No abstract

Formation of a conditioned emotional response (CER), using suppression of food-reinforced bar-pressing as an index, was studied in a group of rats with amygdaloid lesions ( N = 5) and in a sham-operate control group ( N = 5). In contrast to control animals, which typically suppressed in two to three sessions, none of the amygdaloid operates met criterion within the set limit of 15 sessions or showed signs of suppression. Increasing the intensity and duration of shock also proved ineffective in these animals. Only by punishing each bar-press during the CS period could their responding be suppressed. Further tests on generalization of conditioned suppression, performed on two of the control animals, revealed relatively flat generalization gradients, consistent with other findings. Results were discussed in terms of amygdaloid effects on non-reinforced behavior in discrimination situations. “Inhibition” of responding associated with nonreinforcement appears to involve some of the same processes that operate in shock-motivated behavior.

Rats trained in a bar-pressing situation to discriminate between either 2 tones or tone and no-tone, based upon intermittent food reinforcement in the presence of S*, displayed consistent and often severe impairment on retention performance after large bilateral lesions in the amygdaloid area. Histological analysis also implicated the putamen in these effects. Amygdaloid impairment was closely associated with increased responding under nonreinforced conditions, with no concomitant increases in responding to S" 1 ". Hippocampal lesions, by contrast, increased responding to S* without seriously affecting responding to S~. Amygdaloid impairment on stimulus generalization occurred after 2tone but not after tone-no-tone training, and seemed to reflect a defect in generalization of S~ or in behavioral contrast as part of a basic disturbance in S" control of behavior.

No abstract

On each trial 5s were shown two pairs of alphabetical stimuli (a "memory" pair and a "test" pair) separated by 8 sec. of auditory shadowing. After the 8 sec. they were required to decide whether the two test letters had the same names as the two memory letters. When, in fact, the memory and test stimuli had the same names, 5s' responses were more rapid and accurate if those stimuli were also physically identical. Furthermore, these differences were augmented if both the memory and test stimuli were presented in mirror image since that condition had little, if any, effect on responses to physically identical stimuli (that is, when 5s might be able to bypass the process of naming the stimuli by making a visual comparison of the test stimulus to a visual trace, if any, of the memory stimulus). Both of these findings therefore suggest that 5s were often able to maintain such visual traces.