Ethanol modulates cortical activity: Direct evidence with combined TMS andEEG

The motor cortex of 10 healthy subjects was stimulated by transcranial magn etic stimulation (TMS) before and after ethanol challenge (0.8 g/kg resulti ng in blood concentration of 0.77 +/-0.14 ml/liter). The electrical brain a ctivity resulting from the brief electromagnetic pulse was recorded with hi gh-resolution electroencephalography (EEG) and located using inversion algo rithms. Focal magnetic pulses to the left motor cortex were delivered with a figure-of-eight coil at the random interstimulus interval of 1.5-2.5 s. T he stimulation intensity was adjusted to the motor threshold of abductor di giti minimi. Two conditions before and after ethanol ingestion (30 in) were applied: (1) real TMS, with the coil pressed against the scalp; and (2) co ntrol condition, with the coil separated from the scalp by a 2-cm-thick pie ce of plastic. A separate EMG control recording of one subject during TMS w as made with two bipolar platinum needle electrodes inserted to the left te mporal muscle. In each condition, 120 pulses were delivered. The EEG was re corded from 60 scalp electrodes. A peak in the EEG signals was observed at 43 ms after the TMS pulse in the real-TMS condition but not in the control condition or in the control scalp EMG. Potential maps before and after etha nol ingestion were significantly different from each other (P = 0.01), but no differences were found in the control condition. Ethanol changed the TMS -evoked potentials over right frontal and left parietal areas, the underlyi ng effect appearing to be largest in the right prefrontal area. Our finding s suggest that ethanol may have changed the functional connectivity between prefrontal and motor cortices. This new noninvasive method provides direct evidence about the modulation of cortical connectivity after ethanol chall enge. (C) 2001 Academic Press.