Age-related differences in lexical access, spreading activation, and simple pronunciation.

An experiment was conducted to address age-related differences in lexical access, spreading activation, and pronunciation. Both young and older adults participated in a delayed pronunciation task to trace the time course of lexical access and a semantic priming task to trace the time course of spreading activation. In the delayed pronunciation task, subjects were presented a word and then, after varying delays, were presented a cue to pronounce the word aloud. Older adults benefited considerably more from the preexposure to the word than did the younger adults, suggesting an age-related difference in lexical access time. In the semantic priming pronunciation task, semantic relatedness (related vs. neutral), strength of the relationship (high vs. low), and prime–target stimulus onset asynchrony (200 ms, 350 ms, 500 ms, 650 ms, and 800 ms) were factorially crossed with age to investigate age-related differences in the buildup of semantic activation across time. The results from this task indicated that the activation pattern of the older adults closely mimicked that of the younger adults. Finally, the results of both tasks indicated that older adults were slower at both their onset to pronounce and their actual production durations (i.e., from onset to offset) in the pronunciation task. The results were interpreted as suggesting that input and output processes are slowed with age, but that the basic retrieval mechanism of spreading activation is spared by age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The utility of intraindividual variability in selective attention tasks as an early marker for Alzheimer’s disease.

This study explored differences in intraindividual variability in 3 attention tasks across a large sample of healthy older adults and individuals with very mild dementia of the Alzheimer’s type (DAT). Three groups of participants (healthy young adults, healthy older adults, very mild DAT) were administered 3 experimental measures of attentional selection and switching (Stroop, Simon, task switching). The results indicated that a measure of intraindividual variability, coefficient of variation (CoV; SD/M), increased across age and early stage DAT. The CoV in Stroop discriminated the performance of ε4 carriers from noncarriers in healthy older controls and the CoV in task switching was correlated with cerebrospinal fluid (CSF) biomarkers predictive of DAT. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of healthy aging and early stage dementia of the Alzheimer's type on components of response time distributions in three attention tasks.

Objective: The characteristics of response time (RT) distributions beyond measures of central tendency were explored in 3 attention tasks across groups of young adults, healthy older adults, and individuals with very mild dementia of the Alzheimer's type (DAT). Method: Participants were administered computerized Stroop, Simon, and switching tasks, along with psychometric tasks that tap various cognitive abilities and a standard personality inventory (NEO-FFI). Ex-Gaussian (and Vincentile) analyses were used to capture the characteristics of the RT distributions for each participant across the 3 tasks, which afforded 3 components: μ and σ (mean and standard deviation of the modal portion of the distribution) and τ (the positive tail of the distribution). Results: The results indicated that across all 3 attention tasks, healthy aging produced large changes in the central tendency μ parameter of the distribution along with some change in σ and τ (mean ηp2 = .17, .08, and .04, respectively). In contrast, early stage DAT primarily produced an increase in the τ component (mean ηp2 = .06). τ was also correlated with the psychometric measures of episodic/semantic memory, working memory, and processing speed, and with the personality traits of neuroticism and conscientiousness. Structural equation modeling indicated a unique relation between a latent τ construct (–.90), as opposed to σ (–.09) and μ constructs (.24), with working memory measures. Conclusions: The results suggest a critical role of attentional control systems in discriminating healthy aging from early stage DAT and the utility of RT distribution analyses to better specify the nature of such change. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Correction to Hutchison, Balota, and Duchek (2010).

Reports an error in "The utility of Stroop task switching as a marker for early-stage Alzheimer's disease" by Keith A. Hutchison, David A. Balota and Janet M. Ducheck (Psychology and Aging, 2010[Sep], Vol 25[3], 545-559). Author Janet M. Duchek’s name was misspelled as Janet M. Ducheck. The online version has been corrected. (The following abstract of the original article appeared in record 2010-18944-003.) Past studies have suggested attentional control tasks such as the Stroop task and the task-switching paradigm may be sensitive for the early detection of dementia of the Alzheimer's type (DAT). The authors of the current study combined these tasks to create a Stroop switching task. Performance was compared across young adults, older adults, and individuals diagnosed with very mild dementia. Results indicated that this task strongly discriminated individuals with healthy aging from those with early-stage DAT. In a logistic regression analysis, incongruent error rates from the Stroop switching task discriminated healthy aging from DAT better than any of the other 18 cognitive tasks given in a psychometric battery. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The utility of placing recollection in opposition to familiarity in early discrimination of healthy aging and very mild dementia of the Alzheimer’s type.

This study explored the ability to control familiarity-based information in a memory exclusion paradigm in healthy young, older adults, and early stage DAT individuals. We compared the predictive power of memory exclusion performance to standard psychometric performance in discriminating between aging and the earliest stage of DAT and between APOe4-present and APOe4-absent genotype in healthy control individuals. Participants responded “yes” to words that were previously semantically encoded, and “no” to words that were previously read aloud and to new words. The number of targets and distractors on the read “distractor” list was manipulated to investigate the degree to which aging and DAT influence the ability to recollect in the face of distractor familiarity due to repetition. Memory exclusion performance was better for healthy older adults than very mild DAT individuals and better for healthy control individuals with APOe4 allele than those without APOe4 allele even after controlling for standard psychometric performance. Discussion focuses on the importance of attentional control systems in memory retrieval and the utility of the opposition paradigm for discriminating healthy versus pathological aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Component analysis of a rhythmic finger tapping task in individuals with senile dementia of the Alzheimer type and in individuals with Parkinson's disease.

The present experiment examined different components of motor control that may be impaired in normal aging, senile dementia of the Alzheimer type (SDAT), and Parkinson's disease (PD). Specifically, A. M. Wing and A. B. Kristofferson's (1973) formal quantitative model of rhythmic finger tapping was used to obtain estimates of central timekeeping and response execution components of timing control. Ss included young college students, healthy older adults, nondemented individuals with PD. and individuals with very mild and mild SDAT. Individuals with mild SDAT exhibited a breakdown in the central timekeeping mechanism but not in the execution of the response. Both very mild SDAT and PD individuals did not show any deficits in the 2 timing mechanisms relative to age-matched healthy controls. Finally, there was no effect of normal aging on timing control in this task. This study underscores the importance of examining issues of motor control in SDAT as a function of separate processing components and stages of disease progression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of organic modification of layered nanosilicates on mechanical and surface properties of organic–inorganic coatings

The effect of alcohol- and amino-functional compatibilizers in nanocomposites of organic–inorganic (O–I) matrices with layered nanofillers (LN) was studied. The alcohol-functional compatibilizers are shown to have a marked influence on morphology, surface- and mechanical properties of the coatings prepared, in spite of the very small amount of both filler and compatibilizer (together 0.5 wt%). The studied O–I matrices were polyepoxy-functional polysiloxanes cured with organic diamines. Two commercial clays were used as LN in the concentration of 0.5 wt%: natural montmorillonite (Cloisite Na, abbreviated MNa) and Bentonite for water systems (BW). These clays were compatibilized by three hydroxyl-containing substances: Polyethylene glycol 4000, TWEEN 80, and tris(hydroxymethyl)aminomethane (TRIS). All compatibilizers improve the dispersion of the clay fillers, while TRIS always supports full exfoliation. They also cause an increase in the microroughness of the coatings and strongly modify their large-scale surface patterns. Mechanical properties are also strongly affected by the compatibilizers: toughness is increased, sometimes markedly, as well as stress at break. Tensile and shear moduli are reduced by the compatibilizers, while the glass transition temperature is specifically shifted to higher or lower values, sometimes markedly.     

Failure to control prepotent pathways in early stage dementia of the Alzheimer's type: Evidence from dichotic listening.

The authors examined the right ear advantage in a dichotic listening task in healthy aging and very mild and mild stages of Alzheimer's disease. Subjects were simultaneously presented 3 pairs of digits to the left and right ears (e.g., left ear: 4, 3, 1; right ear: 9, 2, 5) for immediate ordered recall. Four lists of triads were presented, varying in presentation rate between digit pairs within a triad (0.5, 1.0, 1.5, 2.0 s). Results indicated that the very mild and mild Alzheimer's groups showed a larger right ear advantage in free recall compared with the healthy controls, indicating a tendency to respond to the prepotent left hemisphere pathway for language processing. Also, the right ear advantage and proportion of switches made during recall were correlated with psychometric measures of frontal lobe function in the mild Alzheimer's group but not in the very mild or healthy control groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)