Fig. 3. Buccal mass shape space analysis (modified from Fig. 3 of Drushel et al., 1998). (A) Ellipse quadrant shape approximation for the mid-sagittal buccal mass outline, showing the dimensions a, b, c and d used to compute the ellipticity and eccentricity parameters (formulae given in the axis labels of C). (B) Mean buccal mass shape changes from nine sequential swallows in a transilluminated juvenile. Note that the ellipse approximation fails in the antero-ventral quadrant around peak retraction (7-9, dotted lines). Images 1-3, 4-8, 9 and 10-11 correspond roughly to the intervals t4, t1, t2 and t3, respectively. Each image is 0.33 s (normalized). (C) Shape space plot of ellipticity versus eccentricity parameters for the 11 images in B. Rest, peak protraction and peak retraction occupy distinctly different points (dark gray geometric shapes) in the two-dimensional shape space. The light gray region in the graph shows the approximate range of responses in the nine individual swallows that were averaged. Individual swallows show hysteresis (i.e. the path from protraction to retraction is different from the path from retraction to protraction), which is removed by averaging and timebase normalization. Each point is 0.33 s (normalized).

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