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K. Neary, S. Anand, B. Gee, J. Hotson; Perceptual Learning Increases the Strength of Early Visual Processing as Measured by Increased Resistance to Transcranial Magnetic Stimulation (TMS) . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4101.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Perceptual learning of a visual task increases neural activity in early visual cortex (Schoups et al., 2001; Furmanski & Engel, 2002). TMS of visual cortex suppresses perception when delivered in a discrete time window after a brief visual display. We asked if learning an odd-element (OE) detection task would increase visual cortex resistance to TMS and decrease the magnitude of TMS suppression of perception. Methods: Subjects detected an OE with an orientation difference (OD) of 5-40° from a 5x5 array of lines oriented 30° counterclockwise of vertical. The OD that gave ~65% correct detections was selected from a psychometric curve for subsequent training. The TMS delay that produced peak perceptual suppression in a vertical displacement task, and an earlier and later delay that moderately perturbed visual perception were selected. Subjects who were trained with the OE display with feedback for >3800 trials over several weeks showed significant improvement in OE detection. Four subjects were tested with TMS delivered through a 7-cm round coil placed over the occipital pole. TMS testing was performed before, intermittently during and after the learning trials. Results: With learning, the magnitude of TMS suppression of OE detection significantly decreased at the early and peak TMS delays, but not at the late delay. A fifth subject was tested with a "focal" butterfly coil centered over early visual cortex. With learning the magnitude of TMS suppression significantly decreased only at the early TMS delay, and not at the peak or late delay. Conclusions: These findings are consistent with perceptual learning strengthening visual activity in early visual cortex at early visual processing times.
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