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Biomedical subjects

G Ratcliff

Publications and source records attributed to G Ratcliff.

12 recordsLinked to original sources
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↗
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

Serial sevens versus world backwards: a comparison of the two measures of attention from the MMSE.

This paper reports on a comparison of the two alternative tests of attention in the Mini-Mental State Examination (MMSE), a well-known cognitive screening tool. The two tests, serial subtraction by seven and backwards spelling of the word world, are often used interchangeably. In a large population-based sample, the two tests were found to be weakly associated with each other, with the former test appearing more difficult, although both were strongly associated with educational level. The authors discuss the implications of this finding in clinical and research settings, and make recommendations for more consistent use of the instrument.

Aged↗