Cognitive Neuroscience of Attention Deficit Hyperactivity Disorder (ADHD) and Its Clinical Translation

Summary & key facts

Brain imaging studies (fMRI) show that ADHD is linked to problems in many brain networks that control attention, timing, working memory, motivation, and emotion. There is also evidence that a brain system normally quiet during tasks (the default mode network) does not switch off properly in people with ADHD. Some early clinical tools — like machine-learning diagnosis, brain stimulation, and neurofeedback — look promising, but the studies are small or mixed and bigger, careful trials are still needed.

Key facts:

• Meta-analyses of fMRI studies report complex, multisystem impairments in ADHD across multiple networks that support cognitive control, attention, timing, and working memory (including dorsal, ventral and medial fronto-cingulo-striato-thalam
• There is emerging evidence of abnormalities in orbital and ventromedial prefrontal and limbic brain areas in ADHD; these areas are linked to motivation and emotion control.
• Many studies find poor deactivation of the default mode network (DMN) in ADHD, suggesting an abnormal balance between task-positive (engaged) and task-negative (usually quiet) brain networks related to thinking and attention.
• Pattern-recognition (machine-learning) analyses of fMRI data have produced diagnostic classification accuracies of over 80% in some studies, but replication studies are still missing.
• Brain stimulation methods (for example, transcranial direct current stimulation, tDCS) have shown some promising results in small and varied proof-of-concept studies, but larger clinical trials are needed to test real clinical benefit and p
• Only three studies have piloted neurofeedback (NF) targeting frontal dysfunctions using fMRI or near-infrared spectroscopy; the two larger NF studies reported some improvements, but these were not better than active control conditions, whic
• The review states that translating cognitive neuroscience findings into clinical practice is still in its early stages. It calls for thorough testing of neurotherapies for short- and long-term clinical and cognitive effects and for their po

Abstract

This review focuses on the cognitive neuroscience of Attention Deficit Hyperactivity Disorder (ADHD) based on functional magnetic resonance imaging (fMRI) studies and on recent clinically relevant applications such as fMRI-based diagnostic classification or neuromodulation therapies targeting fMRI deficits with neurofeedback (NF) or brain stimulation. Meta-analyses of fMRI studies of executive functions (EFs) show that ADHD patients have cognitive-domain dissociated complex multisystem impairments in several right and left hemispheric dorsal, ventral and medial fronto-cingulo-striato-thalamic and fronto-parieto-cerebellar networks that mediate cognitive control, attention, timing and working memory (WM). There is furthermore emerging evidence for abnormalities in orbital and ventromedial prefrontal and limbic areas that mediate motivation and emotion control. In addition, poor deactivation of the default mode network (DMN) suggests an abnormal interrelationship between hypo-engaged task-positive and poorly "switched off" hyper-engaged task-negative networks, both of which are related to impaired cognition. Translational cognitive neuroscience in ADHD is still in its infancy. Pattern recognition analyses have attempted to provide diagnostic classification of ADHD using fMRI data with respectable classification accuracies of over 80%. Necessary replication studies, however, are still outstanding. Brain stimulation has been tested in heterogeneously designed, small numbered proof of concept studies targeting key frontal functional impairments in ADHD. Transcranial direct current stimulation (tDCS) appears to be promising to improve ADHD symptoms and cognitive functions based on some studies, but larger clinical trials of repeated stimulation with and without cognitive training are needed to test clinical efficacy and potential costs on non-targeted functions. Only three studies have piloted NF of fMRI-based frontal dysfunctions in ADHD using fMRI or near-infrared spectroscopy, with the two larger ones finding some improvements in cognition and symptoms, which, however, were not superior to the active control conditions, suggesting potential placebo effects. Neurotherapeutics seems attractive for ADHD due to their safety and potential longer-term neuroplastic effects, which drugs cannot offer. However, they need to be thoroughly tested for short- and longer-term clinical and cognitive efficacy and their potential for individualized treatment.

Topics

Attention Deficit Hyperactivity Disorder Functional Brain Connectivity Studies Transcranial Magnetic Stimulation Studies

Categories

Health Sciences Medicine Psychiatry and Mental health

Tags

Attention deficit hyperactivity disorder Brain stimulation Cognition Electroencephalography Executive functions Functional magnetic resonance imaging Neurofeedback Neuroimaging Neuroscience Psychiatry Psychology Stimulation Working memory