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The time course of different surround suppression mechanisms
Michael-Paul Schallmo1,2, Alex M Kale1, Scott O Murray1
1Department of Psychology, University of Washington, Seattle, WA, USA.
Journal of Vision
|April 6, 2019
Summary
Visual perception is influenced by spatial context. This study reveals two distinct neural mechanisms for surround suppression in the human visual cortex, identified using electroencephalography (EEG) and differing in their timing and orientation tuning.
Area of Science:
- Neuroscience
- Visual Perception
- Cognitive Science
Background:
- Perceived contrast is modulated by surrounding visual stimuli, a phenomenon known as surround suppression.
- Previous research suggests at least two distinct neural mechanisms underlie surround suppression: a low-level and a higher-level mechanism.
- These mechanisms differ in their response characteristics and tuning properties.
Purpose of the Study:
- To investigate the presence and characteristics of two separable neural mechanisms of surround suppression in the human visual system.
- To differentiate these mechanisms using electroencephalography (EEG) based on their temporal and orientation-specific response patterns.
- To provide electrophysiological evidence for distinct neural pathways involved in visual context processing.
Main Methods:
- Utilized electroencephalography (EEG) to record neural responses in 18 adult participants.
- Presented visual stimuli (center and surround gratings) under varying conditions: monoptic (same eye) and dichoptic (opposite eye) presentation, with parallel or orthogonal surround orientations.
- Analyzed early (C1 component, ~60 ms) and later (N1 component, ~160 ms) event-related potential (ERP) components to assess suppression characteristics.
Main Results:
- The earliest cortical response (C1 component) showed suppression irrespective of surround orientation, suggesting a non-orientation-tuned, low-level mechanism.
- A later response component (N1 component) exhibited stronger suppression for parallel and monoptic surrounds, indicating a binocular, orientation-tuned, higher-level mechanism.
- These findings demonstrate distinct temporal profiles for the two surround suppression mechanisms.
Conclusions:
- The human visual system employs at least two distinct neural mechanisms for surround suppression, operating at different stages of visual processing.
- These mechanisms are differentiated by their response latencies and tuning properties (orientation and binocularity).
- Electrophysiology, specifically EEG, is a valuable tool for dissociating these distinct neural processes in visual perception.
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