Torkel Klingberg, MD, PhD, is Professor of Cognitive Neuroscience at the Karolinska Institute in Stockholm, Sweden. Klingbergs work on child brain development and cognitive training is at the international front line with publications including journals such as Science and Nature Neuroscience. He led the original studies demonstrating that working memory can be improved by training, and leads a large Swedish project on child brain development and academic abilities.
Working memory (WM) is the ability to temporary store and manipulate information. The neural mechanisms of visuo-spatial WM are to a large extent identical to those of controlled, or top-down, attention. The similarities between WM and attention is also evident from behavioral studies. In particular are the inattentive symptoms of ADHD associated with deficits in WM capacity. It is also these inattentive symptoms and WM deficits that are the strongest predictors of academic failure in children and adolescents with ADHD. It was previously assumed that WM capacity was a fixed characteristic of the individual. However, research first carried out by Klingberg and collaborators have shown that intensive training on WM tasks over several weeks can enhance performance also on non-trained WM tasks. This training is also is associated with improvement in attention as measured by standard neuropsychological tasks, but also ecologically more relevant tasks, such as tests of the ability to remember and carry out instructions. This suggests that improved WM capacity is in itself relevant to functions in daily life. The neural basis of training is presumably related to the plasticity of prefrontal and parietal cortex and the basal ganglia. Studies with positron emission tomography, as well as genetic studies, has implicated dopaminergic transmission as a key factor in this plasticity. Improvement in attention has been measured with neuropsychological tests, as well as questionnaires of attention in everyday life, such as ratings of inattention according to the diagnostic criteria of DSM, Conner’s rating scales, The Cognitive Failure Questionnaire, and direct observer ratings. The studies, conducted by several independent research groups, include typically developing children and adults, children with ADHD, children born prematurely and children with cognitive deficits as a results of cancer treatment. There are now five, randomized, controlled trials showing improvement of attention after working memory training. A recent meta-analysis of 12 studies using the Cogmed WM training method (Spencer-Smith and Klingberg, 2015), showed that WM capacity is increased with an effect size of around 0.4, although effects differ among different child populations. WM training is an experimental paradigm to study cognitive plasticity, but is also clinically useful in order to improve WM and attention in everyday life of individuals with impaired WM and inattention.