• Daruj Aniwattanapong, Justine J List, Nithya Ramakrishnan, Gursimrat S Bhatti, and Ricardo Jorge.
• Department of Psychiatry, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand; Chulalongkorn Cognitive, Clinical & Computational Neuroscience Lab, Chula Neuroscience Center, King Chulalongkorn Memorial Hospital, Bangkok, Thailand; Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, Houston, TX, USA. Electronic address: daruj.a@chula.ac.th.
• Neuromodulation. 2022 Apr 1; 25 (3): 343-355.

BackgroundIt has been suggested that vagus nerve stimulation (VNS) may enhance attention and working memory. The neuromodulator effects of VNS are thought to activate the release of neurotransmitters involving cognition and to promote neuronal plasticity. Therefore, VNS has been studied for its effects on attention and working memory impairment in neuropsychiatric disorders.ObjectivesThis study aimed to assess the effects of VNS on attention and working memory among patients with neuropsychiatric disorders, examine stimulation parameters, provide mechanistic hypotheses, and propose future studies using VNS.Materials And MethodsWe conducted a systematic review using electronic databases MEDLINE (Ovid), Embase (Ovid), Cochrane library, and PsycINFO (Ovid). Narrative analysis was used to describe the therapeutic effects of VNS on attention and working memory, describe stimulation parameters, and propose explanatory mechanisms.ResultsWe identified 20 studies reporting VNS effects on attention and working memory in patients with epilepsy or mood disorders. For epilepsy, there was one randomized controlled trial from all 18 studies. It demonstrated no statistically significant differences in the cognitive tasks between active and control VNS. From a within-subject experimental design, significant improvement of working memory after VNS was demonstrated. One of three nonrandomized controlled trials found significantly improved attentional performance after VNS. The cohort studies compared VNS and surgery and found attentional improvement in both groups. Nine of 12 pretest-posttest studies showed improvement of attention or working memory after VNS. For mood disorders, although one study showed significant improvement of attention following VNS, the other did not.ConclusionsThis review suggests that, although we identified some positive results from eligible studies, there is insufficient good-quality evidence to establish VNS as an effective intervention to enhance attention and working memory in persons with neuropsychiatric disorders. Further studies assessing the efficacy of such intervention are needed.Copyright © 2021 International Neuromodulation Society. All rights reserved.

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