Age differences in dynamic measures of EEG.

Eighteen older adults and 18 younger adults were compared on two quantitative measures describing changes over time in the spatial distribution of running EEG. EEG was collected from 128 electrodes under resting eyes-open and eyes-closed conditions and during performance of a 13 minute sustained attention task. One EEG measure, the recrudescence rate, represented the number of changes in the location of the highest squared voltage per second. A second EEG measure consisted of the algorithmic complexity of changes in the location of the highest squared voltage over time. Regardless of the task condition, older adults had significantly higher scores than younger adults on both the recrudescence rate and the measure of algorithmic complexity. The implications of the results for neurologically-based theories of performance declines in older adults are discussed.

Adult age differences in the use of distractor homogeneity during visual search.

Previous research has suggested that an age-related decline may exist in the ability to inhibit distracting information during visual search. The present experiments used a conjunction search task in which the within-item features of the target (an upright L) and the distractors (rotated Ls) were identical. In each of 2 experiments, both young and older adults searched the display significantly more rapidly when the distractors were all rotated in the same direction (homogeneous) than when the distractors were rotated in different directions (heterogeneous). The concept of a generalized, age-related slowing was able to account for many aspects of the data, although the degree of relative improvement associated with distractor homogeneity was greater for young adults than for older adults.

Some methods for dynamic analysis of the scalp recorded EEG.

This paper describes methods for quantifying the spatiotemporal dynamics of EEG. Development of these methods was motivated by watching computer-generated animations of EEG voltage records. These animations contain a wealth of information about the pattern of change across time in the voltages observed across the surface of the scalp. In an effort to quantify this pattern of changing voltages, we elected to extract a single quantifiable feature from each measurement epoch, the highest squared voltage among the various electrode sites. Nineteen channels of EEG were collected from subjects using an electrode cap with standard 10-20 system placements. Two minute records were obtained. Each record was sampled at a rate of 200 per second. Thirty seconds of artifact-free data were extracted from each 2 minute record. An algorithm then determined the location of the channel with the greatest amplitude for each 5 msec sampling epoch. We quantified these spatio-temporal dynamics as scalars, vectors and cluster analytic plots of EEG activity for finger tapping, cognitive effort (counting backwards) and relaxation to illustrate the utility of the techniques.

Adult age differences in shifting focused attention.

Young and older adults performed a choice response task in which 1 of 2 target letters was presented visually at 1 of 4 display locations. In 2 experiments, the validity of a target location cue and the presence of nontarget characters (distractors) were varied. With target-only displays and 40% cue validity (Experiment 1), the estimated time to shift attention between display locations was essentially 0 ms for both age groups. With 70% cue validity, Experiment 2 demonstrated significant increases in the attention shift time as a function of both increased age and the presence of distractors (asterisks). The results suggest that age-related changes in the shifting of focused attention are minimal except when the processing of nontarget information is required.

Age-related slowing and the time course of semantic priming in visual word identification.

In 4 experiments, the authors investigated the time course of semantic priming effects during 2 forms of visual word identification, lexical decision and pronunciation. On each trial, a target letter string was preceded by a single-word priming context. The effects of varying the stimulus onset asynchrony between the prime and the target indicated that the time course of semantic priming was equivalent for young and older adults. There were no consistent differences between lexical decision and pronunciation in the time course of semantic priming. The age differences associated with response selection were greater than would be predicted by generalized age-related slowing. The semantic priming effects were also inconsistent with a generalized slowing model, but the reliability of these effects was substantially lower than the reliability of the other task-related variables.

Effects of aerobic exercise on cognitive and psychosocial functioning in patients with mild hypertension.

The effects of 16 weeks of physical exercise training on the psychological functioning of 90 patients with mild hypertension were examined. At baseline and after 16 weeks of training, patients completed a psychometric test battery that included objective measures of neuropsychological performance and standardized self-report measures of psychosocial functioning. Patients were randomly assigned to one of three groups: aerobic exercise, strength training and flexibility exercise, or a waiting list control group. After training, there were no group differences on any of the psychological measures, even though patients who engaged in exercise perceived themselves as functioning better in a number of psychological domains.

Cognitive function and cardiovascular responsivity in subjects with a parental history of hypertension.

College-age subjects with and without a parental history of hypertension completed a battery of tests of cognitive function on two separate occasions. Pulse rate and blood pressure were measured during performance of each task. In one session, subjects were told that their performance was being evaluated and videotaped from behind an observation mirror (Evaluation Condition). In the other session, subjects were told that their performance was not being observed (Nonevaluation Condition). Regardless of Evaluation Condition, Parental History subjects exhibited slower search of short-term memory than Non-Family History subjects during the first but not the second testing session. Parental History subjects displayed greater elevations in pulse rate than Nonparental History subjects during task performance. The results were interpreted as providing evidence that pathophysiological mechanisms associated with essential hypertension are not the only viable explanations of lower levels of cognitive performance exhibited by hypertensive subjects.

Hypertension affects neurobehavioral functioning.

This study compared the neurobehavioral performance of hypertensive and normotensive men and women using neuropsychological, information-processing, and psychometric assessments. One hundred subjects, including 68 hypertensive and 32 normotensive individuals, completed a test battery that yielded scores on measures of speed of information processing, verbal and figural memory, psychosocial functioning, Type A behavior, and locus of control. Results showed that, compared with the normotensive individuals, the hypertensives performed more poorly on a set of tasks that measure speed of information processing and short-term memory (Digit Symbol, Digit Span (Backwards), and Reaction Time (slope)). The hypertensives also reported higher levels of state anxiety relative to their normotensive counterparts. The effects of hypertension on neurobehavioral functioning could not be accounted for on the basis of age or education.

Adult age differences in attentional allocation during memory search.

Young and older adults performed a memory search task in which, before probe onset, a cue indicated which of 4 memory-set items the probe was most likely to be. The results were consistent with an attentional allocation model in which performance represents a weighted combination, across trials, of focused (i.e., selective) versus distributed attention. The model significantly underestimated the reaction time required by miscued trials, probably because of the response inhibition occurring on these trials. The degree to which Ss relied on focused attention was significantly greater for older adults than for young adults. The estimated time required to shift attention between memory-set items was equivalent for the 2 age groups.

Is blood pressure an important variable in research on aging and neuropsychological test performance?

Regression analyses using Blood Pressure, Age, and the multiplicative effect of Blood Pressure and Age as predictors of performance (on selected tests from the Halstead-Reitan neuropsychological test battery) were done. Three hypotheses were tested with subjects ranging in age from 20 to 72 years of age: (1) blood pressure values predict neuropsychological test performance over a wide range of hypertensive and normotensive blood pressure values; (2) blood pressure predicts performance within the narrower range of normal and borderline values; (3) blood pressure X age interactions, when observed over this age and education range, are such that negative blood pressure effects on performance are larger for younger than older subjects. Regression analyses confirmed each of these hypotheses and indicated that strength of prediction was not reduced when participants free from hypertension-related complications and medication were tested. Blood pressure X age interactions were seen for Trailmaking-B Test and the Tactile Performance Test-Localization for the primary sample. However, only Blood Pressure main effects were observed for the Average Impairment Rating, the Categories Test, TPT-Memory and TPT-Localization when age, sex, and education were controlled. Implications of these findings for the role of blood pressure in aging research and for longitudinal studies with subjects free from the need for treatment with antihypertensive medications are discussed.

Determining neuropsychological cut scores for older, healthy adults.

Three age groups (20-31, 37-49, and 55-67 years) of healthy men and women were compared on tests from the Halstead-Reitan neuropsychological test battery. Age-cohort differences in performance were observed for every measure (except Finger Tapping) and for overall indices of cognitive functioning, the Average Impairment Rating (AIR) and the Halstead-Reitan Impairment Index (HR II). When traditional cut scores (developed with age-heterogeneous samples) were used, alarmingly high percentages of subjects in the oldest group were defined as brain damaged. These findings were not attributable to higher levels of psychometrically-assessed anxiety and depression in the older groups or for the impaired subjects. Slightly more conservative criteria (fewer diagnoses of brain impairment) were then employed. The first, AIR greater than or equal to 2.00, resulted in a low and more reasonable base rate of brain impairment for the oldest group. The second, AIR greater than 2.00, resulted in age-parity in incidence of brain impairment. The heuristic value of more conservative AIR scores was discussed as were possible uses in applied clinical research settings. The limitations of this approach were noted with regard to its exclusive focus on the problem of false positive diagnoses. It was emphasized that, from a neuropsychological diagnostic perspective, cut scores based on healthy aging samples must ultimately be tested in the context of traditional neuropsychological studies in which external validation with neurosurgical and neurological criteria is employed.

Validity of a short form of the category test in relation to age, education, and gender.

Data for 289 subjects participating in an ongoing study of neuropsychological test performance were used to evaluate the relationship between age and prediction of performance on the long form of the Halstead-Reitan Category Test (CAT) from a short form developed by Calsyn, O'Leary, and Chaney (1980). The major questions were whether: (a) age, education, or gender would add to prediction of long (Y) from short form scores (X); (b) regression equations would be different for older and younger groups; (c) percent variance accounted for in long form scores by short form scores would be larger for younger as opposed to older subjects. For these relatively healthy subjects, prediction based on the short form was not enhanced in a clinically significantly manner by adding age, education, and gender as predictors. Regression equations for older and younger groups differed in intercept values but not in slopes. Percent variance accounted for in long form scores from short form scores did not differ when separate equations were used for younger and older subjects.