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Ione Fine, Lindsay B. Lewis, Melissa Saenz; Cross-modal plasticity within the occipital cortex of early blind subjects is driven by loss of visual input rather than by unmasking of existing cross-modal responses. Journal of Vision 2009;9(14):39. doi: 10.1167/9.14.39.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction: A variety of studies have demonstrated cross-modal responses within occipital cortex as a result of early blindness. However, little is known about the organizational principles that drive cross-modal plasticity. One possibility is that plasticity is driven by loss of input, and should be strongest within regions that are exclusively visual. Alternatively, cross-modal plasticity may result from the unmasking of weak occipital cross-modal responses that exist within the normally sighted. In this case we might expect stronger plasticity in blind subjects within those occipital cortical regions that are partially multimodal in sighted subjects. Methods: We compared the pattern of BOLD responses to a variety of auditory and tactile tasks (vs. rest) across seven early blind and six sighted subjects. Results: As expected, we found evidence for cross-modal plasticity (greater BOLD responses in early blind than sighted subjects) within occipital cortex for all tasks. While cross-modal responses were weak and generally negative within sighted subjects, there was nonetheless a consistent pattern to these responses across the cortical surface. When comparing responses across blind and subjects we found that the pattern of cross-modal responses within occipital cortex for early blind subjects was positively correlated both with the pattern of responses generated by cross-modal tasks in sighted subjects, and with the pattern of responses generated by visual tasks in sighted subjects. Further analysis revealed that it was mainly those voxels that showed strong visual responses in sighted subjects that showed strong cross-modal plasticity (enhancement of cross-modal responses) in early blind subjects, and these enhanced cross-modal responses were uncorrelated with the strength of cross-modal responses in sighted subjects. Conclusions: Although weak cross-modal responses do exist within the occipital cortex of normally sighted subjects, cross-modal plasticity as a result of early blindness seems to be predominantly driven by the loss of visual input.
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