Null tDCS Effects in a Sustained Attention Task: The Modulating Role of Learning.

Area of Science:

• Neuroscience
• Psychiatry
• Cognitive Psychology

Background:

• Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by inattention and hyperactivity.
• The fronto-cerebral network is implicated in sustained attention and executive functions.
• Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique explored for modulating neural activity.

Purpose of the Study:

• To investigate the effects of tDCS on sustained attention in adults with ADHD.
• To modulate the fronto-cerebral network using tDCS.
• To compare tDCS effects between adults with ADHD and neurotypical controls.

Main Methods:

• A within-subjects design was employed with 37 participants (21 with ADHD).
• Participants underwent three sessions: baseline, active tDCS, and sham tDCS.
• Double anodal tDCS (1.8 mA, 20 min) was applied over the dorsolateral prefrontal cortex (DLPFC), with the cathode over the cerebellum.
• The MOXO Continuous Performance Test (CPT) was used to assess attention and hyperactivity.

Main Results:

• Baseline MOXO-CPT scores showed significant differences between ADHD and control groups in attention and hyperactivity.
• No significant tDCS effects were observed on most MOXO-CPT measures.
• A significant learning effect was noted, potentially masking tDCS effects on hyperactivity.

Conclusions:

• Learning and repetition effects in cognitive tasks can obscure the impact of tDCS in within-subjects designs.
• Careful consideration of practice effects is crucial when designing tDCS experiments, particularly in clinical populations like ADHD.
• The MOXO-CPT demonstrated utility in differentiating ADHD and control groups at baseline.