Biomedical subjects

L H Staib

Publications and source records attributed to L H Staib.

16 recordsLinked to original sources

PubMed2001

Automated measurement of latent morphological features in the human corpus callosum.

Our objective was to develop a novel factor-based analysis of the morphology of the corpus callosum and assess its applicability to the study of normal development, intelligence, and other subject characteristics. The contour of the corpus callosum was defined in the midsagittal planes of the MRI scans of 325 subjects, 6 to 88 years of age. The contours were coregistered, rescaled, and resampled to 50 points that were then entered into a principal components analysis with varimax rotation. The analysis yielded 8 factors for the contours of 138 healthy subjects. A second analysis of contours from 187 subjects in a patient group extracted 8 similar factors. Correlations of factor scores with conventional measures of callosum shape supported the construct validity of the assignment of morphological features to each of the factors. Correlations of factor scores with age, sex, handedness, ventricular volume, and IQ demonstrated the predictive validity of the factor structure and helped to define the neural correlates of these subject characteristics. We conclude that factor-based measures capture latent morphological features of the corpus callosum that are reliable and valid. Future studies will determine whether these novel measures are more closely related to neurobiologically important features of the corpus than are conventional measures of callosum size and shape.

Adolescent↗

PubMed2001

A new method for quantification of spatial and temporal parameters of endocardial motion: evaluation of experimental infarction using magnetic resonance imaging.

BACKGROUND: With the development of high-resolution myocardial imaging there has evolved a need for automated techniques that can accurately quantify regional function. OBJECTIVE: To develop a new method for quantification of spatial and temporal parameters of endocardial motion. DESIGN: Magnetic resonance images were analyzed using a unique, shape-based approach that tracks endocardial surface motion at defined points through the cardiac cycle by minimizing the bending energy. SETTING: Animal instrumentation was performed in the Nuclear Cardiology Experimental Research Laboratory at Yale University, New Haven, Connecticut. Magnetic resonance imaging was performed at the Yale New Haven Hospital Center. ANIMALS: Eight mongrel canines were used. INTERVENTIONS: Electrocardiograph-gated gradient-echo magnetic resonance images were obtained before and after occlusion of the left anterior descending coronary. Thirty-two points along automatically defined endocardial contours were tracked. Average displacements and cumulative path lengths were computed from end-diastole for each point over the entire cardiac cycle. The average cumulative path length was computed for each of four quarters of systole for the normal, border and infarct zones. Shape-based parameters of systolic motion were compared with the centreline approach. Infarct zone was defined by postmortem histochemical staining. MAIN RESULTS: Displacement and cumulative path length over the cardiac cycle decreased significantly in the infarct and border zones (P<0.05), but did not change in the normal zone (P was not significant). Temporal changes in motion were observed in all zones. Displacement measured using the shape-based algorithm was more consistent than cumulative path length when compared with systolic motion measured using the centreline method. CONCLUSIONS: An automated, shape-based approach permits quantitative evaluation of both spatial and temporal parameters of regional endocardial motion from high-resolution electrocardiograph-gated images. Analysis of endocardial motion and cumulative motion over the entire cardiac cycle discriminated infarcted from normal and border regions.

Animals↗

PubMed2001

Gender differences in cognitive and neural correlates of remembrance of emotional words.

Studies suggest that men and women have important differences in specific cognitive functions. Men show superior spatial memory and women demonstrate superior verbal memory, and women rely on emotional content to a greater degree in the processing of information. In spite of extensive research in neural correlates of human cognition, little is known about possible gender differences or the role of emotional content in the mediation of cognition. Two sets of lists of word pairs were developed, one with neutral (e.g., school-grocery) and the other with emotional (e.g., mutilate-beat) content. Male and female subjects were asked to rate emotions related to the words on several dimensions (e.g., nervous, fearful, happy). In a second experiment, men and women underwent positron emission tomographic (PET) measurement of brain blood flow during retrieval of word pairs. Words in the "emotional" category were rated more highly on the emotional dimensions, and women rated them as having more emotional impact than did the men. During retrieval of emotional words (but not neutral words) there was a different pattern of activation among the women compared with the men, with greater activation in bilateral posterior hippocampus and cerebellum, and decreased activity in medial prefrontal cortex, which are brain areas previously implicated in emotion. There were no significant differences in retrieval of emotional versus neutral words, or in differences in memory performance between men and women. The findings suggest differences in cognitive appraisal and involvement of a broader network of brain regions mediating emotion during remembrance of emotional words in women compared with men.

Adolescent↗

PubMed2000

Regional brain volume abnormalities and long-term cognitive outcome in preterm infants.

CONTEXT: Preterm infants have a high prevalence of long-term cognitive and behavioral disturbances. However, it is not known whether the stresses associated with premature birth disrupt regionally specific brain maturation or whether abnormalities in brain structure contribute to cognitive deficits. OBJECTIVE: To determine whether regional brain volumes differ between term and preterm children and to examine the association of regional brain volumes in prematurely born children with long-term cognitive outcomes. DESIGN AND SETTING: Case-control study conducted in 1998 and 1999 at 2 US university medical schools. PARTICIPANTS: A consecutive sample of 25 eight-year-old preterm children recruited from a longitudinal follow-up study of preterm infants and 39 term control children who were recruited from the community and who were comparable with the preterm children in age, sex, maternal education, and minority status. MAIN OUTCOME MEASURES: Volumes of cortical subdivisions, ventricular system, cerebellum, basal ganglia, corpus callosum, amygdala, and hippocampus, derived from structural magnetic resonance imaging scans and compared between preterm and term children; correlations of regional brain volumes with cognitive measures (at age 8 years) and perinatal variables among preterm children. RESULTS: Regional cortical volumes were significantly smaller in the preterm children, most prominently in sensorimotor regions (difference: left, 14.6%; right, 14.3% [P<.001 for both]) but also in premotor (left, 11.2%; right, 12.6% [P<.001 for both]), midtemporal (left, 7.4% [P =.01]; right, 10.2% [P<.001]), parieto-occipital (left, 7.9% [P =.01]; right, 7.4% [P =.005]), and subgenual (left, 8.9% [P =.03]; right, 11.7% [P =.01]) cortices. Preterm children's brain volumes were significantly larger (by 105. 7%-271.6%) in the occipital and temporal horns of the ventricles (P<. 001 for all) and smaller in the cerebellum (6.7%; P =.02), basal ganglia (11.4%-13.8%; P</=.005), amygdala (left, 20.2% [P =.001]; right, 30.0% [P<.001]), hippocampus (left, 16.0% [P =.001]; right, 12.0% [P =.007]), and corpus callosum (13.1%-35.2%; P</=.01 for all). Volumes of sensorimotor and midtemporal cortices were associated positively with full-scale, verbal, and performance IQ scores (P<.01 for all). CONCLUSIONS: Our data indicate that preterm birth is associated with regionally specific, long-term reductions in brain volume and that morphological abnormalities are, in turn, associated with poorer cognitive outcome. JAMA. 2000;284:1939-1947.

Brain↗

PubMed2000

Temporal lobe volume in panic disorder--a quantitative magnetic resonance imaging study.

Although previous studies have used magnetic resonance imaging (MRI) to demonstrate qualitative abnormalities of the temporal lobes in patients with panic disorder, no study to date has applied quantitative volumetric methods to evaluate brain changes in panic disorder. The purpose of this study was to measure the volume of the temporal lobe and the hippocampus in patients with panic disorder and healthy control subjects using quantitative MRI measures. The volume of the temporal lobe, hippocampus and whole brain was measured in 13 patients with panic disorder and 14 healthy subjects. The mean volume of the left and right temporal lobes was significantly smaller in panic disorder compared to healthy subjects (16770+/-909 mm(3) vs. 18343+/-1740 mm(3)). This result was significant after controlling for differences in whole brain volume. There was no significant difference in volume of the hippocampus between patients and control subjects. These findings are consistent with smaller temporal lobe volume in panic disorder despite normal hippocampal volume.

Adult↗

PubMed2000

Kinetic modeling of benzodiazepine receptor binding with PET and high specific activity [(11)C]Iomazenil in healthy human subjects.

Quantitation of the PET benzodiazepine receptor antagonist, [(11)C]Iomazenil, using low specific activity radioligand was recently described. The purpose of this study was to quantitate benzodiazepine receptor binding in human subjects using PET and high specific activity [(11)C]Iomazenil. Six healthy human subjects underwent PET imaging following a bolus injection of high specific activity (>100 Ci/mmol) [(11)C]iomazenil. Arterial samples were collected at multiple time points after injection for measurement of unmetabolized total and nonprotein-bound parent compound in plasma. Time activity curves of radioligand concentration in brain and plasma were analyzed using two and three compartment model. Kinetic rate constants of transfer of radioligand between plasma, nonspecifically bound brain tissue, and specifically bound brain tissue compartments were fitted to the model. Values for fitted kinetic rate constants were used in the calculation of measures of benzodiazepine receptor binding, including binding potential (the ratio of receptor density to affinity), and product of BP and the fraction of free nonprotein-bound parent compound (V(3)'). Use of the three compartment model improved the goodness of fit in comparison to the two compartment model. Values for kinetic rate constants and measures of benzodiazepine receptor binding, including BP and V(3)', were similar to results obtained with the SPECT radioligand [(123)I]iomazenil, and a prior report with low specific activity [(11)C]Iomazenil. Kinetic modeling using the three compartment model with PET and high specific activity [(11)C]Iomazenil provides a reliable measure of benzodiazepine receptor binding. Synapse 35:68-77, 2000. Published 2000 Wiley-Liss, Inc.

Adolescent↗

PubMed2000

Physical model-based non-rigid registration incorporating statistical shape information.

This paper describes two new atlas-based methods of 2D single modality non-rigid registration using the combined power of physical and statistical shape models. The transformations are constrained to be consistent with the physical properties of deformable elastic solids in the first method and those of viscous fluids in the second, to maintain smoothness and continuity. A Bayesian formulation, based on each physical model, an intensity similarity measure, and statistical shape information embedded in corresponding boundary points, is employed to derive more accurate and robust approaches to non-rigid registration. A dense set of forces arises from the intensity similarity measure to accommodate complex anatomical details. A sparse set of forces constrains consistency with statistical shape models derived from a training set. A number of experiments were performed on both synthetic and real medical images of the brain and heart to evaluate the approaches. It is shown that statistical boundary shape information significantly augments and improves physical model-based non-rigid registration and the two methods we present each have advantages under different conditions.

Brain↗

PubMed2000

Hippocampal volume reduction in major depression.

OBJECTIVE: Elevated levels of glucocorticoids in depression have been hypothesized to be associated with damage to the hippocampus, a brain area involved in learning and memory. The purpose of this study was to measure hippocampal volume in patients with depression. METHOD: Magnetic resonance imaging was used to measure the volume of the hippocampus in 16 patients with major depression in remission and 16 case-matched nondepressed comparison subjects. RESULTS: Patients with depression had a statistically significant 19% smaller left hippocampal volume than comparison subjects, without smaller volumes of comparison regions (amygdala, caudate, frontal lobe, and temporal lobe) or whole brain volume. The findings were significant after brain size, alcohol exposure, age, and education were controlled for. CONCLUSIONS: These findings are consistent with smaller left hippocampal volume in depression.

Adult↗

PubMed1999

Quantitation of benzodiazepine receptor binding with PET [11C]iomazenil and SPECT [123I]iomazenil: preliminary results of a direct comparison in healthy human subjects.

Although positron emission tomography (PET) and single photon emission computed tomography (SPECT) are increasingly used for quantitation of neuroreceptor binding, almost no studies to date have involved a direct comparison of the two. One study found a high level of agreement between the two techniques, although there was a systematic 30% increase in measures of benzodiazepine receptor binding in SPECT compared with PET. The purpose of the current study was to directly compare quantitation of benzodiazepine receptor binding in the same human subjects using PET and SPECT with high specific activity [11C]iomazenil and [123I]iomazenil, respectively. All subjects were administered a single bolus of high specific activity iomazenil labeled with 11C or 123I followed by dynamic PET or SPECT imaging of the brain. Arterial blood samples were obtained for measurement of metabolite-corrected radioligand in plasma. Compartmental modeling was used to fit values for kinetic rate constants of transfer of radioligand between plasma and brain compartments. These values were used for calculation of binding potential (BP = Bmax/Kd) and product of BP and the fraction of free non-protein-bound parent compound (V3'). Mean values for V3' in PET and SPECT were as follows: temporal cortex 23+/-5 and 22+/-3 ml/g, frontal cortex23+/-6 and 22+/-3 ml/g, occipital cortex 28+/-3 and 31+/-5 ml/g, and striatum 4+/-4 and 7+/-4 ml/g. These preliminary findings indicate that PET and SPECT provide comparable results in quantitation of neuroreceptor binding in the human brain.

Adult↗

PubMed1999

Neural correlates of exposure to traumatic pictures and sound in Vietnam combat veterans with and without posttraumatic stress disorder: a positron emission tomography study.

BACKGROUND: Patients with posttraumatic stress disorder (PTSD) show a reliable increase in PTSD symptoms and physiological reactivity following exposure to traumatic pictures and sounds. In this study neural correlates of exposure to traumatic pictures and sounds were measured in PTSD. METHODS: Positron emission tomography and H2[15O] were used to measure cerebral blood flow during exposure to combat-related and neutral pictures and sounds in Vietnam combat veterans with and without PTSD. RESULTS: Exposure to traumatic material in PTSD (but not non-PTSD) subjects resulted in a decrease in blood flow in medial prefrontal cortex (area 25), an area postulated to play a role in emotion through inhibition of amygdala responsiveness. Non-PTSD subjects activated anterior cingulate (area 24) to a greater degree than PTSD patients. There were also differences in cerebral blood flow response in areas involved in memory and visuospatial processing (and by extension response to threat), including posterior cingulate (area 23), precentral (motor) and inferior parietal cortex, and lingual gyrus. There was a pattern of increases in PTSD and decreases in non-PTSD subjects in these areas. CONCLUSIONS: The findings suggest that functional alternations in specific cortical and subcortical brain areas involved in memory, visuospatial processing, and emotion underlie the symptoms of patients with PTSD.

Analysis of Variance↗

PubMed1999

Segmentation and measurement of the cortex from 3-D MR images using coupled-surfaces propagation.

The cortex is the outermost thin layer of gray matter in the brain; geometric measurement of the cortex helps in understanding brain anatomy and function. In the quantitative analysis of the cortex from MR images, extracting the structure and obtaining a representation for various measurements are key steps. While manual segmentation is tedious and labor intensive, automatic reliable efficient segmentation and measurement of the cortex remain challenging problems, due to its convoluted nature. Here we present a new approach of coupled-surfaces propagation, using level set methods to address such problems. Our method is motivated by the nearly constant thickness of the cortical mantle and takes this tight coupling as an important constraint. By evolving two embedded surfaces simultaneously, each driven by its own image-derived information while maintaining the coupling, a final representation of the cortical bounding surfaces and an automatic segmentation of the cortex are achieved. Characteristics of the cortex, such as cortical surface area, surface curvature, and cortical thickness, are then evaluated. The level set implementation of surface propagation offers the advantage of easy initialization, computational efficiency, and the ability to capture deep sulcal folds. Results and validation from various experiments on both simulated and real three-dimensional (3-D) MR images are provided.

Algorithms↗

PubMed1999

Neural correlates of memories of childhood sexual abuse in women with and without posttraumatic stress disorder.

OBJECTIVE: Childhood sexual abuse is very common in our society, but little is known about the long-term effects of abuse on brain function. The purpose of this study was to measure neural correlates of memories of childhood abuse in sexually abused women with and without the diagnosis of posttraumatic stress disorder (PTSD). METHOD: Twenty-two women with a history of childhood sexual abuse underwent injection of [15O]H2O, followed by positron emission tomography imaging of the brain while they listened to neutral and traumatic (personalized childhood sexual abuse events) scripts. Brain blood flow during exposure to traumatic and neutral scripts was compared for sexually abused women with and without PTSD. RESULTS: Memories of childhood sexual abuse were associated with greater increases in blood flow in portions of anterior prefrontal cortex (superior and middle frontal gyri-areas 6 and 9), posterior cingulate (area 31), and motor cortex in sexually abused women with PTSD than in sexually abused women without PTSD. Abuse memories were associated with alterations in blood flow in medial prefrontal cortex, with decreased blood flow in subcallosal gyrus (area 25), and a failure of activation in anterior cingulate (area 32). There was also decreased blood flow in right hippocampus, fusiform/inferior temporal gyrus, supramarginal gyrus, and visual association cortex in women with PTSD relative to women without PTSD. CONCLUSIONS: These findings implicate dysfunction of medial prefrontal cortex (subcallosal gyrus and anterior cingulate), hippocampus, and visual association cortex in pathological memories of childhood abuse in women with PTSD. Increased activation in posterior cingulate and motor cortex was seen in women with PTSD. Dysfunction in these brain areas may underlie PTSD symptoms provoked by traumatic reminders in subjects with PTSD.

Adult↗

PubMed1997

Positron emission tomography measurement of cerebral metabolic correlates of yohimbine administration in combat-related posttraumatic stress disorder.

BACKGROUND: We have previously reported an increase in symptoms of anxiety in patients with posttraumatic stress disorder (PTSD) following administration of the beta 2-antagonist yohimbine, which stimulates brain norepinephrine release. Preclinical studies show decreased metabolism in the neocortex and the caudate nucleus with high-dose yohimbine-induced norepinephrine release, but low levels of norepinephrine release result in an increase in metabolism in these areas. METHODS: We used positron emission tomography and fludeoxyglucose F 18 to measure brain metabolism in Vietnam combat veterans with PTSD (n = 10) and healthy age-matched control subjects (n = 10), following administration of yohimbine (0.4 mg/kg) or placebo in a randomized, double-blind fashion. RESULTS: Yohimbine resulted in a significant increase in anxiety in the patients with PTSD, but not in healthy subjects. There was a significant difference in brain metabolic response to yohimbine in patients with PTSD compared with healthy subjects in prefrontal, temporal, parietal, and orbitofrontal cortexes. Metabolism tended to decrease in patients with PTSD and increase in healthy subjects following administration of yohimbine. CONCLUSION: These findings are consistent with our previous hypothesis of enhanced norepinephrine release in the brain with yohimbine in patients with PTSD.

Anxiety Disorders↗

PubMed1997

Positron emission tomography measurement of cerebral metabolic correlates of tryptophan depletion-induced depressive relapse.

BACKGROUND: Short-term depletion of plasma tryptophan has been shown to result in depressive relapse in patients with remission of major depression. Positron emission tomography and single photon emission computed tomography studies implicated the dorsolateral prefrontal cortex, orbitofrontal cortex, thalamus, and caudate nucleus in the pathogenesis of depression. The purpose of this study was to measure cerebral metabolic correlates of tryptophan depletion-induced depressive relapse. METHODS: Patients diagnosed as having major depression (N = 21) who clinically improved with serotonin reuptake inhibitors underwent 2 test days involving tryptophan depletion or placebo, followed 6 hours later by positron emission tomography scanning with fludeoxy-glucose F18. Brain metabolism was compared in patients with (n = 7) and without (n = 14) a tryptophan depletion-induced depressive relapse. RESULTS: Tryptophan depletion resulted in a decrease in brain metabolism in the middle frontal gyrus (dorsolateral prefrontal cortex), thalamus, and orbitofrontal cortex in patients with a depletion-induced depressive relapse (but not in patients without depletion-induced relapse). Decreased brain metabolism in these regions correlated with increased depressive symptoms. Baseline metabolism was increased in prefrontal and limbic regions in relapse-prone patients. CONCLUSION: Specific brain regions, including the middle frontal gyrus, thalamus, and orbitofrontal cortex, may mediate the symptoms of patients with major depression.

Antidepressive Agents↗

PubMed1994

Brain morphology in normal and dyslexic children: the influence of sex and age.

Morphometric magnetic resonance imaging techniques were used to compare the convolutional surface area of the planum temporale, temporal lobe volume and superior surface area, and an estimate of overall brain volume in a homogeneous sample of 17 dyslexic children (7 girls) and 14 nonimpaired children (7 girls). Substantial sex differences were apparent for all measured regions, with all the measurements in boys being significantly larger. Age, even within the narrow range employed here (7.5-9.7 years), was positively correlated with the size of each brain region. While initial analyses suggested smaller left hemisphere structures in dyslexics compared to control subjects, subsequent analyses controlling for age and overall brain size revealed no significant differences between dyslexics and nonimpaired children on a variety of measures, in particular surface area and symmetry of the planum temporale. We suggest that differences in subject characteristics (i.e., sex, age, handedness, and definition of dyslexia) as well as procedural variations in the methods used to acquire images and to define and measure anatomical regions of interest such as the planum temporale all may play an important role in explaining apparent discrepant results in the neuroimaging literature on dyslexia.

Age Factors↗

PubMed1991

Measurement of left ventricular wall motion from contour shape deformation.

This paper has presented the formulation and initial results for a new algorithm aimed at estimating and quantifying the trajectories of points on the left ventricular wall of the heart based on two- dimensional image-derived shape information. The algorithm is based on first automatically estimating the LV contour for two frames and then sampling the contours and tracking the motion of each sample point. Work is currently in progress to evaluate and compare each of three shape-based matching criteria, and to extend the algorithm to multiple frames. Future work will extend the approach to three spatial dimensions, capitalizing on the idea that all of the basic concepts, including curvature measurement, can be readily adapted for the higher dimensional problem.

Algorithms↗