Frequency ratio determines discrimination of concentric radial frequency patterns in the peripheral visual field
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Frequency ratio determines discrimination of concentric radial frequency patterns in the peripheral visual field Yang Feng 1,2 & Qiong Wu 1,3 & Jiajia Yang 3 & Satoshi Takahashi 3 & Yoshimichi Ejima 3 & Jinglong Wu 3,4 & Ming Zhang 1,3,5
# The Psychonomic Society, Inc. 2020
Abstract Using a radial frequency discrimination task that has not been tested in many previous studies, we examined the dependence of the pattern radius (4 to 16 deg) on the radial frequency thresholds of two different types of concentric radial frequency (RF) patterns: constant circular contour frequency (CCF) RF patterns with different radii, which have the constant physical length of modulation cycle in external real-world space, and constant radial frequency magnified RF patterns with different radii, which have the constant cortical length of modulation cycles. These two types RF patterns used as the reference stimuli had an equal maximum orientation difference from circularity regardless of change in radius. The discrimination threshold expressed by the frequency ratio between RF patterns of different frequencies vs. radius functions for the constant CCF RF patterns indicated different functional forms dependent on the modulation amplitude of the RF patterns. The thresholds increased with increasing pattern radius for small modulation amplitude RF patterns but were relatively flattened for large-amplitude RF patterns. This dependence was ascribed to the eccentricity effect wherein the deformation thresholds for discriminating the RF pattern from a circle increase with increasing stimulus eccentricity (Feng et al. 2020). The discrimination thresholds vs. radius functions for the magnified RF patterns were also flattened for different modulation amplitudes and frequencies. The thresholds (frequency ratio) were similar at all eccentricities. Cortical magnification neutralized the eccentricity effect observed for the constant CCF patterns. Keywords Concentric radial frequency pattern . Eccentricity effect . Discriminability . Frequency ratio . Orientation ratio . Retinocortical mapping . Discrimination task
Introduction Radial frequency (RF) patterns, which were introduced by Wilkinson, Wilson, and Habak (1998), have frequently been Yang Feng and Qiong Wu were co-first authors * Qiong Wu [email protected] * Ming Zhang [email protected] 1
Department of Psychology, Suzhou University of Science and Technology, Suzhou, China
2
Biomedical Engineering Laboratory, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
3
Cognitive Neuroscience Lab. Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, 3-1-1 Tsushima-naka, Okayama, Japan
4
Beijing Institute of Technology, Beijing, China
5
Department of Psychology, Soochow University, Suzhou, China
used to investigate aspects of shape processing. The simple mathematical definition of RF patterns has made RF patterns a popular stimulus in psychophysical, physiological, and imaging studies (Wilkinson et al., 2000;
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