title: Initial ocular following in humans: a response to first-order motion energy.
abstract: Visual motion is sensed by low-level (energy-based) and high-level (feature-based) mechanisms. Ocular following responses (OFR) were elicited in humans by applying horizontal motion to vertical square-wave gratings lacking the fundamental ("missing fundamental stimulus"). Motion consisted of successive 1/4-wavelength steps, so the features and 4n+1 harmonics (where n=integer) shifted forwards, whereas the 4n-1 harmonics--including the strongest Fourier component (the 3rd harmonic)--shifted backwards (spatial aliasing). Initial OFR, recorded with the electromagnetic search coil technique, were always in the direction of the 3rd harmonic, e.g., leftward steps resulted in rightward OFR. Thus, the earliest OFR were strongly dependent on the motion of the major Fourier component, consistent with early spatio-temporal filtering prior to motion detection, as in the well-known energy model of motion analysis.
authors.affiliation: Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Building 49 Room 2A50, 49 Convent Drive, Bethesda, MD 20892, USA. bms@lsr.nei.nih.gov
authors.forename: B M
authors.initials: BM
authors.lastname: Sheliga
authors.forename: K J
authors.initials: KJ
authors.lastname: Chen
authors.forename: E J
authors.initials: EJ
authors.lastname: Fitzgibbon
authors.forename: F A
authors.initials: FA
authors.lastname: Miles
mesh_terms: D015350:Contrast Sensitivity / Q000502:physiology; D005133:Eye Movements / Q000502:physiology*; D006801:Humans; D009039:Motion Perception / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D011597:Psychomotor Performance; D011601:Psychophysics; D014795:Visual Pathways / Q000502:physiology