Exploring the Efficacy of Transcutaneous Auricular Vagal Nerve Stimulation on Post-Stroke Aphasia: A Single-Subject Design Study

Background: Anomia or word-retrieval difficulty is a common long-term language impairment for individuals with post-stroke aphasia. Several behavioral interventions like semantic feature analysis (SFA) have shown positive results in naming outcomes, but continue to face difficulty in generalizing the treatment effects to untreated items. With recent advancements in technology, researchers are developing newer neuromodulation devices that aim at promoting neuroplasticity and neural reorganization in post-stroke individuals. Transcutaneous auricular vagal nerve stimulation (taVNS) is a relatively new technology that aims at stimulating the auricular branch of the vagal nerve to promote neuroplasticity. Studies have shown taVNS to potentially facilitate positive improvements in cognitive functions and second language learning. The current study looked at the efficacy of taVNS combined with SFA on word retrieval skills in individuals with post-stroke aphasia. Methods: Five participants with post-stroke aphasia underwent four phases of study (baseline, sham, active taVNS, and extended active taVNS). Probe data for treated and untreated noun words as well as results of standardized assessment were collected. Results: The results indicate that active taVNS combined with SFA enhanced word retrieval abilities with treated words showing greater improvement compared to untreated. Low but significant improvements for untreated words suggest the potential of taVNS intervention to generalize the treatment effects to novel words. Phonemic cue-assisted retrieval of treated words had the maximum improvement when compared to independent responses to the probe data. This suggests that taVNS has the potential to be an added treatment to traditional behavioral intervention for post-stroke aphasia to facilitate enhanced word retrieval functions and promote treatment generalization.