Reduced functional connectivity between central representations of V1 and foveal-biased face-selective region in central vision loss

Abstract

Individuals with central visual deficits exhibit atrophy of the visual cortex in regions representing the central visual field and show little or no functional response there. Information in the central and peripheral visual field appear to be represented preferentially in extrastriate regions that are selective to faces and places, respectively. We recruited individuals with bilateral macular degeneration (age-related or juvenile) and age-matched sighted controls. We used resting state fMRI (RS-fMRI) to examine functional connectivity between striate (V1) and extrastriate face and place selective areas as it allows better comparison between those with unaffected vision and those with visual loss, whose stimulus related signals are already known to differ from those of controls. Selective deficits emerged in our central loss group, showing reduced functional connectivity between regions with foveal biases (central V1-face area) compared to sighted controls, whereas no such difference emerged in the peripheral biased regions (peripheral V1-place area). This result was evident regardless of whether eyes were closed or open and fixating, but was only significant in the right hemisphere, supporting the functional lateralisation of face processing. This pilot study provides some evidence for reduced functional connectivity between foveal-biased visual areas in central vision loss, suggesting that communication within the posterior visual pathway may be selectively affected in partial vision loss. Functional connectivity differences did not appear to be driven by changes in viewing condition. RS-fMRI is a valuable tool that allows us to explore functional brain changes without the need for retinal input.

Keywords: Central visual deficits; Faces; Macular disease; Places; Visual cortex; fMRI.

Fig. 1

Regions of interest (ROIs) for one example participant, displayed on the FreeSurfer inflated cortical surface. a: Two V1 ROIs generated using a retinotopically defined atlas (Benson et al. 2012, 2014), overlaid on the eccentricity map, shown here on the medial surface of the left occipital lobe. b: The V1 ROIs in each hemisphere were divided in two—one portion capturing the central visual field (0-5 deg) and one portion capturing the peripheral visual field (> 5 deg). c: Our higher-level visual ROIs shown on the ventral surface of the right hemisphere

Fig. 2

Correlations transformed into Fisher’s Z scores. a: Results for within-eccentricity ROI pairs. b: Results for between-eccentricity ROI pairs. Box plots: Light grey = sighted control group, dark grey = central loss group. Solid line = group median, dashed line = group mean. Each dot represents a single participant, with central loss patients coloured to allow each individual to be identified across conditions and ROI pairings. Top row: Results for Eyes Closed condition. Bottom row: Results for Eyes Open condition