Locating the functional and anatomical boundaries of human primary visual cortex

Abstract

The primary visual cortex (V1) can be delineated both functionally by its topographic map of the visual field and anatomically by its distinct pattern of laminar myelination. Although it is commonly assumed that the specialized anatomy V1 exhibits corresponds in location with functionally defined V1, demonstrating this in human has not been possible thus far due to the difficulty of determining the location of V1 both functionally and anatomically in the same individual. In this study we use MRI to measure the anatomical and functional V1 boundaries in the same individual and demonstrate close agreement between them. Functional V1 location was measured by parcellating occipital cortex of 10 living humans into visual cortical areas based on the topographic map of the visual field measured using functional MRI. Anatomical V1 location was estimated for these same subjects using a surface-based probabilistic atlas derived from high-resolution structural MRI of the stria of Gennari in 10 intact ex vivo human hemispheres. To ensure that the atlas prediction was correct, it was validated against V1 location measured using an observer-independent cortical parcellation based on the laminar pattern of cell density in serial brain sections from 10 separate individuals. The close agreement between the independent anatomically and functionally derived V1 boundaries indicates that the whole extent of V1 can be accurately predicted based on cortical surface reconstructions computed from structural MRI scans, eliminating the need for functional localizers of V1. In addition, that the primary cortical folds predict the location of functional V1 suggests that the mechanism giving rise to V1 location is tied to the development of the cortical folds.

The Retinotopic Organization of the Human Middle Temporal Area MT/V5 and Its Cortical Neighbors

“…Supplemental Figure S7 (available at www.jneurosci.org as supplemental material) plots the sulcal index (see Materials and Methods) averaged across hemispheres for MT/V5 and its neighbors. Although the average value for V1, shown for reference, is negative, indicating a location on the gyrus, the sulcal index became less negative with increasing eccentricity in V1 corresponding to the known anatomical location of V1 (Hinds et al, 2009). The average sulcal index for MT/V5 is close to zero, indicating that it is located most often in the banks of sulci, mostly the AOS or the IOS.…”

Mechanisms of Cross-Modal Plasticity in Early-Blind Subjects

“…fMRI data were aligned to same-session anatomical volumes and transformed into the cortical surface-based aligned coordinate space. Using a common space based on gyral/sulcal folding patterns allowed us to compare patterns of responses across subjects' occipital cortices relative to their own gyral and sulcal landmarks and this technique has been shown to outperform linear and nonlinear volume-based registration methods at aligning functionally defined visual areas (Fischl et al 1999;Hinds et al 2008Hinds et al , 2009). However, it should be noted that cortical folding patterns may differ between early-blind and sighted subjects (Dehay et al 1989(Dehay et al , 1996.…”

Dynamic brightness induction in V1: Analyzing simulated and empirically acquired fMRI data in a “common brain space” framework

“…Likewise, all sorts of anatomically defined regions can be linked to model areas. If a localizer scan had been lacking, we could have, for example, projected our V1 activity to an anatomically defined V1 (Hinds et al, 2009). …”