Francesco Robustelli

Impaired performance by post-trial injections of cycloheximide in a passive avoidance task

SummaryCycloheximide, injected subcutaneously after training in a passive avoidance task resulted in impaired performances on the retest given 7 days later. A gradient was observed for this effect, injections given immediately after training producing most impairment and injections given 2 h after training producing none.

Retrograde amnesia from detention

Abstract Detention of mice in the passive avoidance apparatus after the training trial decreased their step-through latencies in the retest trial and increased amnesic effect of ECS treatment. Mere detention was found to produce retrograde amnesia even if it occurred outside the apparatus. Finally, detention affected performances in the retest trial only if given immediately after the training trial.

Impairment of delayed matching in monkeys by chlorpromazine and pentobarbital

SummaryMonkeys trained to perform in a delayed matching test under five delay conditions were given chlorpromazine hydrochloride (0.05, 0.1, 0.2 and 0.4 mg/kg) and pentobarbital sodium (1.0, 10.0 and 20.0 mg/kg) before test sessions. Both drugs decreased response rate proportionally as dose increased. Chlorpromazine initially depressed accuracy, but showed no specific effects as delay interval increased. Pentobarbital had little effect upon accuracy, although impairment on the simultaneous conditions was seen at the highest dose. It is concluded that neither drug produced specific effects upon short-term memory.

Biphasicity of the incubation curve

Two experiments were performed using a one-trial passive-avoidance task. In Experiment 1, different groups of mice were retested at different times after training. In Experiment 2, different groups were administered a footshock outside the conditioning apparatus and then were given the step-through experience at different times after the footshock. The time-response curve was found to be triphasic only in Experiment 1, while it produced a monotonie incubation curve in Experiment 2.

Permanence of a long temporal gradient of retrograde amnesia induced by electroconvulsive shock

Electroconvulsive shock (ECS) was administered to mice 10 sec, 120 sec, and 3 h after training in a passive avoidance task. Subgroups were retested at 24 h, 48 h, 72 h, 1 week, and 4 weeks. A temporal gradient of retrograde amnesia was produced, with ECS still being effective even when given 3 h after training. The gradient was maintained over all retest times. No evidence of recovery could be detected.

Cycloheximide induced amnesia: Its interaction with detention

After training in a passive avoidance task, mice were detained in the safe compartment of the conditioning apparatus. This detention produced an impairment of rentention on the retest trial.Detention did not prolong the cycloheximide susceptible phase of memory formation. A summation of the amnestic effects of the two treatments occurred only at a time when both were effective alone. Cycloheximide was without effect upon the detention experience itself.

Potentiation of the amnesic effect of electroconvulsive shock by detention

Electroconvulsive shock (ECS) administered to mice 10 min after training in a one-trial passive avoidance situation decreases their step-through latencies in the retest trial given 24 h later. A similar degree of impairment is found if the animals are detained in the same compartment of the conditioning apparatus for 10 min immediately after the training trial If ECS is given at the end of the detention period, its amnesic effect on the conditioned response is greatly increased.

Biphasicity of the time-response curve and amnesic effect of electroconvulsive shock in passive avoidance conditioning

Mice were trained in a one-trial passive avoidance task and retested 2 min, 5 min, 10 min, 30 min, or 24 h later. A biphasic time-response curve was obtained with art initial increase to 5 min, a subsequent decrease, and another increase to 24 h. Other groups of Ss were administered electroconvulsive shock (ECS) 2, 5, 10, or 30 min after training and retested 24 h later. The response curve shape of the ECS-treated groups was found to correspond to that concerning the different retest times, suggesting a negative correlation between ECS amnesic effect and the strength of the conditioned response at the time of ECS administration. The inadequacy of the hypotheses, according to which ECS interferes with a gradual monotonic process, to explain ECS amnesic effect is discussed.

Extinction in a passive avoidance task and its interaction with electroconvulsive shock

A passive avoidance conditioned response was partially extinguished by giving mice a socially facilitated exploratory session for 10 min immediately after the training trial. Electroconvulsive shock (ECS) administered 10 min after the training trial also resulted in a decrease of the step-through latencies in the retest trial given 24 h later. When ECS was administered at the end of the exploratory session, its amnesic effect on the conditioned response was greatly increased.