Language lateralisation in schizophrenia.
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Diseases in Twins↗
Biomedical subjects
J Tintera
Publications and source records attributed to J Tintera.
The effect of tryptophan depletion on brain activation measured by functional magnetic resonance imaging during the Stroop test in healthy subjects.
We investigated the role of serotonin in cognitive activation of the frontal cortex. The serotonergic system was affected by the administration of an amino acids mixture without tryptophan (tryptophan depletion). In a placebo-controlled double-blind cross-over study with 20 healthy volunteers, we tested the hypothesis that a tryptophan (serotonin) decrease affects the activation of prefrontal cortex by the Stroop test. Cognitive brain activation was evaluated by functional magnetic resonance imaging (fMRI). Tryptophan depletion decreased the plasma tryptophan level up to 90 % for five hours after the tryptophan-free drink had been consumed when compared with the same mixture with tryptophan (p?0.0001). Tryptophan depletion did not affect the Stroop test performance. We compared fMRI activation in both conditions (tryptophan depletion and placebo) with plasma tryptophan levels as the covariates. The tryptophan depletion increased the activation (fMRI signal) in the bilateral mediofrontal cortex, anterior cingulate and left dorsolateral prefrontal cortex. The present findings allow the postulate that serotonergic medial forebrain and cingulum bundle pathways play a role in the activity of cortical structures involved in Stroop test processing.
Adult↗
Quantification of intra-abdominal fat during controlled weight reduction: assessment using the water-suppressed breath-hold MRI technique.
A group of 14 healthy female subjects was studied using MRI during 2 months of life-style intervention. A series of 21 water-suppressed images was used to determine the intra-abdominal fat volume before and after the controlled loss of weight. The average weight decrease was 8.2 %, but the average relative loss of visceral fat was 20.3 %, whereas subcutaneous fat decreased by 13.4 %. A small but significant increase of insulin sensitivity (decrease in fasting insulin and blood glucose) was observed, but no changes in lipoprotein parameters were demonstrated. There was a significant negative correlation (r=-0.633, p=0.028) between the relative abdominal fat decrease and the initial amount of subcutaneous fat.
Abdomen↗
Differences in fMRI and MRS in a monozygotic twin pair discordant for schizophrenia (case report).
OBJECTIVE: This paper presents functional magnetic resonance imaging (fMRI) and magnetic resonance spectroscopy (MRS) findings in a monozygotic twin pair discordant for schizophrenia. METHOD: Functional magnetic resonance imaging was used to determine hemispheric lateralization for speech and proton MRS (1H-MRS) was employed to assess the extent of putative insult to anterior hippocampus. RESULTS: Despite concordant right handedness, subject with schizophrenia displayed bilateral activation in areas subserving speech with greater extent of the total activated area compared with the healthy twin. The affected twin displayed relative bilateral decrease in N-acetylaspartate/creatin concentration in the anterior hippocampus compared with the healthy one. CONCLUSION: This is an evidence for non-genetic impairment of cerebral lateralization in monozygotic twin with schizophrenia.
Adult↗
Olfactory activity in the human brain identified by fMRI.
BACKGROUND: Modern imaging methods such as functional magnetic resonance imaging (fMRI) or positron emission tomography (PET) enable us to map brain activities associated with stimulation of various functional systems in the human brain. Data concerning the localization and lateralization of secondary olfactory areas are not in agreement. SUBJECTIVE THE AIM OF THE STUDY: localization of secondary olfactory brain areas activated by a pleasant stimulus--vanillin. METHODS AND MATERIAL: Our fMRI method was based on the blood-oxygen-level dependent effect. All measurements were carried out on a 1.5 T scanner (Siemens-Vision), using gradient-echo EPI technic. The basic block-like scheme included no odour/and odour was repeated 8 times. In the definitive phase of the study, experiments were performed on 12 healthy volunteers aged from 20 to 68 (9 men and 3 women) stimulated birhinally by vanillin odour. RESULTS: Bilateral activations of the inferior frontal gyrus, anterior insular-periinsular area, hippocampus, amygdala, caudate nucleus and cerebellum were seen. A greater extent of activation was evident in the right hemisphere and in the right half of the cerebellum. CONCLUSIONS: The anterior insular-periinsular area and hippocampus can be considered as secondary olfactory areas in human brain. Strong activation of the right inferior frontal gyrus demonstrated in our study may be related to effort to name the presented odour. Activation of the cerebellum may be evaluated as a consequent phenomenon due to extensive activation of the frontal lobe.
Adult↗
Water ADC, extracellular space volume, and tortuosity in the rat cortex after traumatic injury.
The diffusion parameters in rat cortex were studied 3-35 days following a cortical stab wound, using diffusion-weighted MR to determine the apparent diffusion coefficient of water (ADC(W)) in the tissue, and the real-time iontophoretic tetramethylammonium (TMA) method to measure the extracellular space (ECS) diffusion parameters: ECS volume fraction alpha and the ADC of TMA(+) (ADC(TMA)). Severe astrogliosis was found close to the wound, and mild astrogliosis was found in the ipsilateral but not the contralateral cortex. Chondroitin sulfate proteoglycan (CSPG) expression was increased throughout the ipsilateral cortex. In the hemisphere contralateral to the wound, alpha, ADC(TMA), and ADC(W) were not significantly different from control values. ECS volume fraction was increased only in the vicinity of the wound, in the region of cell death and severe astrogliosis, at 3 and 7 days after injury. However, both ADC(TMA) and ADC(W) were significantly decreased after lesion in the vicinity of the wound as well as in the rest of the ipsilateral hemisphere distant from the wound. Thus, both ADC(W) and ADC(TMA) decreased in regions wherein alpha did not change but CSPG increased. An increase in extracellular matrix expression may therefore impose diffusion barriers for water as well as for TMA molecules.
Animals↗
Medical application of 3-D polymer gel dosemeter evaluated by nuclear magnetic resonance.
A polymer-gel dosemeter, which can be evaluated by nuclear magnetic resonance (NMR), was prepared and then a few samples were homogeneously irradiated by a Leksell gamma knife using an 18 mm collimator (60Co gamma photons) to obtain a calibration curve (NMR 1/T2 response to absorbed dose). To measure dose distribution from the Leksell gamma knife, a testing flask tilled with the gel was fixed in the head phantom and then irradiated based on a calculated treatment plan. Evaluation of dosemeters was performed on a Siemens EXPERT 1T NMR scanner. Dose profiles in X, Y and Z coordinates through the ellipsoidal shape of the dose distribution were obtained to compare experimental results from the irradiated phantom with the treatment planning system calculations. The use of a polymer-gel dosemeter for a verification of stereotactic procedures has some unique advantages which can be summarised as follows: (1) the dosemeter itself is tissue equivalent, (2) three-dimensional dose distributions can be measured, (3) the dosemeter allows patient's procedures to be simulated without any limitations.
Calibration↗
Functional magnetic resonance imaging during deep brain stimulation: a pilot study in four patients with Parkinson's disease.
Functional magnetic resonance imaging (fMRI) was performed in patients with Parkinson's disease during deep brain stimulation of the subthalamic nucleus (three patients) and during deep brain stimulation of the ventral intermedius nucleus of the thalamus (one patient). All showed an increase in blood oxygenation level-dependent signal in the subcortical regions ipsilateral to the stimulated nucleus. This effect cannot be simply explained by a mechanism of depolarization blockade; rather, it is caused by overstimulation of the target nucleus, resulting in the suppression of its spontaneous activity. We confirm that fMRI during deep brain stimulation is a safe method with considerable potential for elucidating the functional connectivity of the stimulated nuclei.
Brain↗
MR in phenylketonuria-related brain lesions.
PURPOSE: Phenylketonuria (PKU) patients were examined by different MR techniques to explain the pathological changes observed in periventricular white brain matter using conventional MR imaging. MATERIAL AND METHODS: Fifteen patients with treated classical PKU were examined by 1H spectroscopy, relaxometry and diffusion imaging on a whole-body 1.5-T MR imager. RESULTS: Known PKU lesions characterized by T2 enhancement in periventricular white matter were observed in all patients. The MR spectra from the lesioned areas showed a significant decrease in choline concentration. The mean ADC of water decreased and tortuosity increased in PKU lesions compared to control data. CONCLUSION: The results support the following hypothesis: The T2 increase in the PKU lesion reflects a raised concentration of free water molecules (about 15%) that have an increased trajectory between collisions compared to the same region in controls. The increase in water mobility might be explained by changes in extracellular space volume and myelin sheaths, which, presumably, have a different geometry with more hydrophobic sites in PKU patients. The changes result in increased tortuosity and may be confirmed by the loss of anisotropy in PKU lesions.
Adult↗
Brain activation during volitional control of breathing.
Functional magnetic resonance imaging (fMRI) was used to demonstrate the brain activation during volitional control of breathing in nine healthy human subjects. This type of breathing was induced by acoustic stimuli dictating the respiratory frequency. During the period of dictated breathing not only the frontal and temporal lobes of the brain, but also the parietal lobes were bilaterally activated. The frontal lobe was activated bilaterally in all subjects, with frequent activation of Brodmann areas 4 and 6. In the parietal lobe, activation could mostly be demonstrated in gyrus postcentralis and the same was true for area 22 in the temporal lobe.
Acoustic Stimulation↗
Functional MRI of human primary somatosensory and motor cortex during median nerve stimulation.
OBJECTIVES: Somatosensory evoked potential (SEP) studies suggested that some early cortical SEP components may be generated in the primary motor cortex (M1) rather than the primary somatosensory cortex (S1). METHODS: We now used functional magnetic resonance imaging (fMRI) to study activation of S1 and M1 by electrical median nerve stimulation in healthy volunteers. RESULTS: The hand areas of both S1 and M1 showed significant activation (correlation coefficients >0.45) in 7 of 9 subjects (activated volume S1 > M1). For comparison, a sequential finger opposition task significantly activated S1 in 7 and M1 in all 9 subjects (activated volume M1 > S1). CONCLUSIONS: These data show that the electrical stimuli used for SEP recording lead to a functional activation of S1 as well as M1.
Adult↗
Control of breathing and brain activation in human subjects seen by functional magnetic resonance imaging.
Functional magnetic resonance imaging (fMRI) was used to demonstrate the brain activation during transition from unconscious to conscious breathing in seven healthy human subjects. In right-handed volunteers, the activated areas were found in both hemispheres. The medial part of the precentral gyrus (area 4) was constantly activated in the left hemisphere. Additional activated areas were demonstrated in the premotor cortex and in the posterior parietal cortex. The activated cortical sites exhibited analogous distribution in the right hemisphere. In two out of the seven subjects. activated sites were also observed in the cerebellar hemispheres, and in the lentiform and caudate nuclei.
Adult↗
Differentiation of recent and old cerebral infarcts by diffusion-weighted MRI.
We performed MRI, including diffusion-weighted imaging, in 15 patients with recurrent strokes with acute ischaemia and at least one old lesion according to the clinical history and/or CT. Routine MRI showed similar signal intensity changes in both situations. Diffusion-weighted images, however, were positive in all acute or subacute infarcts. The high signal of acutely disturbed diffusion due to intracellular oedema could also be identified in small brain stem lesions. Spatial resolution was increased by applying separate gradients in each axis instead of creating anisotropy-independent trace images.
Adult↗
Proton magnetic resonance spectroscopy in dementia of Alzheimer type.
Reduced N-acetyl aspartate (NAA) and increased myo-inositol (MI) levels have been reported in patients with dementia of Alzheimer type (DAT) in comparison with controls. We wished to assess the validity of these findings and to evaluate possible correlations of metabolite proportions with cognitive dysfunction in DAT. Twelve patients with DAT and 10 healthy age-matched controls were included. The severity of dementia was assessed using different scales including the Mini-Mental State Examination. MRS was performed with a conventional 1.5 Tesla scanner in a single voxel in the centrum semi-ovale (TE = 30 ms or TE = 136 ms; TR = 1500 ms). The evaluation of MRS results was limited by low interrater, intermeasurement (different echo times) and test-retest reliabilities, by a high interindividual variance and by the failure to measure absolute metabolite concentrations. These problems in mind, it was remarkable that previously reported reductions of NAA levels in patients with DAT could be reproduced in the present sample. The proportion of NAA was diminished in demented subjects in comparison with controls (37% vs 44.90%, short TE). A non-significant trend towards minor reductions of creatine, choline and MI proportions in these subjects might indicate that proportions of other metabolites necessarily increase when NAA is reduced. Cognitive dysfunction of demented subjects was significantly correlated with reductions of NAA, but not with increases of MI. Due to the present technical and methodological problems and to the non-specificity of findings, proton MRS cannot be applied to support the diagnosis of DAT in a clinical setting.
Aged↗
Microcirculation after cerebral venous occlusions as assessed by laser Doppler scanning.
Research on cerebral venous circulation disturbances (CVCDs) has been limited partly by the paucity of animal models that produce consistent venous infarction. Occlusion of two adjacent cortical veins in rats by means of a photochemical thrombotic technique provides a minimally invasive, clinically relevant, and reproducible model suited to study the pathophysiology of CVCDs. In this study, the effects of venous occlusion on regional cortical blood flow and the brain damage that ensues were evaluated. Cortical vein occlusion was induced by photoactivation of rose bengal via 100-microm fiberoptic illumination. The cerebral venous flow pattern was examined using fluorescence angiography until 90 minutes after venous occlusion, and regional cerebral blood flow (rCBF) was determined at 48 locations by using laser Doppler scanning. Histological damage was assessed 48 hours after vein occlusion. Occlusion of two cortical veins (Group T; seven animals) was compared with single-vein occlusion and its ensuing brain damage (Group S; five animals) and with sham-operated control (five animals). An rCBF reduction occurred 30 minutes after occlusion in Group T and was more extensive than the decrease in Group S after 60 minutes. Observation frequency histograms based on local CBF data obtained in Group T demonstrated that local CBF at some sites decreased to a level below the ischemic threshold within 90 minutes. Six of the seven rats in Group T had a growing venous thrombus with extravasation of fluorescein. The resulting infarction was significantly larger in Group T (9.8 +/- 4.5% of the hemispheric area) than in Group S (only 3 +/- 1.5% of the hemispheric area). In conclusion, microcirculation perturbations occur early after venous occlusion and result in the formation of a venous thrombus accompanied by local ischemia and severe venous infarction. The extent of vein occlusion determines the resulting brain damage. Based on the results of this study, the authors conclude that CVCDs may be attenuated by prevention of venous thrombus progression together with the use of protective measures against the consequences of ischemia.
Animals↗
3D-high resolution imaging of tumors and aneurysms at the cranial base-comparison of CT and MR.
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Adult↗
The effects of linearly increasing flip angles on 3D inflow MR angiography.
As recently demonstrated, spin saturation effects in 3D time-of-flight (TOF) MR angiography (MRA) can be reduced by using RF pulses with linearly increasing flip angles (ramp pulses) in the main direction of flow. We developed a model for calculating the signal distribution of proton flow within the excitation volume (slab) for different ramp slopes and compared the results with the measured distribution for the lower-leg arteries. The ramp pulses were generated using the Fourier transformation of the desired excitation profiles. With a bandwidth of 6 kHz and a pulse length of 2.56 ms satisfactory ramps with variable slopes were generated and applied in a standard flow-compensated 3D FISP sequence. The effects on the signal distribution in the resulting angiograms of the lower limbs revealed a considerable reduction of saturation losses in agreement with the calculations. Calculated optimal ramp slopes are provided for flow velocities ranging from 5 to 50 cm/s and excitation volumes ranging from 5 to 25 cm.
Algorithms↗
The effect of carbon disulphide on tryptophan metabolism.
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Animals↗