Changes in cortical dendritic branching subsequent to partial social isolation in stumptailed monkeys.

Stumptailed monkeys were reared from 1 week after birth to 6 months of age in either a colony condition with the mother or in partial social isolation that allowed visual contact with the colony animals, but not physical contact. At 6 months of age the animals were killed and selected areas of the neocortex stained by the Golgi-Cox method. Relatively nonspiney cells of Layer IV were drawn and analyzed for complexity of dendritic branching. Isolation-reared animals had significantly decreased branching complexity in Motor I cortex when compared to the control animals. A transform of the data that related the number of branches to the number of previous branches showed a slight rearing effect in Somatosensory I cortex with the deprived animals having a lower rate of branching than the controls. We conclude that social isolation also includes a motoric deprivation that could account for these data.