Table 5.

Brain activation amplitude differences between the ADHD-NONE taxometrically- determined subgroup and non-ADHD. The table lists Montreal Neurological Institute stereotactic space coordinates of peak study group difference for each cluster that was found to be significant in two-sample t test (p<.001 corrected for searching the whole brain). Results are reported for motor inhibition and error processing on the Go/NoGo task and reward prospect and reward anticipation for the Monetary Incentive Delay task. For each brain region, the Cohen’s d effect size is depicted using sparkline graph to facilitate comparison of ADHD subgroup differences with non-ADHD. The final columns report omnibus F significance p levels from a secondary ANOVA comparing the ADHD subgroups. Subgroup ANOVA-identified regions that survive False Discovery Rate corrections for multiple comparisons are denoted with ^†.

	Max Peak x, y, z	t	Effect Size Pattern*	ADHD Subgroup ANOVA	ADHD Subgroup Activation Level Pairwise
Motor Inhibition HC > ADHD-NONE
Left caudate	−6, 17, 2	2.91		.010 †	EF, NONE < REW/EF
Motor Inhibition ADHD-NONE > HC
Cerebellum (X)	−3, −43, -37	4.26		.101	-

^*For sparkline graphs, the initial grey datapoint represents the Cohen’s d effect size from a supplemental two-sample t test that compared non-ADHD to all of the ADHD participants. Afterwards, subgroups ADHD¹, ADHD², and ADHD³ are depicted. All sparkline values on this table are scaled relative to the maximum Cohen’s d=1.01 found across all four fMRI task conditions for the ADHD³ subgroup.