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Elizabeth Huber, Fang Jiang, Ione Fine; Frequency-tuned auditory motion responses within hMT+ in early blind individuals. Journal of Vision 2016;16(12):141. doi: 10.1167/16.12.141.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction: Several fMRI studies have demonstrated novel responses to auditory motion in hMT+ in early blind and sight recovery subjects. Recently, Watkins et al. (2013) noted weak frequency-tuned responses within hMT+ in anophthalmic individuals hearing stationary tones. Here, we show that the auditory motion responses produced in hMT+ as a result of early blindness are also frequency selective. Methods: Tonotopic mapping was carried out in 4 early blind and age-matched sighted controls using (1) stationary pure tones and (2) a moving auditory stimulus. The moving stimulus consisted of band pass noise bursts centered at one of 7 frequencies (125-3952 Hz) in a semi-random order, with motion simulated using ITD and Doppler. Each event lasted 2s and contained a pair of 1s bursts travelling at 30 m/sec from left to right, or vice versa, along the fronto-parallel plane. Subjects performed a one-back task on the center frequency. The frequency tuning of each voxel was then estimated as a Gaussian in log frequency space using population receptive field modeling (Thomas et al., 2014). Results and Conclusions: In primary auditory cortex, stationary pure tones and moving band-pass stimuli produced highly similar tonotopic maps for both early blind and sighted subjects. Within hMT+ in sighted subjects, neither the moving nor the stationary stimulus elicited frequency-tuned responses. In contrast, within hMT+ in early blind subjects, robust frequency tuning was evident with the moving stimulus; these responses were much weaker for the stationary stimulus. Thus, after early blindness, hMT+ exhibits selectivity for auditory frequency as well as direction of motion. This is analogous to the selectivity for spatial frequency and motion direction normally seen in hMT+ and may serve to enhance the ability of early blind individuals to segregate individual auditory objects within complex auditory scenes.
Meeting abstract presented at VSS 2016
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