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Abstract:
The apparent motion of a 180-degree phase shift of a
sinusoidal luminance grating is directionally ambiguous. When
preceded by a 90-degree directionally unambiguous motion sweep, the
ambiguous sweep appears to move in the same direction as the
unambiguous sweep. This phenomenon is called motion priming (Pinkus
& Pantle, 1997). To examine the neural responses associated
with the perception of the direction of successive motion sweeps,
we recorded event-related potentials (ERPs) from 14 posterior scalp
sites in 14 young adults (mean age = 20) with normal vision. During
recording, subjects judged the motion direction (either leftward or
rightward) of two successive motion sweeps with different
combinations of directionally ambiguous or unambiguous sweeps (ISI
= 200 ms). The early P1 ERP component was found to be most positive
during motion priming. The P3 component was largest when two
unambiguous motion sweeps were perceived in the same direction.
Motion sweeps in opposite directions elicited the smallest positive
P1 and P3 amplitudes of all conditions. These effects were
strongest in posterior temporal and occipital scalp areas. The
results reveal the temporal modulation of both early visual
cortical and later neural responses during perceptual decisions of
motion direction.
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