The central role of the SCN as light-entrainable oscillator is well documented. The light signal, through the retinohypothalamic tract (RHT), exerts critical control over SCN neurons. Accumulating findings indicate the presence of a food-entrainable oscillator (FEO), probably in either the dorsomedial hypothalamus (DMH) or the ventromedial hypothalamus(VMH), as well as a methamphetamine-sensitive oscillator, which could be localized in the ventral tegmental area (VTA). The functional relationships and circuitry interplay among these centers remains unexplored.