Injection of potassium chloride into the hippocampus produces a disruption of electrical activity; a concomitant of this disruption is a deficit in retention of conditioned suppression learned 24 hours before injection.

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LORE, RICHARD, and AVIS, HARRY (1969). Eflects of Auditory Stii?iulation and Litter Site upon Subsequetzt EmotionalBehavior in the Rat. DEVELOPMENTAL PSUCHOBIOI.OCY, 2(4): 212-215. In Experiment 1, rat litters that contained 3 or 9 pups were exposed to either silence, 55 db, or 90 db radio sounds during the preweaning period. T h e dependent variables were (a) measures of nest height and nest quality, (6) infant mortality, (c) weaning weights, and (d) activity and defecation on 3 open-field trials. Small-litter subjects (Ss) were heavier a t weaning but their open-field performance was virtually identical to that of large-litter Ss. The 55-db group was significantly more active on the 2nd and 3rd open-field trials. In the 2nd experiment, litters of 3 and 9 pups were exposed to 55 db or 90 db radio stimulation throughout the preweaning period. Results similar to those of the first experiment were obtained. Both studies indicate that litter size variations do not influence subsequent emotional behavior, whereas the degree of auditory input during preweaning can have marked effects upon emotional development. infant rats rearing conditions litter size auditory environment emotional development EVERAL RECENT studies have compared the adult s emotional behavior and body weight of rats reared in "quiet" rooms with that of Ss exposed to "busy" or "noisy" colony rooms. Denenberg, Schell, Karas, and Haltmeyer (1966) found that rats reared in a quiet environment during the preweaning period were lighter at weaning and less emotional. In contrast, McMichael (1966), reported the reverse findings in a very similar experiment. In a third study, Henderson (1966) exposed rats to different auditory environments after they were weaned. He found no weight differences between quiet and noisy reared rats, but the quiet reared Ss were more emotional. Levine and King (19G5) found that rats exposed to a noisy colony during both gestation and the preweaning period were heavier at weaning than Ss reared in a sound attenuation room. There were no differences in the weights of Ss exposed to the two treatments during the preweaning period only. Unfortunately, no behavioral observations were taken in this study. No generalizations concerning the effects of exposure to different auditory