Altered intrinsic neuronal interactions in the visual cortex of the blind.

In congenital blindness, the brain develops under severe sensory deprivation and undergoes remarkable plastic changes in both structure and function. Visually deprived occipital cortical regions are histologically and morphologically altered and exhibit a strikingly remodeled functional state: absolute levels of neural activity are heightened and are modulated by nonvisual sensory stimulation as well as higher cognitive processes. However, the neuronal mechanisms that underlie this altered functional state remain largely unknown. Here, we show that the visual cortex of the congenitally blind exhibits a characteristic gain in frequency-specific intrinsic neuronal interactions. We studied oscillatory activity in 11 congenitally blind humans and matched sighted control subjects with magnetoencephalography at rest. We found increased spontaneous correlations of delta band (1-3 Hz) and gamma band (76-128 Hz) oscillations across the visual cortex of the blind that were functionally coupled. Local delta phase modulated gamma amplitude. Furthermore, classical resting rhythms (8-20 Hz) were reduced in amplitude but showed no altered correlation pattern. Our results suggest that both decreased inhibition and circuit mechanisms that support active processing are intrinsic features underlying the altered functional state of the visual cortex in congenitally blind individuals.