Perceptual anisotropies in visual processing and their relation to natural image statistics

Area of Science:

• Visual perception
• Image processing
• Computational neuroscience

Background:

• Natural scenes exhibit orientation bias in amplitude spectra, linked to the oblique effect.
• Previous research showed a 'horizontal effect' with complex noise patterns, where oblique orientations yield higher sensitivity.
• The role of phase spectra in orientation sensitivity for natural scenes remains less understood.

Purpose of the Study:

• To investigate the 'horizontal effect' in relation to the phase spectra of natural scenes.
• To determine if predominant scene content, carried by Fourier phase, affects the detection of oriented amplitude increments.
• To analyze how both amplitude and phase manipulations interact within natural scene perception.

Main Methods:

• Natural scene images were manipulated for orientation bias in both amplitude and phase spectra.
• Sensitivity for detecting oriented amplitude increments was measured across different scene content biases.
• Experiments involved stimuli with predominant structure at cardinal and oblique orientations.
• Results were analyzed within a divisive normalization model framework.

Main Results:

• The 'horizontal effect' was consistently observed, irrespective of the scene's inherent content bias.
• A content-dependent effect was identified, suggesting phase spectra influence amplitude detection.
• Sensitivity for detecting oriented amplitude changes varied based on the interplay between scene content and stimulus manipulation.

Conclusions:

• The 'horizontal effect' is a robust feature of visual sensitivity, extending to natural scenes with complex phase information.
• Natural scene content, conveyed by phase spectra, modulates but does not abolish orientation-dependent sensitivity.
• Divisive normalization models may need refinement to fully account for these content-dependent effects in visual perception.