Kinematic analysis of an appetitive food-handling behavior: the functional morphology of Syrian hamster cheek pouches

Abstract

SUMMARY Prodigious food hoarding in Syrian hamsters Mesocricetus auratusWaterhouse is strongly linked to appetite and is made possible by large internal cheek pouches. We provide a functional analysis of the cheek pouch and its associated retractor muscle. Frame-by-frame analysis of videotaped pouch-filling behavior revealed multiple jaw cycles for each food item pouched and the use of more jaw cycles to pouch large food items (∼2.5 g chow pellets) than small (corn kernels or sunflower seed with husks). These results stand in contrast to previously reported pouching kinematics in the externally pouched Dipodomys deserti, which uses only one jaw cycle per pouching event. Comparison of pouching and mastication in the same individuals also suggests that in Syrian hamsters, feeding jaw cycles are modulated to accommodate pouch filling primarily by the addition of a pause between fast open and fast close phases, which we call `gape phase'. Contrary to previous assertions, the retractor muscle does not merely provide structural support for the full pouch during locomotion. Video analysis of ten hamsters with unilaterally denervated retractor muscles and electrophysiological study of an anaesthetized subject confirmed that retractor muscle activity during pouch filling increases pouching efficiency for food items subsequent to the first.

Long-arm functional individuation of computation

“…available after being in short supply. Nevertheless, the amount of food this hamster typically consumes remains unchanged from pre-fast levels (Buckley et al, 2007). Such behaviour does nothing to decrease the hamster's appetite, and will likely continue until the food stored in its cheek pouches is actually chewed and swallowed, thereby resulting in an increased blood glucose level, and a decrease in the secretion of orexin.…”

Sex differences in motivational responses to dietary fat in Syrian hamsters

“…For these reasons, and because consummatory drive in hamsters does not increase with exposure to various orexigenic stimuli [67–69], it is unlikely that high-fat feeding elevated it. It is noteworthy that hamsters express appetitive responses to food by cheek-pouching it rather than exhibiting hyperphagia [70–72]. Thus, prevention of feeding and pouching by presenting test food in cassettes eliminated the display of consummatory and appetitive behaviors in the RIP test.…”

Ingestive behavior.

“…Both are more-or-less stereotyped responses to an appeted stimulus (finding food), with the decision determined by internal state. Hoarding behavior in hamsters and other pouchfilling species most clearly manifests consummatory qualities because it begins with repetitive jaw movements that are modified masticatory cycles (Buckley, Schneider, & Cundall, 2007). Like other cyclical movements, jaw cycles are governed by central pattern generators (CPGs) in the brainstem (Morquette et al, 2012).…”