Biomedical subjects

J M McDowd

Publications and source records attributed to J M McDowd.

13 recordsLinked to original sources

PubMed2006

Implicit learning of a motor skill after mild and moderate stroke.

OBJECTIVE: To determine if adults in the subacute phase post moderate or mild stroke could learn a motor task under implicit practice conditions. DESIGN: Non-randomized, between-group design. SETTING: Subjects' homes. SUBJECTS: Sample of convenience of 15 adults with moderate stroke, 22 adults with mild stroke, and 32 age-matched controls. Stroke severity was determined using the Orpington Prognostic Scale. INTERVENTION: Practice of movements to target switches in two conditions, a repeated series and a random series. Practice was organized into a single session of six blocks of 80 trials such that blocks 1 and 2 were the random series, blocks 3 and 4 the repeated series, block 5 the random series, and block 6 the repeated series. Explicit knowledge of the two conditions was not provided. MAIN MEASURES: The mean response time and the coefficient of variation were calculated for each block for each group. RESULTS: Regardless of group, participants had a slower response time when practice was unexpectedly switched from the repeated to random condition. The response time and coefficient of variation for those with moderate stroke were persistently greater than those with mild stroke and controls, who were not different from each other. CONCLUSIONS: Implicit motor learning is preserved in adults with moderate stroke and may be a viable strategy for teaching motor skills in rehabilitation. The clinician should be aware that subjects with moderate stroke, even when performing with the less affected upper extremity, have significantly slower and more variable movements than those with mild stroke and controls.

Aged↗

PubMed2001

Implicit learning of a perceptual-motor skill after stroke.

BACKGROUND AND PURPOSE: A motor skill can be learned implicitly, without awareness of what is being learned. The purpose of this study was to examine the ability of adults who had unilateral stroke to learn implicitly a perceptual-motor task. SUBJECTS: Subjects were 47 people who were poststroke and 36 control subjects. METHODS: Participants performed sequences of hand movements in response to target lights in 2 conditions: a patterned sequence and a random sequence. Participants were not given explicit knowledge of the presence of the 2 conditions. Those who had stroke performed with the upper-extremity ipsilateral to the lesion. RESULTS: Subjects who had stroke performed more slowly than control subjects. For both groups, times decreased with practice of the patterned sequence, increased with introduction of the random sequence, and decreased again with reintroduction of the patterned sequence. Group differences persisted in a retention test given the next day of the patterned sequence, and both groups showed decreased times over the course of the retention test. DISCUSSION AND CONCLUSION: People with stroke are able to learn a perceptual-motor task even without explicit instructions regarding the patterned sequence embedded in the task.

Analysis of Variance↗

PubMed1999

Inhibition and aging: similarities between younger and older adults as revealed by the processing of unattended auditory information.

The ability to selectively attend to an auditory stimulus appears to decline with age and may result from losses in the ability to inhibit the processing of irrelevant stimuli (i.e., the inhibitory deficit hypothesis; L. Hasher & R. T. Zacks, 1988). It is also possible that declines in the ability to selectively attend are a result of age-related hearing losses. Three experiments examined whether older and younger adults differed in their ability to inhibit the processing of distracting stimuli when the listening situation was adjusted to correct for individual differences in hearing. In all 3 experiments, younger and older adults were equally affected by irrelevant stimuli, unattended stimuli, or both. The implications for auditory attention research and for possible differences between auditory and visual processing are discussed.

Adolescent↗

PubMed1999

Aging and selective attention: an issue of complexity or multiple mechanisms?

Previous studies have shown age-associated deficits in selective attention that vary as a function of task demands. The present study was conducted to dissociate the effect of task complexity on age-related performance differences from qualitative differences in cognitive demands. Twenty-four young and 24 older adults were administered two versions of the Stroop Test (Hartley, 1993). The Color-Block version required identifying the color of a box while ignoring the name of a color printed either above or below the box. The Color-Word version required naming the color of a word while ignoring the semantic meaning of the word (a color name). Each version of the task included a two- and four-color choice condition as a manipulation of task complexity. Old and young adults performed comparably on the Color-Block Task, but older adults were significantly impaired on both conditions of the Color-Word Task, particularly in the four-choice condition. Results suggest age-related differences in the distinct attentional processes demanded by each task are not attributable to general slowing.

Adult↗

PubMed1997

Inhibition in attention and aging.

The literature on inhibition and aging has grown steadily in the wake of Hasher & Zacks' (1988) inhibitory deficit theory of cognitive aging. Not all of the findings support the notion of an age-related inhibitory decline, and some refinement of the theory is now required. This article has three goals: (a) to evaluate the role of inhibitory mechanisms in selective attention and aging; (b) to provide an evaluation of inhibition as a theoretical concept in theories of cognitive aging, with a specific focus on attention and aging; and (c) to consider the more general problem of evaluating progress in theory development.

Aged↗

PubMed1995

Aging and negative priming in a location suppression task: the long and the short of it.

The role of temporal parameters in aging and inhibitory function was examined using negative priming (NP) and repetition priming (RP) in a task involving a series of visually presented prime-probe sets; responses were made on the basis of the location of a target stimulus. Preparatory intervals (PI) preceding prime-probe sets were 3,000 ms or 1,500 ms. The longer PI resulted in less NP in older adults than did the shorter PI. Further analysis suggest that older adults may be less prepared to inhibit the distractor following the longer PI. The longer PI also produced more RP than did the shorter PI for both age groups, indicating a greater emphasis on facilitatory processes in this condition. In addition, evidence was obtained to suggest that an inverse relationship between NP and RP exists for both young and old adults. These data suggest that individuals or task conditions may emphasize either facilitation or inhibition in selection.

Adult↗

PubMed1995

Age differences and similarities in patterns of cerebral hemispheric asymmetry.

Younger (M age = 20.4 years) and older (M age = 70.7 years) adults participated in 3 visual half-field experiments. These were designed to examine specific aspects of hemispheric asymmetry: (a) hemispheric dominance for phonetic-linguistic processing (as measured by identification of non-word trigrams), (b) hemispheric differences in trigram processing strategy, (c) characteristic perceptual biases thought to reflect hemispheric arousal asymmetries, and (d) hemispheric dominance for processing emotions shown on faces. Patterns of left-right asymmetries were comparable for older and younger participants, and intercorrelations among the various measures of asymmetry were similar for both groups. In view of the present results, it seems unlikely that changes in hemispheric asymmetry contribute significantly to age-related changes in cognitive functioning.

Adolescent↗

PubMed1994

Contributions of surface and conceptual information to performance on implicit and explicit memory tasks.

Four experiments examined the effects of perceptual and conceptual processing operations on 2 implicit and 2 explicit memory tasks. Results show an advantage of visual over auditory presentation for word-fragment completion, word-stem completion, and word-stem cued recall; there was no such advantage in recognition memory. Conceptual processing had no effect on the implicit tasks, a small effect on word-stem cued recall, and a large effect on recognition. It is concluded that there is no necessary trade-off between the 2 types of information. Speculatively, the use of perceptual information may be all or none and relatively automatic, whereas the use of conceptual information appears to be graded and more under conscious control.

Acoustic Stimulation↗

PubMed1993

Item and relational processing in young and older adults.

The item and relational information framework of memory provided a methodology for an analytical approach to age differences in encoding and retrieval processes. Subjects were given related or unrelated words to sort or rate for pleasantness. Young adults performed better than older adults in free recall, but older adults were able to use both item and relational information as well as young adults. In a second experiment, subjects also sorted or rated a list composed of different numbers of category items. The pattern of free recall and cued recall scores indicated that item and relational information affected the memory performance of both age groups in a similar fashion. By examining memory in terms of item and relational information, it appears that older adults do not have difficulty combining two types of target information during encoding and that the information assists in recall of target items.

Adolescent↗

PubMed1993

Sensory gating and inhibitory function in late-life schizophrenia.

Although similarities between the cognitive deficits observed in schizophrenia and those observed in aging have been recognized for over 50 years, little work has been done to directly examine these similarities or their implications for late-life schizophrenia. We review studies of prepulse inhibition, habituation, latent inhibition, and negative priming that indicate marked similarities in the patterns of deficits observed in schizophrenia and in aging. We also present new data from preliminary studies of prepulse inhibition and negative priming in which we compare young normal controls, older adult normal controls, and late-life schizophrenia patients. For both measures, both schizophrenia patients and older adults showed an inhibitory deficit relative to young controls. In the case of negative priming, older schizophrenia patients showed evidence of greater inhibitory dysfunction than did normal older adults, suggesting that older schizophrenia patients suffer a deficit resulting from the combined effects of schizophrenia and aging. The implications of these results and directions for future research are discussed.

Acoustic Stimulation↗

PubMed1992

Aging, selective attention, and inhibitory processes: a psychophysiological approach.

The present study investigated the efficiency with which younger and older adults allocate attention to relevant and irrelevant stimuli. The model of attention guiding this research links the orienting response with the allocation of attention and habituation with the inhibition of the allocation of attention. We adapted a paradigm developed by Iacono and Lykken (1983) in which subjects are instructed unambiguously either to attend to or to ignore a series of innocuous tones, and the skin conductance orienting response elicited by each tone is measured. Results revealed that young subjects instructed to ignore the tones habituated more quickly than did those instructed to attend to the tones. However, older adults exhibited nondifferential orienting across the 2 instruction conditions. These results suggest an age-related deficit in the ability to inhibit attention to irrelevant stimuli.

Adult↗

PubMed1991

Aging, inhibitory processes, and negative priming.

The hypothesis that older adults experience a decline in the efficiency of inhibitory processes was tested in a negative priming experiment. Negative priming is interpreted as being due to the previous inhibition of a subsequent target item. An experiment involving a visual selective attention task with a negative priming condition was conducted with 20 college students and 20 older adults. A letter-reading task with partially superimposed red and green letters was used to assess age differences in negative priming. Subjects read red letters and ignored green letters. Results showed a significant interaction between age and the effect of distracting information, with older adults being more slowed by the presence of green letters than young adults. However, older adults failed to show negative priming effects, whereas young adults did show negative priming. These findings are interpreted in the context of age deficits in inhibitory processes, which may lead to decreased performance on selective attention tasks.

Adolescent↗

PubMed1986

The effects of age and extended practice on divided attention performance.

The present study examined the effects of repeated practice on the divided attention performance of young and old adults. Six young and 6 older adults performed two perceptual-motor tasks under both single- and dual-task conditions across six 1-hr sessions. Absolute levels of performance improved reliably over sessions for both young and old participants, but divided attention performance remained poorer in old than in young adults. Relative divided attention costs (Somberg & Salthouse, 1982) were consistently higher for the older adults across experimental sessions. These results confirm previous suggestions that older people are particularly vulnerable to the effects of divided attention. The findings are discussed further in terms of the validity of single-session studies of age differences in divided attention performance.

Adult↗