Abstract
Previous psychophysical studies have reported conflicting results concerning the effects of short-term visual deprivation upon tactile acuity. Some studies have found that 45 to 90 minutes of total light deprivation produce significant improvements in participants' tactile acuity as measured with a grating orientation discrimination task. In contrast, a single 2011 study found no such improvement while attempting to replicate these earlier findings. A primary goal of the current experiment was to resolve this discrepancy in the literature by evaluating the effects of a 90-minute period of total light deprivation upon tactile grating orientation discrimination. We also evaluated the potential effect of short-term deprivation upon haptic 3-D shape discrimination using a set of naturally-shaped solid objects. According to previous research, short-term deprivation enhances performance in a tactile 2-D shape discrimination task – perhaps a similar improvement also occurs for haptic 3-D shape discrimination. The results of the current investigation demonstrate that not only does short-term visual deprivation not enhance tactile acuity, it additionally has no effect upon haptic 3-D shape discrimination. While visual deprivation had no effect in our study, there was a significant effect of experience and learning for the grating orientation task – the participants' tactile acuity improved over time, independent of whether they had, or had not, experienced visual deprivation.
Highlights
By the 1880’s, it was well known from experiments performed by David Ferrier [1] and Hermann Munk [2] that large portions of the primate and mammalian cerebral cortex were devoted to visual and auditory functions
More recent research [6,7,8,9,10,11,12] has proven that the cerebral cortex is plastic and that significant changes in neuronal responsiveness to sensory information occur with long-term visual deprivation
Kahn and Krubitzer [6] surgically removed both eyes from opossum pups at 4 days of age
Summary
By the 1880’s, it was well known from experiments performed by David Ferrier [1] and Hermann Munk [2] that large portions of the primate and mammalian cerebral cortex were devoted to visual and auditory functions. Given that a period of 5 days is probably insufficient for significant changes in patterns of neuronal connectivity per se, Merabet et al [24] suggested that the improvement obtained for their tactile task was likely caused by ‘‘an unmasking of latent multimodal connections underlying the recruitment of occipital cortex for tactile processing’’ In this view, there are pre-existing tactile inputs to ‘‘visual’’ cortex in all of us, but in everyday life visual input dominates and ‘‘masks’’ the tactile input. The tactile acuity of their visually deprived participants did improve after 45 minutes of blindfolding, but because there was no control group of nondeprived participants with which to compare, this improvement could have occurred as a result of practice and increasing experience with the task In their own study (which did employ control groups of non-deprived participants, who were tested under sighted conditions), Wong et al [29] found no improvement in grating orientation discrimination following up to 110 minutes of visual deprivation. No study to date has simultaneously investigated the potential effects of short-term visual deprivation upon both tactile acuity and haptic shape discrimination
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