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Psychophysical evidence for an extrastriate contribution to a pattern-selective motion aftereffect
P Wenderoth1, R Bray, S Johnstone
1Department of Psychology, University of Sydney, NSW, Australia.
Perception
|January 1, 1988
Summary
The motion aftereffect (MAE) shows that the brain perceives motion after adapting to a moving stimulus. Pattern-specific MAEs are tuned to overall pattern motion, not component grating motion, suggesting extrastriate cortex involvement.
Area of Science:
- Neuroscience
- Visual Perception
- Computational Neuroscience
Background:
- The motion aftereffect (MAE) is a visual illusion where stationary objects appear to move in the opposite direction after prolonged exposure to motion.
- Pattern-specific MAEs (PSMAEs) are induced by complex stimuli like plaids, raising questions about the underlying neural processing.
Purpose of the Study:
- To investigate whether PSMAEs are primarily driven by the perceived motion of the entire pattern or by the motion of its individual components.
- To explore the neural substrates potentially responsible for PSMAEs, particularly the role of extrastriate visual areas.
Main Methods:
- Two experiments were conducted involving adaptation to superimposed gratings (plaids) drifting in specific directions.
- Observers adapted to either the coherent plaid motion or alternating component grating motions.
- The magnitude and characteristics of the subsequent motion aftereffect were measured.
Main Results:
- The PSMAE was found to be more sensitive to the overall motion direction of the plaid pattern than to the orientation and direction of the individual component gratings.
- When adaptation occurred to alternating component gratings, the aftereffect magnitude depended on the individual grating properties.
- These findings suggest a dissociation between pattern motion processing and component motion processing in the visual system.
Conclusions:
- PSMAEs are predominantly driven by pattern motion, indicating a higher-level processing stage.
- The results support the involvement of extrastriate visual areas, such as the middle temporal area (MT), which are known to process pattern motion, rather than earlier areas like V1 that focus on component motion.