A

During a mature (somatic) swallow the lips remain relaxed and the mentalis shows little-to-no electromyographic activity, whereas both simple and complex tongue-thrust swallows rely on a perioral seal produced by active contraction of the lips and mentalis muscles [Murray et al., 1998, PMID 9633157; Dixit & Shetty, 2013, PMID 23853444].