Alzheimer's deterioration in intellectual and neurobiological staging supports the retrogenesis model: a double dissociation between verbal/non-verbal judgments and the left/right parieto-temporal glucose metabolism. A retrospective data analysis from the Tajiri Project.

Abstract

Alzheimer disease (AD) patients demonstrate various clinical features reminiscent of children (the retrogenesis model). The Binet test is available for assessing mental development and deterioration. However, neuroimaging correlations remain to be clarified. Although AD patients also manifest social judgment disability, there are few cognitive tests, contrary to so many memory tests. Among the database, we noticed that the Binet test includes the subscale of social judgement using illogical sentences and pictures. The aim of this study is to clarify the neuroimaging correlations for the Binet test, especially for the illogical questions. Forty participants were selected from the database of the Tajiri Project. The Tanaka-Binet test was used to evaluate the mental age and the basic age. The latter is the age level at which the patient can completely accomplish all questions at the immediately lower age level and is used for calculating the mental age. Using the subtests of illogical sentences/pictures, logical judgment abilities were assessed. Using magnetic resonance imaging, we performed four-grade visual evaluation for cortical atrophy. The cerebral metabolic rate for glucose (CMRglc) was measured using an autoradiographic method of 18 F-fluoreodeoxyglucose - positron emission tomography (FDG-PET). There was a significant Spearman's correlation between the clinical stage and the basic age. Degree of frontal, temporal and hippocampal atrophy were correlated with the basic age. The entire grey matter and frontal and temporal CMRglc were associated with the basic age. The illogical sentences scores were correlated with the bilateral temporal, hippocampal and the left parieto-temporal CMRglc, whereas the illogical picture scores were correlated with the right parieto-temporal CMRglc. We found that frontal and temporal atrophy as well as hypometabolism were associated with the basic age. Regarding the illogical judgment, the current PET data analysis disclosed that there may be a double dissociation between verbal/non-verbal judgments and the left/right parieto-temporal areas.