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Top-down modulation of visual processing and knowledge after 250 ms supports object constancy of category decisions
Haline E Schendan1, Giorgio Ganis2
1School of Psychology, Cognition Institute, University of Plymouth Plymouth, UK.
Frontiers in Psychology
|October 7, 2015
Summary
Top-down processes guide object recognition under visual uncertainty. This study reveals brain mechanisms and timing for perceptual hypothesis testing (PHT), implicating prefrontal and occipitotemporal cortex activity.
Area of Science:
- Cognitive Neuroscience
- Neuroimaging
- Visual Perception
Background:
- Object categorization is slower with impoverished visual input.
- Perceptual hypothesis testing (PHT) theories propose top-down processes are crucial for impoverished input, but their neural basis is unclear.
Purpose of the Study:
- Investigate the brain mechanisms and temporal dynamics of PHT during object categorization.
- Examine how top-down modulation affects object recognition under varying visual clarity.
Main Methods:
- Utilized an event-related potential (ERP) neuroimaging paradigm.
- Subjects categorized real and pseudo objects under conditions of high and low visual input.
- Analyzed neural activity, focusing on specific ERP components (N3, N400, P600, SW).
Main Results:
- Early ERP effects (N3, ~250 ms) localized to prefrontal and occipitotemporal cortex for real objects, indicating top-down PHT.
- Knowledge effects observed by 230 ms in occipitotemporal cortex.
- Later ERP components reflected semantic processing (N400), decision evaluation (P600), and response activity (SW).
Conclusions:
- The N3 component reflects critical top-down processes in PHT.
- A hybrid interactive model combining PHT and decision theory best explains visual object cognition.
- Neural activity patterns reveal distinct temporal stages of object processing, from initial perception to response execution.
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