Search PubMed⌕ Search

Biomedical subjects

D J Madden

Publications and source records attributed to D J Madden.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1989

Improving aerobic capacity in healthy older adults does not necessarily lead to improved cognitive performance.

The effects of aerobic exercise training in a sample of 85 older adults were investigated. Ss were assigned randomly to either an aerobic exercise group, a nonaerobic exercise (yoga) group, or a waiting-list control group. Following 16 weeks of the group-specific protocol, all of the older Ss received 16 weeks of aerobic exercise training. The older adults demonstrated a significant increase in aerobic capacity (cardiorespiratory fitness). Performance on reaction-time tests of attention and memory retrieval was slower for the older adults than for a comparison group of 24 young adults, and there was no improvement in the older adults' performance on these tests as a function of aerobic exercise training. Results suggest that exercise-related changes in older adults' cognitive performance are due either to extended periods of training or to cohort differences between physically active and sedentary individuals.

Adult↗
PubMed1989

Cardiovascular and behavioral effects of aerobic exercise training in healthy older men and women.

The cardiovascular and behavioral adaptations associated with a 4-month program of aerobic exercise training were examined in 101 older men and women (mean age = 67 years). Subjects were randomly assigned to an Aerobic Exercise group, a Yoga and Flexibility control group, or a Waiting List control group. Prior to and following the 4-month program, subjects underwent comprehensive physiological and psychological evaluations. Physiological measures included measurement of blood pressure, lipids, bone density, and cardiorespiratory fitness including direct measurements of peak oxygen consumption (VO2) and anaerobic threshold. Psychological measures included measures of mood, psychiatric symptoms, and neuropsychological functioning. This study demonstrated that 4 months of aerobic exercise training produced an overall 11.6% improvement in peak VO2 and a 13% increase in anaerobic threshold. In contrast, the Yoga and Waiting List control groups experienced no change in cardiorespiratory fitness. Other favorable physiological changes observed among aerobic exercise participants included lower cholesterol levels, diastolic blood pressure levels, and for subjects at risk for bone fracture, a trend toward an increase in bone mineral content. Although few significant psychological changes could be attributed to aerobic exercise training, participants in the two active treatment groups perceived themselves as improving on a number of psychological and behavioral dimensions.

Aged↗
PubMed1989

Amount and duration of attentional demands during visual search.

Previous research has suggested that, in visual-search tasks, the comparison between target and display items does not require attentional capacity. In the present experiment we used a secondary-task paradigm to distinguish the amount and duration of the attentional demands of visual search. The subjects performed visual search (the primary task) and tone detection (the secondary task) concurrently over the course of five experimental sessions (1,440 trials). For each subject, target-response mapping was either consistent or varied for Days 1-5. The results indicate that the amount of attentional demand, as reflected in secondary-task performance, increased as a function of display size in the search task. Switching from consistent to varied mapping in a sixth experimental session increased both the amount and the duration of the attentional demands of the search. The present results support models of visual-search performance in which the comparison of target and display items requires attentional capacity.

Adult↗
PubMed1988

Different patterns of cognitive slowing produced by Alzheimer's disease and normal aging.

Aging has previously been shown to produce a generalized proportional slowing of all cognitive operations. In contrast, the present results suggested that Alzheimer's disease produces a disproportionate reduction in the speed with which patients carry out one or more mental operations. The tasks that demented patients found particularly difficult involved either a self-directed search of their lexicon or the use of familiarity information.

Aged↗
PubMed1988

Adult age differences in the effects of sentence context and stimulus degradation during visual word recognition.

I investigated adult age differences in the efficiency of feature-extraction processes during visual word recognition. Participants were 24 young adults (M age = 21.0 years) and 24 older adults (M age = 66.5 years). On each trial, subjects made a word/nonword discrimination (i.e., lexical decision) regarding a target letter-string that was presented as the final item of a sentence context. The target was presented either intact or degraded visually (by the presence of asterisks between adjacent letters). Age differences in lexical decisions speed were greater for degraded targets than for intact targets, suggesting an age-related slowing in the extraction of feature-level information. For degraded word targets, however, the amount of performance benefit provided by the sentence context was greater for older adults than for young adults. It thus appears that an age-related deficiency at an early stage of word recognition is accompanied by an increased contribution from semantic context.

Adult↗
PubMed1988

Effects of aerobic exercise training, age, and physical fitness on memory-search performance.

We investigated the effects of exercise training on memory performance. One group of 13 men (M = 42.92 years of age) participated in supervised aerobic exercise (jogging) three times a week for 12 weeks. A second group of 15 men (M = 43.67 years of age) performed anaerobic exercise (strength training) for the same period of time. Subjects' reaction time (RT) performance in a memory-search task was assessed both before (Time 1) and after (Time 2) the 12 weeks of exercise training. Results indicated that there was no significant change in memory-search performance over time as a function of exercise training. Analyses of the Time 2 RTs demonstrated that aspects of memory-search performance were related significantly both to subjects' initial (Time 1) level of fitness and to age, but not to the amount of change in fitness associated with aerobic exercise training over this 12-week duration in this age group.

Adult↗
PubMed1988

Short-term behavioral effects of beta-adrenergic medications in men with mild hypertension.

beta-Adrenergic-inhibiting drugs are widely prescribed for the treatment of hypertension. These drugs have previously been found to influence a variety of psychologic and behavioral functions and have, in some cases, been associated with serious psychiatric side effects. The present study examined psychologic changes associated with beta-blockade therapy. Twenty-six men with mild hypertension (diastolic blood pressure 90 to 110 mm Hg) were randomly assigned to receive either a selective beta 1-antagonist (atenolol), a nonselective beta 1- and beta 2-antagonist (propranolol), or a placebo. Both before and after a 2-week period of drug administration, subjects completed a comprehensive assessment of quality of life including measures of mood, memory performance, and side effects. In general, beta-blocker therapy was associated with relatively few adverse symptoms, particularly when compared with control subjects taking placebo. Reductions in negative emotional states (tension and anger) were observed for subjects receiving atenolol, and the largest improvements in memory performance were observed for subjects receiving propranolol. These results suggest that beta-blocker therapy is not invariably associated with negative side effects and that some behavioral functions may actually be improved.

Adult↗
PubMed1988

Effects of beta-blockade and exercise on cardiovascular and cognitive functioning.

Twenty-four men with mild essential hypertension were assigned randomly to receive propranolol (n = 9), atenolol (n = 7), or a placebo (n = 8). All subjects participated in a 12-week study and provided physiological and behavioral data four times during the study: after a medication-free baseline period (Session 1); after 2 weeks of medication, without exercise (Session 2); after 8 weeks of continued medication while participating in a program of aerobic exercise (Session 3); and after 2 weeks of maintenance exercise without medication (Session 4). Subjects' maximal oxygen uptake increased significantly between Sessions 2 and 3, and the magnitude of this increase did not vary across the drug groups. Subjects' resting heart rates varied as a function of the presence of beta-blocking medication, but there was in addition a reduction attributable to exercise training that did not vary across the drug groups. The decrease in blood pressure associated with beta-blockade (Session 2) was not decreased any further by exercise training (Session 3). Despite an increase in blood pressure following the withdrawal of active medication (Session 4), blood pressure remained significantly lower compared with the Session 1 baseline level. Performance in a reaction-time test of short-term memory functioning improved slightly for all three groups between Sessions 1 and 2 and remained constant thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1987

Adult age differences in visual acuity, stereopsis, and contrast sensitivity.

We investigated adult age differences in four measures of visual function: distance acuity, near acuity, stereopsis, and contrast sensitivity. Twenty-four young adults (mean age 19.5 years) and 24 older adults (mean age 68.4 years) participated. Age differences were present in each of the four measures. A stepwise discriminant analysis performed on the four measures revealed that, when the correlations among the measures were taken into account, only contrast sensitivity significantly discriminated young and older adults' performance. The strength of the correlations among the four measures was greater for older adults than for young adults. The results indicated that contrast sensitivity is a useful measure for detecting age-related changes in visual function and that a common mechanism may underlie age differences on various visual tests.

Adolescent↗
PubMed1986

Memory performance by mild hypertensives following beta-adrenergic blockade.

Previous experiments have reported deficits in cognitive performance following the administration of beta-adrenoceptor antagonists. These deficits have not appeared consistently, however, and it is not clear from previous studies whether changes in the central nervous system, rather than end-organ functioning, are responsible. The present experiment investigated the effects of beta blockade in a memory-search paradigm that distinguished the relatively central process of memory comparison from the more peripheral processes of stimulus encoding and response selection. Twenty-six adult men with mild essential hypertension received either a placebo or a beta blocker (atenolol or propranolol) for 2 weeks. Although beta blockade did occur in the active drug groups, there were no significant effects of the drugs on memory-search performance.

Adult↗
PubMed1986

Adult age differences in visual word recognition: semantic encoding and episodic retention.

The present experiment examined adult age differences in semantic priming effects and subsequent episodic retention for visually presented words. Twenty-four young (18-22 years) and 24 older (58-74 years) adults participated. In a lexical decision task, each of the word targets was presented as the final item of a sentence context (i.e., a prime) that was either semantically congruous, incongruous, or neutral with regard to the target. The perceptual difficulty of the target was also varied. The semantic priming effects in lexical decision RT were equivalent in magnitude for the young and older adults. The RT data appeared to represent a generalized, age-related slowing in the speed of information processing. In unexpected tests of recall and recognition for the target words, the older adults performed significantly worse than the young adults. The present results indicate that age-related deficits in episodic memory are not accompanied by substantial changes in semantic encoding ability.

Adolescent↗
PubMed1985

Age-related slowing in the retrieval of information from long-term memory.

The present experiment investigated adult age differences in the retrieval of information from long-term memory. Each trial required a decision regarding the synonymy of two visually presented words. On the yes-response trials, the two words were either identical, differed only in case, or were synonyms that differed in case. Age differences in absolute decision time were greater for the synonyms than for the other word pairs, but the proportional slowing of decision time exhibited by the older adults was constant across word-pair type. A generalized age-related slowing in the speed of information processing can currently account for age differences in the retrieval of letter-identity and semantic information from long-term memory.

Adolescent↗
PubMed1984

Data-driven and memory-driven selective attention in visual search.

The present experiment investigated Rabbitt's (1979) hypothesis that age differences in selective attention occur when memory-driven processing must be employed. Young and older adults performed a visual search task, which, on some trials, provided advance information (a cue) regarding the particular target letter most likely to appear in the display. The nature of the selectivity required by the cue was either data-driven (Condition 1) or memory-driven (Condition 2). Analyses of the benefit in search performance associated with the cued trials and of the cost in performance resulting from the presentation of misleading advance information yielded limited support for Rabbitt's hypothesis. The older adults, but not the young, did exhibit a smaller cuing benefit in Condition 2 than in Condition 1. Both age groups, however, demonstrated substantial benefits and costs within each condition. Age differences in selective attention are thus not determined completely by the requirement to use memory-driven processing.

Adolescent↗
PubMed1983

The effect of age on hemispheric asymmetry in visual and auditory identification.

On psychometric tests, spatial scores typically decline more with age than do verbal scores. Since in humans, visuo-spatial information is more efficiently processed by the right hemisphere (RH) and verbal information by the left (LH), this behavioral pattern could reflect a greater age decline in RH than in LH abilities. To test this possibility, the speed with which young and old subjects identified stimuli in their right and left visual fields was measured. Since each half field, projects to the opposite hemisphere, by presenting stimuli in one half field, RH and LH abilities can be measured relatively independently. Words were identified faster in the right field (i.e., LH), pictorial stimuli in the left (RH). This was equally true for both young and old. Similarly, a right ear advantage in the identification of dichotically presented syllables was of equal magnitude in both age groups. Thus, there was no evidence on these tasks for a selective decline with age in RH processing efficiency.

Adolescent↗