To test whether real tDCS adds benefit to active speech-therapy chewing training and to examine how changes in time and bites relate to each other and to executive functions.

Chewing is a distributed oromotor behavior emergent from cortico-bulbar sensorimotor loops and continuous orosensory feedback.

Across the whole sample, both chewing time and bites increased from pre to post, consistent with a shift toward a slower profile (more cycles over more time): Δ time = +0.79 s (95% CI 0.08–1.51; p=0.04), Δ bites = +1.06 (95% CI 0.08–2.04; p=0.04). Masticatory coupling differed by group: in tDCS (A), Δtime × Δbites was inverse (r=−0.50, p=0.03; ρ=−0.48, p=0.04), suggesting more cycles without proportionally longer time; in Sham (B) there was a positive trend (ρ=+0.41, p=0.10). In a regression Δtime ~ Δbites + group + interaction, we found β_Δbites=−2.55(95% CI−4.39–−0.71;p=0.01) and a significant interaction (B×Δbites=+1.07, 95%CI 0.31–1.83;p=0.01). 

With active chewing training provided to both arms, participants showed small but significant gains in time and bites. These findings support reporting both time and bites and analyzing their coupling when evaluating non-invasive neuromodulation for oromotor rehabilitation.