No abstract

Working memory (WM) capacity is the ability to retain and manipulate information during a short period of time. This ability underlies complex reasoning and has generally been regarded as a ®xed trait of the individual. Children with attention de®cit hyperactivity disorder (ADHD) represent one group of subjects with a WM de®cit, attributed to an impairment of the frontal lobe. In the present study, we used a new training paradigm with intensive and adaptive training of WM tasks and evaluated the effect of training with a double blind, placebo controlled design. Training signi®cantly enhanced performance on the trained WM tasks. More importantly, the training signi®cantly improved performance on a nontrained visuo-spatial WM task and on Raven's Progressive Matrices, which is a nonverbal complex reasoning task. In addition, motor activity ± as measured by the number of head movements during a computerized test ± was signi®cantly reduced in the treatment group. A second experiment showed that similar training-induced improvements on cognitive tasks are also possible in young adults without ADHD. These results demonstrate that performance on WM tasks can be signi®cantly improved by training, and that the training effect also generalizes to nontrained tasks requiring WM. Training improved performance on tasks related to prefrontal functioning and had also a signi®cant effect on motor activity in children with ADHD. The results thus suggest that WM training potentially could be of clinical use for ameliorating the symptoms in ADHD.

Many studies have supported a genetic etiology for autism. Here we report mutations in two X-linked genes encoding neuroligins NLGN3 and NLGN4 in siblings with autism-spectrum disorders. These mutations affect cell-adhesion molecules localized at the synapse and suggest that a defect of synaptogenesis may predispose to autism.