Winding the Clock: Development of Hypothalamic Structures Controlling Biological Timing and Sleep

The daily cycle of sleep and wake governs all aspects of behavior and is under tight homeostatic regulation. The core circadian oscillator in turn restricts sleep to specific intervals of the solar day. The neurons that regulate both sleep and circadian timing reside largely in the hypothalamus, and are linked in a complex, reciprocally connected, and still incompletely characterized network. While our knowledge of the neural circuitry controlling circadian rhythms and sleep has advanced considerably, our understanding of the mechanisms by which they are assembled during embryonic and postnatal development lag far behind. In this chapter, we review advances in the understanding of hypothalamic circuitry controlling circadian rhythms and sleep and our current knowledge of the gene regulatory networks that guide their development. In addition, we discuss the potential for future studies of hypothalamic development to provide new insights into the mechanisms by which animals regulate the timing and duration of sleep.