The Iowa Gambling Task (IGT) is a measure of decision-making, in which alternative metrics have greater construct validity than conventional metrics. No large scale study has examined the neural correlates in healthy adults. We administered the IGT and structural MRI to 124 healthy participants. We analyzed the conventional IGT metric of advantageous minus disadvantageous choices (i.e., decks C + D minus decks A + B), and three alternative metrics based on choices from decks D and A alone, and all selections from each deck. Using regression and voxel-based morphometry, we examined regional gray matter volumes as predictors of IGT performance. No neural correlates of the conventional metric emerged, and the neural correlates of individual deck selections were disparate from one another. Alternative metrics showed expected neural correlates of decision-making in prefrontal cortex, insula, thalamus, and other regions. IGT alternative metrics have neural correlates consistent with decision-making theory as those difference scores reduce heterogeneity in cognitive processes. The CD-AB metric construct failure may reflect an artificial amalgamation of processes. The D-A metric appears to more successfully combine multiple levels of representation (dorsolateral prefrontal cortex, sub-cortical, cerebellar). (JINS, 2012, 18, 585–594)

The purpose of this study was to compare the neuropsychological outcome from blast-related versus non-blast related mild traumatic brain injury (MTBI). Participants were 56 U.S. military service members who sustained an MTBI, divided into two groups based on mechanism of injury: (a) non-blast related (Non-blast; n = 21), and (b) blast plus secondary blunt trauma (Blast Plus; n = 35). All participants had sustained their injury in theatre whilst deployed during Operation Iraqi Freedom or Operation Enduring Freedom. Patients had been seen for neuropsychological evaluation at Walter Reed Army Medical Center on average 4.4 months (SD = 4.1) post-injury. Measures included 14 clinical scales from the Personality Assessment Inventory (PAI) and 12 common neurocognitive measures. For the PAI, there were no significant differences between groups on all scales (p > .05). However, medium effect sizes were found for the Depression (d = .49) and Stress (d = .47) scales (i.e., Blast Plus > Non-blast). On the neurocognitive measures, after controlling for the influence of psychological distress (i.e., Depression, Stress), there were no differences between the Non-blast and Blast Plus groups on all measures. These findings provide little evidence to suggest that blast exposure plus secondary blunt trauma results in worse cognitive or psychological recovery than blunt trauma alone. (JINS, 2012, 18, 595–605)

The purpose of this study was to investigate the relative effects of unilateral (left-sided) versus bilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) on verbal fluency. To do this, 10 Parkinson's disease patients with predominantly bilateral motor symptoms who received bilateral STN DBS were compared with 6 patients suffering from predominantly unilateral symptoms who received STN DBS on the left side only. The results suggest that unilateral STN DBS of the speech dominant hemisphere is associated with significantly less declines in measures of verbal fluency as compared to bilateral stimulation. (JINS, 2012, 18, 606–611)

Post-error slowing (i.e., slowing of a response on correct trials following an error) is thought to reflect adaptive behavior that may be impaired in Attention-Deficit/Hyperactivity Disorder (ADHD). The current study examined post-error slowing in children with ADHD and typically developing controls on two cognitive tasks. Fifty-one ADHD-Combined type, 53 ADHD-Inattentive type, and 47 controls completed a Choice Discrimination and Stop Signal Task with incentive and event rate manipulations. Linear mixed models were used to examine reaction times surrounding errors (trial-by-trial). Pre-error speeding and pre- to post-error slowing occurred on both tasks. Impaired post-error slowing was only present on the Choice Discrimination Task for the ADHD-Inattentive type. Post-error slowing is impaired in children with ADHD-Inattentive type, but not ADHD-Combined type, on a simple attention task. These findings highlight the importance of considering task demands and ADHD subtype when examining post-error slowing and also provide a novel approach to quantifying post-error slowing. (JINS, 2012, 18, 612–617)