Cerebral hemodynamics and functional connectivity changes in stroke patients with dysphagia under acidic taste...

Swallowing difficulties after a stroke are a common complication that significantly impact the quality of life of patients. The cortical activation patterns in patients with dysphagia following a stroke may be influenced by different taste stimuli, but the underlying neural mechanisms remain unclear.

The aim of this study was to investigate the changes in brain cortical hemodynamic signals and functional connectivity in stroke patients with dysphagia during acidic taste stimulation.

We recruited 15 patients with first-time swallowing difficulties due to stroke (53% male; mean age 69 ± 9.43 years; duration 2.47 ± 1.31 months post-stroke, onset between 2 weeks and 6 months). A 41-channel functional near-infrared spectroscopy (fNIRS) was used to measure changes in concentrations of oxygenated hemoglobin (HbO₂) and deoxygenated hemoglobin (HbR) during taste stimulation. A one-sample t-test was used for cohort analysis. A two-sample t-test was used to compare cortical activation differences between pure water and acidic stimuli. Additionally, relative changes in HbO₂ concentration throughout the experiment were extracted for functional connectivity analysis. The Pearson correlation coefficients of HbO₂ concentrations across channels were analyzed in the time series, followed by Fisher Z-transformation, which was defined as the functional connectivity strength between channels.

During acidic taste stimulation, significant activation of multiple cortical regions, including Dorsolateral Prefrontal Cortex (DLPFC), Supplementary Motor Cortex (PSMC), and Primary Somatosensory Cortex (PSC) was observed compared to the neutral water condition (p < 0.05). Functional connectivity analysis revealed that the average functional connectivity strength of the cortical network during acidic taste stimulation was significantly higher than during the neutral water condition (acidic taste: 0.337 ± 0.134; neutral water: 0.249 ± 0.142, p = 0.03).

This study demonstrates that acidic taste stimulation can significantly activate multiple cortical regions in stroke patients with dysphagia and enhance the connectivity strength of brain functional networks, which may have a positive effect on swallowing function regulation. These findings provide a theoretical basis for future taste-based neurorehabilitation interventions and offer new insights into the treatment strategies for dysphagia after stroke.