Spatial training and high-frequency stimulation engage a common pathway to enhance glutamate release in the hippocampus

We have measured depolarization-induced release of endogenous glutamate in synaptosomes prepared from the dentate gyrus after the induction of LTP by high-frequency stimulation in anesthetized rats, and after training in the water maze. Both spatial training and LTP in untrained rats were accompanied by an increase in glutamate release from dentate synaptosomes. The enhancement of synaptosomal glutamate release induced by high-frequency stimulation was abolished in well-trained rats, and was reduced in partially trained rats and in rats trained in a nonspatial task. However, the magnitude of LTP was similar in well-trained and untrained groups. These results indicate that spatial training activates a glutamate release pathway that converges with that activated in LTP, and demonstrate an unexpected dissociation between increased glutamate release and LTP.     

A methodological study in a space flight simulation context]

To study the effects of isolation and confinement on small groups during long space flights, it is habitual to use closed hyperbaric ground chambers. For the first time, the European Space Agency made use of a nautral environment taking advantage of an Antarctic winter-over at the French Dumont d'Urville Station. The main objective of that study ("International Antarctic Psychological Programme"), was to compare different Russian tests used for training cosmonauts to a W. European approach validated during previous winter studies and European ground chamber simulations. Russian techniques appeared to be oriented to a narrow range of phenomena and unsuited to discern the adjustment to stress conditions.     

Use of experimenter-given cues in dogs

Since the observations of O. Pfungst the use of human-provided cues by animals has been well-known in the behavioural sciences (“Clever Hans effect”). It has recently been shown that rhesus monkeys (Macaca mulatta) are unable to use the direction of gazing by the experimenter as a cue for finding food, although after some training they learned to respond to pointing by hand. Direction of gaze is used by chimpanzees, however. Dogs (Canis familiaris) are believed to be sensitive to human gestural communication but their ability has never been formally tested. In three experiments we examined whether dogs can respond to cues given by humans. We found that dogs are able to utilize pointing, bowing, nodding, head-turning and glancing gestures of humans as cues for finding hidden food. Dogs were also able to generalize from one person (owner) to another familiar person (experimenter) in using the same gestures as cues. Baseline trials were run to test the possibility that odour cues alone could be responsible for the dogs’ performance. During training individual performance showed limited variability, probably because some dogs already “knew” some of the cues from their earlier experiences with humans. We suggest that the phenomenon of dogs responding to cues given by humans is better analysed as a case of interspecific communication than in terms of discrimination learning. Received: 30 May 1998 / Accepted after revision: 6 September 1998     

Fixation point offsets facilitate endogenous saccades

Subjects produced saccades to continuously visible targets that were signaled by the pitch, not the location, of an auditory signal. Such endogenous saccades were initiated more quickly when the visual fixation point disappeared 200 msec before the signal (thus producing a “gap”), even though the alerting benefits of such a warning were eliminated by an earlier warning tone. The presence of the gap effect under these circumstances shows that the effect is more general than was previously believed: Visual fixation point offsets facilitate saccades by affecting oculomotor processes related to both visually elicited (exogenous) and centrally produced (endogenous) saccades. In addition, the magnitude of the gap effect for endogenous saccades was significantly smaller than that for exogenous saccades, suggesting that at least some of the effect arises in relatively early processes, such as those involved in the processing of sensory signals, and not exclusively in later processes, such as those involved in the preparation and production of saccades.     

Mapping symbols to response modalities: Interference effects on Stroop-like tasks

Attention, Perception, & Psychophysics - Response compatibility effects were assessed with a Stroop-like task which involved arrow and word stimuli. The subjects were required to respond to one...     

Was the Soviet Union Totalitarian? The View of Soviet Dissidents and the Reformers of the Gorbachev Era

The article explains why Soviet dissidents and the reformers of the Gorbachev era chose to characterize the Soviet system as totalitarian. The dissidents and the reformers strongly disagreed among themselves about the origins of Soviet totalitarianism. But both groups stressed the effects of totalitarianism on the individual personality; in doing so, they revealed themselves to be the heirs of the tsarist intelligentsia. Although the concept of totalitarianism probably obscures more than it clarifies when it is applied to regimes like the Nazi and the Soviet, the decision of the dissidents and the reformers to use the term enabled them to clarify their own values and the reasons they felt compelled to criticize the Soviet Union and to call for its radical reform.     

Approximate entropy and point correlation dimension of heart rate variability in healthy subjects

The contribution of nonlinear dynamics to heart rate variability in healthy humans was examined using surrogate data analysis. Several measures of heart rate variability were used and compared. Heart rates were recorded for three hours and original data sets of 8192 R-R intervals created. For each original data set (n=34), three surrogate data sets were made by shuffling the order of the R-R intervals while retaining their linear correlations. The difference in heart rate variability between the original and surrogate data sets reflects the amount of nonlinear structure in the original data set. Heart rate variability was analyzed by two different nonlinear methods, point correlation dimension and approximate entropy. Nonlinearity, though under 10 percent, could be detected with both types of heart rate variability measures. More importantly, not only were the correlations between these measures and the standard deviation of the R-R intervals weak, the correlation among the nonlinear measures themselves was also weak (generally less than 0.6). This suggests that in addition to standard linear measures of heart rate variability, the use of multiple nonlinear measures of heart rate variability might be useful in monitoring heart rate dynamics.     

Effects of contextual interference on learning technical sports skills.

The effects of contextual interference on learning skills of volleyball (volley, bump, serve) are influenced by the scheduling of actual practice sessions: the activities can be proposed in a repetitive practice schedule (blocked practice) by continuously repeating the same task (low interference) or in random practice schedules by performing more tasks or variations of one same activity (high interference). High contextual interference, even though causing immediate limited performance, leads to superior performance on retention and transfer tests. Four experimental groups (13 students each) were placed in conditions of random, blocked, serial, and serial with high interference practice for 8 meetings (2 tests and 6 practice). Analysis yielded significant differences among the groups on a transfer test (long transfer) for the serve, so results in this instructional setting are partially in line with those generally found in laboratory experiments.