["I'm not crazy!" Studies of agnosia in Alzheimer's disease]

Anosognosia corresponds to a lack of awareness about the own clinical disease of a patient. Anosognosia is frequent in Alzheimer's disease (AD). Researchers explore several hypotheses, psychological (deny) or cognitive (an association of memory and executive impairment), and recently models describing the dynamics of self representation provided convincing interpretations. Self models are modular. They comprise a central executive organising information processing according to subject's objectives. The central executive takes into account personal beliefs and social schemata and it uses autobiographical memory. The analysis of information by the self system leads to decision taking that relies on two principles, self continuity and adaptation. Neuroimaging studies showed that self reflection activates specific brain regions, comprising the ventromedial prefrontal cortex, the medial parietal and posterior cingulate cortex and the inferior parietal lobule. Other studies demonstrated that the same regions are particularly affected by AD. Experimental data currently allows making relationships between regional brain involvement, diverse difficulties in self representation and different forms of anosognosia for clinical status in AD patients.