Neonatal exposure to novel environment enhances hippocampal-dependent memory function during infancy and adulthood

Early life experience affects behavior and brain mechanisms. Handling rats during the first three weeks in life can slow age-related cognitive decline (as measured by a hippocampal-dependent spatial learning task) and reduce age-related hippocampal neuron loss. It is not clear, however, whether this early environmental influence on learning is selective for old age or is more general, affecting cognitive development during infancy and young adulthood as well. We briefly exposed neonatal rats to a novel non-home environment for 3 min daily during the first three weeks of life (as a component of the handling method). We found that this brief early environmental manipulation resulted in enhanced hippocampal-dependent learning immediately after weaning and that this learning enhancement persisted into adulthood. These results suggest that subtle early life events can affect cognitive development in all developmental stages and that changes in neural mechanisms other than neuron number are likely to mediate the learning enhancement at multiple developmental stages.     

Retrieval conditions and false recognition: testing the distinctiveness heuristic

High levels of false recognition are observed after people study lists of semantic associates that all converge on a nonpresented lure word. In previous experiments, we have found that orienting participants to encode distinctive information about study list items by presenting them as pictures as opposed to words produces marked reductions in false recognition. We have suggested that these reductions reflect the operation of a distinctiveness heuristic: Participants demand access to detailed pictorial information in order to support a positive recognition decision. The present experiments provide additional evidence on this point and allow us to distinguish between the distinctiveness heuristic account and an alternative account based on the impoverished encoding of relational information that occurs when one is studying pictures. In Experiment 1, even when only half of the items in a study list were presented as pictures, a general suppression of false recognition was observed that could be attributable to impoverished encoding of relational information. Experiment 2 provided a critical test of the distinctiveness heuristic account: We manipulated test instructions and found that differences in false recognition rates between picture and word encoding were attenuated in a retrieval condition that did not encourage reliance on a distinctiveness heuristic.     

The use of fruiting synchrony by foraging mangabey monkeys: a ‘simple tool’ to find fruit

Previous research has shown that a considerable number of primates can remember the location and fruiting state of individual trees in their home range. This enables them to relocate fruit or predict whether previously encountered fruit has ripened. Recent studies, however, suggest that the ability of primates to cognitively map fruit-bearing trees is limited. In this study, we investigated an alternative and arguably simpler, more efficient strategy, the use of synchrony, a botanical characteristic of a large number of fruit species. Synchronous fruiting would allow the prediction of the fruiting state of a large number of trees without having to first check the trees. We studied whether rainforest primates, grey-cheeked mangabeys in the Kibale National Park, Uganda, used synchrony in fruit emergence to find fruit. We analysed the movements of adult males towards Uvariopsis congensis food trees, a strongly synchronous fruiting species with different local patterns of synchrony. Monkeys approached within crown distance, entered and inspected significantly more Uvariopsis trees when the percentage of trees with ripe fruit was high compared to when it was low. Since the effect was also found for empty trees, the monkeys likely followed a synchrony-based inspection strategy. We found no indication that the monkeys generalised this strategy to all Uvariopsis trees within their home range. Instead, they attended to fruiting peaks in local areas within the home range and adjusted their inspective behaviour accordingly revealing that non-human primates use botanical knowledge in a flexible way.     

Measuring QoL with SF-36 in Older Americans with TBI

This study demonstrated reliability and factor structure of the Medical Outcomes Study Short-Form Health Survey (SF-36) among older Americans with Traumatic brain injury (TBI), and evaluated effects of injury severity and race on SF-36's items and latent domains. A representative sample of 654 older, racially diverse patients with TBI was selected from the South Carolina Traumatic Brain Injury Follow-up Registry. Reliability and factor structure of SF-36 were evaluated using Cronbach’s alpha and confirmatory factor analysis (CFA). Multiple-indicator multiple-causes (MIMIC) models were used to study effects of injury severity and race on items (differential item functioning, DIF) and latent domains (population heterogeneity) of SF-36. SF-36 was reliable and its current eightfactor structure was confirmed. While TBI severity did not impact latent domain scores of SF-36, race did. Blacks had higher vitality and lower role-emotional scores than whites. The measurement model was invariant to injury severity and race (free of DIF), and DIF did not contribute to the differences of vitality and role-emotional between black and white older TBI patients. SF-36 was valid to measure quality of life (OoL) after TBI in racially diverse elderly population. Blacks tend to assert to strong coping behaviors in the presence of physical stress while admitting low performance due to emotional stress. In QoL research where the primary outcomes are usually composite scores from instruments, MIMIC models have advantages over conventional multivariable regression models in testing the validity of the instruments and assessing covariate effects on latent traits of instruments while controlling for DIF effects.