Networks of neurons in the nervous system can produce a variety of temporal patterns of different frequency; the same network can produce different rhythms at different times, or several rhythms at one time. We focus here on the gamma (30-90 Hz) and theta (4-12 Hz) rhythms produced in the hippocampus, a part of the nervous system critical for learning and recall. We discuss experiments and mode...

Circadian rhythms of mammalian physiology and behavior are coordinated by the suprachiasmatic nucleus (SCN) in the hypothalamus. Within SCN neurons, various aspects of cell physiology exhibit circadian oscillations, including circadian clock gene expression, levels of intracellular Ca2+ ([Ca2+]i), and neuronal firing rate. [Ca2+]i oscillates in SCN neurons even in the absence of neuronal firing...

Drosophila melanogaster display overt circadian rhythms in rest:activity behavior and eclosion. These rhythms have an endogenous period of approximately 24 hr and can adjust or "entrain" to environmental inputs such as light. Circadian rhythms depend upon a functioning molecular clock that includes the core clock genes period and timeless (reviewed in and ). Although we know that a clock in the...

This essay discusses the relationship between the physiology of rhythms and potential functional roles. We focus on how the biophysics underlying different rhythms can give rise to different abilities of a network to form and manipulate cell assemblies. We also discuss how changes in the modulatory setting of the rhythms can change the flow of information through cortical circuits, again tying ...

Oscillators coupled in a network can synchronize with each other to yield a coherent population rhythm. If multiple such networks are coupled together, the question arises whether these rhythms will synchronize. We investigate the impact of noise on this synchronization for strong inhibitory pulse-coupling and find that increasing the noise can synchronize the population rhythms, even if the no...

Circadian rhythms in circulating leukocyte and lymphocyte counts persisted with halved amplitudes in constant light (LL) of 300 lx intensity for 8 wk, whereas circadian rhythms in body temperature, locomotor activity, and plasma catecholamines were completely suppressed. Subsequent exposure to constant darkness (DD) normalized all circadian rhythms within 2 wk. Rhythms in circulating T lymphocy...