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Ben Thompson, Hongjing Lu, Zili Liu; Perceptual learning of motion discrimination with suppressed and un-suppressed MT. Journal of Vision 2005;5(8):711. doi: 10.1167/5.8.711.
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© ARVO (1962-2015); The Authors (2016-present)
Visual area MT has long been implicated in the perceptual learning of motion discrimination. However, it is not well understood whether learning is still possible without MT. We investigated psychophysically with normal participants the role of MT using paired-dots stimuli that suppress MT activity (Qian, Andersen, & Adelson 1994).
MT suppression was achieved because the dots in each pair moved counter-phase to one another so that the net motion directional signal was locally balanced. We further destroyed the Glass pattern per static frame so that the motion-axis information was available only via motion signals (Lu, Qian, & Liu 2004). In each trial, two stimuli were presented sequentially, participants decided whether the motion-axis changed clockwise or counter-clockwise. Psychometric functions of all participants were first measured. A threshold angle was then chosen per participant such that threshold angles at 60%, 65%, 70%, and 75% correct would be used for daily learning, with at least one pair of participants each. One of the two participants in a pair would be trained with counter-phase paired dots, the other with in-phase paired dots as a control.
Suppressed MT activity by counter-phase paired dots reduced or eliminated learning relative to non-suppressed MT by in-phase paired dots. This effect was more pronounced with reduced signal-noise-ratio (SNR) of the stimulus. Therefore, MT, whilst not necessarily essential for perceptual learning of motion discrimination with stimuli of substantial SNR, does facilitate learning particularly when stimulus SNR is low.
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