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D N Kennedy

Publications and source records attributed to D N Kennedy.

53 records · Page 3Linked to original sources
PubMed1996

Functional magnetic resonance imaging of symptom provocation in obsessive-compulsive disorder.

BACKGROUND: The new technique of functional magnetic resonance imaging was used to investigate the mediating neuroanatomy of obsessive-compulsive disorder symptoms. METHODS: Ten patients with obsessive-compulsive disorder and 5 normal subjects were studied via functional magnetic resonance imaging during control and provoked conditions. Data analysis entailed parametric and nonparametric statistical mapping. RESULTS: Statistical maps (nonparametric; P < 10(-3)) showed activation for 70% or more of patients with obsessive-compulsive disorder in medial orbitofrontal, lateral frontal, anterior temporal, anterior cingulate, and insular cortex, as well as caudate, lenticulate, and amygdala. No normal subjects exhibited activation in any brain region. CONCLUSIONS: Results of functional magnetic resonance imaging were consistent with past studies of obsessive-compulsive disorder that used other functional neuroimaging modalities. However, paralimbic and limbic activations were more prominent in the present study.

Adult↗
PubMed1996

Cerebral structural abnormalities in obsessive-compulsive disorder. A quantitative morphometric magnetic resonance imaging study.

BACKGROUND: A previous pilot study of only posterior brain regions found lower white-matter volume in patients with obsessive-compulsive disorder than in normal control subjects. We used new cohorts of patients and matched normal control subjects to study whole-brain volume differences between these groups with magnetic resonance imaging-based morphometry. METHODS: Ten female patients with obsessive-compulsive disorder and 10 female control subjects, matched for handedness, age, weight, education, and verbal IQ, underwent magnetic resonance imaging with a 3-dimensional volumetric protocol. Scans were blindly normalized and segmented by means of well-characterized semiautomated intensity contour mapping and differential intensity contour algorithms. Brain structures investigated included the cerebral hemispheres, cerebral cortex, diencephalon, caudate, putamen, globus pallidus, hippocampus amygdala, third and fourth ventricles, corpus callosum, operculum, cerebellum, and brain stem. Anterior to posterior neocortical regions, including precallosum, anterior pericallosum, posterior pericallosum, and retrocallosum, with adjacent white matter were also measured. Volumes found different between groups were correlated with Yale-Brown Obsessive Compulsive Scale score and Rey-Osterieth Complex Figure Test measures. RESULTS: Confirming results of our earlier pilot study and expanding the findings to the whole brain, patients with obsessive-compulsive disorder had significantly less total white matter but, in addition, significantly greater total cortex and opercular volumes. Severity of obsessive-compulsive disorder and nonverbal immediate memory correlated with opercular volume. CONCLUSIONS: Replication of volumetric white-matter differences suggests a widely distributed structural brain abnormality in obsessive-compulsive disorder. Whereas determining the etiogenesis may require research at a microscopic level, understanding its functional significance can be further explored via functional neuroimaging and neuropsychological studies.

Adult↗
PubMed1992

Dynamic magnetic resonance imaging of human brain activity during primary sensory stimulation.

Neuronal activity causes local changes in cerebral blood flow, blood volume, and blood oxygenation. Magnetic resonance imaging (MRI) techniques sensitive to changes in cerebral blood flow and blood oxygenation were developed by high-speed echo planar imaging. These techniques were used to obtain completely noninvasive tomographic maps of human brain activity, by using visual and motor stimulus paradigms. Changes in blood oxygenation were detected by using a gradient echo (GE) imaging sequence sensitive to the paramagnetic state of deoxygenated hemoglobin. Blood flow changes were evaluated by a spin-echo inversion recovery (IR), tissue relaxation parameter T1-sensitive pulse sequence. A series of images were acquired continuously with the same imaging pulse sequence (either GE or IR) during task activation. Cine display of subtraction images (activated minus baseline) directly demonstrates activity-induced changes in brain MR signal observed at a temporal resolution of seconds. During 8-Hz patterned-flash photic stimulation, a significant increase in signal intensity (paired t test; P less than 0.001) of 1.8% +/- 0.8% (GE) and 1.8% +/- 0.9% (IR) was observed in the primary visual cortex (V1) of seven normal volunteers. The mean rise-time constant of the signal change was 4.4 +/- 2.2 s for the GE images and 8.9 +/- 2.8 s for the IR images. The stimulation frequency dependence of visual activation agrees with previous positron emission tomography observations, with the largest MR signal response occurring at 8 Hz. Similar signal changes were observed within the human primary motor cortex (M1) during a hand squeezing task and in animal models of increased blood flow by hypercapnia. By using intrinsic blood-tissue contrast, functional MRI opens a spatial-temporal window onto individual brain physiology.

Animals↗
PubMed1992

Magnetic resonance imaging mapping of brain function. Human visual cortex.

Magnetic resonance imaging (MRI) studies of human brain activity are described. Task-induced changes in brain cognitive state were measured using high-speed MRI techniques sensitive to changes in cerebral blood volume (CBV), blood flow (CBF), and blood oxygenation. These techniques were used to generate the first functional MRI maps of human task activation, by using a visual stimulus paradigm. The methodology of MRI brain mapping and results from the investigation of the functional organization and frequency response of human primary visual cortex (V1) are presented.

Brain Mapping↗
PubMed1992

Quantitative magnetic resonance imaging and studies of degenerative diseases of the developing human brain.

The Rett syndrome is a progressive disorder which is associated with regression of psychomotor development and precipitous deceleration of brain growth during the first year of life. General histopathological surveys in postmortem specimens have identified degeneration of subpopulations of neurons of the nigrostriatal system but no other evidence of degenerative process. Magnetic resonance imaging-based morphometry may usefully guide application of rigorous but demanding quantitative histologic search for evidence of neuronal degeneration. The volumes of the principal set of cortical and nuclear structures of principal interest in the disorder may be measured by currently available MRI-based methods. Optimized levels of precision now allow detection of volumetric changes over time in the same brain of approximately 10% at the 95% confidence level.

Brain↗
PubMed1991

Functional mapping of the human visual cortex by magnetic resonance imaging.

Knowledge of regional cerebral hemodynamics has widespread application for both physiological research and clinical assessment because of the well-established interrelation between physiological function, energy metabolism, and localized blood supply. A magnetic resonance technique was developed for quantitative imaging of cerebral hemodynamics, allowing for measurement of regional cerebral blood volume during resting and activated cognitive states. This technique was used to generate the first functional magnetic resonance maps of human task activation, by using a visual stimulus paradigm. During photic stimulation, localized increases in blood volume (32 +/- 10 percent, n = 7 subjects) were detected in the primary visual cortex. Center-of-mass coordinates and linear extents of brain activation within the plane of the calcarine fissure are reported.

Blood Volume↗
PubMed1991

Contrast agents and cerebral hemodynamics.

Contrast-enhanced magnetic resonance imaging of regional cerebral hemodynamics is discussed. Techniques for measuring cerebral blood volume (CBV) have been validated in animal models and have recently been applied to human studies. Factors affecting CBV measurement in pathologic tissue are addressed. Extension of these techniques to the measurement of cerebral blood flow is presented.

Blood Volume↗
PubMed1991

Overall body fat and regional fat distribution in young women: quantification with MR imaging.

Overall body fat and its distribution in different regions are important predispositions to known aberrations in lipid and glucose metabolism. The accuracy of MR imaging in estimating overall body fatness and regional fat distribution at individual landmarks was determined by comparing it with well-accepted measures by deuterium-oxide (D2O) dilution and bioimpedance analysis. Fourteen normal young women (athletes and control subjects) were studied. A total of 308 axial, T1-weighted, spin-echo MR images over a specific region in the trunk (21-24 scans per subject) were obtained. Morphometric computer image analysis was performed to determine the subcutaneous, internal, and total fat volumes in each image. The data were analyzed in two ways: data from all slices were summed to assess overall body fatness, and six anatomic landmarks were chosen for regional comparisons. MR-determined estimates of overall body fatness strongly correlated with total body fat measures by D2O dilution in both total fat (r = .91) and subcutaneous fat (r = .92) determinations. Athletes in both the low- and high-intensity training phases had significantly lower values of MR-determined total body fatness than did control subjects. Parallel to total body fatness, athletes had significantly lower MR-determined ratios of total fat/total volume in four of six individual landmarks compared with control subjects. Our experience suggests that MR is an accurate method to quantify overall body fatness, when compared with D2O dilution and bioimpedance analysis. MR could also discriminate regional components of subcutaneous and internal body fat at individual landmarks.

Adipose Tissue↗
PubMed1990

Functional cerebral imaging by susceptibility-contrast NMR.

In vivo measurement of cerebral physiology by dynamic contrast-enhanced NMR is demonstrated. Time-resolved images of the cerebral transit of paramagnetic contrast agent were acquired using a new ultrafast NMR imaging technique and a novel mechanism of image contrast based on microscopic changes in tissue magnetic susceptibility. Global hypercapnia in dogs was used to establish the relationship between susceptibility-induced signal change and brain blood volume, and the response of gray and white matter to this microvascular stimulus was measured.

Animals↗
PubMed1989

Magnetic resonance imaging-based brain morphometry: development and application to normal subjects.

A semiautomated computerized method of in vivo morphometric analysis that is based upon high-resolution three-dimensional magnetic resonance imaging has been developed. This morphometric method is efficient and is of greater analytical precision than any other morphometric method currently applied to living human tissue. Including error inherent in image data acquisition, the aggregate error of the methodology, as estimated by the phantom studies, ranges from 4.5 to 9.6%, with incremental error above 4.5% a function of magnetic resonance slice thickness. This method was applied to magnetic resonance scans of 7 normal volunteers. The derived volumes of whole brain and of individual substructures were closely concordant with previously published volumes of normal fresh (unfixed) brains obtained post mortem. This morphometric methodology is potentially applicable to any structure or lesion that can be visualized by magnetic resonance imaging.

Adolescent↗
PubMed1989

Magnetic resonance technology in human brain science: blueprint for a program based upon morphometry.

Magnetic resonance images provide a comprehensiveness of analysis of the human brain and levels of resolution never achieved by other modes of pathoanatomic analysis. We review a strategy and technology of MRI-based image analysis which extracts independent measures of brain volumes, shape and position. These parameters are readily correlated with behavioral as well as physiological measures derived from PET and the emerging technology of MRI-based in vivo spectroscopy. A coordinate program which draws upon these methods will have wide applications in human brain science and the study of dynamic properties of human brain disease.

Brain↗
PubMedDate not supplied

Advanced application of magnetic resonance imaging in human brain science.

Magnetic resonance imaging (MRI) has revolutionized the practical demands of clinical neurology. This technology promises now to advance neurology in theoretical and applied realms of fundamental human brain science. We emphasize here two domains in which these advances will occur. The first is volumetric morphometry of the human brain. With MRI the multiple levels of processing of the brain may be characterized in terms of their absolute volumes and their relative sizes, perspectives indispensable for our understanding of the development and operation of neural systems. Volumetric morphometry also promises substantial increases in the specificity and sensitivity of neurological diagnosis, particularly where applied to disorders where structural abnormalities will be reflected only in volumetric abnormalities. The second direction of advance considered here is application of MRI in cortical mapping in support of cognitive neuroscience. In this application MRI provides means to map at high resolution the distribution of subcomponents of neural systems activated by behavioral paradigms. This line of investigation will carry forward rapidly our understanding of how the information processing algorithms of the brain are mapped upon the coordinates of the various gray matter structures of the brain. Among the practical consequences of this application will be a reasoned design of surgical field in tumor and epilepsy surgery.

Adult↗
PubMedDate not supplied

Volumetric analyses of central nervous system neoplasm based on MRI.

Morphometric analyses were performed using an objective semiautomated algorithm on 5 sequential three-dimensional T1-weighted magnetic resonance imaging scans of a metastatic choroid plexus carcinoma, concurrent with a course of chemotherapy. The 5 scans were positionally normalized in a three-dimensional coordinate system for uniform definition of the borders of the mass. Volumes were calculated for the gadolinium-DTPA enhancing and nonenhancing cystic-appearing regions. Volumetric changes of up to 145% were measured using this method which were associated with changes in the calculated (spherical) radii of only up to 2.7 mm. Volumetric changes of up to 59% were not appreciated by visual inspection, most probably due to irregular borders and positional variability across the scans. Volumetric analyses were also performed on the right cerebellar hemisphere, producing a 1.83% coefficient of variability across the 5 scans. The growth rates of this mass were estimated from the sequential computations, permitting in vivo observations on tumor behavior otherwise not obtainable. These analyses demonstrate the potential of this morphometric method to detect significant volumetric changes, and illustrate its use to define in vivo the growth properties of central nervous system tumors in response to therapeutic interventions.

Antineoplastic Combined Chemotherapy Protocols↗
PubMedDate not supplied

Using locations to store shape: an indirect effect of a lesion.

This study had three general points. First, it examined possible visual consequences of frontal lesions. A patient with focal damage to the subcortical regions of the left frontal lobe, and a small amount of damage near Broca's area, was predicted to have impaired brain function in posterior regions that are anatomically connected to the damaged site. Second, it showed the utility of using positron emission tomography (PET) in conjunction with magnetic resonance imaging to characterize "functional lesions." PET revealed reduced metabolism in posterior cortical loci that are innervated by fibers from the damaged regions. Some of the affected areas are hypothesized to be involved in visual functions, specifically the encoding of lines and edges. Third, a series of tests was designed to document that the patient had difficulty encoding visual stimuli, and then to distinguish among alternative possible causes of this deficit. The results suggested that the patient encoded shapes as sets of filled locations if possible, which allowed him to use intact processes subserved by brain areas that were not affected by the damage. The data were best explained if the lesion slowed processing in the ventral system (which encodes object properties), allowing the dorsal system (which encodes spatial properties) to produce a response more quickly than the ventral system.

Adult↗
PubMedDate not supplied

The young adult human brain: an MRI-based morphometric analysis.

Morphometric analysis was performed on three-dimensional MRI scans of 10 male and 10 female young adults with four principal objectives: (1) to characterize in vivo volumes of whole brain and substructures, (2) to explore volumetric symmetry in bilateral structures, (3) to consider the extent to which volumetric measures are dimorphic in the male and female brain, and (4) to provide a normal volumetric database for the young adult brain. Total brain volumes ranged between 1173 and 1626 cm3. All bilateral structures were symmetric or nearly symmetric in volume, with the exception of a slightly larger right neocortex and amygdala, and larger left lateral ventricle. Male brains were larger in volume than female brains, a difference that reached significance for cerebellar but not for cerebral hemisphere volume. In females, there was less cerebral white matter while caudate volume was larger than in the male brains. The proportions of caudate and hippocampus relative to total cerebral volumes were larger in females than in males. These four measures accurately predicted gender in 85% of the subjects by discriminant analysis. No gender differences were noted in the structural symmetry analysis. These results represent the first step in establishing a comprehensive database of morphometric parameters, with unexpected findings relative to brain symmetry and sexual dimorphism.

Adolescent↗
PubMedDate not supplied

The human brain age 7-11 years: a volumetric analysis based on magnetic resonance images.

Volumetric magnetic resonance image (MRI)-based morphometry was performed on the brains of 30 normal children (15 males and 15 males) with a mean age of 9 years (range 7-11 years). This age range lies in a late but critical phase of brain growth where not volumetric increment will be small but when the details of brain circuity are being fine-tuned to support the operations of the adult brain. The brain at this age is 95% the volume of the adult brain. The brain of the female child is 93% the volume of the male child. For more than 95% of brain structures, the volumetric differences in male and female child brain are uniformly scaled to the volume difference of the total brain in the two sexes. Exceptions to this pattern of uniform scaling are the caudate, hippocampus and pallidum, which are disproportionately larger in female than male child brain, and the amygdala, which is disproportionately smaller in the female child brain. The patterns of uniform scaling are generally sustained during the final volumetric increment in overall brain size between age 7-11 and adulthood. There are exceptions to this uniform scaling of child to adult brain, and certain of these exceptions are sexually dimorphic. Thus, with respect to major brain regions, the cerebellum in the female but not the male child is already at adult volume while the brainstem in both sexes must enlarge more than the brain as a whole. The collective subcortical gray matter structures of the forebrain of the female child are already at their adult volumes. The volumes of these same structures in the male child, by contrast, are greater than their adult volumes and, by implication, must regress in volume before adulthood. The volume of the central white matter, on the other hand, is disproportionately smaller in female than male child brain with respect to the adult volumes of cerebral central white matter. By implication, relative volumetric increase of cerebral central white matter by adulthood must be greater in the female than male brain. The juxtaposed progressive and regressive patterns of growth of brain structures implied by these observations in the human brain have a soundly established precedent in the developing rhesus brain. There is emerging evidence that sexually dimorphic abnormal regulation of these terminal patterns of brain development are associated with gravely disabling human disorders of obscure etiology.

Adolescent↗