Relationship between ethanol-induced changes in brain regional metabolism and its motor, behavioural and cognitive effects.

AIMS AND METHODS Acute alcohol administration induces marked decreases in glucose metabolism throughout the human brain. However, the relationship between alcohol's effects on brain metabolism and the behavioural changes that occur with intoxication are still unclear. Here we assessed this association using principal component analysis for dimension reduction and canonical correlations to gauge inter-class relationships. We also used canonical correlations in the polynomial space to assess for possible nonlinear relationships. RESULTS After normalizing the regional measures to account for the large whole brain decreases observed with intoxication we show that the largest decreases occurred in occipital cortex and that there were relative increases in basal ganglia. Principal component analysis of the changes in the normalized measures revealed that 60% of the variance was accounted for by two factors; one that contrasted cerebellum versus frontal and anterior cingulate metabolism, and another that contrasted basal ganglia and insula. The square of the first factor was significantly correlated with the deterioration in cognitive performance. The second factor showed a significant linear correlation with self-reports of intoxication and with deterioration in cognitive and motor performance. CONCLUSIONS These findings suggest that the contrasting effects of alcohol in basal ganglia versus the insula are involved in the perception of 'feeling drunk' and that its contrasting effects in cerebellum versus those in frontal and parietal cortices are involved in its motor incoordinating effects. On the other hand alcohol's impact on cognitive performance implicates a more complex pattern of brain effects that includes linear as well as non-linear associations.