Local Velocity Representation: Evidence from Motion Adaptation
Paul R Schrater
and
Eero P Simoncelli
Published in:
Vision Research
38(24), pp. 3899-3912, 1998.
© Elsevier Science Ltd.
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
two-dimensional 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 two-dimensional 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.
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