Table 1.

Mean circadian period (± SEM) as determined by chi square periodogram analysis (significance level p=0.01) for each experimental group during different phases of the experiment. In the two groups of animals pre-exposed to methamphetamine (Meth pre-exposure), most rats displayed activity rhythms during methamphetamine pre-exposure that were split into two distinct components; a 24 hour component (∼24:) and a long period (L:) component. The other animals displayed either a 24-hour period or a long period. Likewise, in the two groups exposed to chronic jet lag (CJL), activity rhythms were often split into two components; a short period component (S:) and a long period component, while the remaining animals displayed either a short period or long period rhythms. Values under the Transients heading show free-running circadian period during the time following the chronic jet lag treatment when the activity rhythm is in the process of entraining to the final light:dark cycle. Values under Post-Transient show the activity rhythm period following stable entrainment to the final light:dark cycle.

	Baseline	Meth pre-exposure		Chronic Jet Lag (CJL)		Transients	Post-Transient
Meth CJL	24.00±0.01 (n=8/8)	24.07 (n=1/8)	L: none	S: 23.38 ±0.70* (n=2/8)	L: 24.42±0.17* (n=2/8)	23.67 ±0.26 (n=8/8)	23.98 ±0.01 (n=8/8)
		∼24: 23.99±0.03		S: 22.76 ±0.39*
		L: 26.67 ±0.31*		L: 25.15 ±0.26*
		(n=7/8)		(n=4/8)
Meth No CJL	23.99±0.01 (n=8/8)	24.15±0.15 (n=2/8)	L: 24.67 ±0.08* (n=2/8)	23.97 ±0.02 (n=8/8)	n/a	n/a	23.98 ±0.01 (n=8/8)
		∼24: 24.07±0.07
		L: 27.81 ±1.11*
		(n=4/8)
Water CJL	24.01±0.01 (n=8/8)	23.97±0.01 (n=8/8)	n/a	S: 23.10 ±0.06* (n=3/8)	L: none	23.36 ±0.21 (n=8/8)	24.01 ±0.01 (n=8/8)
				S: 23.04 ±0.19*
				L: 25.12 ±0.07*
				(n=5/8)
Water No CJL	23.99±0.01 (n=8/8)	24.01+0.01 (n=8/8)	n/a	24.00 ±0.01 (n=8/8)	n/a	n/a	24.00 ±0.00 (n=8/8)

^*indicates significant difference from baseline period, Student's t-test, p <0.05.