Fig. 1.

Glottal shape for the interaction between maximal TA activation and graded LCA activation. Columns correspond to temporal sequence of medial surface shape changes following ILM stimulation starting at the left-most column, 0 ms, rest. Each subsequent column is then some time interval later as denoted by the title above each column. Total recorded duration was 50 ms. Each row corresponds to a particular ILM combination. All rows have full TA activation (grade 5) but LCA grade varies by row with grade 0, or no LCA, for row 1 and increasing LCA grades for subsequent rows as denoted by the title beside each row; ‘LCA 0’ corresponds to LCA activation grade 0. Each plot is a color-coded contour plot of the vocal fold medial surface. Left edges is posterior (vocal process), right edge is anterior (anterior commissure), inferior edge is inferior, superior edge is superior. Colorbar denotes surface height or glottal width; the distance from the vocal fold medial surface to the glottal midline; midline is denoted as ‘0’. Each subsequent figure is designed in this exact same format except a different muscle with be held at maximum stimulation while another muscle is added in a graded fashion. TA provides robust near complete adduction of the mid membranous vocal fold (96%, row 1). This level of adduction is maintained with combined graded LCA activation. Further, TA shortens the vocal fold by 5% and thickens it in the vertical dimension by 8%. Thickening is more evenly distributed in the glottal anteroposterior axis with LCA activation and adduction is overall more complete for the entire medial surface. Posterior glottal closure is seen for LCA grades 3-6 and is observed as early as 20 ms. Final posture is rectangular with full TA and LCA activation. (inf – sup = inferior to superior, LCA = lateral cricoarytenoid, ms = millisecond, post – ant = posterior to anterior, TA = thyroarytenoid).