Release from proactive interference by experimental amnesia: electroconvulsive shock improves radial-arm maze performance in rats

Rats were trained in an eight-arm radial maze and tested using a proactive interference (PI) procedure. Each test trial consisted of forced choices of four randomly selected arms followed, after a 2-h delay, by free choices among all eight arms. Normally, rats chose correctly during the free choices by entering and retrieving food from the four arms not yet visited during the test trial. Occasionally, an interference trial preceded the test trial by 1.5 or 3 h; interference trials consisted of forced choices of another four arms and an immediate test. The presence of an interference trial lowered test-trial performance (PI). Electroconvulsive shock (ECS) administered immediately after the interference trial had no effect; i.e., PI was still observed. When ECS was administered at the midpoint of the 3-h intertrial interval, performance increased to control (no ECS, no PI) levels. Such release from PI, however, was not obtained, and test-trial performance remained inaccurate when ECS was delivered immediately after the forced choices of the test trial (either 1.5 or 3 h after the interference trial).     

Measurement of electroconvulsive shock Intensity

This paper discusses the error introduced in administering ECS by calibrating intensity on the S’s dc rather than ac resistance. Since the ac resistance of rats and mice can be lower than their corresponding dc resistance by a factor of 50, calibrating on dc resistance can introduce appreciable error depending on the current regulation of the ECS device. Examples are included to illustrate the range of possible error. In addition, an alternative method for measuring ECS intensity is presented that greatly reduces measurement error including those due to between-animal resistance differences that necessarily occur when using the usual methods.     

Extinction of a runway response following runway or goal box partial reinforcement

Rats were trained on a consistent reinforcement schedule in a straight runway. They were then switched to one of two partial reinforcement procedures. One group continued to run the full length of the runway, another was placed directly in the goal box. When extinguished in the full length of the runway both groups were more resistant to extinction than groups trained only on consistent reinforcement. An attempt was made to delineate the conditions for a demonstration of the partial reinforcement extinction effect. The results were discussed in relation to frustration theory.     

Relative effects of scopolamine and electroconvulsive shock upon habit reversal in white rats

30 adult male white rats were equally divided into control, scopolamine, and electroconvulsive shock groups to learn 20 successive reversal problems in an E-maze for water after 23 1/2 hr. of deprivation. The noncorrection method was used. After 1 mo. of preliminary training, each scopolamine animal received an intraperitoneal injection of 1 mgm of scopolamine hydrobromide per kgm of body weight while each in the shock group was given an ECS of 35 mA for .2 sec. at the end of every 10 daily trials. When a rat obtained 9 correct of 10 trials, the goal was switched to the opposite side of the maze. Controls were much superior to both experimental groups. While scopolamine animals experienced more detrimental effects initially, they caught up with the shock group and finally became superior. This shift is interpreted in terms of building tolerance to scopolamine and increasing anxiety to shock as effects of differential treatments accumulated.