The thickness of posterior cortical areas is related to executive dysfunction in Alzheimer's disease

Abstract

Objective: To establish whether alterations of brain structures in Alzheimer's disease are associated with executive dysfunction.

Methods: Nineteen patients with Alzheimer's disease and 22 older control subjects underwent a comprehensive evaluation. The clock drawing test, digit span test, executive motor function test, Behavioral Assessment of the Dysexecutive Syndrome battery (Rule Shift Cards test), and Stroop test were used to evaluate executive dysfunction. A multiparametric approach using the FreeSurfer image analysis suite provided a description of volumetric and geometric features of the gray matter structures.

Results: The cortical thickness maps showed a negative correlation between the Behavioral Assessment of the Dysexecutive Syndrome battery (Rule Shift Cards test) and the right middle frontal gyrus; a positive correlation between the executive motor function test and the left superior parietal gyrus, left middle temporal gyrus, bilateral supramarginal gyri, right middle frontal gyrus, and right precuneus; a negative correlation between the Stroop test (part III) and the right superior parietal gyrus; and a negative correlation between the Stroop test (part III) and the right middle temporal gyrus.

Conclusion: Executive dysfunction in Alzheimer's disease is correlated with alterations not only in the frontal areas but also within many temporal and parietal regions.

Figure 1

Flow diagram of the subject selection procedure. For the control group, 66 elderly individuals were invited to participate in the study. Of these individuals, 21 missed the clinical assessment or were not included due to their meeting clinical exclusion criteria. Of the 45 remaining subjects, 17 were excluded because they missed the neuropsychological assessment. Of the 28 remaining subjects, four missed the magnetic resonance imaging (MRI) assessment. The images of three elderly controls were not included in the study because they were considered to be of low quality. Regarding the patient group, 46 AD patients were invited to participate in the study. Of these patients, 16 missed the clinical assessment or were not included due to their meeting clinical exclusion criteria. Of the 30 remaining subjects, seven were excluded because they missed the neuropsychological assessment. Of the 23 remaining subjects, two missed the MRI assessment. The images of two AD patients were not included in the study because they were considered to be of low quality.

Figure 2

Cortical thickness maps of associations between brain regions and executive functions. Red, orange, and yellow colors represent positive correlations, and blue represents negative correlations. 1A and 2A illustrate the negative correlation between the BADS score (Rule Shift Cards test, rule 2, errors) and the thickness of the right rostral middle frontal gyrus; 1B, 2B, 1C, and 2C illustrate the positive correlation between the executive motor function test and the left superior parietal gyrus, left middle temporal gyrus, bilateral supramarginal gyri, right caudal middle frontal gyrus, and right precuneus thickness; 1D illustrates the negative correlation between the results of the Stroop test part III (errors) and the right superior parietal gyrus; and 2D illustrates the negative correlation between the results of the Stroop test part III (time) and the right middle temporal gyrus. The scale indicates z-scores. Scatterplots of the correlations between the executive motor function test scores and the left middle temporal gyrus and bilateral supramarginal gyri cortical thickness are provided. Table 2 provides the parameters of the lesion extension and the location of the findings shown in this figure.