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. 2014 Jan 23;9(1):e86240. doi: 10.1371/journal.pone.0086240

Figure 6. MPTP-treated monkeys show normal masking responses to darkness in a 1 h light–1 h dark regime.

Figure 6

The control monkey (A) shows a clear 24 h rhythmicity coupled with a strong masking effect of darkness on locomotor activity. MPTP-treated monkeys show attenuated amplitude of the rhythm (B, mildly symptomatic, C, highly symptomatic) but nevertheless a strong masking effect of darkness proportionately similar to that of controls. (D) Mean relative total activity during light and dark phases. (E) Amplitude of the rhythm analysed separately for light and dark phases (controls n = 4; MPTP n = 5). *P<0.05, **P<0.001.