Comparison of the structure of hyperactive behavior in rats after brain damage from x-irradiation, carbon monoxide and pallidal lesions.

Nocturnal hyperactivity, as measured by photocell counts of locomotion in a residential maze, was produced in rats by 3 different kinds of brain damage, X-irradiation at gestational day 14 or 15, exposure to carbon monoxide on the fifth day of postnatal life, or bilateral stereotaxic lesions of the globus pallidus in adult rats. These brain-damaged rats and their controls were photographed at 1 frame/sec during their first exploratory experience in a simple cage. Frequency of 15 motor acts, duration of each occurrence and associations of pairs of acts were calculated. The 15 motor acts were divided into 3 clusters of acts labeled grooming, exploratory and attention behaviors. Hyperactivity was associated with shortened durations and increases in frequency of exploratory acts, while grooming and attention behaviors tended to decrease in duration and frequency. Sequences of behavior acts were less structured in hyperactive animals than in controls. In spite of the marked differences known to be produced on brain structures by the 3 different kinds of damage, no changes in behavior structure were found which were uniquely associated with one kind of brain damage. Hyperactivity appeared to be a continuum in that the intensity of effects produced on behavior as measured by the photographic technique correlated well with the amount of increase in photocell activity.