Abstract
A fundamental property of early cortical visual areas is the spatial arrangement of the functional responses of neurons in a retinotopic map. Measurement of this organization requires participants to engage in a visual mapping scan, which is infeasible in the study of cortical alteration in blinding diseases. Our recent work measures the retinotopic organization of visual cortex using non-visual approaches, specifically the topology of cortical folding and the pattern of spontaneous neural signals evoked in darkness (a.k.a., “resting state” signals).
We have found that the pattern of cortical surface folding is tightly linked to retinotopic organization not only in primary visual cortex (V1; NC Benson et al., 2012) but in extra-striate (V2, V3) cortex as well. These techniques require only an image of brain anatomy to assign polar angle and eccentricity values to cortical points within visual areas V1-V3, with accuracy comparable to a 15–30 minute BOLD fMRI study.
We have applied this anatomy-based approach to measure and compare the fine-scale structure of resting-state signals in sighted and blind participants. Resting-state signals have been proposed to reflect the retinotopic organization of visual cortex (e.g., Heinzle et al., 2011). We replicate these prior results and find that blindness alters the pattern of functional correlation of mirror-symmetric points between the hemispheres, and the organization of correlation between the dorsal and ventral halves of visual areas (O Butt et al., In Press).