The Journal of Neuroscience, June 15, 2002, 22(12):5149-5163
Parallel Motion Processing for the Initiation of Short-Latency
Ocular Following in Humans
Guillaume S.
Masson and
Eric
Castet
Centre de Recherche en Neurosciences Cognitives, Centre National de
la Recherche Scientifique, FRE2098, 13402 Marseille, France
With the scleral search coil technique, we recorded ocular
following responses elicited by either grating or plaid pattern motions. Grating motion elicited tracking responses at short latencies (~85 msec). Type I plaid motion made by summing two orthogonal moving
gratings elicited ocular following with identical short latencies.
Trial-by-trial vector decomposition showed that plaid-driven responses
were best predicted by a vector average of the component-driven responses. Similar results were found with micropatterns made of 16 Gabor patches with drifting carriers of two different orientations. "Unikinetic" plaids were constructed by summing a moving and
stationary grating, with a 45° orientation difference, so that
component and pattern motion directions were separated by 45°. Eye
movements exhibited two components. Ocular following was first
initiated in the grating motion direction, at ultra-short latency. A
second component was initiated ~20 msec later, curving the responses toward the pattern motion direction. The later component was
specifically, and independently, affected by both relative spatial
frequency and contrast between component gratings. The early response
components showed a much steeper contrast response function than the
late component. These results suggest that initial ocular following is
underpinned by parallel processing of component- and pattern-related velocities followed by an integrative stage that computes the two-dimensional surface motion.
Key words:
ocular tracking; plaid motion; Fourier; non- Fourier; parallel processing; 2D visual motion integration
Copyright © 2002 Society for Neuroscience 0270-6474/02/22125149-15$05.00/0
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