台大心理系

A recent study has shown that the intrinsically photoreceptive retinal ganglion cells (ipRGCs: melanopsin cells) play an important role for encoding ambient illuminance. The stimulation of melanopsin cells is associated with many physiological and psychophysical responses induced by light, such as pupil response, sleep, migraine pain, seasonal affective disorder. Therefore it is very important to investigate how a modulation of melanopsin cells influences a luminance and colour perception. A personal computer controlled the four-primary illumination system, which allowed us to generate stimuli that independently modulate melanopsin, and three types of cones. Four different types of light-emitting diode were used. The annular ring test stimulus was superposed on the circular adaptation field using a beam splitter. A detailed description of the illumination system has previously been published (Tsujimura et al, Proc Biol Sci., 2010; Brown et al, Curr. Biol., 2012). In the experiment we measured a contrast sensitivity function, flicker detection and colour discrimination. The following two types of test stimuli were presented in the measurement of contrast sensitivity function: one varying L-, M- and S-cone stimulation without change in stimulation of melanopsin cells (cone stimulus) and another varying radiant flux of the stimuli without change in spectral composition which reduced/increased the radiant flux uniformly at all wavelengths (light flux stimulus). It was found that the two thresholds were different at low temporal frequency less than 5 Hz whereas the thresholds were almost the same at high temporal frequency. These results indicated that the melanopsin cells play an important role in visual performance. Influence of melanopsin cells on the variable visual attributes that illustrates the benefits of understanding image- and non-image forming functions will be presented.