Motor activity of squirrel monkeys measured with an ultrasonic motion sensor.

We describe an ultrasonic motion sensing system for measuring the motor activity of individual squirrel monkeys in their home cage. The system utilizes an inexpensive Commodore 64 microcomputer for data collection and can distinguish between movements of short (i.e., less than 1.0 s) and longer (i.e., greater than or equal to 1.0 s) duration, and between number of movements and time spent in motion. The diurnal pattern of spontaneous activity is illustrated along with the dose-dependent effects of d-amphetamine (0.025-1.6 mg/kg) and haloperidol (0.025-0.4 mg/kg).