[Features of spontaneous locomotor activity in neonatal rats in a novel environment].

Dynamics of spontaneous locomotor activity was investigated in neonatal rats. The increased level of activity and its subsequent decrease in testing were observed already on postnatal day 6 and persisted during the second week of development. These behavioral features were due to simultaneous changes in motility of both front and hind limbs. The analysis of the dynamics of activity revealed two principal components which determined more than 84% of the variability in spontaneous locomotor activity of animals beginning from postnatal day 6. The second component responsible for the increased activity level during the first minute of testing and its subsequent decrease was not correlated with the first component, which determined the basic activity level on the 3-5 min oftesting. This first component was associated with formation of the pyramidal tract.