The effects of daily trimming of the whiskers in rat pups from day 2 or day 9 to day 20 on eye opening time and the formation of early behavioral reactions, i.e., walking, rearing, grooming, and manipulatory activity, were studied in rat pups subjected to deprivation and siblings reared with them. Rat pups subjected to vibrissectomy from day 2 of life and their siblings showed acceleration of eye opening, maturation of grooming, and rearing without support; the formation of manipulatory activity was delayed, as were changes in the structures of correlational relationships between the times at which behavioral reactions formed and eye opening occurred. Vibrissectomy from day 9 of life eliminated most correlational relationships in deprived animals without impairing the dynamics of the development of early behavioral reactions. Siblings showed delayed formation of manipulatory activity, though changes in the structure of correlational relationships were less significant than in deprived animals.

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The effects of restriction of sensory afferentation in rats by vibrissectomy performed daily on days 9 to 20 of life on the formation of defensive reactions in early postnatal ontogenesis were studied. Vibrissectomized and control rat pups were assessed in terms of the extent of motor defensive reactions in response to touching the skin from days 10 to 18 of life, the duration of the freezing reaction at age 20 days, and behavior in the open field at age 25 days. Vibrissectomized rat pups showed the following significant differences from controls: a decrease in the extent of early withdrawal from a potentially dangerous stimulus (at age 12 and 13 days), a decrease in the duration of the freezing reaction, and decreases in that extents of the flight reaction and emotional reactivity in the open field test.