Patterns of Whisker Movement Activity in the States of Sleep and Waking in Neonatal Rats
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Patterns of Whisker Movement Activity in the States of Sleep and Waking in Neonatal Rats A. R. Nasretdinov,1 G. R. Valeeva,1 and R. N. Khazipov1,2
Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 105, No. 10, pp. 1215– 1224, October, 2019. Original article submitted June 29, 2019. Revised version received July 25, 2019. Accepted July 26, 2019. The aims of the present work was to describe primitive whisker movements in neonatal Wistar rats (postnatal days 4–7) in the states of sleep and waking and to study correlations between whisker movements and body movements. Whisker movements were recorded by high-speed video recording and the animals’ behavioral state was determined by recording electromyographic activity of the cervical muscles and simultaneous recording of limb movements using piezo elements. During active sleep, movements consisted mostly of short-term whisker movements, and a significant proportion of these movements arose simultaneously with short-term bursts of activity in the cervical muscles and transient myoclonic twitches of the animal’s body. During periods of waking, movements were mostly complex long-lasting whisker movements, which were accompanied by long-term increases in cervical muscle tone and complex body and limb movements. Both types of whisker movement occurred mainly in the rostral and caudal directions, and the amplitude of movements during waking was only slightly greater than the amplitude of whisker movements during sleep. The data obtained here provide evidence that the temporal organization of whisker movement activity in neonatal rats is significantly different in the states of sleep and waking and that whisker movements in both behavioral states showed strong correlations with the animal’s body movements. It is suggested that generalized primitive whisker and body movements in neonatal rats are due to the activity of a single central pattern generator both in the state of active sleep and in the state of waking. Keywords: ontogeny, neonatal movements, whiskers, physiological myoclonia, generalized movements, electromyography.
Whiskers are long, rigid hairs located on the snouts of animals and in rodents (for example rats and mice) and a number of other mammals are specialized sensory organs. In contrast to the normal hairs of the coat and undercoat, which mainly serve to insulate, the whiskers of rodents provide active tactile investigation of surrounding objects. The bases of whiskers are inserted into subcutaneous follicles served by about 200 nerve endings from the trigeminal nerve, and the position of the follicle itself, its tilt angle, and, thus, the position of the whisker itself in space, are controlled by protractor and retractor muscle groups [1–3]. On investigating external objects, the whiskers perform looplike movements at a frequency of about 10 Hz, mainly in the
rostrocaudal direction (so-called whisking), and tactile information received as a result of these movements passes via ascending pathways to the somatosensory cortex of
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