Pupillary dilations in a Target/Distractor visual task paradigm and attention deficit hyperactivity disorder (ADHD).

ADHD is a neurocognitive disorder characterized by attention difficulties, hyperactivity, and impulsivity, often persisting into adulthood with substantial personal and societal consequences. Despite the importance of neurophysiological assessment and treatment monitoring tests, their availability outside of research settings remains limited. Cognitive neuroscience investigations have identified distinct components associated with ADHD, including deficits in sustained attention, inefficient enhancement of attended Targets, and altered suppression of ignored Distractors. In this study, we examined pupil activity in control and ADHD subjects during a sustained visual attention task specifically designed to evaluate the mechanisms underlying Target enhancement and Distractor suppression. Our findings revealed some distinguishing factors between the two groups which we discuss in light of their neurobiological implications.

Examining the effect size and duration of retrieval-induced facilitation.

Under certain conditions, the retrieval of some information can increase the recall of other information, a phenomenon known as retrieval-induced facilitation. Chan (Journal of Memory and Language 61:153-170, 2009) proposed two moderating factors to account for why retrieval causes facilitation in some situations and forgetting in others: (1) integration at the time of encoding and (2) the delay between retrieval practice and final test. Chan found a 9-11% facilitation effect when the materials were well integrated and the final test occurred after a 24-h delay. Two sets of experiments sought to replicate and extend Chan's study by examining retrieval-induced facilitation not only following a 24-h delay but after longer delays (i.e., 1 or 2 weeks). A meta-analysis including these replications and the original experiments was also conducted. The results provide additional evidence of retrieval-induced facilitation, with no evidence that the effect varies as a function of the final delay. However, the size of the effect was found to be somewhat smaller than previously observed.

Gestational Smoking and Hypertension as Predictors of Working Memory Functioning in Childhood Attention-Deficit/Hyperactivity Disorder.

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental condition affecting between 5 and 8% of all children and adolescents, characterized by impairing levels of inattention, hyperactivity, and impulsivity. Existing cognitive models of ADHD have placed working memory (WM) deficits at the core of ADHD and suggest that primary WM deficits may also underlie the additional deficits associated with the condition. Although not all children with ADHD show WM deficits, those with such deficits have been found to have worse functional outcomes when compared to their diagnosed peers with typical WM functioning. Even so, contributors to the variability of impaired WM functioning seen within this population remain unknown. In the present study, we examined the association between two known prenatal and perinatal risk factors for impaired cognitive functioning - gestational smoking and hypertension - in three independent samples of children and adolescents with ADHD (samples varied with respect to sample size and WM measurement procedures). Contrary to hypotheses and existing literature, presence of high blood pressure during pregnancy was unexpectedly found to be a positive predictor of offspring WM capacity in one of three samples (a sample of all girls with ADHD). Implications and considerations for future research are discussed.