Scopolamine affects the cognitive processes involved in selective object exploration more than locomotor activity

Abstract

Three experiments were conducted to investigate the effects of a scopolamine injection (1 mg/kg, i.p.) on object exploration, response to change, and locomotor activity. Rats injected before exploration displayed a lower level of object investigation and a higher level of locomotor activity than did saline-injected controls (Experiment 1). Locomotor activity, but not object investigation, decreased with time. In addition, scopolamine-injected rats did not renew exploration after object changes. When treated after exploration (Experiment 2), scopolamine-injected rats showed a marked increase in object investigation, but not in locomotor activity. In this condition, they were able to detect a new object on the basis of its spatial location. The same pattern of overall activity was observed in Experiment 3 (a control condition with no change and animals treated after exploration). Taken together, these results suggest that the cholinergic system is more involved in cognitive components of exploration, such as the processing of object quality and location, than in sensorimotor processing. It is suggested that the memory deficits usually associated with an anticholinergic blockade might result from an impairment in the gathering and encoding of relevant information.