In behavioural terms, it appeared that the anosognosia scores were significantly 'disrupted' in Alzheimer's patients in comparison with healthy patients. The same can be said of the third-party perspectives, this ability to evaluate one's own behaviour from the point of view of another person - e.g.: 'My wife thinks I am an angry person.'. Increasingly, it appeared that the alteration of perspective of the third person enabled much of the anosognosia relating to the personality of patients to be explained.

Based on this information, Jedidi then established a correlation between anosognosia in Alzheimer's patients and their cerebral metabolism acquired by TEP. It revealed hypometabolism at the dorsomedial prefrontal cortex. 'Our study suggests that this probably plays a role in the mechanisms governing a sense of perspective', the neurologist states.

My wife's spitting image

There is a rare syndrome, called Capgras, where patients think that one or more of their loved ones have been replaced by imposters. The most widespread explanatory model of this syndrome suggests that this is the consequence of an inability to access emotional information relating to a face. Thus, when the person finds themselves looking at a loved one, the patient recognises their face perfectly, but cannot access the emotional information which should be connected with identifying a loved one. This explains the appearance of delirium because the patients, seeing the face of a loved one but feeling nothing for them, come to the singular conclusion that the person before them is not their loved one but a look-alike, often seen to be an evil imposter.

In a third study, Jedidin looked at a case of an Alzheimer's patient presenting Capgras syndrome. His hypothesis was that the medial prefrontal regions play a role in the origins of this problem. A structural image (MRI) and a functional image at rest obtained by TEP were taken in the Alzheimer's patient and compared to those recorded in 24 healthy control subjects and 26 patients suffering from the early stages of Alzheimer's.

'We were able to highlight the hypometablism of a particular region of the dorsomedial prefrontal cortext' says the researcher. 'On the basis of current knowledge relating to facial recognition, our results appear to provide new arguments in favour of the hypothesis according to which the dorsomedial prefrontal cortex plays a role in retrieving information relating to a familiar face and plays a central role in integration information relating to a face and the representation of the other person and his or her intentions.'

Combining the hypotheses of several authors, this study suggests that the dorsomedial prefrontal cortext is a significant crossroads for a complex combination of cognitive processes involved in the representation of the other, his or her intentions and mental condition. 'This region will be an integral part of what is known as the social brain', concludes Jedidi.