Figure 2. Double-plotted actograms illustrating alteration of circadian expression of locomotor activity in constant light (LL) in an untreated control and in 5 MPTP treated animals in addition to that shown in Figure 1.

Note that while daily locomotor rest activity rhythms are observed for all animals during the LD cycle preceding and subsequent to LL. In MPTP-treated animals the circadian rhythm of locomotor activity was strongly altered (D, E, F) or abolished (B, C) in LL. C and F were highly symptomatic cases, D and E were mildly symptomatic and B was asymptomatic. The dark phase is shown by shaded areas and light phase by light areas.