Adaptation to a moving visual pattern induces shifts in the perceived motion of subsequently viewed moving patterns. Explanations of such effects are typically based on adaptation-induced sensitivity changes in spatio-temporal frequency tuned mechanisms (STFMs). An alternative hypothesis is that adaptation occurs in mechanisms that independently encode direction and speed (DSMs). Yet a third possibility is that adaptation occurrs in mechanisms that encode 2D pattern velocity (VMs). We performed a series of psychophysical experiments to examine predictions made by each of the three hypotheses. The results indicate that: (1) adaptation-induced shifts are relatively independent of spatial pattern of both adapting and test stimuli; (2) the shift in perceived direction of motion of a plaid stimulus after adaptation to a grating indicates a shift in the motion of the plaid pattern, and not a shift in the motion of the plaid components; and (3) the 2D pattern of shift in perceived velocity radiates away from the adaptation velocity, and is inseparable in speed and direction of motion. Taken together, these results are most consistent with the VM adaptation hypothesis.
Bibliographical noteFunding Information:
We thank Ted Adelson, Mary Bravo, Jacob Nachmias, E.J. Chichilinsky, and David Knill for valuable discussions, and Andrew Smith and a second anonymous reviewer for their helpful suggestions. PRS was supported by NEI Vision Training Grant EY07035-17. The majority of this research was performed while EPS was in the Computer and Information Science Dept, U. Pennsylvania, where he was partially supported by NSF Science and Technology Center Grant SBR-89-20230, and ARO/MURI Grant DAAH04-96-1-0007. EPS is currently supported by the Sloan Foundation through the NYU Theoretical Neurobiology Program, and by NSF CAREER grant 9624855.
- After effect