Table 2.

Performance differences in the prefrontal cortex functioning tasks and the impulsivity scales between SDI and control subjects.

Tasks of prefrontal cortex functioning and impulsivity scales	Stimulant-dependent individuals (SDI)	Control subjects	T df = 27	p
	Mean	Mean
Tasks for Assessing Attentional Performance
Phasic alertness [index]	0.031	0.019	.456	.150
Focused attention [index]	6.86	7.11	.189	.667
2-back working memory [N valid reactions]	13.00	13.86	1.866	.090
Digit span forward [points]	7.93	10.13	1.995	.085
Digit span backward [points]	5.67	9.13	4.377	.023*
Barratt Impulsivity Scale (BIS)
Non-planning impulsivity	28.4	20.7	13.933	.0005*
Motor impulsivity	28.6	20.2	10.646	.002*
Attention/cognition impulsivity	17.9	14.1	7.403	.006*

^*significant difference with initial alpha level of .05. Bonferroni-adjusted for multiple tests (Digit span: p < 0.025; BIS: p < 0.0167)