Abstract
While recent findings demonstrate an unexpected coupling between functional and cytoarchitectonic regions relative to the folding of human visual cortex, a unifying principle linking these anatomical and functional features of cortex remains elusive. To fill this gap in knowledge, we summarize findings from two of our recent studies that examined two main questions: 1) Does differential gene expression among cytoarchitectonic areas contribute to the arealization of occipito-temporal cortex into a processing hierarchy? 2) Does differential gene expression also contribute to the topological layout of orthogonal functional maps within visual areas? Our multimodal approach revealed two main findings. First, there are two large-scale opposing gene expression gradients in human occipito-temporal cortex: one that contains a series of genes with expression magnitudes that ascend from posterior (e.g. areas hOc1, hOc2, etc.) to anterior cytoarchitectonic areas (e.g. areas FG1-FG4) and another that contains a separate series of genes that show a descending gradient from posterior to anterior areas. Using data from the living human brain, we show that each of these gradients correlates strongly with variations in measures related to either thickness or myelination of cortex, respectively. Second, additional transcription gradients exist within single visual field maps that capture the orthogonal functional maps of receptive field eccentricity and polar angle. The genes contributing to the fine-scale layout of maps within areas are largely distinct from those contributing to the large-scale expression gradients contributing to the arealization of human visual cortex. The combination of these findings suggest a new rule of cortical organization in which the adult brain employs opposed transcriptional gradients at multiple spatial scales. Altogether, these findings help pinpoint the genes contributing to healthy cortical development, as well as establish essential groundwork for understanding future work linking genetic mutations with the function and development of human visual cortex.