Elevated motor threshold in drug-free, cocaine-dependent patients assessedwith transcranial magnetic stimulation

Background: Transcranial magnetic stimulation (TMS) provides a noninvasive method of examining cortical inhibitory and excitatory processes and cortic al excitability in awake subjects. There is evidence from clinical and elec troencephalographic (EEG) data that cortical excitability may be abnormal i n some psychiatric populations. Chronic cocaine abuse influences a number o f neurotransmitters that are involved in the excitatory/inhibitory balance of the cerebral cortex. This pilot study was conducted to ascertain the pos sible utility of TMS in examining cortical excitability in a population of chronic cocaine abusers. Methods: The right and left motor thresholds of ten cocaine-dependent subje cts, according to DSM-IV, and ten normal control subjects were examined usi ng single pulse TMS. Results: The resting motor thresholds resulting from stimulation of the rig ht or the left motor cortical regions were significantly elevated in cocain e-dependent subjects compared with matched control subjects. Conclusions: These pilot data suggest that chronic cocaine use significantl y alters cortical excitability in the direction of increased inhibition or decreased excitability, We hypothesize that this observation reflects adapt ation to those effects of cocaine intoxication that promote cortical excita bility and seizures., (C) 2001 Society of Biological Psychiatry.