Distinctive feature sensitivity of ocular following initiation during global motion perception.

We investigate how sensory and motor components of the visual system respond to carrier (first-order) and envelope (second-order) motion features for global motion perception. While both ocular following responses (OFRs) and perceptual judgments exhibit higher responsivity to envelope motion, carrier motion alone was insufficient, leading to large perceptual direction errors and speed biases and minimal OFRs. Shorter presentation times selectively impaired perceptual speed discriminability by decreasing the signal and increasing noise, with no corresponding effect on oculomotor responses. In direction discriminability analysis, in contrast, OFRs and perceptual responses have a similar relative noise pattern to motion features, suggesting shared noise sources in global motion processing. Trial-by-trial correlation analysis confirmed the dissociation where perceptual speed was uncorrelated with OFR speed, whereas perceptual direction showed a delayed correlation with eye direction relative to movement onset. This delayed correlation timing for direction suggests global motion modulates both systems via feedback control processes.