Effect of ethanol on BOLD response to acoustic stimulation: implications for neuropharmacological fMRI

The effects of ethanol on acoustically stimulated blood oxygenation level-d ependent (BOLD) signal response in healthy humans was examined with echo pl anar functional magnetic resonance imaging (fMRI). An acquisition mode mini mizing neuronal activation by scanner noise in combination with acoustic ex citation by a pulsed 1000-Hz sine tone was used. Paradigms were repeated th ree times before and after the ingestion of 0.7 g of ethanol/kg(body weight ) Linear correlation analyses (r greater than or equal to 0.40) revealed bi lateral BOLD responses in the auditory cortex. Significant voxels covered a cortical volume of similar to 3 mi that was reduced by similar to 40% afte r ethanol. The BOLD signal change initially reaching similar to 3% was redu ced by 12-27%, depending on the definition of the region of interest for si gnal quantitation. Because ethanol produces vasodilation, the hemodynamic c ontribution to the BOLD signal change was estimated by modeling the relatio nship between regional cerebral blood flow (rCBF) and BOLD signal changes. Assuming a baseline flow increase by 10% after ethanol intake, the resultin g 'Flow-BOLD-Dependence' (FBD) curve suggested that the ethanol-related BOL D signal reduction was similar to 7-12% greater than the reduction contribu ted purely by vasodilation. However, simultaneous determination of rCBF and regional cerebral blood volume would be: required for an exact quantitatio n of the neuronally induced BOLD response. Although the FED model needs emp irical validation, its cautious implementation appears to be helpful if fMR I is used in combination with vasoactive drugs. (C) 2000 Elsevier Science I reland Ltd. All rights reserved.