Figure 9.3.

Phase response curve for a nocturnal animal in response to light pulses given at different times of day. This is an example of a phase response curve, where CT0–CT12 indicates the subjective day (light) for a nocturnal animal and CT12–CT24 is subjective night (dark). During the first 12 h (CT0–CT12) administering light pulses have no effect on phase of locomotor behavior in a nocturnal animal. In contrast, a light pulse given in the early subjective night (CT12–CT16) will produce phase delays in the onset of locomotor activity. Whereas, the same light pulse given between CT16–CT22 induces phase advances in the onset of locomotor activity. This example just provides repeatable behavioral evidence in mice demonstrating a time of day effect for the response to a defined light cue.