Differences in reaction time (RT) variability have been documented between children with and without Attention Deficit Hyperactivity Disorder (ADHD). Most previous research has utilized estimates of normal distributions to examine variability. Using a nontraditional approach, the present study evaluated RT distributions on the Conners' Continuous Performance Test in children and adolescents from the Multimodal Treatment Study of ADHD sample compared to a matched sample of normal controls (n = 65 pairs). The ex-Gaussian curve was used to model RT and RT variability. Children with ADHD demonstrated faster RT associated with the normal portion of the curve and a greater proportion of abnormally slow responses associated with the exponential portion of the curve. These results contradict previous interpretation that children with ADHD have slower than normal responding and demonstrate why slower RT is found when estimates of variability assume normal Gaussian distributions. Further, results of this study suggest that the greater number of abnormally long RTs of children with ADHD reflect attentional lapses on some but not all trials.

Collectively, these findings support previous studies suggesting heritability of frontostriatal structures among individuals with ADHD and suggest disruption in frontostriatal white matter tracts as one possible pathway to the disorder.

This study extends findings of fronto-striatal dysfunction to adults with ADHD and highlights the importance of frontostriatal and frontocerebellar circuitry in this disorder, providing evidence of an endophenotype for examining the genetics of ADHD.

Objective We examine remission rate probabilities, recovery rates, and residual symptoms across 36 weeks in the Treatment for Adolescents with Depression Study (TADS). Method TADS, a multisite clinical trial, randomized 439 adolescents with major depressive disorder (MDD) to 12 weeks of treatment to fluoxetine (FLX), cognitive behavioral therapy (CBT), their combination (COMB), or pill placebo (PBO). The PBO group, treated openly after week 12, was not included in the subsequent analyses. Treatment differences in remission rates and probabilities of remission over time are compared. Recovery rates in remitters at week 12 (acute phase remitters) and week 18 (continuation phase remitters) are summarized. We also examined whether residual symptoms at the end of 12 weeks of acute treatment predicted later remission. Results At Week 36, the estimated remission rates for intention-to-treat cases were: COMB: 60%, FLX: 55%; CBT: 64%; overall: 60%. Paired comparisons reveal that at week 24 all active treatments converge on remission outcomes. The recovery rate at Week 36 was 65% for acute phase remitters and 71% for continuation phase remitters, with no significant between-treatment differences in recovery rates. Residual symptoms at the end of acute treatment predicted failure to achieve remission at weeks 18 and 36. Conclusions The majority of depressed adolescents in all three treatment modalities achieved remission at the end of nine months of treatment.

We have recently cast doubt (Craik, Govoni, Naveh-Benjamin, & Anderson, 1996; Naveh-Benjamin, Craik, Guez, & Dori, 1998) on the view that encoding and retrieval processes in human memory are similar. Divided attention at encoding was shown to reduce memory performance significantly, whereas divided attention at retrieval affected memory performance only minimally. In this article we examined this asymmetry further by using more difficult retrieval tasks, which require substantial effort. In one experiment, subjects had to encode and retrieve lists of unfamiliar name-nouns combinations attached to people's photographs, and in the other, subjects had to encode words that were either strong or weak associates of the cues presented with them and then to retrieve those words with either intra- or extra-list cues. The results of both experiments showed that unlike division of attention at encoding, which reduces memory performance markedly, division of attention at retrieval has almost no effect on memory performance, but was accompanied by an increase in secondary-task cost. Such findings again illustrated the resiliency of retrieval processes to manipulations involving the withdrawal of attention. We contend that retrieval processes are obligatory or protected, but that they require attentional resources for their execution.

This demonstrates the importance of including analytic strategies that can accurately model the actual distributional pattern, including the positive skew. Further, the results of the study relate to several theoretical models of ADHD.

Processing speed is often described as a fundamental resource determining individual (e.g., I.Q.) and group (e.g., developmental) differences in cognition. However, most tests that measure speed present many items on a single page. Because many groups with slowed responding are also distractible, we compared younger and older adults on high-(i.e., standard) versus low-distraction versions of two classic speed tasks. Reducing distraction improved the performance of older adults while having little or no effect on younger adults, suggesting that the ability to limit attentional access to taskrelevant information can affect performance on tests designed to measure processing speed. Distraction and Processing SpeedThe idea that "faster is better" is powerful in cars, computing, and cognitive psychology. Group differences, especially age differences, are often ascribed to the better-performing group's faster processing. We report two studies that assessed the contribution of an attentionalperceptual variable, visual distraction, in determining age differences in classic speed tasks.Many standard speed tests use items that are individually simple, but fit many such items onto a single page, resulting in a cluttered, potentially distracting display. Many groups thought to have deficits in processing speed also have difficulties regulating attention, and thus might be especially vulnerable to distraction. These groups include children, older adults, poor readers, and young adults who score less well on intelligence tests (e.g.,

The present study serves to detail the specific procedures for a mock scanner protocol, report on its use in the context of a multi-site study, and make suggestions for improving such protocols based on data acquired during study scanning. Specifically, a mock scanner compliance training protocol was used in a functional imaging study with a group of adolescents and adults with Attention Deficit Hyperactivity Disorder (ADHD) and a matched sample of healthy children and adults. Head motion was measured during mock and actual scanning. Participants across groups exhibited excess motion (>2 mm) on 43% of runs during the mock scanner. During actual scanning, excessive motion was limited to 10% of runs. There was clear task-correlated head motion during a go/no-go task that occurred even after the compliance training: Participants had a tendency to respond with increased head motion immediately after committing an error. This study illustrates the need to (1) report data attrition due to head motion, (2) assess task-related motion, and (3) consider mock scanner training in functional imaging protocols.