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Shaleeza Kaderali, Yeon Jin Kim, Alexandre Reynaud, Kathy T. Mullen; Effect of continuous theta burst stimulation (cTBS) of human brain areas MT+ and V1 on color and motion perception.. Journal of Vision 2014;14(10):285. doi: 10.1167/14.10.285.
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Introduction: Previous studies on chromatic and luminance defined global motion have established a dissociation between visual thresholds for direction discrimination and stimulus detection (Michna & Mullen, JOV 8(5):10, 2008). Here we use cTBS (a repetitive TMS protocol) to investigate the differential effects of stimulation on these thresholds in areas hMT+ and V1. We use both luminance and isoluminant chromatic global motion stimuli. Methods: Brain areas hMT+ and V1 were localized using the reported induction of moving or stationary phosphenes, respectively. The vertex was stimulated as a control. Eight participants performed a motion discrimination task in which the direction of Gaussian dots in a random dot kinematogram was identified, and a detection task, in which the dots was detected regardless of motion, for isoluminant chromatic and luminance stimuli. Thresholds were measured before cTBS and after stimulation for one hour. Results: For the motion discrimination task, cTBS stimulation of area hMT+ selectively impaired visual performance for both luminance and isoluminant chromatic stimuli in comparison to area V1 and vertex. Maximal effects occurred 3-18 minutes after stimulation, and by one hour performance had returned to baseline. For the detection task, no selective effect of cTBS was observed. Conclusion: Our study demonstrates that the use of cTBS impairs the function of area hMT+, providing further evidence that hMT+ is involved in the analysis of luminance defined global motion. Also, even though isoluminant color vision is poor for motion perception, we show that area hMT+ is contributing to residual chromatic motion at isoluminance. The results indicate a causal link between neural activity in area hMT+ and the perception of chromatic motion. This effect may be mediated by the response of M-cells to the chromatic stimuli, which feed into the motion pathway.
Meeting abstract presented at VSS 2014
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