recruited for evaluating the personal valence of an information. These regions are not activated in Alzheimer's disease. The decrease of awareness for own deficits in a patient with Alzheimer's disease would depend on a reduction of episodic memory capacities and a worsening of judgment for self significance.

A comparison of unawareness in frontotemporal dementia and Alzheimer's disease.

BACKGROUND: Loss of insight is a core diagnostic feature of frontotemporal dementia (FTD) and anosognosia is frequently reported in Alzheimer's disease (AD). AIM: To compare unawareness (anosognosia) for different symptoms, measured with a discrepancy score between patient's and caregiver's assessment, in AD and FTD. METHOD: In a prospective, multi-centre study, 123 patients with probable AD, selected according to the NINCDS-ADRDA procedure, were matched for age, sex, education, disease duration and dementia severity to patients with FTD (n = 41), selected according to international consensus criteria. A research complaint questionnaire was used to obtained patient's and caregiver's assessment concerning neuropsychological and behavioural symptoms. Data were compared in each group and between groups. Unawareness (measured by discrepancy scores) was compared between patients with AD and FTD. RESULTS: The caregivers generally assessed symptoms more severely than did patients, but both patient groups reported changes in affect (depressive mood or irritability) as their caregivers did. Unawareness was greater in patients with FTD than in patients with AD for language and executive difficulties, and for changes in behaviour and daily activities. CONCLUSION: The main finding is that unawareness was observed in both patients with FTD and patients with AD for most clinical domains. However, qualitative and quantitative differences showed that lack of awareness was greater in patients with FTD.