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Biomedical subjects

G Ratcliff

Publications and source records attributed to G Ratcliff.

At least 37 records · Page 2Linked to original sources
PubMed1996

Effect of education and gender adjustment on the sensitivity and specificity of a cognitive screening battery for dementia: results from the MoVIES Project. Monongahela Valley Independent Elders Survey.

The Monongahela Valley Independent Elders Survey (MoVIES) used a multiphase process to identify demented persons among 1,366 randomly selected noninstitutionalized individuals 65 years and older. Raw test scores from a cognitive screening battery were used to identify cognitively impaired individuals who were referred for a clinical evaluation. Subsequently, test scores were adjusted for education and gender within age strata. Adjusting test scores affected sensitivity for dementia only among the most educated, increasing sensitivity among younger subjects and decreasing among the older subjects. Specificity increased among the least educated and the oldest subjects. Overall, the adjusted criteria did not perform as well as the unadjusted criteria in this sample. Adjustment for education will not necessarily improve the ability of a screening battery for cognitive function to identify demented persons, particularly if unadjusted scores perform well.

Aged↗
PubMed1994

Studies of the epidemiology of dementia: comparisons between developed and developing countries.

By the year 2025, 68% of the world's population aged 65 and above, nearly 277 million people, will be residing in developing countries. The less industrialized nations have been the least studied to date, and may yield significant new information about the etiology and risk factors for Alzheimer's disease (AD) and other dementias. Although it is readily apparent that cross-national and cross-cultural comparisons are desirable, these can be meaningful only if based on comparable methodology. In this work we will discuss some general conceptual and methodological issues regarding epidemiological studies of dementia in developing countries. The topics discussed include community-based screening for dementia, screening instruments and their application in cross-cultural studies, steps in standardization of new or modified neuropsychological tests, and some special considerations in studying uneducated/illiterate populations.

Aged↗
PubMed1993

Sensitivity and specificity for dementia of population-based criteria for cognitive impairment: the MoVIES project.

BACKGROUND: Few norms exist for the elderly on the cognitive tests commonly used to screen for dementia; conventional cutpoints used in clinical settings may be of limited value in population screening. A particular problem is posed by elderly populations with low educational levels, as performance on most cognitive tests is affected by education. Thus, a healthy but poorly educated population may obtain test scores in the range considered impaired in the clinical setting. METHODS: A random sample of 1,367 subjects aged 65+ years was screened for dementia in a rural community in Southwestern Pennsylvania. Two sets of cognitive measures were used: a global cognitive scale (the MMSE) and a brief battery of tests tapping a variety of cognitive domains. Rather than using a priori cutoff scores, we examined the specificity and sensitivity for dementia of two operationally defined levels of cognitive impairment, at the 5th and 10th percentiles of the study sample on each set of measures. RESULTS: Results suggest that the screening of multiple cognitive domains at the 10th percentile had significantly greater sensitivity but not lower specificity for definite dementia than did the use of the single global scale. CONCLUSION: Our data support the use of population-based cutpoints over standard cutoff scores, in that the global scale at the conventional cutoff was less sensitive than the battery at the same percentile, and because adequate norms do not exist for tests such as those in the battery.

Aged↗
PubMed1991

Effects of age, gender, and education on cognitive tests in a rural elderly community sample: norms from the Monongahela Valley Independent Elders Survey.

A random sample of 1,350 persons aged 65 years and older in a rural community underwent cognitive screening as part of a survey to establish a population-based registry of dementing disorders. The screening battery included the neuropsychological tests of the assessment protocol used in the National Institute on Aging multicenter Consortium to Establish a Registry for Alzheimer's Disease (CERAD). This paper reports a large body of normative neuropsychological data from this sample with members of relatively low socioeconomic status. Age, sex, and educational level were found to have statistically significant effects on test scores. The implications of these findings for the establishment of screening cutoff scores are discussed.

Aged↗
PubMed1990

Predicting cognitive recovery from closed head-injury in children and adolescents.

Longitudinal data from 84 head-injured children and adolescents, who were tested at three points in the first year postinjury, were analyzed to determine the best combination of demographic, injury-related, and behavioral factors predicting cognitive performance. Dependent variables were language, memory, visuomotor, and speeded performance factor scores obtained through confirmatory factor analyses of an extensive test battery. Multiple regression analyses indicated that injury severity and the existence of previous psychological, physical, or cognitive disorders were primary for predicting acute (1 month post-hospital discharge) performance for older subjects. For younger subjects, however, parental marital status was the most important correlate of acute cognitive performance. Those residing in homes with both parents fared better than children in one-parent families. At 6 months and 1 year postinjury, the older subjects who performed most poorly initially remained the most impaired. For younger children, acute cognitive standing was also an important predictor of later performance, but parental marital status remained a crucial influence on their longer-term recovery of cognitive skills.

Adolescent↗
PubMed1989

The alien hand syndrome. Clinical and postmortem findings.

Two patients had automatonlike movements of their left hands and arms (alien hand syndrome) following damage to the brain. Autopsy findings in one patient demonstrated gunshot wound damage to the medial frontal white matter bilaterally, as well as the corpus callosum, right basal ganglia, internal capsule, and thalamus. The other patient had a ruptured anterior communicating aneurysm, with subsequent resection of the right frontal gyrus rectus. We postulate that this syndrome is due to the combination of a partial callosectomy and mesial frontal lesions.

Adult↗
PubMed1989

Category-specificity and modality-specificity in semantic memory.

Studies of agnosia have revealed two apparently orthogonal dimensions along which knowledge may break down. In some cases, knowledge of specific categories (such as living things) seems lost, regardless of the modality being tested. In other cases, knowledge in specific modalities (such as vision) seems lost, regardless of the category of stimuli being tested. These different sets of phenomena suggest different organizations for knowledge in the brain, the first by category and the second by modality. Unfortunately, possible confoundings between category, modality, and difficulty level in the previous studies prevent us from drawing strong conclusions from these data. The present study was aimed at assessing the nature of the breakdown in the semantic memory of a prosopagnosic patient, by orthogonally varying category and modality, while assessing difficulty level. The findings do not implicate a simple categorical or modality-dependent organization of his knowledge, but rather an organization in which both category and modality play a role.

Adult↗
PubMed1987

Dissociable visual and spatial impairments following right posterior cerebral lesions: clinical, neuropsychological and anatomical evidence.

A double dissociation of visual and spatial performance is reported in two men with chronic focal missile injuries of the right cerebral hemisphere. The clinical, neuropsychological and post-mortem anatomical data are considered in relation to evidence from physiological research of two major cortico-cortical pathways for object-recognition and spatial perception.

Brain Mapping↗
PubMed1986

Cognitive and affective changes after myelography: a comparison of metrizamide and iohexol.

A battery of brief cognitive tests and a mood scale were administered to 42 patients before and after cervical myelography with either metrizamide (20 patients) or iohexol (22 patients). The patients receiving metrizamide experienced a deterioration in mood after myelography and a relatively greater decline in cognitive test performance than did those receiving iohexol. These two side effects tended to occur together in the metrizamide group, suggesting a common underlying cause; but there was no correlation between changes in mood and cognitive function after myelography with iohexol. These results suggest that metrizamide has a greater neurotoxic effect than iohexol.

Adult↗
PubMed1980

Measuring the duration of post traumatic amnesia.

A simple quantitative test is described for measuring the duration of post-traumatic amnesia. It was used in a study of 336 patients with closed head injury; and the results matched closely the independent estimates of experienced neurosurgeons. A systematic procedure of this kind is clinically useful in its sensitivity to fluctuations or deterioration in the patient's mental state. It could also be used with advantage in multi-centre research by providing a standard criterion for the assessment of post-traumatic amnesia.

Adolescent↗
PubMed1977

Spatial disorientation in the monkey.

The incidence of misdirected movements of the hand during tactile discrimination performance in the dark has been tabulated for monkeys with bilateral removals of parieto-prestriate cortex. The observations support the existence of a spatial disorientation (in addition to their inaccuracies of reaching) in these animals.

Animals↗
PubMed1973

Spatial orientation in man: effects of left, right, and bilateral posterior cerebral lesions.

Men with chronic, penetrating missile wounds of the brain were examined with two `spatial' tasks: a visually-guided stylus maze and a locomotor map-reading task. Men whose lesions involved the posterior part of the right cerebral hemisphere were significantly worse than those with left posterior lesions at stylus maze-learning. On the locomotor task, however, a highly significant deficit was found in the group of men with bilateral posterior cerebral lesions, while those with unilateral lesions of either hemisphere and those with bilateral frontal lesions were unimpaired. The contributions of the two cerebral hemispheres to the analysis of spatial information are discussed in the light of these results and it is suggested that, while the right hemisphere has a special role in the perception of space, it does not bear exclusive responsibility for the maintenance of spatial orientation.

Brain Injuries↗
PubMedDate not supplied

A brief cognitive screening battery for dementia in the community.

Screening community samples for dementia often necessitates administering a cognitive test battery by trained personnel. Because diagnostic examinations are expensive, a useful screening battery must be highly specific in addition to having high sensitivity. The Monogahela Valley Independent Elders Survey (MoVIES) includes a random sample of community-dwelling participants at least 65 years of age who were screened using an extensive test battery of cognitive tests that required over 30 min to administer. Classification and Regression Trees (CART) was used to identify a subset of the battery that could be administered quickly and which maintained high levels of sensitivity and specificity for a diagnosis of dementia. The Short and Sweet Screening Instrument (SASSI) is a brief battery consisting of three standard cognitive tests that can be administered in approximately 10 min. Compared to the full battery, it was more sensitive (94% vs. 90%) and had comparable specificity (91% vs. 92%) for dementia in this sample.

Aged↗