NeuroImage
abstract
A number of recent studies have established a link between behavior and the anatomy of the primary visual cortex
(V1). However, one often-raised criticism has been that these studies provide little insight into the mechanisms
of the observed relationships. As inhibitory neural interactions have been postulated as an important
mechanism for those behaviors related to V1 anatomy, we measured the concentration of inhibitory gammaamino
butyric acid (GABA) in the medial occipital cortex where V1 is located using magnetic resonance spectroscopy
(MRS) and estimated the surface area of V1 using fMRI retinotopic mapping. We found a significant positive
relationship between GABA concentration and V1 surface area. This relationship was present irrespective of
whether the MRS voxel had a fixed size across participants or was proportionally sized to each individual's V1
surface area. Hence, individuals with a larger V1 had a higher GABA concentration in the medial occipital cortex.
By tying together V1 size and GABA concentration, our findings point towards individual differences in the level
of neural inhibition that might partially mediate the relationships between behavior and V1 neuroanatomy. In
addition, they illustrate how stable microscopic properties of neural activity and function are reflected in
macro-measures of V1 structure.
© 2015 Elsevier Inc. All rights reserved