5-HT1a receptor antagonists block perforant path-dentate LTP induced in novel, but not familiar, environments

Numerous studies suggest roles for monoamines in modulating long-term potentiation (LTP). Previously, we reported that both induction and maintenance of perforant path-dentate gyrus LTP is enhanced when induced while animals explore novel environments. Here we investigate the contribution of serotonin and 5-HT1a receptors to the novelty-mediated enhancement of LTP. In freely moving animals, systemic administration of the selective 5-HT1a antagonist WAY-100635 (WAY) attenuated LTP in a dose-dependent manner when LTP was induced while animals explored novel cages. In contrast, LTP was completely unaffected by WAY when induced in familiar environments. LTP was also blocked in anesthetized animals by direct application of WAY to the dentate gyrus, but not to the median raphe nucleus (MRN), suggesting the effect of systemic WAY is mediated by a block of dentate 5-HT1a receptors. Paradoxically, systemic administration of the 5-HT1a agonist 8-OH-DPAT also attenuated LTP. This attenuation was mimicked in anesthetized animals following application of 8-OH-DPAT to the MRN, but not the dentate gyrus. In addition, application of a 5-HT1a agonist to the dentate gyrus reduced somatic GABAergic inhibition. Because serotonergic projections from the MRN terminate on dentate inhibitory interneurons, these data suggest 5-HT1a receptors contribute to LTP induction via inhibition of GABAergic interneurons. Moreover, activation of raphe 5-HT1a autoreceptors, which inhibits serotonin release, attenuated LTP induction even in familiar environments. This suggests that serotonin normally contributes to dentate LTP induction in a variety of behavioral states. Together, these data suggest that serotonin and dentate 5-HT1a receptors play a permissive role in dentate LTP induction, particularly in novel conditions, and presumably, during the encoding of novel, hippocampus-relevant information.     

Students' perceptions and reported use of their memories after a memory-improvement course

23 college students who had taken a memory-improvement course completed a questionnaire at three different times: the beginning of the course, the end of the course, and two months after the end of the course. The questionnaire assessed the students' perceptions of their memory abilities, e.g., how good their memories were and how confident they were in their memories and knowledge about their memories, and their reported use of the memory techniques; it did not assess actual memory performance or ability. The students' responses to the questionnaire were compared with those of 23 control students who completed the questionnaire at the same three times. The memory students reported more positive changes in how they perceived their memory abilities and knowledge, and these reported changes in perceptions were still evident two months later. The students also reported that they were still using their memory techniques two months later.     

Conditioned suppression under positive, negative, and no contingency between conditioned and unconditioned stimuli

Using a conditioned suppression procedure, the effects of three contingent relationships between conditioned (CS) and unconditioned (US) stimuli were investigated. A traditional positive (if CS—then US) contingency suppressed response rate during the CS relative to responding during stimulus-free minutes of the session. A negative (if CS—then no US) contingency resulted in suppressed responding during CS-off minutes, and rate increases during the CS. A no-contingency control procedure, during which CS and US were randomly related, almost totally suppressed responding throughout the session and showed no differential effects of the CS on response rate. An analysis of changes in response rate during the minute after US-offset revealed acceleration under the no-contingency condition and, to a somewhat lesser degree, under the negative contingency. Both conditioned suppression and non-suppression are analyzed in terms of the temporal relationship between CS and US.     

Differential reinforcement of other behavior (DRO): a yoked-control comparison

After training to press a lever on a variable-interval 30-sec schedule, one group of rats was shifted to a differential-reinforcement-of-other-behavior 10-sec schedule, while a second group was shifted to a noncontingent yoked-control schedule that provided the same frequency and distribution of reinforcement. Then, both groups were extensively retrained on the variable-interval schedule, after which the first group was shifted to a series of differential-reinforcement-of-other-behavior 30-sec sessions alternating daily with variable-interval 30-sec sessions, while the second group was treated like the first on variable-interval days and yoked with the first as before on differential-reinforcement-of-other-behavior days. In both phases, response-decrement was more rapid and more marked in the differential-reinforcement-of-other-behavior animals than in the controls. The difference was due, at least in large measure, to sustainment of response in the control animals by adventitious reinforcement. All the differential-reinforcement-of-other-behavior animals developed “other” behavior—the same distinctive pattern of waiting at the foodcup—but there was no direct evidence that it contributed in any way to the decrement in lever pressing.     

The measurement of response force during a lever-press shock-escape procedure in rats

Three albino rats were given extensive exposure to an escape procedure in which shocks were scheduled to occur 30 sec apart. The amount of downward force exerted on the lever was continuously recorded and compared with traditional discrete measurement in which only responses above an arbitrary force threshold were recorded. Subjects typically remained in contact with the lever throughout the shock-free intertrial interval. Shock onset reliably occasioned a brief lurch from and return to the lever, which resulted in a lever-press escape response being recorded. Lever contact, which occupied an average of 90% of session time, showed great stability in force after a brief (e.g., 5-sec) period of instability after each shock terminated. In general, continuous measurement revealed considerably different results than discrete measurements of on-lever behavior. For example, continuous lever contact fluctuating near response threshold was often recorded as discrete responding, and sustained lever contact occurring below response threshold was omitted from discrete measurement.     

Body fat distribution and hemodynamic stress responses in premenopausal obese women: a preliminary study.

To examine the relationship between body fat distribution and hemodynamic stress responses, cardiovascular responses to a speech task and a forehead cold pressor task were evaluated with 24 premenopausal women classified a priori as either centrally or peripherally obese. Results showed that women with central adiposity exhibited greater stress-related increases in diastolic blood pressure and total peripheral resistance, whereas women with peripheral adiposity exhibited greater stress-related increases in cardiac output. Depression, self-consciousness, hostility, and mood scores did not explain significant variance in the stress response differences between regional adiposity groups. The findings suggest that central adiposity may increase the risk of cardiovascular disease in women at least in part by enhancing vascular responses to stress.     

Exposure to parental and community violence and the relationship to bullying perpetration and victimization among early adolescents: A parallel process growth mixture latent transition analysis

This study examined heterogeneity in parental and community violence exposure during middle school and its association with bullying perpetration and victimization in high school. Youth (N = 1,611) in four Midwestern middle schools participated. Parallel process growth mixture latent transition analysis was used to understand how trajectory profiles of middle school violence exposure was associated with high school bullying profiles. Impulsivity, depression, school belonging, and delinquency were assessed as moderators of the transition probabilities. A three class solution was found for violence exposure: decreasing parental violence/increasing community violence (n = 103; 6.4%), stable high parental violence and low community violence (n = 1,027; 63.7%), and increasing parental violence and stable high community violence (n = 481; 29.8%). Similarly, a three class solution was found for high school bullying: High Bullying Perpetration and High Victimization class (n = 259; 16%), Victimization only (n = 1145; 71%), and low all class (n = 207; 13%). The largest proportion of youth transitioning into the high bullying and high victimization class were from the decreasing parental violence/increasing community violence. Depression, impulsivity, school belonging, and delinquency all had various moderating effects on transition probabilities. Our findings make it apparent that early forms of parental and community violence are associated with aggressive behaviors and experiences with victimization during high school. Prevention and intervention efforts should target individuals who display early and chronic patterns of exposure to violence as these individuals have the greatest risk of later aggressive and victimization in high school.