1. ¹BioMag Laboratory, Engineering Centre, Helsinki University Central Hospital, Helsinki, Finland
2. ²Cognitive Brain Research Unit, University of Helsinki, Helsinki, Finland
3. ³Nexstim Ltd, Helsinki, Finland
4. ⁴Helsinki Brain Research Center, Helsinki, Finland

Correspondence: Dr S Kähkönen, BioMag Laboratory, Helsinki University Central Hospital, PO Box 340, FIN-00029 HUS, Finland. Tel: +1 358 9 47175542; Fax: +1 358 9 47175781; E-mail: seppo.kahkonen@helsinki.fi

Received 26 April 2002; Revised 11 October 2002; Accepted 18 October 2002.

Abstract

The effects of alcohol (0.8 g/kg) on the prefrontal cortex were studied in nine healthy subjects using the technique of transcranial magnetic stimulation (TMS) combined with electroencephalography (EEG). A total of 120 magnetic pulses were delivered with a figure-of-eight coil to the left prefrontal cortex at the rate of 0.4–0.7 Hz. The EEG was recorded simultaneously with 60 scalp electrodes (41 electrodes were used for analysis); the TMS-evoked activation was estimated by the area under the global mean field amplitude (GMFA) time curve. TMS caused changes in EEG activity lasting up to 270 ms poststimulus. Alcohol decreased GMFA at 30–270 ms poststimulus (713303 vs 478142 V ms; p=0.007). Alcohol-induced differences were most pronounced at anterior electrodes. These results suggest that alcohol reduces the excitability in the prefrontal cortex.