Group data showing the amplitude of tremor in the pathological frequency range (3.9–6.6 Hz).

<p> The amplitude of tremor (i.e. power in the fast Fourier transform) for the ecstasy, amphetamine, cannabis, and control groups are shown. A) Mean power in self-paced movement. B) Peak power in self-paced movement. C) Mean power in auditory-paced movement. D) Peak power in auditory-paced movement. *Significantly different from control group (P = 0.034).