Contrast sensitivity measured during smooth pursuit movement.
When pursuit eye movement is guided by a light spot which moves at the same velocity as that of a drifting grating, the reciprocal of the threshold contrast (TC) needed for the eye to perceive the grating moving at the same velocity as the auxiliary spot is defined as the guided pursuit contrast sensitivity (GP-CS). GP-CS and flicker (F-) or motion-CS are determined for 20-21 out of 25 possible combinations of 0.75, 1.5, 3, 6 and 12 c/deg grating drifting at 1, 2, 4, 8 or 16 Hz. Up to a drifting velocity of about 5 degrees/s, the GP-CS is near to the pattern recognition (PR)-CS for a stationary grating (+20 to -40%), while the F-CS shows systematic higher (100-200%) to lower (30-60%) values than the PR-CS from low to high spatial frequency (SF) gratings as found by previous investigators. These differences can be most easily seen when the GP-CSF's for gratings drifting at 2, 4 and 8 Hz are plotted and compared with the respective F-CSF's against SF. The general shape of the GP-CSF's shows remarkable similarity to that of PR-CSF at 0 Hz which is generally regarded to be mediated by the so-called sustained system. Apparent motion sensation is inevitably associated with GP. Participation of sustained system in the mediation of motion sensation and the implication of pattern vision during smooth pursuit eye movement are discussed.
D005133:Eye Movements; D005425:Flicker Fusion; D006801:Humans; D010364:Pattern Recognition, Visual / Q000502:physiology; D013997:Time Factors