Functional neural correlates of adult reading test performance

Abstract

Background: Adult reading tests (ART) have been widely used in both research and clinical settings as a measure of premorbid cognitive abilities or cognitive reserve. However, the neural substrates underlying ART performance are largely unknown. Furthermore, it has not yet been examined whether the neural substrates of ART performance reflect the cortical regions associated with premorbid intelligence or cognitive reserve. The aim of the study is to identify functional neural correlates of ART performance using 18F-fluorodeoxyglucose (FDG) positron-emission tomography (PET) imaging in healthy adults.

Methods: The current study included 271 cognitively normal middle and old-aged adults. All participants underwent comprehensive clinical and neuropsychological assessments, FDG-PET scans, and 11C-labelled Pittsburgh Compound B (PiB)-PET scans. ART performance was assessed using the Korean Adult Reading Test (KART). Voxel-wise analyses of FDG-PET images were used to investigate the

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correlations between regional cerebral glucose metabolism and KART performance. The same analyses were performed for a subgroup of individuals without pathological beta-amyloid (Aβ) deposition on PIB-PET (Aβ negative) in order to reexamine the relationship while the influence of Alzheimers disease (AD) process on ART performance was removed as much as possible.

Results: The study sample consisted of 271 participants of which 51.7% were female and 87.7% were Aβ negative. Participants had a mean age of 69.0 years (SD = 8.1) and average years of education of 11.8 (SD = 4.8). Voxel-wise analyses revealed positive correlations between glucose metabolism and KART performance in the frontal and primary somatosensory regions, more specifically the lateral frontal cortex, anterior cingulate cortex and postcentral gyrus independent of the effects of age and gender. When conducted again only for Aβ negative individuals, the voxel-wise analysis showed significant correlations in broader areas of the frontal and primary somatosensory regions.

Conclusions: This is the first neuroimaging study directly demonstrating the neural substrates associated with ART performance. The positive correlation found between glucose metabolism and KART in the frontal and primary somatosensory regions serves as important evidence at the neural level that ART predicts premorbid general intelligence and cognitive reserve, as these regions are previously reported to be associated with general intelligence and cognitive reserve.