Phototransduction for human melatonin suppression.

Human adult males were exposed to combinations of two illuminances and two broadband spectral power distributions over the course of four night-time sessions. Results showed that melatonin suppression is dominated by short visible wavelengths (420-520 nm), consistent with recently published studies. Although the authors of these recent studies suggest that a novel opsin underlies melatonin suppression, the present paper offers a more conservative interpretation of the data based on what is known about existing photoreceptors and associated neuroanatomy and neurophysiology.