Retinotopic Maps, Spatial Tuning, and Locations of Human Visual Areas in Surface Coordinates Characterized with Multifocal and Blocked fMRI Designs

Abstract

The localization of visual areas in the human cortex is typically based on mapping the retinotopic organization with functional magnetic resonance imaging (fMRI). The most common approach is to encode the response phase for a slowly moving visual stimulus and to present the result on an individual's reconstructed cortical surface. The main aims of this study were to develop complementary general linear model (GLM)-based retinotopic mapping methods and to characterize the inter-individual variability of the visual area positions on the cortical surface. We studied 15 subjects with two methods: a 24-region multifocal checkerboard stimulus and a blocked presentation of object stimuli at different visual field locations. The retinotopic maps were based on weighted averaging of the GLM parameter estimates for the stimulus regions. In addition to localizing visual areas, both methods could be used to localize multiple retinotopic regions-of-interest. The two methods yielded consistent retinotopic maps in the visual areas V1, V2, V3, hV4, and V3AB. In the higher-level areas IPS0, VO1, LO1, LO2, TO1, and TO2, retinotopy could only be mapped with the blocked stimulus presentation. The gradual widening of spatial tuning and an increase in the responses to stimuli in the ipsilateral visual field along the hierarchy of visual areas likely reflected the increase in the average receptive field size. Finally, after registration to Freesurfer's surface-based atlas of the human cerebral cortex, we calculated the mean and variability of the visual area positions in the spherical surface-based coordinate system and generated probability maps of the visual areas on the average cortical surface. The inter-individual variability in the area locations decreased when the midpoints were calculated along the spherical cortical surface compared with volumetric coordinates. These results can facilitate both analysis of individual functional anatomy and comparisons of visual cortex topology across studies.

Target sites for transcallosal fibers in human visual cortex – A combined diffusion and polarized light imaging study

“…This, in turn, would be in agreement with recent evidence that hOcV4 might contain a complete hemi-field representation (Wilms et al, 2010). Based on our results, it could thus be assumed that cytoarchitectonic area hOcV4 could be regarded as the microstructural correlate of the retinotopically defined hemifield hV4 (Henriksson et al, 2012;Winawer et al, 2010).…”

“…Later, retinotopic mapping studies provided evidence for a complete hemi-field representation within the cortex directly anterior to area V3v (Brewer, Liu, Wade, & Wandell, 2005;Wade, Brewer, Rieger, & Wandell, 2002;Winawer, Horiguchi, Sayres, Amano, & Wandell, 2010). The edges of this hemi-field representation, termed human V4 (hV4) indeed responded to stimuli at the upper and lower vertical meridian (Henriksson, Karvonen, Salminen-Vaparanta, Railo, & Vanni, 2012;Winawer et al, 2010).…”

Cytoarchitecture of the human lateral occipital cortex: mapping of two extrastriate areas hOc4la and hOc4lp

“…The borders between these areas represent the lower (V3/LO-1) and upper (LO-1/LO-2) vertical meridian. These and the studies of Swisher et al (2007), Wandell et al (2007), Kolster et al (2010) and Henriksson et al (2012) have established LO-1 and LO-2 as distinct, functionally defined areas within the higher lateral extrastriate human visual cortex. Furthermore, recent studies have demonstrated functional differences between LO-1 and LO-2.…”

Frequency-dependent spatiotemporal profiles of visual responses recorded with subdural ECoG electrodes in awake monkeys: Differences between high- and low-frequency activity

“…The stimulus position was randomized across the display at 61 positions, which consisted of the central fixation location and 5 levels of eccentricity (e.g., visual angles of 0.7°-2.5°, 2.5°-5°, 5°-10°, 10°-15°, and 15°-20°) and 12 polar angles, as depicted in Fig. 1B (right panel), similar to those employed in previous studies (Hansen et al, 2004, Henriksson et al, 2012. A sequence of mapping stimuli appeared up to 7 (for monkey Q) or 4 (for monkey B) times during a single fixation.…”