Gender-related differences in physiologic color space: a functional transcranial Doppler (fTCD) study

Simultaneous color contrast and color constancy are memory processes associated with color vision [1-8], however, the gender-related differences of 'physiologic color space' remains unknown. Simultaneous color contrast is the phenomenon that surrounding colors profoundly influence perceived color [1,9]. The mechanism for simultaneous color contrast involves wavelength-differencing [10]. However, recently, it was suggested that, simultaneous color contrast involved wavelength-differencing in men [11], while in women, implicated frequency-differencing [12]. The latter study implemented functional transcranial Doppler spectroscopy (fTCDS) technique, which demonstrated the process of wavelength-encoding, whereby the effects of longer wavelength color (Yellow) was accentuated over shorter wavelength color (Blue). The converse process of energy-encoding accentuated the effects of higher frequency color (Blue), over lower frequency color (Yellow). Wavelength-differencing involves wavelength-encoding main effect at subcortical peaks, and energy-encoding effects at cortical peaks [11]. On the other hand, frequency-differencing involved energy-encoding main effect at cortical and subcortical peaks [12]. Beyond the physiologic evidence, genetic studies suggest gender-related differences in color vision in primates. Whereas both trichromatic and dichromatic color vision occurs among female monkeys, males appear exclusively dichromatic [13]. It was proposed that unlike humans, squirrel monkeys have only a single photopigment locus on the X chromosome [13]. The presumed genetic and psychophysiologic effects of the physical qualities of light underlie the proposal for light hypothesis of cerebral asymmetry [12].Color constancy relates to the invariance of hue, or perceived color of a surface under variation in the spectral content of illumination [3,14,15]. More specifically, color constancy refers to the unchanging nature of the perceived color of an object despite considerable v