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Claudia Lunghi, Uzay Emir, Maria Concetta Morrone, David Charles Burr, Holly Bridge; Transient monocular deprivation affects binocular rivalry and GABA concentrations in adult human visual cortex. . Journal of Vision 2014;14(10):378. doi: 10.1167/14.10.378.
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We have recently shown that the adult human visual system is more plastic than previously thought, as 150 minutes of monocular deprivation causes severe perceptual consequences on the dynamics of binocular rivalry (Lunghi, Burr, Morrone 2010), with the deprived eye dominating rivalrous perception for twice as long as the non-deprived eye. The duration of the effect depends on the stimulus tested, lasting for up to 180 minutes for equiluminant chromatic gratings (Lunghi, Burr, Morrone 2013). We hypothesized that this plasticity in adult cortex could result from a homeostatic boost of the contrast gain of the deprived-eye, which could be mediated by a decrease in intracortical inhibition. To test this hypothesis we measured metabolite concentrations from a 2x2x2cm voxel within the visual cortex (comprising the calcarine sulcus) in 12 adult human observers, using ultra-high field (7T) magnetic resonance spectroscopy before and after 150 min of monocular deprivation. Metabolite concentrations were quantified with LCModel using the unsuppressed water signal as reference. We coupled the MRS measurements with psychophysical testing of binocular rivalry between orthogonal red and blue gratings (SF 2cpd, contrast 50%, size 2°) presented separately to the eyes through anaglyph goggles. We found significant (paired t-test) modification of three metabolite concentrations following monocular deprivation: GABA (−11%), Glutamine (−11%), Taurine (+12%). Interestingly, only the variation in GABA showed a correlation with the perceptual effect of monocular deprivation on binocular rivalry, with the monocular deprivation induced decrease in GABA being significantly correlated with the increase in predominance of the deprived eye (Spearman's ranked correlation coefficient, rho = 0.86, p<0.001). Taken together these results suggest that one of the mechanisms mediating short-term monocular deprivation driven adult human visual cortical plasticity is a reduction in GABA-ergic inhibition in early visual cortices.
Meeting abstract presented at VSS 2014
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