Perception of Length and Direction in Wave Motion

Abstract

It is known that changes in the functioning of the vestibular system affect visual perception. We studied the effect of gravitoinertial impact on the sensorimotor assessment of the length and direction of segments of different orientations by the leading hand before and during the wave motion (n = 6) in comparison with the control group (n = 22). At the memorization stage, the subjects moved their leading hand along a visible segment located at different angles to the horizontal on the center of the touchscreen, and at the reproduction stage they repeated this movement in the same place on an empty screen. In both groups, when memorizing, the error in estimating the length and direction of segments was small and had no pronounced dynamics; during reproduction, a motor oblique effect was obtained, that is repulsion of segments of oblique directions from the canonical axes, vertical and horizontal. During wave motion, the length of the segment began to be estimated less accurately (movements became more hypermetric). This error pattern supports the vector encoding hypothesis, in which the direction and length of the planned movement are encoded independently of each other. Moreover, the gravitoinertial effect selectively affects the accuracy of length coding, and not the coding of the direction of movement of the leading hand.