Abstract
In adult animals, regions of primary visual cortex deprived of normal input show “reorganization” (Kaas et al., 1990): they begin responding to stimuli that normally activate adjacent cortex only. However, it is unknown how quickly this cortical reorganization can happen, and some studies have failed to find it at all, spawning considerable controversy (e.g., Smirnakis et al., 2005). We investigated the existence and speed of reorganization in the adult human visual system, using a novel perceptual test. Specifically, we patched one eye, thus depriving input to the cortical region corresponding to the natural blind spot (BS) in the unpatched eye. To ask whether and how quickly deprivation produces reorganization, we tested for perceptual distortions that have recently been shown to reflect cortical reorganization in retinotopic cortex following stroke (Dilks et al., 2007). Within only one minute of eye patching, participants perceived rectangles placed adjacent to the BS to be elongated toward the BS, exactly as expected if deprived cortex starts to respond to stimuli adjacent to the BS. These findings further document the existence of cortical reorganization in the adult human visual system, show that this reorganization can occur very rapidly, and implicate unmasking of horizontal connections in early visual cortex as the underlying mechanism.
Supported in part by: NIH grant EY016159 to NK, and NIH NRSA EY017507 to DD.