The Impact of Task-Specific Transcranial Direct Current Stimulation (tDCS) on Sustained Attention in a Healthy Population

Objective: To examine the impact of task-specific anodal transcranial direct current stimulation (tDCS) administered over the left dorsolateral prefrontal cortex (L-DLPFC) on sustained attention in healthy participants. Methods: This study examined the effects of task-training and tDCS over the left dorsolateral prefrontal cortex on sustained attention. Participants (n=13) completed four sessions consisting of either true-stimulation (2 mA for 10 minutes) or sham-stimulation (2 mA for 30 sec) in counterbalanced order. Participants completed one session every 7 to 10 days and were randomly assigned to one of two task-specific conditions in counterbalanced order. All sessions consisted of a 10-minute Go/No-Go Task (GNGT) immediately prior to and after stimulation. Between pre- GNGT and post-GNGT, participants completed either another 10-minute GNGT or a passive cartoon viewing task. Changes in reaction times and response accuracy on post-GNGT were compared across conditions using repeated measures ANOVA. Results: 2x2 repeated measures ANOVA revealed no significant main effects of task (practice vs. passive) or stimulation type (true vs. sham) for reaction times or response accuracy; interaction was also nonsignificant. Unplanned post-hoc analyses using 2x2 repeated measure ANOVA to assess fatigue were conducted on the first half of Go/No-Go performances and revealed an interaction effect for task and stimulation on accuracy. To assess isolated sustained attention, performances during Go trials were assessed at full length, midway, and a quarter through sessions. Analyses revealed a significant main effect of stimulation (diminished performance with true stimulation) and a significant interaction between task and stimulation for total Go trials (i.e., true hits) accuracy performance. Conclusion: This study revealed no significant effect of task type or stimulation type on accuracy performance or reaction time. Post-hoc analyses reveal diminished accuracy performance during Go trials/sustained attention with true stimulation that may be related to interhemispheric inhibition, but ceiling effects may skew data. Interaction effects during Go-Trial intervals will be explained in the discussion portion of this paper.