Relationships between cognitive performance and cerebral metabolism in Alzheimer's disease

The presence of correlations between cerebral metabolism and performance on cognitive tasks (digit span, verbal fluency, Hayling inhibition task and the Mattis dementia rating scale) was assessed in AD patients and elderly controls. Results showed that in both groups the cerebral areas where metabolism was correlated to performance were similar to those found in functional activation studies with young healthy subjects. The comparison of cognitivo-metabolic correlations in AD patients and control subjects showed that the single significant difference was a correlation between posterior cingulate metabolism and performance on the Mattis dementia rating scale in AD patients only. These results are consistent with two neurobiological causes of cognitive impairment in AD : a less efficient functioning of some areas involved in specific cognitive tasks and a deficit of integration of information coming from different areas.