Effects of alcohol on TMS-evoked N100 responses.
TMS combined with simultaneous EEG is a novel brain imaging tool allowing investigation local excitability of human cortex. As alcohol acts through increasing function of A-type gamma-aminobutyric acid receptors and attenuating the function of glutaminergic NMDA-receptors-related excitation, we tested whether TMS-evoked N100 response which is thought to reflect cortical inhibitory processes, might be affected by alcohol. Ten healthy subjects ingested alcohol (0.8 g/kg) and EEG responses from 60 channels before and after alcohol ingestion were recorded after left motor-cortex stimulation. Alcohol almost abolished TMS-evoked N100 response. Control experiments with a piece of plastic placed between the head and coil to exclude auditory artefacts were conducted. Alcohol effects were similar when EEG responses from control experiments were subtracted from real-TMS. Alcohol-induced decrease was similar at ipsilateral, contralateral and frontal EEG sites suggesting that alcohol may change cortico-cortical connectivity of motor cortex. Alternative explanation is that alcohol has overall suppression effect on motor cortex. N100 may provide a useful marker of neural inhibition of human cortex for drug research.
Kähkönen
Seppo
S
BioMag Laboratory, Helsinki University Central Hospital, Finland. seppo.kahkonen@helsinki.fi
Wilenius
Juha
J
D000328:Adult; D015415:Biomarkers / Q000032:analysis; D001931:Brain Mapping / Q000379:methods; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D004566:Electrodes / Q000592:standards; D004569:Electroencephalography / Q000379:methods; D000431:Ethanol / Q000494:pharmacology*; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology; D019054:Evoked Potentials, Motor / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000187:drug effects* / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects* / Q000502:physiology; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D011963:Receptors, GABA-A / Q000187:drug effects / Q000378:metabolism; D050781:Transcranial Magnetic Stimulation / Q000379:methods*
D015415:Biomarkers; D002492:Central Nervous System Depressants; D011963:Receptors, GABA-A; D000431:Ethanol