Task-Specific Facilitation of Cognition by Anodal Transcranial Direct Current Stimulation of the Prefrontal Cortex

Abstract

We previously speculated that depression of cerebellar excitability using cathodal transcranial direct current stimulation (tDCS) might release extra cognitive resources via the disinhibition of activity in prefrontal cortex. The objective of the present study was to investigate whether anodal tDCS over the prefrontal cortex could similarly improve performance when cognitive demands are high. Sixty-three right-handed participants in 3 separate groups performed the Paced Auditory Serial Addition Task (PASAT) and the more difficult Paced Auditory Serial Subtraction Task (PASST), before and after 20 min of anodal, cathodal, or sham stimulation over the left dorsolateral prefrontal cortex (DLPFC). Performance was assessed in terms of the accuracy, latency, and variability of correct verbal responses. All behavioral measures significantly improved for the PASST after anodal DLPFC stimulation, but not the PASAT. There were smaller practice effects after cathodal and sham stimulation. Subjective ratings of attention and mental fatigue were unchanged by tDCS over time. We conclude that anodal stimulation over the left DLPFC can selectively improve performance on a difficult cognitive task involving arithmetic processing, verbal working memory, and attention. This result might be achieved by focally improving executive functions and/or cognitive capacity when tasks are difficult, rather than by improving levels of arousal/alertness.

Transcranial Direct Current Stimulation Improves Executive Dysfunctions in ADHD: Implications for Inhibitory Control, Interference Control, Working Memory, and Cognitive Flexibility

“…We suggest that increasing activity of the lDLPFC by anodal tDCS leads to enhanced cognitive control over relevant stimuli (naming the color but not the word) by maintaining them in WM. The observation that performance of the GoNo/Go and Stroop tasks are differently altered by DLPFC activation implicates that the activation of these regions is task-specific (Pope, Brenton, & Miall, 2015). Moreover, it also suggests that the relevance of the interhemispheric balance for task performance is also task-or domain-specific, since an impact of suggested alterations of interhemispheric balance on performance was only observed for response inhibition, but not other EF domains.…”

Effects of anodal tDCS of the lower limb M1 on ankle reaction time in young adults

“…Pope et al (2015) showed that tDCS over prefrontal cortex may have differential effects depending on the complexity of the task. In their study, after anodal tDCS they observed an enhancement of a cognitive subtraction task but not of a less challenging addition task (Pope et al 2015). It is possible that the SDMT is not sensitive or challenging enough to be affected by fatigue.…”

Neurocognitive effects of transcranial direct current stimulation (tDCS) in unipolar and bipolar depression: Findings from an international randomized controlled trial

“…In addition to antidepressant properties, some research has suggested that tDCS may have beneficial neurocognitive effects in both healthy participants and patients with neuropsychiatric disorders, including unipolar and bipolar depression (Martin et al, 2015; Minchino et al, 2015; Moreno et al, 2015; Oliveira et al, 2013; Pope, Brenton, & Miall, 2015). Specific effects include improvement in neurocognitive functions such as attention, processing speed, learning and memory, and working memory.…”