Figure 3.

A model for cell–cell interactions that promote precision of behavioral rhythms and morning and evening activity. A highly simplified view of the clock neural circuit involving two neurons. Each cell has a functional clock that helps drive rhythmic neuronal signals. The morning (light gray) neuron promotes morning activity, and its output signals also modify the phase of the evening (dark gray) neuron. Similarly, signals from the evening neuron regulate both evening activity and input to the morning neuron. The behavioral output signals and the input signals to the other neuron could either be the same or they could be different.