The hyperkinetic abnormal movements scale: a tool for measuring levodopa-induced abnormal movements in squirrel monkeys.

The Hyperkinetic Abnormal Movements Scale (HAMS) was developed based on extensive observation of normal and abnormal movements in squirrel monkeys. The observations of abnormal movements were performed using animals that had undergone prior lesioning with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) that subsequently developed levodopa-induced abnormal movements. Specific and easily observable changes in behavior were used to delineate the boundaries between each rating level of the scale.