Passive Avoidance Errors Research Articles

Scopolamine and acquisition of go-no go avoidance: a further analysis of the perseverative antimuscarinic deficit.

Rats treated with scopolamine (0.5 mg/kg SC daily) during the acquisition of a discrimination task with symmetrical negative reinforcement (light-go, noise/light-no go) showed a learning impairment, with both active and passive avoidance deficits. In the initial stage of such training, however, fewer passive avoidance errors and more active avoidance errors were made by treated animals if active avoidance pretraining had occurred in the no-drug state. A similar experiment using the same stimulus arrangement with asymmetrical reinforcement (no punishment of intertrial, and no go signal, responses) showed a scopolamine effect consisting mainly of increased responding to extinction signals and during intertrial intervals, with little or no active avoidance deficit. Furthermore, interactions due to changes in treatment conditions in successive stages of training were minimized in the latter task, suggesting that the effects of the shift-no shift factor on distribution of errors in the early stages of active-passive avoidance learning were unlikely to have been due to a genuine drug dissociation. Overall, these results and others obtained previously in the same and related tasks tend to rule out some unidimensional explanations of antimuscarinic effects, e.g., response disinhibition (an exclusively motor deficit) or impairment of stimulus sensitivity (an exclusively sensory deficit). The data rather confirm the notion of a sensorimotor drug bias leading to a shift in response prepotencies depending jointly on stimuli, responses, and response consequences. Prior learning history and behavioural compensation for adverse treatment consequences at the reinforcement level may interact with the sensorimotor bias so as to produce "set perseveration" (perseveration of response tendencies).

Depression of two-way avoidance learning and enhancement of passive avoidance learning by small doses of physostigmine

The effects of physostigmine on the acquisition of two-way active avoidance and of GO-NO GO avoidance discrimination were studied in rats. The drug was without effect on active avoidance learning at the lowest dose tested (0·025 mg/kg s.c.), while a significant retardation was observed after the administration of 0·05 or 0·75 mg/kg. Both 0·025 and 0·05 mg/kg of the drug changed the distribution of errors during the acquisition of the GO-NO GO discrimination, by increasing the frequency of active avoidance errors and decreasing the frequency of passive avoidance errors. The overall effect, in terms of total errors, was in the direction of a slight facilitation of discrimination learning, which was significant only in the second of 10 training sessions. These opposite results on active and passive avoidance learning are interpreted as showing that small doses of physostigmine enhance the activity of response-inhibiting systems, without producing general changes in sensory and/or associative functions.