Regional differences in hyoid muscle activity and length dynamics during mammalian head shaking

Abstract

The sternohyoid (SH) and geniohyoid (GH) are antagonist strap-muscles that are active during a number of different behaviors, including sucking, intraoral transport, swallowing, breathing, and extension/flexion of the neck. Because these muscles have served different functions through the evolutionary history of vertebrates, it is quite likely they will have complex patterns of electrical activity and muscle fiber contraction. Different regions of the sternohyoid exhibit different contraction and activity patterns during a swallow. We examined the dynamics of the sternohyoid and geniohyoid muscles during an unrestrained, and vigorous head-shake behavior in an animal model of human head, neck and hyolingual movement. A gentle touch to infant pig ears elicited a head shake of several head revolutions. Using sonomicrometry and intramuscular EMG we measured regional (within) muscle strain and activity in SH and GH. We found that EMG was consistent across three regions (anterior, belly and posterior) of each muscle. Changes in muscle length however, were more complex. In the SH, mid-belly length-change occurred out of phase with the anterior and posterior end-regions, but with a zero-lag timing; the anterior region shortened prior to the posterior. In the GH, the anterior region shortened prior to, and out of phase with the mid-belly and posterior regions. Head-shaking is a relatively simple reflex behavior, yet the underlying patterns of muscle length-dynamics and EMG activity are not. The regional complexity in SH and GH, similar to regionalization of SH during swallowing, suggests that these ‘simple hyoid strap muscles’ are more complex than textbooks often suggest.

Characterization of the head-twitch response induced by hallucinogens in mice

“…These findings are supported by the magnetometer recordings, with the frequency content of HTR-induced responses typically peaking between 80 Hz and 100 Hz. Electromyography (EMG) studies have characterized the head movement that occurs during spontaneous head twitches in cats (Richmond et al, 1992) and infant pigs (Wentzel et al, 2011). In cats, the head makes 1–5 full oscillatory cycles during a head twitch, with each cycle completed in approximately 100–150 ms (Richmond et al, 1992).…”

“…In cats, the head makes 1–5 full oscillatory cycles during a head twitch, with each cycle completed in approximately 100–150 ms (Richmond et al, 1992). Likewise, for head twitches in pigs, the head makes 2–8 full oscillations, each lasting for ~100 ms (Wentzel et al, 2011). It is important to note that the EMG studies analyzed the responses in terms of oscillatory cycles (one full oscillation consisting of a head roll to one side and then back to the opposite side), whereas our studies counted the number of individual head movements and quantified the reciprocation frequency.…”

Variation in the Timing and Frequency of Sucking and Swallowing over an Entire Feeding Session in the Infant Pig Sus scrofa

“…Although sucking and swallowing are not “power” behaviors, such as mastication of hard food, they still require significant muscle activity. Many of the supra- and infrahyoid muscles involved are much smaller, parallel-fibered muscles, some with negligible cross-sectional area [25, 34]. It is possible that over time some of these muscles tire.…”

Regional Variation in Geniohyoid Muscle Strain During Suckling in the Infant Pig

“…These muscles are commonly referred to as “strap muscles” due to their simple architecture as long, relatively thin muscles with parallel fibers. Although the strap muscles traditionally have been described as anatomically simple, recent studies have identified regional variation in the muscle strain of two strap muscles, the sternohyoidmuscle (SH) and geniohyoid muscle (GH), during reflexive head shaking (Wentzel et al, ) and in the sternohyoid during swallowing (Konow et al, ). To better understand muscle strain, we recorded length change and muscle activity, since muscle activity alone does not necessarily correlate to length change (Ahn et al, ; Konow et al, ).…”