Automating the measurement of locomotor activity.

General locomotor activity is assessed in many ways ranging from observer ratings to sophisticated computer-assisted electronic monitoring with the aim of determining the unconditioned and conditioned effects of various pharmacological compounds. A system was constructed utilizing 6 independent test chambers each equipped with 14 infrared emitters and detectors arranged in two tiers and controlled by a microcomputer. The effects of the stimulant, d-amphetamine and its antagonism by the tranquilizer, pimozide, on unconditioned and conditioned activity as assessed using this system were found to be almost identical to results obtained using observer rating techniques. Other data showed that activity assessed by the system was subject to habituation and that this learning interacted with the effects of some drugs. Activity as measured by the system showed dose and time effects of various stimulants assessed over a 6 hr test period. Finally, the breakdown of activity into counts on the upper and lower tier of beams resulted in the finding that these two components of behavior were differentially affected by stimulants. These results demonstrate the validity and reliability of automated systems for assessing locomotor activity and show their promise for gaining further insight into the elements of behavior that are affected by various drugs.