Neurogenesis and the spacing effect: learning over time enhances memory and the survival of new neurons

Information that is spaced over time is better remembered than the same amount of information massed together. This phenomenon, known as the spacing effect, was explored with respect to its effect on learning and neurogenesis in the adult dentate gyrus of the hippocampal formation. Because the cells are generated over time and because learning enhances their survival, we hypothesized that training with spaced trials would rescue more new neurons from death than the same number of massed trials. In the first experiment, animals trained with spaced trials in the Morris water maze outperformed animals trained with massed trials, but there was not a direct effect of trial spacing on cell survival. Rather, animals that learned well retained more cells than animals that did not learn or learned poorly. Moreover, performance during acquisition correlated with the number of cells remaining in the dentate gyrus after training. In the second experiment, the time between blocks of trials was increased. Consequently, animals trained with spaced trials performed as well as those trained with massed, but remembered the location better two weeks later. The strength of that memory correlated with the number of new cells remaining in the hippocampus. Together, these data indicate that learning, and not mere exposure to training, enhances the survival of cells that are generated 1 wk before training. They also indicate that learning over an extended period of time induces a more persistent memory, which then relates to the number of cells that reside in the hippocampus.     

Mindestanforderungen für Prognosegutachten1

Die aus Richtern am Bundesgerichtshof, Bundesanw?lten, forensischen Psychiatern und Psychologen, Sexualmedizinern und weiteren Juristen bestehende interdisziplin?re Arbeitsgruppe, die sich bereits mit Mindestanforderungen für Schuldf?higkeitsgutachten befasst hat², hat nun auch die nachfolgenden Empfehlungen für die vielf?ltig zu erstattenden forensischen Prognosegutachten erarbeitet. Wegen der H?ufigkeit und der Bedeutung dieser Gutachten in der Strafvollstreckung ist die Arbeitsgruppe um drei erfahrene Vollstreckungsrichter erweitert worden. Die Mitglieder waren: VRinBGH Dr. Rissing-van Saan, VRiBGH Nack, RiBGH Basdorf, RiBGH Dr. Bode, RiBGH Dr. Boetticher, RiBGH Maatz, RiBGH Pfister, VRiBGH a.D. Dr. Sch?fer, die Bundesanw?lte Hannich und Altvater, die Vollstreckungsrichter RiOLG B?hm, Karlsruhe, RiOLG Dr. Müller-Metz, Frankfurt a.M., VRiLG Dr. Wolf, Marburg, der Kriminologe Prof. Dr. Sch?ch, München, der Rechtsanwalt Dr. Deckers, Düsseldorf, die forensischen Psychiater Prof. Dr. Berner, Hamburg, Prof. Dr. Dittmann, Basel, Prof. Dr. Kr?ber, Berlin, Prof. Dr. Leygraf, Essen, Dr. Müller-Isberner, Gie?en, Prof. Dr. Nedopil, München, Prof. Dr. Sa?, Aachen, Dr. Habermeyer, Rostock, die Sexualmediziner Prof. Dr. Dr. Beier, Berlin, Prof. Dr. Bosinski, Kiel, und der Rechtspsychologe Prof. Dr. K?hnken, Kiel. ¹ Dieser Beitrag ist bereits erschienen in NStZ 26:237–544 (2006), Abdruck mit freundlicher Genehmigung des Verlages C. H. Beck ² NStZ 25:57–62 (2005), Nervenarzt 76:1154–1159 (2005), Forens Psychiatr Psychol Kriminol 1:3–9 (2007)     

The context counts: Congruent learning and testing environments prevent memory retrieval impairment following stress

Stress before retention testing impairs memory, whereas memory performance is enhanced when the learning context is reinstated at retrieval. In the present study, we examined whether the negative impact of stress before memory retrieval can be attenuated when memory is tested in the same environmental context as that in which learning took place. Subjects learned a 2-D object location task in a room scented with vanilla. Twenty-four hours later, they were exposed to stress or a control condition before memory for the object location task was assessed in a cued-recall test, either in the learning context or in a different context (unfamiliar room without the odor). Stress impaired memory when assessed in the unfamiliar context, but not when assessed in the learning context. These results suggest that the detrimental effects of stress on memory retrieval can be abolished when a distinct learning context is reinstated at test.     

The effects of implicit attentional learning and habituation on inhibition of return

In two experiments, the effects of implicit attentional learning and habituation on inhibition of return (IOR) were assessed. Experiment 1 consisted of an informative variant of the spatial cuing paradigm (Posner, 1980), with the target appearing most often at the location next to the cue. Short-term as well as long-term learning of the regularities could be observed. This learning took place even though the participants were not able to verbalize the learned information, suggesting that the learning was implicit. By spatially separating the effects of implicit learning and IOR, we demonstrated that the magnitude of IOR slightly decreased because of long-term implicit orienting. In Experiment 2, a noninformative variant of the spatial cuing paradigm, IOR was still found to decrease over the course of the experiment. This suggests that habituation due to the mere repeated initiation of IOR also affects the magnitude of the IOR. This theory is supported by the finding that IOR recovered after short breaks in Experiment 2. However, habituation presumably only played a secondary role in Experiment 1. In sum, IOR was abolished by neither implicit attentional learning nor habituation. Here, the finding that IOR is not easily replaced by implicitly learned orienting clearly indicates that IOR is a powerful, low-level mechanism. We discuss implications of these results for the debate on the function of IOR.     

A rule-based presentation order facilitates category learning

We investigated the mechanisms by which concepts are learned from examples by manipulating the presentation order in which the examples were presented to subjects. We introduce the idea of a rule-based presentation order, which is a sequence that respects the internal organization of the examples within a category. We find that such an order substantially facilitates learning, as compared with previously known beneficial orders, such as a similarity-based order. We discuss this result in light of the central distinction between rule-based and similaritybased learning models.     

Why are idioms recognized fast?

It is an established fact that idiomatic expressions are fast to process. However, the explanation of the phenomenon is controversial. Using a semantic judgment paradigm, where people decide whether a string is meaningful or not, the present experiment tested the predictions deriving from the three main theories of idiom recognition—the lexical representation hypothesis, the idiom decomposition hypothesis, and the configuration hypothesis. Participants were faster at judging decomposable idioms, nondecomposable idioms, and clichés than at judging their matched controls. The effect was comparable for all conventional expressions. The results were interpreted as suggesting that, as posited by the configuration hypothesis, the fact that they are known expressions, rather than idiomaticity, explains their fast recognition.