Context-Dependent Learning in People With Parkinson's Disease

Context-dependent learning is a phenomenon in which people demonstrate superior performance in the context in which they originally learned a skill but perform less well in a novel context. This study investigated context-dependent learning in people with Parkinson's disease (PD) and age-matched nondisabled adults. All participants practiced 3 finger sequences, each embedded within a unique context (colors and locations on a computer screen). One day after practice, the participants were tested either under the sequence-context associations remained the same as during practice, or the sequence-context associations were changed (SWITCH). Compared with nondisabled adults, people with PD demonstrated significantly greater decrement in performance (especially movement time) under the SWITCH condition, suggesting that individuals with PD are more context dependent than nondisabled adults.     

Inference generation in young,young–old and old–old adults: evidence for semantic architecture stability

Participants (31 young, 27 young–old, and 28 old–old) read 12 narratives, pausing periodically to think aloud. The resulting protocols were analysed for 17 types of inferences and for non‐content (off‐target) information. Factor analysis yielded three inference factors: character, causal and physical. Age difference across these factors were not significant, suggesting that inferential processing architecture may be stable. Each narrative also included an unfamiliar word. Immediately following each narrative, four definition choices and a definition rating scale were presented. The definition scores of old–old adults were lower than young and young–old. In addition, definition scores were negatively related to non‐content comment counts. Taken together, these findings suggest that off‐target working‐memory intrusions may interfere with interpretation specificity in older adults even though semantic architecture remains stable. This study extends the aging and inference literature by addressing age‐related changes across categories of inferential processing and by including a sample of old–old adults. Copyright © 2007 John Wiley & Sons, Ltd.     

Estimating age change in list recall in asset and health dynamics of the oldest-old: the effects of attrition bias and missing data treatment

Average change in list recall was evaluated as a function of missing data treatment (Study 1) and dropout status (Study 2) over ages 70 to 105 in Asset and Health Dynamics of the Oldest-Old data. In Study 1 the authors compared results of full-information maximum likelihood (FIML) and the multiple imputation (MI) missing-data treatments with and without independent predictors of missingness. Results showed declines in all treatments, but declines were larger for FIML and MI treatments when predictors were included in the treatment of missing data, indicating that attrition bias was reduced. In Study 2, models that included dropout status had better fits and reduced random variance compared with models without dropout status. The authors conclude that change estimates are most accurate when independent predictors of missingness are included in the treatment of missing data with either MI or FIML and when dropout effects are modeled.     

Longitudinal hierarchical linear models of the memory functioning questionnaire

Three hypotheses about the nature of self-rated memory as measured by the Memory Functioning Questionnaire (MFQ; M. J. Gilewski, E. M. Zelinski, & K. W. Schaie, 1990) were tested: that ratings reflect memory performance, that personality traits underlie ratings, and that ratings reflect implicit theories of memory change. Baseline scores and 19 year change slopes for the 4 MFQ factor ratings of a sample of 97 participants aged 30-81 were investigated. There were significant mean declines for all MFQ ratings except Frequency of Forgetting and significant individual differences in slopes for Frequency, Retrospective Functioning, and Mnemonics. Personality predicted baseline Frequency and Seriousness ratings and list and text recall slopes predicted Mnemonics slopes. Different mechanisms may underlie baseline ratings and changes in ratings for different factors.     

Forecasting “friends forever”: A longitudinal investigation of sustained closeness between best friends

Using data collected across 19 years, the chief goal of this study was to discover predictors of continued relational closeness between best friends. Participants were same‐sex and cross‐sex best friend pairs recruited from a small Midwestern college. In 1983, participants completed several tests and activities designed to assess facets of intimacy, with follow‐up studies in 1987 and 2002 measuring relational closeness. Regression analysis indicates that both manifest similarity and months of closeness in 1983 are associated with relational closeness in 2002. These results suggest that the investment of resources in the friendship and similarity between friends facilitate friendship longevity and that Kelley et al.’s (1983) conceptualization of closeness as related to interdependence is empirically robust.     

Memory Functioning Questionnaire: concurrent validity with memory performance and self-reported memory failures

Concurrent validity of factor scores from the Memory Functioning Questionnaire (MFQ; Gilewski, Zelinski, & Schaie, in press) with memory performance was investigated in 2 studies. Study 1 involved 198 adults aged 55-85; Study 2, 89 adults aged 50-87. After effects of depression, education, and health were partialed out, MFQ scores predicted performance on laboratory memory tests in Study 1 and performance on clinical memory tests and diaries of memory failures over 2 weeks in Study 2. Additional variance in predicting performance and failures recorded in diaries is accounted for by MFQ scores after partialing out subjects' responses to a yes-no question about whether they have memory problems. Results suggest that the MFQ has moderate concurrent validity with memory measures and is preferable to responses to a single question about memory self-perception in assessing memory complaints in normal adults.     

Understanding unfamiliar words: the influence of processing resources, vocabulary knowledge, and age

In a 2-experiment design, the authors assessed the role of age and ability in defining unfamiliar words from context. In Experiment 1, 60 adults aged 18-33 and 60 adults aged 61-96 read passages with cues to the meaning of rare words, then defined them. Older adults produced fewer components of the words' meanings and were more likely to produce generalized interpretations of the precise meaning. In Experiment 2, 726 adults aged 30-97 selected definitions from 4 choices: the exact definition, a generalized interpretation of the exact definition, a generalized interpretation of the story, and definition-irrelevant information from the story. Adults over age 75 selected fewer precise definitions and more generalized interpretations of the story than younger ones. Findings suggest that older adults may have special difficulties in deriving the meaning of unfamiliar words from context.     

Understanding unfamiliar words in young, young-old, and old-old adults: inferential processing and the abstraction-deficit hypothesis

Previous research suggests that older adults derive interpretations of unfamiliar words that are less precise than those of young adults (D. McGinnis & E. M. Zelinski, 2000). Thirty-one adults aged 18-37, 27 aged 65-74, and 28 aged 75-87 read passages containing unfamiliar words (1 per passage) and were asked to think aloud during reading. After reading each passage, participants selected meaning-relevant cues and rated the quality of 4 definition options. Compared with the 2 younger groups, the oldest group rated thematic and irrelevant definitions significantly higher, and their think-aloud protocols included more generalized inferences. Results pertaining to cue selection were not significant. Taken together, these results suggest that age differences in meaning derivation may be related to inferential processing that is overgeneralized, providing support for the abstraction-deficit hypothesis.     

Persistent impairments in hippocampal function following a brief series of photoperiod shifts in rats

The impact of an acute circadian disruption on learning and memory in male and female rats was examined. Circadian disruption was elicited using a brief series of photoperiod shifts. Previous research using male rats showed that acute circadian disruption during acquisition of a spatial navigation task impaired long-term retention and that chronic circadian disruption impaired acquisition of the same task. However, the long-term effects of acute circadian disruption following circadian re-entrainment and whether sex differences in response to circadian disruption exist are still unknown. For the present study, rats were trained on the standard, spatial version of the Morris water task (MWT) and a visual discrimination task developed for the eight-arm radial maze. After reaching asymptotic performance, behavioural training was terminated and the experimental group experienced a series of photoperiod shifts followed by circadian re-entrainment. Following circadian re-entrainment, the subjects were given retention tests on the MWT and visual discrimination task. Following retention testing, an extra-dimensional shift using the eight-arm radial maze was also performed. An acute episode of circadian disruption elicited via photoperiod shifts negatively impacted retention of spatial memory in male and female rats. Retention of the visual discrimination task and the ability to detect extra-dimensional shifts were not impaired. The observed impairments on the MWT indicate that hippocampal representations are susceptible to a small number of photoperiod shifts even if the association is acquired prior to rhythm manipulation and retention is assessed following rhythm stabilization. Effects were limited to a hippocampus-dependent task, indicating that impairments are specific, not global.