The 'internal clocks' of circadian and interval timing.

Animals engage in a startlingly diverse array of behaviours that depend critically on the time of day or the ability to time short intervals. Timing intervals on the scale of many hours to around a day is mediated by the circadian timing system, while in the range of seconds to hours a different system, known as interval timing, is used. Recent research has illuminated some of the neural mechanisms underlying the 'internal clocks' of these two different timing systems in both animals and humans. Therapeutic applications for humans with impairments in either timing system may ultimately result from these endeavours.