The role of the cerebral coherence in the evolution of the patient with Alzheimer's disease

INTRODUCTION: Coherence is a quantitative measurement used to express the degree of functional connection between two or more cerebral regions. MATERIAL AND METHODS: We studied 27 patients with Alzheimer's disease (EA), diagnosed according to the criteria of the NINCDS-ADRDA group. Inter and intrahemispheric cerebral coherence was analyzed to evaluate its usefulness for differentiation between different patient sub-groups, according to the GDS and MMSE scales, age and length of illness. The sample was divided into various subgroups. RESULTS AND CONCLUSIONS: We found low values of coherence between the frontal regions as compared with mediotemporal and mediocentral regions of both hemispheres, being most marked on the left side. Equally, there were inter-hemisphere differences, although these were less significant than the intra-hemisphere differences. The intra-regional coherencies showed high values in all the groups studied. This may be explained by the relative conservation of short cortico-cortical association fibres which have been found in neuropathological studies in patients with EA. The factors of frequency, region and hemisphere show a marked effect in relation to coherence values, showing higher significance values for the slower theta and delta bands of the frontal regions compared with the temporal and central regions of the left hemisphere. An analysis of tendencies shows that there are low levels of correlation between the subgroups formed by the GDS and MMSE scales for the different frequencies analyzed and the regions studied, with those patients of the most deteriorated subgroups showing a lower grade of correlation.