The morphogenesis of motor rituals in rats treated chronically with the dopamine agonist quinpirole

Rats injected repeatedly with the dopamine agonist quinpirole develop motor rituals that evolve through a cascade of 4 behavioral processes. The I st involves increased activity. The 2nd involves increased path stereotypy, reflected in traveling repeatedly along the same few paths. The 3rd is an increase in the frequency of stopping in a few places, along with a decrease in stopping in other places. The 4th is a decrease in the repetition of movements performed in the specific stopping places. Altogether, these processes culminate in stereotypy, a typical short set of movements composed of a single performance of each movement type. Thus, stereotypy arises from changes in the temporal and spatial organization, but not the content, of behavioral patterns. These results provide a model for the development of motor rituals and their linkage to normal behavior and to the physical proper-ties of the environment.