Movements of the cranial vibrissae in the Golden hamster (Mesocricetus auratus)

Abstract

Vibrissae are highly refined vibrotactile receptors that are present on most mammals. The Golden hamster exhibits three different behaviours of its mystacial, supraorbital, and genal vibrissae. During rest, all the vibrissae are reclined and motionless. When hamsters are alert, the vibrissae are partly or fully erect and essentially motionless. During active investigation, the mystacial vibrissae “whisk” or “sweep” through antero–posterior excursions. The genal vibrissa moves only slightly in periodic erection. The supraorbital vibrissae carry through a wide erection arc and have limited excursions with movements of the upper eyelid. The mystacial vibrissae whisk quickly (about 16 sweepsls). Whisking is divisible into contact (relatively high amplitude, low frequency), non–contact (relatively low amplitude, high frequency), and double–pump (combination contact and non–contact) types, and can be either bilaterally symmetric or asymmetric. The dimensions of the mystacial territory around the snout change throughout whisking due to coordinated changes in the shape of the mystacial pad and the tilting of the vibrissae relative to the pad. Such differential movements have implications for sensory physiology as they point to an ability for fine sensory monitoring of the environment.

Active vibrissal sensing in rodents and marsupials

“…Episodes in which the final (F2) model explained less than 33 per cent of the variance in NMA (1, 7, 4 per species), as well as those less than two whisk periods in length after model fitting (6,7,13), were excluded from further analysis. This left 24, 30 and 35 episodes for the three species (mean duration across all species 540 ms).…”

“…At the same time, rodent whisking patterns are often reported to be highly variable [6,22,28,45]. One form of variability is where multiple (typically two) peaks are observed to occur within a single forwardbackward sweep; these 'double pumps' have been described in both hamsters [6] and rats [45]. A specific pattern that we have observed in mouse whisking data (figure 3, traces 4 and 5) and that has also been described for hamster [6], is an alternating sequence of larger and smaller pumps.…”

“…While phylogenetic relationships are clearly important, body-size and lifestyle also appear to matter; for instance, vigorous whisking has been hypothesized to be more common in nocturnal animals of smaller size [6]. The circumstances in which whisking is expressed also need to be further investigated.…”

“…High-speed video recordings show that the whisker movements of freely moving animals often diverge from the regular, bilaterally symmetric and synchronous motor patterns that are usually seen in head-restrained animals. Asymmetries, asynchronies and changes in whisk amplitude and timing have been noted, some of which appear likely to boost the amount of useful sensory information obtained by the animal [6,9,16,25]. Forms of whisking modulation that can be considered to be elements of active sensing control include the following.…”

“…Rodents, such as rats and mice, have the ability to control the position and movement of their long facial whiskers (the mystacial microvibrissae) relative to the head [5]. This control is afforded by a specialized musculature, which includes dedicated muscles, one per whisker, that are intrinsic to the whisker pad, as well as muscles external to the pad that can move all of the whiskers together by shifting the pad or by transforming its shape [3,[6][7][8]. The characteristic pattern of rat whisker movement, and also its principal component when viewed from above [9], is for all of the macrovibrissae (around 35 on each side of the snout) to move forward together (protract), and then be pulled back together (retract).…”