Effects of Transcranial Direct Current Stimulation on Rapid Automatized Naming Performance in Healthy Individuals

This study investigated the effects of anodal, cathodal, and sham transcranial direct current stimulation (tDCS) on rapid automatized naming (RAN) performance, a task assessing accuracy and speed in naming visual stimuli, closely linked to phonological processing and language production.

Sixty healthy, right-handed young adults were randomly assigned to anodal, cathodal, or sham tDCS groups. RAN performance was evaluated using measures of accuracy, vocal reaction time (vRT), and task completion time (TCT) before and after 20-min tDCS targeting the left temporo-parieto-occipital junction. Each RAN subtask (color, number, letter, and combination) included 36 stimuli.

Anodal tDCS significantly reduced vRT in the color subtask (d = 0.92) and significantly reduced TCT across all subtasks: color (d = 0.85), number (d = 0.68), letter (d = 0.79), and combination (d = 0.62). Cathodal tDCS significantly increased vRT in the color subtask (d = -0.65) and significantly increased TCT in the letter (d = -0.62) and combination (d = -0.84) subtasks. Sham stimulation had no significant effects.

Anodal tDCS enhances RAN performance in healthy adults, primarily by reducing TCT across all categories and selectively shortening vRT in color naming. In contrast, cathodal tDCS slowed performance in specific subtasks. These findings indicate that temporal measures-particularly TCT-are more sensitive than accuracy for detecting neurostimulation effects in healthy populations. Beyond its established role in addressing reading difficulties, RAN may also provide early insights into broader cognitive-linguistic disorders, underscoring its potential value for future clinical and therapeutic applications.