Experiments have been made on rats and mice within the first month of postnatal life. Common age dynamics of grooming reactions for these animals was shown which consists of a sharp intensification of grooming movements at the 3rd week, i.e. at the period of "behavioral arousal", as well as of heterochronous onset of different types of movements which results from successive maturation of the brain structures in which rhythmic centres of these movements are located. Quantitative differences in grooming of rats and mice are presumably due to ecological peculiarities of these animals. Periodic pattern of realization of grooming, as well as the parameters of its rhythmic components suggests that stereotype behavioural reactions are governed by mechanisms of autorhythmic excitation which are typical for the early stages of the development of the nervous system.
Aging Animals