Corticospinal Excitability in the Hand Muscles is Decreased During Eye Movement with Visual Occlusion

Abstract

Corticospinal excitability in the hand muscles decreases during smooth pursuit eye movement. The present study tested a hypothesis that the decrease in corticospinal excitability in the hand muscles at rest during eye movement is not caused by visual feedback but caused by motor commands to the eye muscles. Healthy men (M age = 28.4 yr., SD = 5.2) moved their eyes to the right with visual occlusion (dark goggles) while their arms and hands remained at rest. The motor-evoked potential in the hand muscles was suppressed by 19% in the third quarter of the eye-movement period, supporting a view that motor commands to the eye muscles are the cause of the decrease in corticospinal excitability in the hand muscles. The amount of the suppression was not significantly different among the muscles, indicating that modulation of corticospinal excitability in one muscle induced by eye movement is not dependent on whether eye movement direction and the direction of finger movement when the muscle contracts are identical. Thus, the finding failed to support a hypothetical view that motor commands to the eye muscles concomittantly produce motor commands to the hand muscles. Moreover, the amount of the suppression was not significantly different between the forearm positions, indicating that the suppression was not affected by proprioception of the forearm muscles when visual feedback is absent.

Interactions Elicited by the Contradiction Between Figure Direction Discrimination and Figure-Ground Segregation

“…Characteristics of eye fixations and movements are expected to provide insightful suggestions for the investigation of the neural mechanism underlying the perception of local DOF discrimination along a contour and global FG segregation. The location and duration of eye fixations and movements are often utilized as the perceptual indices for understanding a variety of fields (e.g., Chujo et al, 2016 ; Zimmermann et al, 2018 ), especially, the strategy of visual processing reflects in the characteristics of eye movements and fixations (e.g., Henderson, 1993 ; Rayner, 1998 ; Itti and Koch, 2001 ; Straube et al, 2010 ; Sheridan and Reingold, 2017 ). If perception of DOF is determined based on local processing while that of FG is global, the strategy of eye movements could be different.…”