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The processing of compound radial frequency patterns
Gunnar Schmidtmann1, Frederick A A Kingdom2, Gunter Loffler3
1Eye & Vision Sciences Research Group, School of Health Professions, University of Plymouth, Plymouth, Devon, England, United Kingdom.
Vision Research
|May 15, 2019
Summary
Complex shapes are perceived by combining radial frequency (RF) patterns. Our study shows additive summation, not just probability summation, suggesting efficient combination of RF components by a single noise-limited mechanism.
Area of Science:
- Visual perception
- Computational neuroscience
Background:
- Complex visual shapes can be constructed by combining radial frequency (RF) patterns.
- Previous research suggests that the brain may encode these complex shapes using multiple, narrowly-tuned RF shape channels.
Purpose of the Study:
- To test the hypothesis that complex RF shapes are encoded by multiple, narrowly-tuned channels.
- To investigate the summation mechanisms underlying the detection and discrimination of combined RF components.
Main Methods:
- Measured detection and discrimination thresholds for combinations of two RF components.
- Compared empirical data against predictions from various models: winner-take-all, single-channel additive summation (AS), and multi-channel probability summation (PS) and AS models.
- Evaluated multi-channel models under Fixed and Matched Attention Window scenarios.
Main Results:
- Sensitivity for compound RF patterns was significantly better than for individual components, indicating summation.
- Summation effects exceeded predictions of probability summation (PS), suggesting additive summation (AS) via a common mechanism.
- Winner-take-all and single-channel models were rejected based on the data.
Conclusions:
- The findings support a model where detection of combined RF patterns involves channels that are efficiently combined.
- The best-performing model was an additive summation (AS) model with a Fixed Attention Window.
- This suggests that RF component detection is limited by a single source of internal noise for both components and compounds.
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