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Bo Hu, David Knill; Kinesthetic information modulates visual motion perception. Journal of Vision 2010;10(7):864. doi: 10.1167/10.7.864.
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© ARVO (1962-2015); The Authors (2016-present)
Previously we showed that actively moving a grating pattern disambiguates the perceived direction of visual motion. We demonstrate here that active movement is not necessary, but that kinesthetic signals from passive movement of the hand can disambiguate the perceived motion direction. Eight subjects did 4 active and 4 passive blocks in Experiment 1. In active blocks, subjects slid a dumb-bell shape device (bar connecting two 6′′ plates) on a tabletop along self-chosen directions for 4000ms. Its position was recorded at 250Hz. Square-wave gratings (2 deg/cycle), rendered on a monitor, were reflected by a mirror onto the plane co-aligned with the top plate and moving at the same velocity as the subjects' hand movement. Subjects viewed the gratings through a 12-degree round aperture and reported the perceived grating motion direction. In passive blocks, the device was mounted on a robot arm, which regenerated the motion recorded in active blocks. Subjects, grasping the bar, were moved by the robot without seeing their arms and performed the same task. Seven subjects' direction judgments showed modulation from the hand movement in both conditions. The weights given to kinesthetic signal were not statistically significant in active and passive conditions (paired t(7)=0.46). In Experiment 2, 8 new subjects did 4 passive and 4 vision-only blocks, in which subjects reported the motion without grasping the bar. Six subjects showed kinesthetic modulation in the passive condition, but none in the vision-only condition, excluding the possibility that subjects used visual cues in judging the true motion direction. The results confirm that kinesthetic information modulates motion perception. That a similar magnitude of perceptual modulation occurred in passive and active conditions indicate that high-level intentional signals about the planned movement direction cannot explain the effect, rather the brain integrates kinesthetic and visual signals when estimating the visual motion direction.
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