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Biomedical subjects

G Schlaug

Publications and source records attributed to G Schlaug.

68 records · Page 4Linked to original sources
PubMed1994

Cerebral network underlying unilateral motor neglect: evidence from positron emission tomography.

In 4 male patients (age range 50-73 years) with unilateral motor hemineglect as a sequelae of circumscribed cerebral infarction, depressions of the regional cerebral glucose metabolism (rCMRGlu) were mapped to identify the metabolically affected cerebral structures. Motor neglect was defined according to Castaigne by lack of spontaneous and pain-induced motor activity on one side of the body in the absence of paresis, pyramidal signs, and sensory loss. The depressions of the rCMRGlu as determined by positron emission tomography (PET) were found to exceed the areas of structural damage but to be restricted to the affected cerebral hemisphere. Significant mean rCMRGlu depressions followed a focal pattern involving the premotor, prefrontal, parietal and cingulate cortex, as well as the thalamus. In correspondence to the lack of significant mean rCMRGlu depressions in primary sensorimotor cortex, basal ganglia, and cerebellum the cortico-spinal pathway was spared as indicated by preserved magnetic evoked motor potentials. Our data provide evidence suggesting that motor hemineglect is a disturbance in a cerebral network of higher order cortical areas subserving motor activity in the presence of an intact motor cortical output system.

Aged↗
PubMed1994

Dynamic changes of focal hypometabolism in relation to epileptic activity.

The interictal hypometabolism in patients with focal epilepsy is usually regarded as stationary. In this study we investigated to which extent the hypometabolism may depend on the activity of the epileptic focus. In focal penicillin-induced epilepsy in rats the epileptic focus is hypermetabolic. This focus is accompanied by hypometabolism in widespread areas of adjacent cerebral cortex. The experiments revealed that these metabolic alterations are transient. Data from a patient experiencing a focal seizure during PET scanning gave similar results. They showed that the transition from interictal to ictal activity was accompanied by the development of hypermetabolic epileptic focus and the dynamic enlargement of the surrounding hypometabolism. Both, the experimental and clinical data provide evidence that the cerebral hypometabolism may vary in size depending on the activity of the epileptic focus. It is hypothesized that in human PET studies the large interictal hypometabolism may prevent the identification of hyperactive interictal epileptic foci due to the partial volume effects resulting from the limited spatial resolution of PET cameras.

Animals↗
PubMed1993

Layer V pyramidal cells in the adult human cingulate cortex. A quantitative Golgi-study.

The anterior and posterior parts of the human cingulate cortex differ in their absolute number of neurons per unit volume, with fewer neurons in the anterior part. To test the hypothesis that lower absolute number and packing density of neurons in the anterior cingulate cortex are associated with an increased complexity in the neuropil compartment, dendritic arborizations of layer V neurons in both cingulate parts were analyzed in a Golgi study. Results show that these neurons in the anterior cingulate cortex have more primary and secondary basal dendrites than those in the posterior cingulate cortex. This establishes an association of a higher complexity of the dendritic arborization in the anterior cingulate cortex with a lower cell number per unit volume and larger neuropil compartment. The significant lower degree of dendritic arborization in the posterior cingulate cortex is accompanied by a higher cell packing density. These structural differences are associated with functional differences between the two parts of the human cingulate cortex.

Adult↗
PubMed1992

Individual somatotopy of primary sensorimotor cortex revealed by intermodal matching of MEG, PET, and MRI.

A method for comparing estimated magnetoencephalographic (MEG) dipole localizations with regional cerebral blood flow (rCBF) activation areas is presented. This approach utilizes individual intermodal matching of MEG data, of rCBF measurements with [15O]-butanol and positron emission tomography (PET), and of anatomical information obtained from magnetic resonance (MR) images. The MEG data and the rCBF measurements were recorded in a healthy subject during right-sided simple voluntary movements of the foot, thumb, index finger, and mouth. High resolution 3D-FLASH MR images of the brain consisting of 128 contiguous sagittal slices of 1.17-mm thickness were used. MEG/MR integration was performed by superimposing the 3D head coordinate system constructed during the MEG measurement onto the MR image data using identical anatomical landmarks as references. PET/MR integration was achieved by a phantom-validated iterative front-to-back-projection algorithm resulting in one integrated MEG/PET/MR image. The estimated dipole locations followed the somatotopic organisation of the task-specific rCBF increases as evident from PET, although they did not match point-to-point. Our results demonstrate that intermodal matching of MEG, PET and MR data provides a tool for relating estimated neuromagnetic field locations to task-specific rCBF changes in individual subjects. Our method offers the perspective of refined dipole modelling.

Adult↗
PubMed1992

Individual integration of positron emission tomography and high-resolution magnetic resonance imaging.

We have developed, validated, and employed a technique of retrospective spatial alignment and integrated display of positron emission tomographic (PET) and high-resolution magnetic resonance (MR) brain images. The method was designed to improve the anatomical evaluation of functional images obtained from single subjects. In the first computational step, alignment of PET and MR data sets is achieved by iteratively matching in three orthogonal views the outermost scalp contours derived from front-to-back projections of each data set. This procedure avoids true three-dimensional modeling, runs without user interaction, and tolerates missing parts of the head circumference in the image volume, as usually the case with PET. Thereafter, high-resolution MR sections corresponding to the PET slices are reconstructed from the spatially transformed MR data. In a phantom study of this method, PET/MR alignment of the phantom's surface was accurate with average residual misfits of 2.17 to 2.32 mm as determined in three orthogonal planes. In-plane alignment of the phantom's insertion holes was accurate with an average residual misfit of 2.30 mm. In vivo application in six subjects allowed the individual anatomical localization of regional CBF (rCBF) responses obtained during unilateral manual exploration. In each subject, the maxima of the rCBF activations in the hand area were precisely allocated to gray matter in the anterior or posterior wall of the central sulcus. The configuration of the rCBF responses closely followed the gyral structures. The technique provided a better topographical understanding of rCBF changes in subtraction images of PET activation studies. It opens the perspective for studies of structural-functional relationships in individual subjects.

Brain↗
PubMed1992

Sex but no hand difference in the isthmus of the corpus callosum.

We performed high-resolution magnetic resonance morphometry of the total midsagittal area and seven midsagittal subareas of the corpus callosum in healthy young adult dextrals and sinistrals (N = 52). There was no influence of handedness on these anatomic measurements. However, an effect of sex emerged, with women (N = 26) having a larger proportional isthmus segment of the callosum. This may reflect a sex-specific difference in the interhemispheric connectivity and functional organization of the temporoparietal association cortex.

Adult↗
PubMed1986

Quantitative cytoarchitectonics of the posterior cingulate cortex in primates.

The cytoarchitecture of four cortical areas within the posterior cingulate region and the differences among them are quantitatively analyzed in 17 primate species. The transition from allocortex (area 29) to isocortex (areas 30, 23, and 31) is characterized by shifts in laminar proportions and cellular densities. The molecular layer and inner main lamina (layers V and VI) occupy a smaller proportion of the cortex in iso- than in allocortex, while conversely, the outer main lamina (layers II and III) makes up a larger proportion of the cortex in iso- than in allocortex. Layer IV is relatively larger in area 31 than in area 23. The packing densities of cell bodies were determined by gray-level index values. These values show that the isocortex has lower cell densities in the outer main lamina, but higher cell densities in the inner main layers. Furthermore, the granular layer of area 31 is more densely packed than it is in area 23. These results are discussed as structural correlates of a relative increase in the receptive and processing capacities of the isocortex over the adjacent allocortex.

Animals↗
PubMed1986

Comparative aspects of the primate posterior cingulate cortex.

Cytoarchitecturally defined cortical areas of the posterior cingulate gyrus differ morphometrically among the major taxonomic divisions of primates. Prosimians and anthropoids have different laminar proportions in the isocortical regions (areas 30, 23, and 31); anthropoids have relatively larger outer main laminae and granular layers than prosimians. In the granular retrosplenial cortex (area 29), however, prosimians and anthropoids differ only in the proportion of the molecular layer to the rest of the cortex. On the other hand, the proportions of the inner and outer main laminae of area 29 differ between the infraorder divisions of Anthropoidea, the catarrhines, and the platyrrhines. The platyrrhines (New World monkeys) have apparently specialized by increasing the outer main lamina of area 29, which contains afferent and intracortical connections. Among all primates, the amount of neuropil in each cortical region changes as a function of brain weight, but within each area, the neuropil maintains a constant ratio between the outer and inner laminae. These observations suggest that neuropil ratios are conservative features in primates and that evolutionary changes more frequently involve shifts in volumetric proportions. Furthermore, the platyrrhine-catarrhine differences in area 29 likely evolved after the prosimian-anthropoid differences were established in the isocortical cingulate regions.

Animals↗
PubMedDate not supplied

Brain (A) symmetry in monozygotic twins.

Origin and ontogenesis of human brain laterality are unknown. Using in vivo magnetic resonance morphometry we measured cerebral hemispheric asymmetry of the planum temporale, a structural substrate of functional laterality, in pairs of monozygotic twins concordant or discordant for handedness. In both groups, intraclass (i.e., within twin pair) correlations were low. The right-handers showed leftward asymmetry whereas the left-handers lacked asymmetry. The discordance for lateralized brain anatomy can be accounted for by ontogenetic models assuming twinning of an asymmetrical germ or differential action of nongenetic factors within twin pairs in utero. The findings confirm a coupling of lateralized structure and function of the human brain. At least in monozygotic twins, early epigenetic factors must play a role in anatomofunctional laterality development.

Adolescent↗
PubMedDate not supplied

The relationship between corpus callosum size and forebrain volume.

Using high-resolution in vivo magnetic resonance morphometry we measured forebrain volume (FBV), midsagittal size of the corpus callosum (CC) and four CC subareas in 120 young and healthy adults (49 women, 71 men). We found moderate linear and quadratic correlations, indicating that the CC and all CC subareas increase with FBV both in men and women (multiple r2 ranging from 0.10 to 0.28). Allometric equations revealed that these increases were less than proportional to FBV (r2 ranging from 0.02 to 0.30). Absolute CC measurements, as well as CC subareas relative to total CC or FBV (the latter measures termed the CC ratios), were further analyzed with regard to possible effects of handedness, gender, or handedness by gender interaction. Contrary to previous reports, left-handers did not show larger CC measurements compared to right-handers. The only apparent influence of gender was on the CC ratios, which were larger in women. However, smaller brains had larger CC ratios which were mainly independent of gender, a result of the less than proportional increase of callosal size with FBV. We suggest that the previously described gender differences in CC anatomy may be better explained by an underlying effect of brain size, with larger brains having relatively smaller callosa. This lends empirical support to the hypothesis that brain size may be an important factor influencing interhemispheric connectivity and lateralization.

Adult↗
PubMedDate not supplied

MRI of the brain in Wilson disease: T2 signal loss under therapy.

Repeat examinations in a de novo patient with Wilson disease revealed an expansion of decreased signal intensities in the basal ganglia on T2-weighted imaging after initiation of copper trapping therapy. Since marked clinical improvement was associated with continued urinary copper excretion, iron depositioning in exchange for copper might explain these findings.

Adult↗
PubMedDate not supplied

Clinical correlations of diffusion and perfusion lesion volumes in acute ischemic stroke.

The aim of this study was to describe the clinico-radiological correlations of magnetic resonance (MR) perfusion and diffusion-weighted imaging (DWI) abnormalities in ischemic stroke. Eighteen patients had undergone MR imaging and clinical evaluation within 24 h of symptom onset and at or after 7 days. During the first 24 h the volume of perfusion abnormality (measured on the relative mean transit time map) was larger than the DWI lesion in 12/18 patients. In 6/18 patients the DWI lesion volume was larger. Acutely (<24 h) all lesion volumes showed a significant correlation with acute clinical severity measured by the National Institutes of Health Stroke Scale score. The correlations of the hypoperfusion volume (rho = 0.86, p = 0.0001) and the volume 'tissue at risk' (larger than the DWI and perfusion lesion volumes, rho = 0.86, p = 0. 0001) with acute clinical severity were slightly higher than for the DWI lesion volume (rho = 0.76, p = 0.0001). The difference between the volume of tissue at risk (acutely) and the infarct on follow-up T(2)-weighted imaging correlated significantly with change in clinical severity from acute to chronic time points (rho = 0.72, p = 0.001). Such clinico-radiological relationships may support the use of DWI and perfusion MR in decisions concerning the administration and evaluation of stroke therapies.

Acute Disease↗
PubMedDate not supplied

Clinical experience with diffusion-weighted MR in patients with acute stroke.

PURPOSE: Our purpose was to evaluate the clinical efficacy, sensitivity, and specificity of echo-planar diffusion-weighted MR imaging in patients with acute infarction. METHODS: We retrospectively analyzed 194 cases of acute ischemic stroke diagnosed clinically within 24 hours of onset and studied with echo-planar diffusion-weighted MR imaging. Examinations were considered to be positive for infarction when an increase in signal was noted on images acquired at a high b value but absent on images with a low b value. A final clinical diagnosis of acute stroke was used as the standard of reference. A subset of 48 patients scanned within 6 hours was also analyzed. RESULTS: Diffusion-weighted MR imaging studies were positive in 133 of 151 cases of infarction (88% sensitivity) and negative in 41 of 43 cases with no infarction (95% specificity). Two cases identified as positive on diffusion-weighted images had nonischemic diagnoses (1.5% false-positive rate). Diffusion-weighted imaging had a positive predictive value of 98.5% and a negative predictive value of 69.5%. Use of T2-weighted sequences as well as diffusion-weighted imaging produced no false-positive findings. Of the negative scans, 69.5% corresponded to transient ischemic attacks or infarcts (mostly small brain stem infarcts). When only cases scanned within 6 hours of onset were considered, the sensitivity rose to 94% and the specificity to 100%. CONCLUSION: Despite bias due to dependence between diffusion-weighted imaging and the final diagnosis, this analysis suggests high sensitivity and specificity for echo-planar diffusion-weighted imaging in the diagnosis of acute cerebral infarction, although negative scans did not rule out an ischemic pathogenesis.

Acute Disease↗