Improved correspondence of fMRI visual field localizer data after cortex-based macroanatomical alignment

Abstract

The study of the visual system and its role for human cognition in health and disease with fMRI often requires the use of localizer paradigms to define anatomical regions of interest (ROIs). However, the considerable degree of interindividual variability of the cerebral cortex represents an important confound, especially when analyzing visual localizer data on the group level. Cortex-based alignment (CBA) techniques lead to a reliable reduction of interindividual anatomical variability. Yet, the potential benefits of CBA has not been investigated for visual field localizer paradigms used to map specific parts of the visual field within retinotopically organized early visual areas. We evaluated CBA for an attention-enhanced visual field localizer mapping a homologous part of each visual quadrant in a cohort of 50 participants. After CBA, group ROIs showed markedly increased spatial consistency. CBA also led to an increase in the probability of activation overlap of up to forty percent. Furthermore, the size of group ROIs for the lower visual hemifield was larger than for the upper visual hemifield after CBA. This asymmetry, which mirrors previous findings from electrophysiological and fMRI studies, was not detectable before CBA. Our results confirm and extend the utility of CBA for the study of the visual system particularly in the context of group analyses. This method should be particularly important for the study of neuropsychiatric disorders with abnormally increased interindividual anatomical variability.