Mental slowing in elderly persons: A cognitive psychophysiological analysis.

In recent attempts to formulate an integrative model of mental slowing in elderly persons, regression analyses have been done in which reaction-time (RT) data from a large number of studies spanning a broad range of speeded decision-making tasks were combined. The results of these meta-analyses were then used to support the conclusion that there is a generalized, proportional decline in mental processing speed among elderly adults that affects all elements of mentation equally. We present a series of similar regression analyses in which both RT and the latency of the P300 component of the event-related brain potential are included. The results of these analyses indicate that there are elements of mental processing that may be slowed additively, not proportionately, in older persons. Furthermore, the results raise some questions about the logic underlying the interpretation of the meta-regression analysis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of paroxetine and nefazodone on 5-HT1A receptor sensitivity

OBJECTIVE: To evaluate whether age-related slowing of mental processing assessed by event-related potentials is more prominent in patients with Parkinson disease (PD) than in age-matched control subjects. DESIGN: Consecutive case series of patients with PD and an age-matched control group. SETTING: A university hospital in Nishinomiya, Japan. STUDY PARTICIPANTS: Twenty-eight nondemented patients with PD and 28 age-matched control subjects. MAIN OUTCOME MEASURES: The P3 component of the event-related potentials was elicited during a visual semantic discrimination task. The relation of the P3 latency and the reaction time (RT) to age within each group was evaluated using correlation and regression analysis. The relationship among the P3 latency, the RT, and age was also assessed by dividing both groups into younger (age < 60 years) and older (age > or = 60 years) subgroups. RESULTS: The P3 latency and the RT of patients with PD were significantly longer than those of the control subjects (P < .01 and P < .02, respectively). There was a significant correlation between the P3 latency and age in both the parkinsonian and control groups (P < .01 and P < .05, respectively). The slope (b = 3.54 ms/y) of the P3 latency vs age was steeper among the patients with PD than among the control subjects (b = 1.66 ms/y) at the Pz site. The P3 latency in the older parkinsonian group (n = 16) was significantly prolonged compared with that in the older control group (n = 16) (P < .01), while no difference was found between the younger patients (n = 12) and the younger control group (n = 12). Similar trends were found for the RTs (P < .05). Neither the P3 latency nor the RT was correlated with any variable (eg, medication, mental status, illness duration, or motor disability). CONCLUSION: The results provide evidence that patients with PD experience excessive cognitive slowing with advancing age.     

Personality, reaction time, and event-related potentials.

Reaction time (RT), movement time (MT), and the amplitude and latency of the P300 ERP were recorded from 30 Ss during the performance of 6 simple cognitive tasks. Extraversion was negatively associated with MT, a result that endorses the view that extraversion is determined, in part, by individual differences in motor mechanisms. Higher neuroticism scores were associated with faster P300 latency, a measure that is regarded as an index of stimulus evaluation time that is independent of response production. Paradoxically, higher neuroticism scores were associated with slower RT, a measure that is also regarded as an index of speed of information processing. Higher psychoticism scores were associated with smaller P300 amplitude, an effect that may be indicative of less attentional effort invested in the tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The information-loss model: A mathematical theory of age-related cognitive slowing.

A model of cognitive slowing is proposed with the following assumptions: Information is lost during processing, processing occurs in discrete steps with step duration inversely related to the amount of information currently available, and the effect of aging is to increase the proportion of information lost per step. This model correctly predicts a positively accelerated relation between latencies of older and younger adults and provides a unified account of the effects of task complexity, practice, speed–accuracy tradeoffs, and fluctuations in individual performance. Strong support for the thesis that cognitive slowing is global, and not localized in specific age-sensitive components, is provided by the fact that the model accurately predicts the latencies of older adults on the basis of those of younger adults, without regard to the nature of the task, across a latency range of nearly 2 orders of magnitude. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The attentional demands of encoding and retrieval in younger and older adults: 2. Evidence from secondary task reaction time distributions.

Three studies examined the effects of encoding or retrieval on properties of secondary task reaction time (RT) distributions in younger and older adults. Relative to full attention conditions, encoding and retrieval increased secondary task RT medians and standard deviations more for older adults than for younger adults, and the age-related RT increase was most pronounced among the slowest RTs. Hierarchical regression analyses revealed two age-related mechanisms underlying these effects, which were interpreted as cognitive slowing and reductions in attentional resources. Cognitive slowing affects the entire RT distribution regardless of the memory task. By contrast, reduced attentional resources result in very long RTs, especially when the tasks require self-initiated encoding or retrieval operations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Constraints on general slowing: a meta-analysis using hierarchical linear models with random coefficients

General slowing (GS) theories are often tested by meta-analysis that model mean latencies of older adults as a function of mean latencies of younger adults. Ordinary least squares (OLS) regression is inappropriate for this purpose because it fails to account for the nested structure of multitask response time (RT) data. Hierarchical linear models (HLM) are an alternative method for analyzing such data. OLS analysis of data from 21 studies that used iterative cognitive tasks supported GS; however, HLM analysis demonstrated significant variance in slowing across experimental tasks and a process-specific effect by showing less slowing for memory scanning than for visual-search and mental-rotation tasks. The authors conclude that HLM is more suitable than OLS methods for meta-analyses of RT data and for testing GS theories.     

Cognitive functioning ten years following traumatic brain injury and rehabilitation.

Many previous studies investigating long-term cognitive impairments following traumatic brain injury (TBI) have focused on extremely severely injured patients, relied on subjective reports of change and failed to use demographically relevant control data. The aim of this study was to investigate cognitive impairments 10 years following TBI and their association with injury severity. Sixty TBI and 43 control participants were assessed on tests of attention, processing speed, memory, and executive function. The TBI group demonstrated significant cognitive impairment on measures of processing speed (Symbol Digit Modalities Test [SDMT], Smith, 1973; Digit Symbol Coding, Wechsler, 1997), memory (Rey Auditory Verbal Learning Test [RAVLT]; Rey, 1958; Lezak, 1976), Doors and People tests; Baddeley, Emslie & Nimmo-Smith, 1994) and executive function (Hayling C [Burgess & Shallice, 1997] and SART errors, Robertson, Manly, Andrade, Baddeley & Yiend, 1997). Logistic Regression analyses indicated that the SDMT, Rey AVLT and Hayling C and SART errors most strongly differentiated the groups in the domains of attention/processing speed, memory and executive function, respectively. Greater injury severity was significantly correlated with poorer test performances across all domains. This study shows that cognitive impairments are present many years following TBI and are associated with injury severity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reaction time impairment in insulin-dependent diabetes: Task complexity, blood glucose levels, and individual differences.

The effects of hypoglycemia on cognitive processing speed as measured by reaction time (RT) were evaluated in 25 adults (13 women and 12 men) with insulin-dependent diabetes. Simple, choice, and complex RT tasks were administered in a single-blind repeated measures cross-over design. On the experimental day, participants performed tests at euglycemia (80-120 mg/dl), then at mild (55-70 mg/dl) and moderate (33-50 mg/dl) hypoglycemia, and again at euglycemia. On the control day, participants performed tests 4 times at euglycemia. Three months later, 15 participants repeated the experimental day protocol. Results indicated significant increases in RT at moderate hypoglycemia. Individuals varied greatly in their response to mild and moderate hypoglycemia. Individual differences in hypoglycemia sensitivity were not reliable across time and did not correlate with individual difference variables. Complex and simple RT tasks were equally sensitive to cognitive slowing associated with hypoglycemia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Factors contributing to attentional impairments after traumatic brain injury.

The aim of the present study was to investigate the contribution of impaired information processing speed and strategic control of attention to performance on attentional tasks after traumatic brain injury (TBI). Forty moderately to severely injured rehabilitation inpatients and 40 healthy controls completed a selection of attentional tasks. Slowed processing speed in the TBI group was identified on the Symbol Digit Modalities Test (SDMT), 2&7 Selective Attention Test (2&7), Selective Attention (SAT), and Four Choice Reaction Time (4CRT) tasks. Impaired working memory was evident on the Letter Number Sequencing (LNS) task. Structural equation modeling revealed that the group difference in RT on the complex SAT was accounted for by slowed speed of processing on the simple SAT, and not working memory. TBI participants made more errors and missed responses on the complex version of the SAT, suggesting impairment in some aspects of strategic control of attention, and appeared unable to benefit from the automatic condition of the 2&7 Test. There was little evidence of deficit on the Sustained Attention to Response Task (SART). The present study provides evidence for a significant contribution of slowed processing speed to impaired performance on attentional tasks after TBI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Can longitudinal changes in processing speed explain longitudinal age changes in fluid intelligence?

The processing-speed theory of cognitive aging contends that age-related declines in intellectual function reflect the consequences of age-related slowing of processing speed. Cross-sectional data support this assumption. The association between 4-year changes in processing speed and 4-year changes in fluid intelligence was examined with a sample of 417 older adults. Changes in processing speed correlated .53 with changes in fluid intelligence. The difference in the explanatory power of processing speed regarding age-related differences and age-related changes is discussed with reference to other longitudinal studies and methodological considerations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Why do semantic priming effects increase in old age? A meta-analysis.

Reports a meta-analysis comparing the size of semantic priming effects on young and older adults' lexical decision and pronunciation latency. The analysis included 15 studies with 49 conditions varying the semantic relatedness of a prime stimulus (single word or whole sentence) and a target word. An effect-size analysis on the difference between young and older adults' semantic priming effect (unrelated minus related latency) indicated that semantic priming effects are reliably larger for older than for young adults. There was no evidence for nonhomogeneity in this age difference across the different conditions. The relationship between young and older adults' semantic priming effects was described by a function with a positive intercept and a slope of 1.0. This pattern of findings favors aging models postulating process-specific slowing rather than general cognitive slowing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Free testosterone levels, attentional control, and processing speed performance in aging men.

Psychometric measures of processing speed are strong predictors of cognitive functioning with aging; however, the neurobiological mechanisms underlying this association remain unclear. Recently, the authors reported a negative association between calculated free testosterone levels (cEFT) and processing speed in men aged between 50 and 70 years (Martin, Wittert, Burns, & McPherson, 2008). Ex-Gaussian decomposition of reaction time (RT) distributions allows for the robust estimation of skew in the distribution, which may reflect poorer attentional control. In a reanalysis of data from this previous study, the authors examined the associations between age, cEFT levels, and ex-Gaussian parameters derived from four RT tasks as predictors of cognitive functioning performance in 96 middle-to-older aged men. Results indicated that cEFT levels were significantly associated with increased skew in the RT distribution (i.e., the exponential portion) but not with the estimates derived from the Gaussian portion of the curve. Further, path analysis across the entire data set showed that this association was a strong predictor of processing speed performance. Taken together these results suggest that cEFT levels moderate cognitive functioning performance in males via attentional control processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Search, Enumeration, and Aging: Eye Movement Requirements Cause Age-Equivalent Performance in Enumeration but Not in Search Tasks.

Response time (RT) and fixation frequency were measured for young and older adults in search and enumeration tasks under high- and low-attentional competition conditions. There was an age-related decrement in search rates for single targets both for RT and fixation frequency, but there was no deficit in enumeration rates either with or without distractors even though serial enumeration rates were much slower than single target search rates. Fixation frequency per item in serial enumeration was much greater than in serial visual search for a single target. Enumerating targets with distractors produced an overall increase in RT and fixation frequency that was greater for older adults. The data are contrary to a generalized slowing account, and an alternative is proposed on the basis of the need to make eye movements in enumeration but not in search tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cross-sectional and longitudinal relationships among age, cognition, and processing speed.

Cross-sectional and longitudinal age effects on cognitive function were examined in 302 older adults followed longitudinally. Processing speed was related to cognitive performance at cross-section, and change in speed predicted within-person longitudinal cognitive decline. Statistical control of processing speed greatly reduced cross-sectional age effects but did not attenuate longitudinal aging effects. This difference in processing speed's ability to account for cross-sectional and longitudinal age effects is discussed in the context of theories of cognitive aging and methodological and statistical issues pertaining to the cross-sectional and longitudinal study of cognitive aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age differences in dual-task performance after practice.

This study investigated whether older adults could acquire the ability to perform 2 cognitive operations in parallel in a paradigm in which young adults had been shown to be able to do so (K. Oberauer & R. Kliegl, 2004). Twelve young and 12 older adults practiced a numerical and a visuospatial continuous memory updating task in single-task and dual-task conditions for 16 to 24 sessions. After practice, 9 young adults were able to process the 2 tasks without dual-task costs, but none of the older adults had reached the criterion of parallel processing. The results suggest a qualitative difference between young and older adults in how they approach dual-task situations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aging and goal-directed emotional attention: Distraction reverses emotional biases.

Previous findings reveal that older adults favor positive over negative stimuli in both memory and attention (for a review, see Mather & Carstensen, 2005). This study used eye tracking to investigate the role of cognitive control in older adults' selective visual attention. Younger and older adults viewed emotional-neutral and emotional-emotional pairs of faces and pictures while their gaze patterns were recorded under full or divided attention conditions. Replicating previous eye-tracking findings, older adults allocated less of their visual attention to negative stimuli in negative-neutral stimulus pairings in the full attention condition than younger adults did. However, as predicted by a cognitive-control-based account of the positivity effect in older adults' information processing tendencies (Mather & Knight, 2005), older adults' tendency to avoid negative stimuli was reversed in the divided attention condition. Compared with younger adults, older adults' limited attentional resources were more likely to be drawn to negative stimuli when they were distracted. These findings indicate that emotional goals can have unintended consequences when cognitive control mechanisms are not fully available. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibitory attentional mechanisms and aging

Two experiments sought to elicit distractor suppression in older adults. Experiment 1 used a procedure that increased suppression in younger adults, thus creating a more sensitive measure of suppression in older adults. To compensate for older adults' slowed processing, Experiment 2 used a longer stimulus exposure duration. Neither experiment produced suppression in older adults; both experiments, however, included trial types that elicited parallel facilitatory effects for both age groups. Older adults thus seemed to process distractors but failed to engage inhibitory mechanisms in their rejection of distracting stimuli. Finally, both experiments tested the relationships among suppression, interference, and everyday cognitive failure. Neither experiment suggested relationships between reaction time effects and self-reported cognitive lapses. Results are discussed within L. Hasher and R. T. Zacks's (1988) attentional framework.     

Age differences in mental multiplication: evidence for peripheral but not central decrements

This study reports two mental multiplication experiments that were designed to measure age differences in central and peripheral processes. Experiment 1 varied task type (verification vs production), and Experiment 2 varied exposure duration (presentation until response, 600 ms, and 300 ms) on a production task. Neither experiment showed evidence of age differences in central processes (e.g., retrieval speed); however, there was some evidence of a peripheral-process (e.g., encoding) decrement for older adults. Specifically, there were no Age X Problem Size interactions for either experiment. Experiment 2 revealed decreasing age differences as problem difficulty increased. Indeed, for the 300-ms exposure duration, there were no age differences in RT or error rate. These results suggest that the magnitude of age differences in central processing speed are significantly less extreme than are age differences for peripheral processing speed for this type of mental arithmetic task. Also, older adults, in general, may have a higher skill level for basic fact retrieval in mental arithmetic than do young adults.     

Handwriting performance in younger and older adults: Age, familiarity, and practice effects.

The main goals of 2 experiments on the aging of handwriting skills were to investigate (1) age differences in speed of handwriting performance, (2) effects of task familiarity on age differences in performance, and (3) effects of practice on age differences in performance. Younger adults performed reliably faster than older adults on all tasks. An Age?×?Familiarity interaction in both experiments indicated that age differences were magnified for unfamiliar but attenuated for familiar tasks. In the 2nd experiment, an Age?×?Trial interaction revealed that older adults improved at a faster rate than younger adults. Regressions with initial trial data indicated that the older were slower than the younger adults by a factor of about 1.6. With practice, however, this slowing factor was only 1.02. Results suggest that familiarity and practice play a role in speed of handwriting. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Age, target-distractor similarity, and visual search

Younger and older adults were asked to find a single target in both feature- and conjunction- search conditions. Display size varied between 2 and 8 items, and target-distractor similarity ranged from relatively low to high levels. The accuracy data indicated that older adults had particular difficulty finding targets in high-similarity conjunction-search displays containing a large number of distractors. The reaction time (RT) analyses found larger age deficits in many of these same conditions. For both groups, predictions of conjunction search based on Treisman and Sato's additive model (Journal of Experimental Psychology: Human Perception and Performance, 1990: 16, 459-478) departed significantly from actual performance. The RT data of older observers were, in large part, predicted as a simple linear function of the young adults' data. These results are discussed with respect to age differences in selective attention, generalized slowing, and an age-related loss in search efficiency.