Color from invisible patterns

Abstract

Human pattern resolution is limited by optical blurring as well as neural filtering by a cascade of retinal and cortical sites with progressively lower resolution limits. Curiously, pattern structure can influence perceived color: a high-contrast, monochromatic (single wavelength) pattern appears desaturated (closer to white) relative to a uniform field of the same wavelength. Here we show that this desaturation is evident even when the pattern's frequency is too high for conscious perception, implicating a nonlinear process--namely light adaptation--at the level of single cone photoreceptors. We propose a neural mechanism in which fast, involuntary eye movements serve to shift control over perception between two competing cone populations, each operating at different levels of adaptation.

Induction from a below-threshold chromatic pattern

“…Additionally, adaptation to a uniform disk flickering above the CFF, which appears as a steady field, can significantly reduce contrast sensitivity (Shady et al, 2004). A monochromatic grating too high in spatial frequency to be resolved can alter color appearance (Shady & MacLeod, 2002), and the orientation of a central patch can be altered by a surrounding grating even when the surround is not seen due to masking (Clifford & Harris, 2005). …”

“…Several studies demonstrate that stimuli either too fast (Shady, MacLeod, & Fisher, 2004) or too small (Shady & MacLeod, 2002) to be consciously perceived can nonetheless affect perception. A tentative conceptualization is that conscious perception is restricted to relatively late stages of neural processing (Carmel, Lavie & Rees, 2006).…”

Colour Vision: Primary Visual Cortex Shows Its Influence

“…Correctly categorising the context-modulated V1 cells is difficult because the taxonomy itself is under challenge. We now know that 'single-opponent' cells are probably not a distinct type at all, but rather one end of a parvocellular continuum, ranging from pure cone-opponent weightings to non-opponent weightings in which the center and surround have identical spectral sensitivities [11,12]. The 'double-opponent' cell, following its initial discovery thirty-odd years ago [13,14], disappeared under further scrutiny, and has only recently been revived [5,6,16].…”