Anterior Temporal Lobe Morphometry Predicts Categorization Ability.

Béatrice Garcin,Marika Urbanski,Michel Thiebaut de Schotten,Emmanuelle Volle,Richard Levy

doi:10.3389/fnhum.2018.00036

Abstract

Categorization is the mental operation by which the brain classifies objects and events. It is classically assessed using semantic and non-semantic matching or sorting tasks. These tasks show a high variability in performance across healthy controls and the cerebral bases supporting this variability remain unknown. In this study we performed a voxel-based morphometry study to explore the relationships between semantic and shape categorization tasks and brain morphometric differences in 50 controls. We found significant correlation between categorization performance and the volume of the gray matter in the right anterior middle and inferior temporal gyri. Semantic categorization tasks were associated with more rostral temporal regions than shape categorization tasks. A significant relationship was also shown between white matter volume in the right temporal lobe and performance in the semantic tasks. Tractography revealed that this white matter region involved several projection and association fibers, including the arcuate fasciculus, inferior fronto-occipital fasciculus, uncinate fasciculus, and inferior longitudinal fasciculus. These results suggest that categorization abilities are supported by the anterior portion of the right temporal lobe and its interaction with other areas.

Highlights

Categorization is the mental operation by which the brain classifies objects and events
To determine what fibers were passing through this region, we explored the anatomical connectivity of the white matter (WM)-voxel-based morphometry (VBM) region using tractography-based analyses
We showed a rostrocaudal specialization within the temporal lobe: performance in the semantic (Category) tasks was associated with more anterior regions of the middle and inferior right temporal gyri than performance in the perceptual (Shape) tasks (Figure 3 and Supplementary Figure 2)

Summary

Introduction

Categorization is the mental operation by which the brain classifies objects and events. Normative studies focused on these tests show inter-individual variability in healthy subjects’ performances with a relative standard deviation (i.e., rSD = standard deviation/mean) of 4–12% in the PPT test (Howard and Patterson, 1992; Rami et al, 2008; Klein and Buchanan, 2009; Gamboz et al, 2009; Callahan et al, 2010), an rSD of 25–45% in the similarities subtest of the WAIS (Wechsler, 2008; Wisdom et al, 2012; Harrison et al, 2014), an rSD of 20–40% in the D-KEFS sorting test (Delis et al, 2001; Homack et al, 2005; Mattioli et al, 2014), and an rSD of 20%–60% in the number of categories found in the WCST (Caffarra et al, 2004; Shan et al, 2008; Arango-Lasprilla et al, 2015) Whether this inter-individual variability in categorization tasks is related to variability in brain structure remains unknown

Methods

Results

Discussion

Conclusion