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Biomedical subjects

D J Madden

Publications and source records attributed to D J Madden.

At least 19 recordsLinked to original sources
PubMed1992

Selective attention and visual search: revision of an allocation model and application to age differences.

The present experiments examined a revised version of the Eriksen and Yeh model of attentional allocation during visual search. The results confirmed the assumption of the model that performance represents a weighted combination of focused- and distributed-attention trials, although Ss relied on focused attention more than was predicted. Consistent with the model, predictions on the basis of the assumption of a terminating search fit the data better than predictions on the basis of an exhaustive search. The effects of varying cue validity favored an interpretation of focused attention in terms of a processing gradient rather than a zoom lens. Although the allocation of attention across trials was similar for young and older adults, there was an age-related increase in the time required to allocate attention within individual trials.

Adolescent↗
PubMed1992

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.

Adolescent↗
PubMed1992

Four to ten milliseconds per year: age-related slowing of visual word identification.

This experiment examined the age-related slowing of visual word identification. Each of 108 subjects between 20 and 78 years of age performed a word/nonword discrimination (lexical decision) task in which the target was preceded by a single-word prime. Several aspects of the data were consistent with a generalized slowing model: There was a positive correlation between age and mean reaction time, the absolute magnitude of age differences increased as a function of task complexity, and the statistical control of a relatively task-independent index of processing speed attenuated the age-related variance in mean reaction time. The degree of age-related slowing was more pronounced for visually degraded targets (10 msec per year) than for intact targets (4 msec per year). Other aspects of lexical decision performance, however, suggested that some components of word identification, especially those involved in semantic activation, are relatively exempt from age-related slowing.

Adult↗
PubMed1992

Impact of age, redundancy, and perceptual noise on visual search.

We examined adult age differences in the impact of redundancy and perceptual noise during visual search. Using a two-choice, visual search task, subjects responded to letters presented in one to four corners of an imaginary display square. On each trial, one, two, or three instances of a given target letter were presented. In the target-plus-noise condition, all nontarget corners of the imaginary square were filled with distractor (i.e., noise) letters. In the target-only condition, all nontarget corners were left blank. The results indicated that older adults showed relatively greater redundancy benefits than the young adults for the target-plus-noise trials than for the target-only trials. These results are interpreted within an internal noise framework.

Adolescent↗
PubMed1992

Age differences in short-term memory: organization or internal noise?

Older and young adults' letter search performances were examined on a short-term memory (STM) task where subjects compared a five-letter target sequence stored in short-term memory to a subsequently presented five-letter probe sequence. The same five letters were always presented on target and probe portions of a given trial, but on half of the trials, two letters were transposed in the first chunk, second chunk, or between the first and second chunks of the probe sequence ("No" trials). On the remaining half of the trials, the target and probe sequences were identical ("Yes" trials). Both young and older adults showed increases in reaction time (RT) when the chunk boundary for "yes" trials was different for the target and probe sequences of a given trial. This finding indicated that both age groups were organizing the sequences in STM in the same qualitative manner. However, older adults showed a relatively greater increase in RT and errors than young adults for second-chunk transpositions than for first-chunk or between-chunk transpositions, and this finding suggested that an age difference in task complexity could not account for this effect. We propose, though, that these data are consistent with an internal noise model.

Adolescent↗
PubMed1992

The effect of age on driving skills.

OBJECTIVE: To assess the effect of age on driving skills independent of the limitations related to disease or dementia. DESIGN: Prospective comparison of driving skills across three age groups. SETTING: A university-based research study of student and university-affiliated volunteers. PARTICIPANTS: Healthy elderly (age 65+), teen-age (age 18-19), and young adult drivers (age 25-35). Twenty subjects in each age group were recruited after meeting entry criteria for the study. MAIN OUTCOME MEASURES: Total error count and score on the Miller Road Test, a standardized road test developed by the Division of Bus and Traffic Safety in North Carolina. RESULTS: The elderly were found to have fewer errors than either of the two younger groups of drivers (P = 0.0013). Specific driving skills were judged to be either superior or unchanged in the elderly subjects in comparison to their younger counterparts. CONCLUSIONS: Road test skills appear to be well preserved in the healthy elderly population. More road test studies are needed on elderly individuals with mental and physical impairments to determine if road tests can play a role in identifying the driver at high risk for a crash.

Adolescent↗
PubMed1991

Effects of exercise training on cardiorespiratory function in men and women older than 60 years of age.

This study reports the physiologic effects of up to 14 months of aerobic exercise in 101 older (greater than 60 years) men and women. After an extensive baseline physiologic assessment (Time 1), in which aerobic capacity and blood lipids were measured, subjects were randomized to an aerobic exercise condition (cycle ergometry, 3 times per week for 1 hour), nonaerobic yoga (2 times per week for 1 hour), or a waiting list nonexercise control group for 4 months, and then underwent a second (Time 2) assessment. At the completion of the second assessment, all remaining subjects completed 4 months of aerobic exercise and were reevaluated (Time 3). Subjects were given the option of participating in 6 additional months of supervised aerobic exercise, and all available subjects completed a fourth assessment (Time 4) 14 months after their initial baseline evaluation. Results indicated that subjects generally exhibited a 10 to 15% improvement in peak oxygen consumption after 4 months of aerobic exercise training, and a 1 to 6% improvement in aerobic power with additional aerobic exercise training. On the other hand, subjects, especially men, continued to have improvements in submaximal exercise performance (i.e., anaerobic threshold). In addition, aerobic exercise was associated with an improved lipid profile; subjects participating in aerobic exercise for up to 14 months exhibited increased levels of high-density lipoprotein cholesterol. Maintenance of regular aerobic exercise for an extended time interval is associated with greater cardiovascular benefits among older adults than has been reported previously.

Aged↗
PubMed1991

Adult age differences in letter-level and word-level processing.

Older and young adults' letter detection and lexical decision performance were examined as word frequency varied to determine whether there were age differences in word recognition. Allen and Madden (1989) found that older adults' pattern of reaction time (RT) across word frequency categories was different from young adults' pattern for a letter detection task. In this study, for both letter detection and lexical decision tasks, older adults exhibited a monotonically decreasing RT function as word frequency increased. However, young adults exhibited a nonmonotonic RT function across word frequency for the letter detection task but a monotonically decreasing RT function as word frequency increased for the lexical decision task. An expanded parallel input serial analysis model of word processing was hypothesized.

Adolescent↗
PubMed1991

Adult age differences in the rate of information extraction during visual search.

We investigated adult age differences in the function relating accuracy to speed during visual-search performance. Twenty-four young adults between 17 and 26 years of age, and 24 older adults between 59 and 75 years of age, participated. The level of accuracy at which performance was first improved by increasing RT was higher for older adults than for young adults. Independently of this age difference in accuracy, however, a significant age-related slowing was present in the rate of information extraction during visual-search performance.

Adolescent↗
PubMed1991

Long-term effects of exercise on psychological functioning in older men and women.

The purpose of this study was to determine the psychological, behavioral, and cognitive changes associated with up to 14 months of aerobic exercise training. For the first 4 months of the study, 101 older (greater than 60 years) men and women were randomly assigned to one of three conditions: Aerobic exercise, Yoga, or a Waiting List control group. Before and following the intervention, all subjects completed a comprehensive assessment battery, including measures of mood and cognitive functioning. A semi-crossover design was employed such that, following completion of the second assessment, all subjects completed 4 months of aerobic exercise and underwent a third assessment. Subjects were given the option of participating in 6 additional months of supervised aerobic exercise (14 months total), and all subjects, regardless of their exercise status, completed a fourth assessment. Results indicated that subjects experienced a 10-15% improvement in aerobic capacity. In general, there were relatively few improvements in cognitive performance associated with aerobic exercise, although subjects who maintained their exercise participation for 14 months experienced improvements in some psychiatric symptoms. However, the healthy subjects in this study were functioning at a relatively high level to begin with, and exercise training may produce greater improvements among elderly with concomitant physical or emotional impairments.

Affect↗
PubMed1991

Effects of exercise training on bone density in older men and women.

OBJECTIVES: To determine the effects of up to 14 months of aerobic exercise on measures of bone density in older adults. DESIGN: Randomized controlled trial with subjects assigned to either an aerobic exercise condition, non-aerobic yoga, or a wait list non-exercise control group for 4 months. Aerobic fitness and bone density were evaluated in all subjects at baseline (Time 1) and after 4 months (Time 2). A semi-crossover design was utilized with all subjects completing 4 months of aerobic exercise, followed by another evaluation (Time 3). All subjects were then given the option of 6 additional months of aerobic exercise, after which they had a fourth evaluation (Time 4). SETTING: An outpatient exercise rehabilitation facility at a large, major medical center. SUBJECTS: One-hundred-one healthy men (n = 50) and women (n = 51) over age 60 (Mean age = 67.0), recruited from the community. INTERVENTION: The exercise program included stretching, cycle ergometry, and walking three times per week for 60 minutes throughout the course of the study. OUTCOME MEASURES: Aerobic fitness (VO2max) as assessed by cycle ergometry, and bone density (bone mineral content) measured by single photon absorptiometry. RESULTS: Subjects achieved a 10%-15% increase in VO2max after 4 months of exercise training, and 1%-6% further improvement with additional training. Aerobic fitness was associated with significant increases in bone density in men, but not women, who maintained aerobic exercise for 14 months.

Aged↗
PubMed1991

Elaeophora schneideri in moose (Alces alces) from Colorado.

Two adult moose (Alces alces) from Colorado (USA) were naturally infected with Elaeophora schneideri. Both animals had patent infections indicating that moose may serve as definitive hosts. Gross and histological lesions were characterized by fibromuscular intimal proliferation within the carotid arteries and rete mirabile cerebri. This is the first report of Elaeophora schneideri in moose from Colorado.

Animals↗
PubMed1991

A preliminary study of the effects of cardiac procedures on cognitive performance.

The effects of three commonly performed cardiac procedures on cognitive performance were evaluated in patients undergoing coronary artery bypass graft (CABG) surgery (N = 20), percutaneous transluminal coronary angioplasty (PTCA) procedure (N = 8), or cardiac valve repair (N = 11). Patients completed a neuropsychological test battery on the day prior to their surgery and at discharge. Results showed that valve and CABG patients exhibited declines in performance on the Digit Symbol subtest, while PTCA patients did not change. Reaction time performance improved for the PTCA patients but declined significantly for valve patients. These results suggest that common cardiac procedures may have measurable effects on cognitive performance, as assessed by a relatively brief test battery.

Angioplasty, Balloon, Coronary↗
PubMed1991

The Ocutech Vision Enhancing System (VES): utilization and preference study.

An NIH-sponsored user and prescriber preference trial was conducted comparing a new low vision telescope system, the Ocutech Vision Enhancing System (VES) to two conventional Keplarian spectacle telescope systems in a controlled cross-over clinical study performed at four independent low vision clinics. Fifty-five visually impaired individuals, 18-81 years of age, with both previous and no telescope experience, were followed for 8-16 weeks. The experimental and control devices were compared on a series of subject-selected visual tasks using a standardized clinical protocol. Subjects were trained in the use of the systems with standardized clinical methods. The data shows a statistically significant preference of the new design by both patient and clinician with the overriding factors relating to appearance, weight, adjustability and the fit of the frame.

Adolescent↗
PubMed1990

Evidence for a parallel input serial analysis model of word processing.

A parallel input serial analysis (PISA) model of word processing was developed and tested. The goal was to expand on the "critical processing duration" hypothesis of Johnson, Allen, and Strand (1989) so that both single-word and multiple-word presentation, letter detection data could be explained. In Experiments 1-3 four different word frequency categories on a single-presentation, letter detection task were used. These three experiments indicated that there was a curvilinear relationship between word frequency and letter detection reaction time (RT). That is, letter detection RTs for medium-high-frequency words were significantly longer than letter detection RTs for very-high-, low-, and very-low-frequency words. These results support the PISA model rather than the Healy, Oliver, and McNamara (1987) version of the unitization model. In Experiments 4-5 multiple-presentation (i.e., two words), letter detection tasks were used. The PISA model could also account for the results from these two experiments, but the unitization model could not.

Adolescent↗
PubMed1990

Adult age differences in the time course of visual attention.

On each trial in this experiment, subjects made a choice response regarding which of two target letters was present in a visual display. A cue, occurring between 50 and 183 ms prior to display onset, indicated the location of the target. The results indicated that reaction time (RT) increased as a function of both the distance of the target from fixation and the presence of nontarget letters in the display. These RT effects were more pronounced for older adults than for young adults, in a manner consistent with a generalized age-related slowing of visual processing. The changes in RT associated with the cue indicated that, when nontarget letters were present in the display, the buildup of attention over the cue-target interval was slower for older adults than for young adults. This age difference in the time course of attention was independent of the generalized age-related slowing.

Adolescent↗
PubMed1989

Slowing of memory-search performance in men with mild hypertension.

Previous reports have associated hypertension with a slowing of cognitive performance, although the component processes involved have not been identified. Our report compares the performance of 24 men with mild hypertension and 28 age-matched normotensive men on a test of short-term memory search in which the duration of component processes could be estimated. The results indicated that the rate of search through short-term memory was slower for the hypertensive than for the normotensives, whereas the duration of encoding and response processes was equivalent for the two groups. This hypertension-related slowing of memory comparison was independent of participants' error rates and education levels.

Adult↗