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.     

Darwin, Design and Dawkins’ Dilemma

Richard Dawkins has a dilemma when it comes to design arguments. On the one hand, he maintains that it was Darwin who killed off design and so implies that his rejection of design depends upon the findings of modern science. On the other hand, he follows Hume when he claims that appealing to a designer does not explain anything and so implies that rejection of design need not be based on the findings of modern science. These contrasting approaches lead to the following dilemma: if he claims that Darwinism is necessary for rejecting design, he has no satisfactory response to design arguments based on the order in the laws of physics or the fine-tuning of the physical constants; alternatively, if Humean arguments are doing most of the work, this would undermine one of his main contentions, that atheism is justified by science and especially by evolution. In any case, his Humean arguments do not provide a more secure basis for his atheism because they are seriously flawed. A particular problem is that his argument for the improbability of theism rests on a highly questionable application of probability theory since, even if it were sound, it would only establish that the prior probability of God’s existence is low, a conclusion which is compatible with the posterior probability of God’s existence being high.     

Normal aging and the dissociable prototype learning systems

Dissociable prototype learning systems have been demonstrated behaviorally and with neuroimaging in younger adults as well as with patient populations. In A/not-A (AN) prototype learning, participants are shown members of category A during training, and during test are asked to decide whether novel items are in category A or are not in category A. Research suggests that AN learning is mediated by a perceptual learning system. In A/B (AB) prototype learning, participants are shown members of category A and B during training, and during test are asked to decide whether novel items are in category A or category B. In contrast to AN, research suggests that AB learning is mediated by a declarative memory system. The current study examined the effects of normal aging on AN and AB prototype learning. We observed an age-related deficit in AB learning, but an age-related advantage in AN learning. Computational modeling supports one possible interpretation based on narrower selective attentional focus in older adults in the AB task and broader selective attention in the AN task. Neuropsychological testing in older participants suggested that executive functioning and attentional control were associated with better performance in both tasks. However, nonverbal memory was associated with better AN performance, while visual attention was associated with worse AB performance. The results support an interactive memory systems approach and suggest that age-related declines in one memory system can lead to deficits in some tasks, but to enhanced performance in others.     

Avoidant coping in panic disorder: a yohimbine biological challenge study

Few studies have addressed whether the use of avoidance-oriented coping strategies is related to the development of panic in patients with panic disorder(PD). Self-report, clinician-rated, and physiological data were collected from 42 individuals who participated in a yohimbine biological challenge study, performed under double-blind, placebo-controlled conditions. Participants included 20 healthy controls and 22 currently symptomatic patients who met DSM-IV-TR diagnostic criteria for PD. Consistent with prediction, patients with PD who had higher perceived efficacy of avoidance-oriented strategies in reducing anxiety-related thoughts reported increased severity in panic symptoms during the yohimbine challenge condition as compared to the placebo. Further, patients with PD who had more fear of cognitive dyscontrol, cardiovascular symptoms, and publicly observable anxiety also reported increased severity in panic symptoms during the challenge. Healthy controls who had more fear of cardiovascular symptoms similarly reported increased severity in panic symptoms during the challenge. No effects were found for heart rate response to the challenge agent. These results provide support for the role of avoidance-oriented coping strategies and fear of anxiety-related symptoms as risk and maintenance factors in the development of panic symptoms, particularly within a biological challenge model.     

Obsessive-Compulsive Disorder in Late Life

Although obsessive-compulsive disorder (OCD) has received increasing attention, the study and treatment of OCD in late life has been neglected. The obsessions and compulsions seen with older adults do not appear to differ from the symptoms experienced by other age groups, although developmental issues might influence symptom focus (e.g., memory functioning-related obsessions). Hoarding difficulties might be prevalent in late life, although additional studies are needed. Seniors with OCD can present with comorbid psychiatric disorders, multiple general medical problems, and impaired cognitive functioning, complicating evaluation. There have not been controlled clinical trials of cognitive-behavioral therapy (CBT) for late-life OCD, although initial reports suggest older adults respond to CBT that includes age-related treatment modifications. We illustrate the challenges to assessing and treating older adults with OCD with case examples involving memory-related obsessions and clinical hoarding. The successful strategies used for adapting CBT for the treatment of late-life generalized anxiety disorder might serve as a model for advancing the study and treatment of late-life OCD.     

Retrieval independence between parts and wholes in successive recognition tasks

Participants studied AB word pairs and completed three recognition tests. In one recognition test each A word was presented with two distractors that did not appear on the study list. In another recognition test each B word was presented with two distractors that did not appear on the study list. In a third recognition test an AB target was presented with two distractors composed of words not on the study list. Six different groups of participants each performed the recognition tests in a different order, so that all possible orders were tested. Recognition of the A, B, and AB targets for a given study pair were independent of each other when single-word recognition preceded double-word recognition. There was almost complete independence in the reverse order. Even when recognition judgements were restricted to those for which the participants were most confident, there was independence of recognition among the three tests. A pair recognition test served as an additional study trial for the individual words; however, the reverse was not the case. All of these results were predicted by a single three-parameter mathematical model derived from the hypothesis that single-word and double-word targets had independent representations in memory.     

Contextual Factors for Research on Psychological Therapies for Aboriginal Australians

This paper is to provide a commentary to Can cognitive behavioural therapy (CBT) be effective for Aboriginal Australians? Perspectives of Aboriginal practitioners trained in CBT. It is inspiring that this study has found that CBT can play a useful role in therapy for Aboriginal and Torres Strait Islander people but the outcomes need to be considered with caution. CBT can provide a useful tool when working with Aboriginal and Torres Strait Islander people, but in itself is not adequate for a number of reasons. Firstly, it is not culturally responsive but can be part of an approach that might be culturally appropriate. The authors are compelled at this point to give a history of mental health and Aboriginal and Torres Strait Islander people to provide a background context to the discussion and to illustrate why some psychological approaches such as CBT can only ever be part of the tools that might be used in a broader framework, that is required to address and strengthen Aboriginal and Torres Strait Islander people's well‐being.     

Facial Feature Assessment of Popular U.S. Country Music Singers Across Social and Economic Conditions

The facial features of the artists of the top Country Billboard song for each year from 1946 to 2010 were investigated across changes in U.S. socioeconomic conditions. When conditions were relatively poor, country music artists with more mature facial features of smaller eyes and larger chins were popular, and when conditions were more prosperous, country music artists with more baby-faced features of larger eyes and smaller chins were popular. Results extend previous findings with pop singers, movie actresses, and Playboy Playmates, and suggest the social and economic environment influences preferences for country singers across time.     

The exclusive induction of extinction is gated by BDNF

We have previously reported that the reconsolidation and extinction of hippocampal-dependent contextual fear memory can be initiated by a single context conditioned stimulus (CS) presentation of either short or long duration, and that both processes require protein synthesis in this brain region. Furthermore, reconsolidation depends on Zif268 activity in this region. Here we show that by infusing a recombinant brain-derived neurotrophic factor (rBDNF) directly into the brain of rats, that high levels of mature BDNF in the hippocampus at retrieval constrain the extinction of the fear memory after prolonged memory recall. We also show after a short CS exposure that reconsolidation was impaired using antisense oligonucleotides targeting Zif268, and that, similarly, reductions in conditioned behavior were observed after prolonged CS presentation when extinction is constrained by high levels of BDNF. This is direct evidence that in the mammalian brain extinction proceeds exclusively after prolonged CS exposure. In addition, that BDNF activity in the hippocampus contributes to a molecular switch for the extinction of hippocampal-dependent memory.