Dissertations, Theses, and Capstone Projects

Date of Degree

9-2025

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy

Program

Psychology

Advisor

Israel Abramov

Committee Members

Daniel Kurylo

Aaron Kozbelt

Subject Categories

Applied Behavior Analysis | Cognition and Perception | Cognitive Psychology | Experimental Analysis of Behavior

Keywords

STCSF. Chromatic CSF. Uniform Appearance Diagram (UAD). Magnocellular, Parvocellular, Koniocellular pathways. lateral geniculate nucleus (LGN)

Abstract

Contrast sensitivity (CS) measures the ability to discriminate objects from their backgrounds under varying conditions(Campbell & Robson, 1968). Contrast sensitivity is important for navigating the real world and operating under different light conditions. The contrast sensitivity function (CSF) reflects how the visual system performs under different conditions. This measure is crucial in assessing the health of the visual system (Chen & Gardner, 2021). CSF contributes to a deeper understanding of how the visual system processes and integrates properties of light to create visual sensation and perception. Human contrast sensitivity depends on the viewing conditions such as field size, luminance, color, pupil size, stimulus type, orientation, and temporal modulation (Abramov et al., 2012a; Barten, 2003; Kelly, 1983; Kim et al., 2013; Watson, 2000). This study examines how spatial and temporal frequencies interact with wavelength to determine human contrast sensitivity by linking psychophysical contrast sensitivity to underlying retinal magnocellular (M), parvocellular (P), and koniocellular (K) pathways. Six adults with normal vision completed three experiments: hue scaling of monochromatic patches (Gordon & Abramov, 1988), spatio-temporal contrast sensitivity functions (STCSFs) using the Quick CSF (qCSF) method (Lesmes, 2010), and hue scaling of monochromatic gratings. Hue scaling results transformed into the Uniform Appearance Diagram (UAD) showed expected chromatic organization and strong observer agreement (Abramov et al., 2012b). CSFs across achromatic and six colors showed classic band-pass form (Campbell & Robson, 1968). Green (505 – 515 nm) peaked at higher spatial frequencies ~2 cycles per degree (cpd) than blue (465 – 475 nm) and yellow (575 – 585 nm), ~1.4 – 1.8 cpd, respectively. Achromatic gratings retained the strongest sensitivity, particularly at higher temporal modulation. Increasing temporal frequency from 1 to 8 Hz, shifted the CSFs toward lower spatial frequencies, and reduced high-frequency sensitivity. CSF using achromatic gratings showed relatively increased sensitivity under 8 Hz temporal modulation, which is consistent with M-pathway dominance (Petrova et al., 2013). Green (parvocellular-weighted) gratings yielded finer spatial detail when temporal modulation was low. 475 nm blue produced the weakest sensitivity among stimuli, particularly at high spatial frequencies and when temporal modulation increased. Hue scaling of patches at varying temporal frequencies (1–8 Hz) and spatial frequencies (1, 5, 20 cpd) revealed that UAD coordinate shifts were minimal and participants’ saturation scalings were similar. This indicates that the color appearance of the monochromatic sinusoidal gratings remained stable and did not significantly change under different spatial and temporal modulations. These findings suggest that spatio-temporal CSFs are shaped by cone weighting. The current study shows that the overall shape of the CSF depends on different pathway contributions. M pathway dominates high-flicker luminance contrast, where P pathway supports fine spatial detail, and K pathway contributes weakly under these experimental conditions. By combining contrast sensitivity with hue scaling (Abramov et al., 2012a, 2012b), this study links color appearance to spatial vision. It provides deeper insight into how wavelength and luminance interact to influence contrast sensitivity between two temporal modulation rates.

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