Relationships between body weight and skull development in rats raised in enriched and impoverished conditions.

Abstract

AbstractRats experiencing an enriched environment develop a heavier, thicker visual cortex than rats living in an isolated condition (Bennett et al., '64). The present experiment was carried out to determine if these enriched‐environment animals also possessed a larger neurocranium.Eleven pairs of male littermate rats from the S1 strain were used in Experiment I and ten pairs in Experiment II. At 25 days of age one animal of each littermate pair was placed in an enriched environment, and his brother was assigned to an isolated condition. Roentgenograms were taken eight days after the animals entered their respective conditions and again 69 days later. Skeletal measures were made from the roentgenograms, and endocasts were also made.The intracranial dimensions and the endocast weights did not differ significantly between the two experimental groups. However, other aspects of skull development, e.g., bizygomatic width, maxillary width, and skull weight did differ significantly, with the isolated animals having the greater measures. The differences in the skulls appear simply to reflect differences in body weight with a positive correlation between body weight and facial bone development in both young and old animals. The positive correlation between body weight and cranial size in young animals is not maintained in old animals.