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Biomedical subjects

S M Resnick

Publications and source records attributed to S M Resnick.

67 records · Page 4Linked to original sources
PubMed1991

Relations among clinical scales in schizophrenia.

OBJECTIVE: Clinical scales have become established as tools to quantify phenomenological features of schizophrenia. The goal of this study was to examine relations among the following: the Brief Psychiatric Rating Scale (BPRS), the Scale for the Assessment of Positive Symptoms, the Scale for the Assessment of Negative Symptoms, and the deficit-nondeficit classification. METHOD: Forty-seven patients with schizophrenia were recruited according to specific inclusion and exclusion criteria. The standardized assessment procedures were administered by a trained psychiatric research team. RESULTS: Examination of the BPRS showed that the patients had highest scores on the thought disorder factor and the symptoms specific to schizophrenia. Classification of patients as having the positive, negative, or mixed type of schizophrenia resulted in a finding of seven with the positive, seven with the negative, and 33 with the mixed type. The division of patients into those with the deficit syndrome (N = 29) and those without (N = 18) was related to symptom specificity and to positive and negative symptoms. Deficit syndrome patients had more symptoms specific to schizophrenia, fewer nonspecific symptoms, and, as expected, greater severity of negative symptoms. Cluster analysis revealed three clusters of patients: those with low negative symptom scores and high scores on specific symptoms (the majority were without the deficit syndrome); those with high scores on negative, positive, and specific symptoms (the majority had the deficit syndrome); and those with lower scores on specific symptoms and high scores on negative and positive symptoms (the majority had the deficit syndrome). CONCLUSIONS: The scales showed some overlap but also seemed to measure complementary aspects of the phenomenology of schizophrenia. Subtypes of patients identified by the combined use of these scales may differ in underlying pathology.

Cluster Analysis↗
PubMed1989

Laterality and frontality of cerebral blood flow and metabolism in schizophrenia: relationship to symptom specificity.

Two of the hypotheses on regional brain dysfunction in schizophrenia that have received some support in studies of cerebral blood flow (CBF) and cerebral metabolic rate (CMR) are: (1) left hemispheric dysfunction and overactivation (laterality) and (2) frontal lobe deactivation or failure to activate (frontality). Although these hypotheses are not mutually exclusive, their relative importance for providing clues to neural underpinnings of symptoms specific to schizophrenia depends on their ability to predict variation in symptomatology. A potentially efficient strategy for such study is to start with physiological parameters of laterality and frontality, and correlate them with measures of severity of clinical symptoms specific to schizophrenia. For two schizophrenic samples reported earlier, we derived laterality (left-right hemispheres) and frontality (frontal-posterior regions) measures of CBF (Study 1) and CMR (Study 2), and correlated them with symptom specificity, defined as the difference in severity of symptoms specific and nonspecific to schizophrenia assessed by the Brief Psychiatric Rating Scale. In both studies, low but significant positive correlations were obtained between the specificity score and laterality for CBF in Study 1 and for CMR in Study 2, but not frontality. The results suggest that in these samples disturbances in lateralized activity are more prominently associated with the phenomenology of schizophrenia than disturbed frontal lobe activity.

Blood Glucose↗
PubMed1988

Positron emission tomography and subcortical glucose metabolism in schizophrenia.

Our previous observation of a disturbed subcortical-to-cortical gradient of activity in schizophrenia was further elucidated by examining glucose metabolism in three subcortical structures: lenticular nucleus, caudate nucleus, and thalamus. Local cerebral glucose metabolism was determined with 18F-fluorodeoxyglucose using positron emission tomography (PET) in a sample of 20 unmedicated schizophrenics and 18 normal volunteers. Repeated evaluations were performed for 12 schizophrenics following treatment with psychotropic medications and for 11 controls. Unmedicated schizophrenics had lower cortical and caudate absolute metabolic rates. Subcortical-to-cortical ratios for the lenticular nucleus and thalamus were increased in schizophrenics compared with controls, reflecting a preservation of activity in these structures relative to decreased cortical metabolism. When patients were grouped by length of medication-free period before the initial study, there was a trend for patients who had been medication free less than 6 months to have higher subcortical ratios. However, there were no consistent effects of medication in the subsample of patients whose PET studies were repeated following treatment. The results demonstrate relative hypermetabolism in structures implicated in dopamine pathways. An understanding of the physiological significance of this finding awaits the combined measurement of metabolic activity and neuroreceptors in schizophrenics.

Adult↗
PubMed1987

Regional brain function in schizophrenia. I. A positron emission tomography study.

Local cerebral glucose metabolism was determined with 18-F-fluorodeoxyglucose using positron emission tomography in a sample of 12 unmedicated schizophrenics and 12 matched normal controls. The data were analyzed for absolute metabolic rates and region/whole-brain ratios using the cortical-subcortical, antero-posterior, and laterality dimensions. Lobar areas within cortical regions were also compared. Across groups, subcortical metabolism was higher than cortical metabolism. Patients had lower metabolism, cortically and subcortically, and a steeper subcortical to cortical gradient. Patients with higher scores on the Brief Psychiatric Rating Scale had higher absolute metabolism and higher left relative to right hemispheric metabolism than did patients with lesser severity. The results did not show "hypofrontality" in schizophrenia. These findings provide some support for cerebral dysfunction in schizophrenia and indicate the need for further examination of the cortical-subcortical dimension.

Brain↗
PubMed1987

Regional brain function in schizophrenia. II. Repeated evaluation with positron emission tomography.

Cerebral glucose metabolism was measured twice in a sample of 15 schizophrenics and eight controls, using positron emission tomography (PET) with 18-F-fluorodeoxyglucose. Studies were separated by three to 33 weeks. Patients were unmedicated during the first study, and the majority were receiving neuroleptics during the second study. There were no changes from study 1 to study 2 in average whole-brain metabolic rates, regional cortical activity, or the gradient of subcortical to cortical activity. The steeper subcortical to cortical gradient in schizophrenics, present in the first study, persisted in the second. Changes in this gradient were uncorrelated with changes in clinical status. Laterality (right-left) was stable across studies, and changes toward higher right relative to left hemispheric metabolism were correlated with clinical improvement. The results support the hypothesis of abnormal hemispheric activity in schizophrenia and implicate the subcortical-cortical gradient as another dimension that merits further exploration.

Adult↗
PubMed1987

The effect of anxiety on cortical cerebral blood flow and metabolism.

The relation between anxiety and cortical activity was compared in two samples of normal volunteers. One group was studied with the noninvasive xenon-133 inhalation technique for measuring cerebral blood flow (CBF) and the other with positron emission tomography (PET) using 18Flurodeoxyglucose (18FDG) for measuring cerebral metabolic rates (CMR) for glucose. The inhalation technique produced less anxiety than the PET procedure, and for low anxiety subjects, there was a linear increase in CBF with anxiety. For higher anxiety subjects, however, there was a linear decrease in CBF with increased anxiety. The PET group manifested a linear decrease in CMR with increased anxiety. The results indicate that anxiety can have systematic effects on cortical activity, and this should be taken into consideration when comparing data from different procedures. They also suggest a physiologic explanation of a fundamental behavioral law that stipulates a curvilinear, inverted-U relationship between anxiety and performance.

Adolescent↗
PubMedDate not supplied

Longitudinal effects of estrogen replacement therapy on PET cerebral blood flow and cognition.

Observational studies suggest that estrogen replacement therapy (ERT) may protect against age-related memory decline and lower the risk of Alzheimer's disease (AD). This study aimed to characterize the neural substrates of those effects by comparing 2-year longitudinal changes in regional cerebral blood flow (rCBF) in 12 ERT users and 16 nonusers. Positron emission tomography (PET) measurements of rCBF were obtained under three conditions: rest, and verbal and figural recognition memory tasks. Groups showed different patterns of change in rCBF over time in a number of brain areas. These group differences, for the most part, reflected regions of increased rCBF over time in users compared to nonusers. The greatest differences between ERT users and nonusers were in the hippocampus, parahippocampal gyrus, and temporal lobe, regions that form a memory circuit and that are sensitive to preclinical AD. Across a battery of standardized neuropsychological tests of memory, users obtained higher scores than did nonusers of comparable intellect. Group differences in longitudinal change in rCBF patterns may reflect one way through which hormones modulate brain activity and contribute to enhanced memory performance among ERT users.

Aged↗
PubMedDate not supplied

Age differences in spatial memory in a virtual environment navigation task.

The use of virtual environment (VE) technology to assess spatial navigation in humans has become increasingly common and provides an opportunity to quantify age-related deficits in human spatial navigation and promote a comparative approach to the neuroscience of cognitive aging. The purpose of the present study was to assess age differences in navigational behavior in a VE and to examine the relationship between this navigational measure and other more traditional measures of cognitive aging. Following pre-training, participants were confronted with a VE spatial learning task and completed a battery of cognitive tests. The VE consisted of a richly textured series of interconnected hallways, some leading to dead ends and others leading to a designated goal location in the environment. Compared to younger participants, older volunteers took longer to solve each trial, traversed a longer distance, and made significantly more spatial memory errors. After 5 learning trials, 86% of young and 24% of elderly volunteers were able to locate the goal without error. Performance on the VE navigation task was positively correlated with measures of mental rotation and verbal and visual memory.

Adult↗
PubMedDate not supplied

Verbal and figural recognition memory: task development and age associations.

The goal of the present study was to develop and validate parallel tests of verbal and figural delayed-recognition memory with similar task demands and difficulty levels. Such tasks would allow examination of age differences and longitudinal age changes in visual recognition memory for two types of stimuli, activate divergent neural systems, and allow us to use the same procedures within the confines of functional neuroimaging as those we use in standard neuropsychological administration. The tasks introduced here include a delay between target presentation and test phase, are matched in difficulty, and yield moderate levels of performance. Individual and group differences in task performance were examined in 80 cognitively normal men and women in two older age groups: 60 to 69 and 70 to 85. Accuracy averaged 74% in both tasks, with lower performance in the oldest age group. Although accuracy was equivalent between tasks, subjects had a more liberal response bias in the figural than verbal task. Performance on the new recognition-memory tests was significantly related to Benton Visual Retention Test (BVRT; Benton [1963]. New York: The Psychological Corporation) and California Verbal Learning Test (CVLT; Delis, Kramer, Kaplan, & Ober [1987]. New York: The Psychological Corporation) performance measures. The absence of floor or ceiling effects, wide range of individual variability, and demonstrated concurrent validity of the present tasks suggest their potential utility in functional neuroimaging studies and in the early detection of cognitive decline.

Acoustic Stimulation↗
PubMedDate not supplied

Sex differences in anatomic measures of interhemispheric connectivity: correlations with cognition in women but not men.

A robust sex difference in the splenium of the corpus callosum, reflecting greater interhemispheric connectivity in women, was observed on magnetic resonance images from 114 individuals. In addition, bulbosity of the corpus callosum correlated with better cognitive performance in women but not in men, indicating that the degree of interhemispheric connectivity has different implications for men and women. These findings were based on a new image analysis technique which allows investigation of local variability in brain morphology.

Aged↗
PubMedDate not supplied

A computerized approach for morphological analysis of the corpus callosum.

OBJECTIVE: A new technique for analyzing the morphology of the corpus callosum is presented, and it is applied to a group of elderly subjects. MATERIALS AND METHODS: The proposed approach normalizes subject data into the Talairach space using an elastic deformation transformation. The properties of this transformation are used as a quantitative description of the callosal shape with respect to the Talairach atlas, which is treated as a standard. In particular, a deformation function measures the enlargement/shrinkage associated with this elastic deformation. Intersubject comparisons are made by comparing deformation functions. RESULTS: This technique was applied to eight male and eight female subjects. Based on the average deformation functions of each group, the posterior region of the female corpus callosum was found to be larger than its corresponding region in the males. The average callosal shape of each group was also found, demonstrating visually the callosal shape differences between the two groups in this sample. CONCLUSION: The proposed methodology utilizes the full resolution of the data, rather than relying on global descriptions such as area measurements. The application of this methodology to an elderly group indicated sex-related differences in the callosal shape and size.

Aged↗
PubMedDate not supplied

An image-processing system for qualitative and quantitative volumetric analysis of brain images.

In this work, we developed, implemented, and validated an image-processing system for qualitative and quantitative volumetric analysis of brain images. This system allows the visualization and quantitation of global and regional brain volumes. Global volumes were obtained via an automated adaptive Bayesian segmentation technique that labels the brain into white matter, gray matter, and cerebrospinal fluid. Absolute volumetric errors for these compartments ranged between 1 and 3% as indicated by phantom studies. Quantitation of regional brain volumes was performed through normalization and tessellation of segmented brain images into the Talairach space with a 3D elastic warping model. Retest reliability of regional volumes measured in Talairach space indicated errors of < 1.5% for the frontal, parietal, temporal, and occipital brain regions. Additional regional analysis was performed with an automated hybrid method combining a region-of-interest approach and voxel-based analysis, named Regional Analysis of Volumes Examined in Normalized Space (RAVENS). RAVENS analysis for several subcortical structures showed good agreement with operator-defined volumes. This system has sufficient accuracy for longitudinal imaging data and is currently being used in the analysis of neuroimaging data of the Baltimore Longitudinal Study of Aging.

Aged↗