Callosal connectivity and interhemispheric bilateral advantage: a Diffusion Tensor Imaging study

Abstract

There is wide acknowledgement that the cerebral hemispheres do not operate in isolation when processing complex visual stimuli (Singh, 2000; Schulte & Muller-Oehring, 2010). Patterns of interhemispheric communication are believed to be integral to such cognitive abilities, yet the circumstances under which communication takes place and the nature of information being processed is poorly understood. This experiment addresses the role of interhemispheric communication regarding inter-individual differences in underlying white matter (WM) relating to the matching facial identity. Several studies have already documented the role of WM in processing abilities such as with differences in gender, age and disease (Schulte & Muller-Oehring, 2010). This study though, specifically aimed at establishing whether a bilateral advantage (BA) in processing facial identity of 21 healthy individuals, could too be explained by inter-individual differences in underlying callosal microstructure. In a behavioural task, participants performed a perceptually complex physical identity task using facial stimuli presented to either one hemisphere or split between both before making a key press in response to identity. Fractional anisotropy (FA) and Tract-based Spatial Statistics (TBSS) analysis of diffusion tensor imaging (DTI) was employed to measure the underlying tissue structure of the brain in areas of the corpus callosum (CC). This was then correlated with the BA data collected from the behavioural task. Results revealed no significant relationship between BA and individual WM, however tracts identified were in line with prior research and some were seen to be approaching significance.