Relationships of behavioral measures of frontal lobe dysfunction with underlying electrophysiology in cocaine-dependent patients.

BACKGROUND AND OBJECTIVES: Despite evidence that frontal lobe functioning is impaired in cocaine-dependent individuals, relationships between behavioral measures of frontal dysfunction and electrophysiological measures of inhibition in cocaine use have not been explored. METHODS: Using the Frontal Systems Behavior Scale (FrSBe), frontal dysfunction was assessed in a group of abstinent cocaine-dependent subjects (N = 49) and healthy controls (N = 32). Using transcranial magnetic stimulation (TMS) and evoked potential (EP)-based electrophysiological measures of inhibition, we assessed associations between these measures and FrSBe estimates of frontal dysfunction. RESULTS: Patients had significantly higher FrSBe scores for executive dysfunction, disinhibition, and apathy than controls. Lower TMS-based resting motor thresholds (ie, hyperexcitability) were significantly associated with higher executive dysfunction scores in the patients. CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE: Relationships between FrSBe scores and TMS-based measures highlight neurophysiological aberrations underlying frontal lobe dysfunction in cocaine abusers. TMS and EP measures may be useful probes of the intermediary steps between frontal lobe dysfunction and addictive behavior.