A systematic review of cortical dynamics in swallowing: insights from functional near-infrared spectroscopy (fNIRS)

This systematic review synthesizes the current evidence on cortical activation during swallowing, focusing on three key paradigms: sour swallowing, postural swallowing, and swallowing in stroke patients. A systematic search of PubMed, Web of Science, and Cochrane Library was conducted up to August 15, 2025. Studies were included if they used fNIRS to measure cortical hemodynamic responses during swallowing‑related tasks in healthy adults or patients with dysphagia. Methodological quality was assessed using the JBI checklist (stroke studies) and MINORS scale (sour/postural studies). A narrative synthesis was performed due to heterogeneity in paradigms and outcome measures. Eleven studies (total N = 370 participants) were included. Sour swallowing (4 studies, n = 74) showed enhanced cortical activation in M1, SMA, and DLPFC. Motor and postural swallowing (3 studies, n = 65) demonstrated that effortful swallowing and chin‑up positions increased cortical recruitment. Stroke‑related swallowing (4 studies, n = 231) showed compensatory unaffected‑hemisphere activation and rTMS‑associated cortical reorganization. fNIRS is a valuable tool for exploring cortical dynamics during swallowing. However, most evidence comes from healthy young adults, limiting generalizability to clinical populations. Findings are preliminary and hypothesis‑generating; clinical recommendations cannot yet be drawn. The review was not prospectively registered.