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Biomedical subjects

R D Nebes

Publications and source records attributed to R D Nebes.

At least 55 records · Page 3Linked to original sources
PubMed1987

Learning deficit in Parkinson's disease. Comparison with Alzheimer's disease and normal aging.

The learning ability of 12 patients with Parkinson's disease (PD) was studied using a verbal paired-associate learning task, and was compared with that of ten patients with Alzheimer's Disease (AD) and 12 controls (NC). Overall, the PD patients performed significantly better than the AD patients but significantly worse than the NC subjects. Their performance was not related to their overall level of cognitive functioning as measured by the Mattis' Dementia Rating Scale, but was unequally distributed suggesting that the PD population actually consisted of more than one subgroup. A low error group performed like controls, while a high error group had a learning impairment comparable to that of AD patients. It is concluded that PD patients may have three patterns of neuropsychologic performance: some are unimpaired, some have "focal" abnormalities, and some have a generalized impairment of cognitive function.

Aged↗
PubMed1987

The use of language structure by demented patients in a visual search task.

Recent findings suggest that some components of semantic memory are spared by Alzheimer's disease. The present study used a visual-search task to determine whether knowledge of the sequential letter dependencies present in spelling remains intact in demented patients. The speed with which twenty Alzheimer patients, twenty young and twenty old controls searched an array of letters for a target was measured. Arrays varied in how closely they approximated English-spelling patterns (zero-order, and third-order approximations and actual words). Despite differing in their overall speed of response, normal and demented subjects were affected equally by the approximation to English of the stimuli (i.e., both searched words faster than low-order approximations). Thus, knowledge of the probability patterns of spelling appears to remain intact and accessible in the semantic memory of demented patients.

Aged↗
PubMed1987

Cognitive deficits and clinical diagnosis of Alzheimer's disease.

We used cognitive deficits detected by neuropsychological testing to evaluate clinical diagnosis of Alzheimer's disease. Deficits were defined with respect to performance of control subjects according to procedural guidelines set by a NINCDS-ADRDA Work Group. The most frequent deficits were in recent memory and lexical-semantic language abilities. Clinical diagnosis of Alzheimer's disease was compared with diagnosis based on a criterion of two or more cognitive deficits both on initial neuropsychological testing and on testing repeated a year later in some subjects. Initial clinical diagnosis identified 96% of cases who met the criterion when first tested and 100% of those with multiple deficits at follow-up. Specificity with respect to the criterion was 86% on initial testing and 89% at follow-up. These findings support the validity of clinical diagnosis of Alzheimer's disease using the NINCDS-ADRDA criteria.

Aged↗
PubMed1986

Vasopressin peptide (DDAVP) may narrow the focus of attention in normal elderly.

Administration of DDAVP (1 desamino-8-D-arginine vasopressin), a form of vasopressin with little pressor action, has been shown to improve cognitive performance in the elderly. It remains unclear whether memory processes are specifically influenced or more general processes are altered. Fifteen elderly subjects performed a central mental arithmetic task and a peripheral choice reaction time task in DDAVP and control conditions. DDAVP slowed reaction times to peripheral lights but did not alter arithmetic performance. The results suggest that DDAVP increases the proportion of attention allocated to primary task performance by decreasing attention to secondary tasks. This shift does not appear to be mediated by any action of DDAVP on peripheral cardiovascular function.

Aged↗
PubMed1986

Use of semantic context by patients with Alzheimer's disease.

In this study we used semantic-priming procedures to examine limitations in the use of semantic context by patients with Alzheimer's disease. We also tried to determine whether any such contextual effects were mediated solely through automatic processes or whether attentional processes were also involved. Three tasks were applied to examine the effect of semantic context on the performance of 18 normal elderly and 18 normal young subjects, and on 18 patients with Alzheimer's disease. When normal and demented subjects were asked to decide whether a given item was a member of a certain category, results showed that their response times were equally affected by the item's dominance in the category. The time that demented patients took to recognize a word was actually affected more by the semantic context provided by a priming sentence than was that of normal subjects. When asked to generate the final word of an incomplete sentence, demented subjects performed very poorly unless potential responses were highly constrained by sentence context.

Adult↗
PubMed1984

The effect of vasopressin on memory in the healthy elderly.

The effect that vasopressin has upon memory in young and old males was tested in a double-blind crossover study. There were two 1-week medication periods; during one, subjects received 60 micrograms of vasopressin daily; during the other, placebo. Reaction time tasks were used to measure their speed of retrieval from: short-term memory (STM), long-term memory (LTM), and semantic memory (SM). While vasopressin did not affect SM retrieval time or simple vocal reaction time, it did reduce memory comparison time and perceptual-motor time in STM and retrieval time in LTM. The degree of facilitation was similar in young and old.

Adult↗
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↗
PubMed1983

The use of focused attention in visual search by young and old adults.

A deficit in focused attention has recently been suggested to underlie some of the cognitive decrements seen in the elderly. This hypothesis was tested in two visual search studies. Subjects had to decide whether or not a given target was present among an array of six digits, three of which were red, the rest black. For the "yes" trials, prior information regarding target color substantially reduced search time in comparison to warning signal that did not provide color information. This reduction in search time was equivalent in the young and the old, both at long (ad lib) and shorter (250-1000 msec) array durations. This result suggests that both age groups are equally proficient in focusing their attention on the digits of the relevant color. On the "no" trials, prior color-information was not effective in reducing search time. There was some evidence in experiment two that the older subjects were using a different search strategy on these trials.

Adolescent↗
PubMed1981

Signal-detection analysis of hemispheric differences in visual recognition memory.

In the present experiment, subjects decided on each trial whether or not a unilaterally presented probe digit was a member of a previously memorized set of two, three, or four digits. The probe was presented at a near-threshold duration and followed by a visual pattern mask. Signal-detection estimates of detectability and response bias were obtained from subjects' confidence ratings regarding their decisions. The detectability of the probe in memory was significantly better when the probe was presented to the right visual field-left hemisphere than when presented to the left visual field-right hemisphere. The response criterion became significantly more lax as memory-set size increased, but only for probes presented to the left visual field-right hemisphere. The present results are consistent with reaction-time studies using verbal stimuli that indicate a left hemisphere advantage in the efficiency of memory comparison.

Adult↗
PubMed1980

Memory for verbal and spatial information as a function of age.

The present study investigated whether there is a differential decline with age in verbal and spatial memory, by measuring the ability of 24 young (mean age = 18.8) and 24 elderly (mean age = 69.5) subjects to remember verbal and spatial information under identical task conditions. Subjects recalled either the identities or spatial locations of seven letters arranged randomly within a 5 x 5 grid. To determine whether subjects actually encoded the verbal and spatial characteristics of the array differently, verbal and spatial interference tasks were administered during the retention interval. Results showed that the memory decrement in the elderly was not greater for the spatial aspects of the stimulus array than for its verbal aspects. Thus, there was no evidence for a greater decline with age in spatial memory than in verbal memory. Limited support was found for the utility of the selective interference paradigm to demonstrate separate and independent verbal and spatial memory codes.

Adolescent↗
PubMed1978

Vocal versus manual response as a determinant of age difference in simple reaction time.

The decrease in response speed usually found to occur with advancing age is felt by many investigators to be a phenomenon common to all speeded tasks, regardless of the exact nature of the sensory stimulus or motor response involved. In the present experiment, however, the type of response the subject made determined whether or not an age difference existed in simple reaction time to a visual stimulus. When subjects responded manually, by releasing a key, the usual age decrement in response latency was found. When the same subjects responded vocally, by saying a word, there was no significant age difference in reaction time. This result suggests that slowing of psychomotor latency with age is not a general phenomenon, but may be limited to certain neural systems.

Adult↗
PubMed1976

The effect of age on the speed of sentence formation and incidental learning.

To test the hypothesis that older persons tend not to use verbal mediators in paired-associate learning because it takes them too long to form an appropriate mediator, the time needed by young and old subjects to generate sentences incorporating given pairs of nouns was measured. Older subjects formed sentences just as rapidly as did the young. Despite their equivalent speed in creating these verbal associations when tested later for the occurrence of incidental learning of the noun pairs, the older subjects showed much poorer recall than did the younger subjects. This age difference in learning did not appear to be a function of any major dissimilarities in the generated sentences themselves, i.e., in the grammatical constructions used, or in the imageability of the relationships expressed by the sentences. The rated imagery value of the stimulus nouns was found to affect both the speed of sentence formation and the accuracy of incidental learning; in both younger and older subjects, formation time was less, and recall was better for the high imagery noun pairs.

Adolescent↗