Temporal dynamics of human masticatory sequences.

Many motor behaviors produced by humans and other mammals are temporally segmented. That is, sequences of rhythmic or repetitive behavior occur as a series of brief, 2- to 4-s bouts separated from each other by pauses or posture adjustments. Little is known about the physiological mechanisms underlying temporal segmentation, although several hypotheses have been advanced. Experimental and modeling studies are currently underway to gain insight into this phenomenon. One of the problems hampering advancement is the lack of relatively simple behavior models that can be studied in both humans and other mammals. We have recently reported that temporal segmentation occurs in guinea pig chewing sequences. Thus, it seems logical to explore whether temporal segmentation occurs in human chewing sequences as well. Toward this end, the current study evaluated the temporal dynamics of chewing sequences in humans. Thirteen subjects were videotaped on campus eating areas during lunch-time. Inter-occlude intervals, i.e., time between maximum jaw closures, were calculated using a custom computer program, which also recorded whether the interval represented a chew or a pause in chewing. Chewing rate, pause durations, and chewing burst durations, i.e., duration of continuous chewing uninterrupted by pauses, were calculated. Median chewing burst duration for the sample was 2.91 s. This corroborates other studies' findings of 3-s temporal segmentation in repetitive movements. We conclude that automatic chewing sequences contain temporal segmentation. Future work is required to gain insight into whether the physiological mechanisms of this time-based phenomenon are similar among different species.