Despite some disagreements that are not relevant to the issue, my discussion with r. norman (and others) has shown that, in essence, we agree that 1. INFORMATION IS TRANSMITTED FROM THE NEURAL CIRCUIT TO THE PINEAL CELLS (r.n. writes: "there is a sense of "information transfer" in all cell signaling, including the binding of a hormone or neurotransmitter to its receptor and the subsequent downstream pathway.") 2. Being generated by processing of the external stimulus, that INFORMATION IS EPIGENETIC (r.n. writes: "The nervous system computes something like "tell the pineal to go" or "don't tell the pineal to go".) 3. This EPIGENETIC INFORMATION CONTROLS THE EXPRESSION OF MELATONIN GENES in pineal cells (r.n.: "The nervous system computes something like "tell the pineal to go" or "don't tell the pineal to go".) My question in the original post was"Since the activation of these genes is not a random process, it requires information. Where does that information come from?") and we could agree that this epigenetic information comes from the neural circuit. Here is my second question: Is this epigenetic control of gene expression an isolated case (hence insignificant), or is it a general epigenetic mechanism of gene expression in animals?