DYNAMIC MOTOR FACTORS IN DETERMINING EFFECTS OF RETINAL IMAGE FEEDBACK REVERSAL AND DELAY*
Karl Ulrich Smith, Vernon R. Putz · Optometry and Vision Science · 1970
This experiment measured the dynamic motor factors involved in response to reversal and delay of retinal feedback of eye and head movements. The experiment compared the velocity and tracking accuracy of head and eye motions under conditions in which the action feedback of the two motions was operationally isolated and varied by means of a real-time computer system and experimental systems methods of yoking visual targets to the two movement mechanisms both separately and coordinately. Results showed that with reversed retinal feedback: (1) velocity and accuracy of eye movements were degraded more than head movement; (2) smooth pursuit head and eye motions were reduced to saccadic movements; (3) ocular tracking tended to dominate coordinate head-eye tracking; and (4) little dynamic adaptation occurred to the modified retinal feedback. Delay of the retinal feedback had the same relative effects on the two motions. More variation occurred in the velocity of eye movements than in the speed of head movements with increase in the magnitude of the delay of retinal feedback. The results support the movement-compensation hypothesis of adaptation to reversed vision by indicating that compensatory movement correction of altered feedback of eye or head motion is not possible when control of the altered feedback is restricted experimentally to the movement system affected. The response of the visual system to reversal and delay of the retinal image is a direct function of the intrinsic directional specificity of eye and head movements in governing retinal input.