title: Motor cortex and corticospinal excitability in humans with a history of illicit stimulant use.
abstract: Illicit use of stimulant drugs such as methamphetamine, ecstasy, and cocaine is a current and growing problem throughout the world. The aim of the current study was to investigate the long-term effect of illicit stimulant use on human motor cortical and corticospinal circuitry. We hypothesized that individuals with a history of primarily methamphetamine and ecstasy use would exhibit altered corticospinal excitability and intracortical inhibition within motor cortex. The study involved 52 healthy adults (aged 26 ± 7 yr) comprising 26 abstinent stimulant users, 9 cannabis users, and 17 nondrug users. The experiment involved a routine urine drug screen, drug history questionnaire, neuropsychological assessment, and single- and paired-pulse transcranial magnetic stimulation (TMS) over motor cortex. EMG responses to stimulation [motor evoked potentials (MEPs)] were recorded from the contralateral first dorsal interosseus. At a given stimulus intensity, MEP area was significantly larger in abstinent stimulant users than in nondrug users during both relaxation (P = 0.045) and muscle contraction (P < 0.001). MEP latency was also significantly longer in abstinent stimulant users (P < 0.009), and they exhibited significantly greater muscle activity during performance of a given task (P = 0.004). However, resting motor threshold and the response to paired-pulse TMS were unaffected. The results suggest that abstinent stimulant users exhibit long-term changes in the excitability of motor cortical and corticospinal circuitry and muscle activity during movement. These changes may partly underlie anecdotal and objective reports of movement dysfunction in chronic stimulant users.
authors.affiliation: School of Pharmacy and Medical Sciences, Division of Health Sciences, University of South Australia, South Australia, Australia.
authors.forename: Stanley C
authors.initials: SC
authors.lastname: Flavel
authors.forename: Jason M
authors.initials: JM
authors.lastname: White
authors.forename: Gabrielle
authors.initials: G
authors.lastname: Todd
mesh_terms: D000293:Adolescent; D000328:Adult; D019969:Amphetamine-Related Disorders / Q000503:physiopathology; D000697:Central Nervous System Stimulants; D004576:Electromyography; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000503:physiopathology; D008694:Methamphetamine; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D018817:N-Methyl-3,4-methylenedioxyamphetamine; D011712:Pyramidal Tracts / Q000503:physiopathology*; D019966:Substance-Related Disorders / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
chemical_list: D000697:Central Nervous System Stimulants; D008694:Methamphetamine; D018817:N-Methyl-3,4-methylenedioxyamphetamine