Neural basis of working memory in ADHD: Load versus complexity

Prerona Mukherjee, Tadeus Hartanto, Ana-Maria Iosif, J. Faye Dixon, Stephen P. Hinshaw, Adnan Murat Pakyurek, Wouter van den Bos, Amanda E. Guyer, Samuel M. McClure, Julie B. Schweitzer, Catherine Fassbender

Research output: Contribution to journalArticlepeer-review

Abstract

Working memory (WM) deficits are key in attention deficit hyperactivity disorder (ADHD). Nevertheless, WM is not universally impaired in ADHD. Additionally, the neural basis for WM deficits in ADHD has not been conclusively established, with regions including the prefrontal cortex, cerebellum, and caudate being implicated. These contradictions may be related to conceptualizations of WM capacity, such as load (amount of information) versus operational-complexity (maintenance-recall or manipulation). For instance, relative to neurotypical (NT) individuals, complex WM operations could be impaired in ADHD, while simpler operations are spared. Alternatively, all operations may be impaired at higher loads. Here, we compared the impact of these two components of WM capacity: load and operational-complexity, between ADHD and NT, behaviorally and neurally. We hypothesized that the impact of WM load would be greater in ADHD, and the neural activation would be altered. Participants (age-range 12–23 years; 50 ADHD (18 females); 82 NT (41 females)) recalled three or four objects (load) in forward or backward order (operational-complexity) during functional magnetic resonance imaging scanning. The effects of diagnosis and task were compared on performance and neural engagement. Behaviorally, we found significant interactions between diagnosis and load, and between diagnosis, load, and complexity. Neurally, we found an interaction between diagnosis and load in the right striatum, and between diagnosis and complexity in the right cerebellum and left occipital gyrus. The ADHD group displayed hypo-activation compared to NT group during higher load and greater complexity. This informs mechanisms of functional problems related to WM in adolescents and young adults with ADHD (e.g., academic performance) and remedial interventions (e.g., WM-training).

Original languageEnglish (US)
Article number102662
JournalNeuroImage: Clinical
Volume30
DOIs
StatePublished - Jan 2021

Keywords

  • ADHD
  • Caudate
  • Cerebellum
  • fMRI
  • Functional imaging
  • Prefrontal cortex
  • Working memory capacity

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging
  • Neurology
  • Clinical Neurology
  • Cognitive Neuroscience

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