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).</p

Experimental apparatus and acceleration traces from one subject.

<p>A) Experimental apparatus. B) Raw acceleration trace during relaxation. C) Result of the fast Fourier transform during relaxation. D) Flexion and extension of the index finger with the accelerometer attached. E) Raw acceleration trace during self-paced movement. F) Result of the fast Fourier transform during self-paced movement.</p

Classes of illicit drugs consumed in the ecstasy, amphetamine, and cannabis groups.

<p>Data are percentage of subjects that have consumed the class of illicit drug in their lifetime. The term ‘hallucinogen’ describes LSD (lysergic acid diethylamide), LSA (d-lysergic acid amide), ‘magic’ mushrooms, DOI (2,5-dimethoxy-4-iodoamphetamine), and/or mescaline. The term ‘opiate’ describes heroin, methadone, opium, and recreational use of codeine, oxycodeine, and/or morphine (total use <3 occasions per subject). The term ‘inhalant’ describes amyl nitrate, ethyl chloride, and/or nitrous oxide. The term ‘sedative’ describes recreational use of benzodiazepine.</p

Subject characteristics for the control, stimulant, and cannabis groups.

<p>Data are mean±standard deviation.</p>*<p>Significantly different from control group (P<0.05).</p>§<p>Significant difference between cannabis group and the ecstasy or methamphetamine groups (P<0.05).</p

Illicit stimulant use is associated with abnormal substantia nigra morphology in humans.

Use of illicit stimulants such as methamphetamine, cocaine, and ecstasy is an increasing health problem. Chronic use can cause neurotoxicity in animals and humans but the long-term consequences are not well understood. The aim of the current study was to investigate the long-term effect of stimulant use on the morphology of the human substantia nigra. We hypothesised that history of illicit stimulant use is associated with an abnormally bright and enlarged substantia nigra (termed 'hyperechogenicity') when viewed with transcranial sonography. Substantia nigra morphology was assessed in abstinent stimulant users (n = 36; 31±9 yrs) and in two groups of control subjects: non-drug users (n = 29; 24±5 yrs) and cannabis users (n = 12; 25±7 yrs). Substantia nigra morphology was viewed with transcranial sonography and the area of echogenicity at the anatomical site of the substantia nigra was measured at its greatest extent. The area of substantia nigra echogenicity was significantly larger in the stimulant group (0.273±0.078 cm(2)) than in the control (0.201±0.054 cm(2); P<0.001) and cannabis (0.202±0.045 cm(2); P<0.007) groups. 53% of stimulant users exhibited echogenicity that exceeded the 90(th) percentile for the control group. The results of the current study suggest that individuals with a history of illicit stimulant use exhibit abnormal substantia nigra morphology. Substantia nigra hyperechogenicity is a strong risk factor for developing Parkinson's disease later in life and further research is required to determine if the observed abnormality in stimulant users is associated with a functional deficit of the nigro-striatal system

Maximum rate of change in force (i.e. maximum derivative of force) during the lift phase.

<p>A–C) Group data (mean ± sem) for grip force (black symbols) and lift force (white symbols) in trials one to three for the A) non-drug control group, B) stimulant group, and C) cannabis group. D–F) Single-subject data showing the relationship between peak grip force and maximum rate of change in grip force in the D) non-drug control group, E) stimulant group, and F) cannabis group. Solid line shows result of linear regression analysis (P<0.001).</p

Experimental apparatus used in task one (total weight 0.342 kg).

<p>The index finger and thumb contacted the test object on two polished brass disks positioned 35<i> </i>mm apart.</p

Subject characteristics for the control, stimulant, and cannabis groups.

<p>Subject characteristics for the control, stimulant, and cannabis groups.</p

Group data (mean ± sem) for peak force measured in the lift phase.

<p>Peak grip force (black symbols) and lift force (white symbols) are shown for trials one to three. A) Non-drug control group. B) Stimulant group. C) Cannabis group. * Significantly different from non-drug control group (P = 0.022) and cannabis group (P = 0.013).</p