The relation of lifetime cognitive activity and lifetime access to resources to late-life cognitive function in older African Americans

Research in older Caucasians has demonstrated that cognitive activity is related to cognitive function in late adulthood. Knowledge of this association is limited in older minority populations. We examined the relation of cognitive activity and access to cognitive resources, with cognitive function in a group of 108 older African Americans. We constructed two scales to measure the frequency of cognitive activity and the presence of resources that promote cognitive activity during early and late life. Both measures had high internal consistency and the cognitive activity scale had adequate temporal stability over a 4-week interval. In analyses that controlled for age and education, more frequent lifetime cognitive activity was related to current cognitive function, but lifetime cognitive resources only approached significance. The results suggest that both measures are psychometrically sound in a minority population and that lifetime cognitive activity may contribute to current cognitive function in African Americans.     

Competence in everyday activities as a predictor of cognitive risk and mortality

This study examined the association of a performance-based measure of everyday functioning with clinically meaningful outcomes. Elderly participants in a prospective study of dementia were assessed at two occasions on the Everyday Problems Test for Cognitively Challenged Elderly (EPCCE), a performance-based measure of everyday functioning. Older adults who remained cognitively intact performed approximately 0.66 SD units higher on the EPCCE at both occasions than elders rated as impaired, when covarying on age, education, gender, and cognitive status. Relative to the nonimpaired participants, decline in EPCCE performance over a 2-year interval was significantly greater for impaired participants and those participants who transitioned from nonimpaired to impaired over the course of the study. Increased risk of mortality was associated with lower baseline scores and decline in EPCCE performance even after controlling for demographic variables and performance on the Mini-Mental State Examination. Given the clinical importance of identifying "at risk" elders for impairment, the findings from this study provide initial evidence for the predictive utility of performance-based measures of everyday functioning.     

Ethics, biotechnology, and global health: the development of vaccines in transgenic plants

As compared with conventional vaccine production systems, plant-made vaccines (PMVs) are said to enjoy a range of advantages including cost of production and ease of storage for distribution in developing countries. In this article, we introduce the science of PMV production, and address ethical issues associated with development and clinical testing of PMVs within three interrelated domains: PMVs as transgenic plants; PMVs as clinical research materials; and PMVs as agents of global health. We present three conclusions: first, while many of the ethical issues raised by PMVs are familiar, PMVs add a new dimension to old issues, and raise some novel issues for ethicists and policy-makers; secondly, it is premature to promise broad applicability of PMVs across the developing world without having demonstrated their feasibility; thirdly, in particular, proponents of PMVs as a solution to global health problems must, as a condition of the ethical conduct of their research, define the commercial feasibility of PMVs for distribution in the developing world.     

Retrieval-induced facilitation: initially nontested material can benefit from prior testing of related material

Classroom exams can assess students' knowledge of only a subset of the material taught in a course. What are the implications of this approach for long-term retention? Three experiments (N = 210) examined how taking an initial test affects later memory for prose materials not initially tested. Experiment 1 shows that testing enhanced recall 24 hr later for the initially nontested material. This facilitation was not seen for participants given additional study opportunities without initial testing. Experiment 2 extends this facilitative effect to a within-subjects design. Experiment 3 demonstrates that this facilitation can be modulated by conscious strategies. These results have implications for educational practice and the theoretical developments of the testing effect, associative memory, and retrieval inhibition.     

Concreteness and item-to-list context associations in the free recall of items differing in context variability

Context variability can be defined as the number of preexperimental contexts in which a given concept appears. Following M. Steyvers and K. J. Malmberg's (2003) work, the authors have shown that concepts that are experienced in fewer preexperimental contexts generally are better remembered in episodic memory tasks than concepts that are experienced in a greater number of preexperimental contexts. The purpose of this article is to demonstrate that low context variability confers its memorial advantage because of stronger item-to-list context associations as compared with high context variability. Three experiments that use environmental context changes from study to test demonstrate that the low context variability advantage is eliminated when item-to-list context associations are not available because of environmental changes at test. In addition, the low context variability advantage is eliminated when inward processing at study prevents the formation of item-to-list context associations.     

Is it impossible to inhibit isoluminant items, or does it simply take longer? Evidence from preview search

Visual search can be facilitated when participants receive a preview of half the distractors (the preview benefit in search; Watson & Humphreys, 1997). Donk and Theeuwes (2001) have argued that preview-based benefits are abolished if the display items are isoluminant to a background. This is consistent with the preview benefit being due to onset capture by the new stimuli. In contrast, the present experiments challenge this suggestion and show that preview benefits can occur under isoluminant conditions, providing that they are given enough time to occur. In Experiment 1, we showed that a preview benefit can occur even with isoluminant stimuli, provided that the old items are previewed for a sufficient time. In Experiment 2, we tested and rejected the idea that this advantage is due to low-level sensory fatigue for the preview stimuli. These findings indicate that the preview effect is not caused solely by onset capture.     

Neural modeling and imaging of the cortical interactions underlying syllable production

This paper describes a neural model of speech acquisition and production that accounts for a wide range of acoustic, kinematic, and neuroimaging data concerning the control of speech movements. The model is a neural network whose components correspond to regions of the cerebral cortex and cerebellum, including premotor, motor, auditory, and somatosensory cortical areas. Computer simulations of the model verify its ability to account for compensation to lip and jaw perturbations during speech. Specific anatomical locations of the model's components are estimated, and these estimates are used to simulate fMRI experiments of simple syllable production.     

A contextual interference account of distinctiveness effects in recognition

In this article, we report on two experiments that aimed to shed light on the memorability effect that derives from varying the uniqueness of contextual cues presented at encoding and retrieval. We sought to understand the locus of the recognition advantage for studying and testing words with nominally irrelevant features that are rarely shared with other words ("low-fan" features) as compared with features that are studied with more words ("high-fan" features). Each word was studied with one high-fan feature and one low-fan feature, but only one of the two features was reinstated at test. Recognition judgments were more accurate when the low-fan feature was reinstated than when the high-fan feature was reinstated. The data suggest that encoding cues that suffer from contextual interference negatively affect retrieval and do so by hindering recollection-based processing.     

Cognitive decline in old age: separating retest effects from the effects of growing older

Repeated administration of cognitive tests improves test performance, making it difficult for researchers to gauge the true extent of age-related cognitive decline. The authors examined this issue using data from the Rush Religious Orders Study and linear mixed-effects models. At annual intervals for up to 8 years, more than 800 older Catholic clergy members completed the same set of 19 cognitive tests from which previously established composite measures of cognitive domains were derived. Retest effects on some measures were substantial and continued to accumulate even after 8 annual test readministrations, but effects on other measures were minimal. Across cognitive measures, retest effects were not related to age, sex, or education. Individual differences in retest effects were substantial but not consistent across cognitive measures. The results suggest that retest-based improvement in cognitive test performance can be substantial and persistent.     

An examination of two-process theories of false recognition

Contemporary theories of false memory suggest there are two processes that combine to produce false memory: one that increases false memory (error-inflating processes) and one that counteracts false memory (error-editing processes). Two experiments using the DRM paradigm (Deese, 1959; Roediger & McDermott, 1995) explored the influence of manipulating the number of associates studied, study item presentation frequency, backward associative strength, and study time on error-inflating and error-editing processes separately by examining speeded and unspeeded recognition decisions. The results of these studies indicate that (1) increasing the number of associates studied primarily influenced error-inflating processes; (2) increasing backward associative strength increased error-inflating processes and impaired error-editing processes; (3) increasing study item presentation frequency increased both error-inflating and error-editing processes; and (4) increasing study time had a weak effect on error-editing processes. Further, the results of these studies suggest that comprehensive theories of false memory phenomena must propose the existence of two different factors: one that increases false memory and is available early in memory retrieval, and one that usually, but not always, decreases false memory and is available later in retrieval.