Does the stria of Gennari integrity reflect acquired visual field defects?

Abstract

Visual input reaches the primary visual cortex (V1) at the stria of Gennari, a band of highly myelinated fibers at the level of layer IV. Damage to the visual pathways can cause visual field defects (scotomas) that prevent visual input from reaching V1. Here, we evaluate whether the stria of Gennari degrades in the absence of visual input. Using 7 Tesla MRI, we investigate the integrity of the stria of Gennari in case of acquired homonymous visual field defects, in particular hemianopia: the loss of vision in half of the visual field. These visual field defects allow us to compare stria of Gennari integrity between the two hemispheres within the same participant, i.e., the hemisphere that is deprived of visual input (affected hemisphere) versus the hemisphere receiving visual information (unaffected hemisphere). Therefore, we focus on cases of acquired blindness following damage between the optic chiasm and V1. We quantify the stria of Gennari integrity both by measuring the T1-weighted intensity at the middle of cortical depth and using a modeling approach that captures T1-weighted intensity variations across cortical depth. Our results show that the stria of Gennari remains intact in both the affected and unaffected hemisphere, suggesting that the stria of Gennari integrity is not altered in the absence of visual input.