Transcranial Direct Current Stimulation (tDCS) With Active Chewing Training: A Randomized, Double-blind, Sham-controlled Trial in Healthcare Professionals
Marta Lira-Batista1, Rogério Batista2, Marcela Silagi3, Maria do Carmo Martins4
1Fonoaudiologia |UMULTI, Afya Uninovafapi | HUUFPI, 2DIASPA, IFPI, 3Fonoaudiologia, UNIFESP, 4Biofísica e Fisiologia, UFPI
Objective:
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.
Background:
Chewing is a distributed oromotor behavior emergent from cortico-bulbar sensorimotor loops and continuous orosensory feedback.
Design/Methods:
We conducted a randomized, double-blind, sham-controlled trial with pre- and post-assessments. Healthy adult healthcare professionals were assigned to Group A (real tDCS; anode F4/cathode F3, 2.0 mA, 20 min) or Group B (sham). Both groups received the same active speech therapy for chewing training. The matched sample for the primary endpoint was N=36 (A=19; B=17). Outcomes: average chewing time (s; mean of two cookies) and number of bites; executive tests (TMT-A, TMT-B, B–A; Stroop Conditions 1–3) and Epworth Sleepiness Scale (ESS). Statistics: paired t-tests; Pearson/Spearman correlations between deltas (post–pre); ANCOVA for post-time (primary) adjusted by pre-time and group. Significance α=0.05 (two-tailed).
Results:
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).
Conclusions:
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.
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