Abstract
BACKGROUND: How the biophysics of electrical conductivity measures relate to brain activity is poorly understood. The sedative, ethanol, reduces metabolic activity but its impact on brain electrical conductivity is unknown. PURPOSE: To investigate whether ethanol reduces brain electrical tissue conductivity. STUDY TYPE: Prospective. SUBJECTS: Fifty-two healthy volunteers (aged 18-37 years, 22 females, 30 males). FIELD STRENGTH/SEQUENCE: 3 T, T1-weighted, multi-shot, turbo-field echo (TFE); 3D balanced fast-field echo (bFFE). ASSESSMENT: Brain gray and white matter tissue conductivity measured with phase-based magnetic resonance electrical properties tomography (MREPT) compared before and 20 minutes after ethanol consumption (0.7 g/kg body weight). Differential conductivity whole brain maps were generated for three subgroups: those with strong ( ∆σmax > 0.1 S/m; N = 33), weak (0.02 S/m ≤ ∆σmax ≤ 0.1 S/m; N = 9) conductivity decrease, and no significant response ( ∆σmax < 0.02 S/m, N = 10). Maps were compared in the strong response group where breath alcohol rose between scans, vs. those where it fell. STATISTICAL TESTS: Average breath alcohol levels were compared to the differential conductivity maps using linear regression. T-maps were generated (threshold P < 0.05 and P < 0.001; minimum cluster 48 mm(3)). Differential conductivity maps were compared with ANOVA. RESULTS: Whole-group analysis showed decreased conductivity that did not survive statistical thresholding. Strong responders (N = 33) showed a consistent pattern of significantly decreased conductivity ( ∆σmax > 0.1 S/m) in frontal/occipital and cerebellar white matter. The weak response group (N = 9) showed a similar pattern of conductivity decrease (0.02 S/m ≤ ∆σmax ≤ 0.1 S/m). There was no significant relationship with breath alcohol levels, alcohol use, age, ethnicity, or sex. The strong responders' regional response was different between ascending (N = 12) or descending (N = 20) alcohol during the scan. DATA CONCLUSION: Ethanol reduces brain tissue conductivity in a participant-dependent and spatially dependent fashion. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 2.