Single olfactory bulb units were studied in two macrosmatic species of rodents under conditions intended to preserve the cyclical stimulation which normally accompanies nasal breathing. Patterns of unit activity related to the inhalation cycle were observed in all animals, often in the absence of specific stimuli, and could not be explained in simple mechanical terms. Distinctive changes in these patterns occurred in response to certain odors, and were generally independent of changes in the overall firing frequency. These findings indicate that a change in the overall firing frequency of unit discharges is neither a necessary nor sufficient measure of responsiveness to odors in the rodent olfactory bulb, and that stimulus-specific temporal distributions of unit firing may be involved in olfacto-endocrine activities.

Retroactive effects of electroconvulsive shock (ECS) were studied in 477 male hooded rats which received ECS 0.5-60.0 sec. after single passive avoidance training trials. As in previous studies, impairment in retention was inversely related to duration of ECS-delay interval. However, unlike earlier studies, impairment was observed only at relatively short (0.5-10.0 sec.) ECS-delays. Impairment is attributed to brief RA and not to aversive effects of ECS which were shown to develop only after repeated ECS treatments. The results are discussed in terms of both the consolidation hypothesis and alternative "conflict" and "competing-response" hypotheses of ECS effects.

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