Within task exploratory analysis
In the Oddball task (Figure 9A) alcohol induced changes to SPN amplitude
(illustrated with upward arrow in the ERP inset) correlated with
participant’s self-reported drinking behaviour (AUDIT) (r = -0.59, p =
.002). Alcohol reduced the SPN in participants who drink less, but
increased the SPN in participants who drink more. The same trend was
present, but non-significant, in the Regularity task (r = -19, p =
.347). In the Oddball task, alcohol induced subjective light-headedness
correlated with alcohol induced P300 reduction. The direction of this
effect is surprising: Participants who were more subjectively affected
by alcohol bucked the overall trend for alcohol to reduce P300. However,
this was driven by two anomalous participants, with usually high alcohol
induced light-headedness.
In the Regularity Task (Figure 9B), alcohol induced change in
behavioural performance negatively correlated with alcohol induced
change in N1 drop. Also in the Regularity task, alcohol induced changes
in behavioural performance correlated with alcohol induced changes in
subjective alertness.
We should emphasize that the variables in the correlation analyses were
differences between alcohol and placebo conditions. We can also run the
same analysis with amplitude averaged across alcohol and placebo
conditions. Although the literature suggests N1 and P300 components are
altered by chronic drinking, there was no evidence that amplitude of any
of our ERP components correlated with AUDIT, and no other correlations
were significant at the 0.01 level (see supplementary materials on SPN
catalogue /Project 43).