Search results for "cortical"
showing 10 items of 324 documents
Motor intracortical inhibition in PD: L-DOPA modulation of high-frequency rTMS effects
2007
Dopaminergic drugs and deep brain stimulation restore cortical inhibition in Parkinson disease (PD) patients. High-frequency rTMS was also found to increase cortical inhibition in PD but its therapeutic effect is still controversial. Here we hypothesize that, if dopaminergic drugs reverse to normal cortical excitability in M1, the effect of high-frequency (hf)-rTMS in PD patients could depend on whether they are in a medicated or unmedicated state. The present study aims to explore the lasting effects of sub-threshold hf rTMS trains over M1 on cortical inhibition in patients with "on" and without "off" L-DOPA treatment. Fourteen PD patients were examined twice while "on" and "off" medicatio…
Focal cortical damage parallels cognitive impairment in minimal hepatic encephalopathy
2012
Little attention has been paid to cortical integrity in patients with minimal hepatic encephalopathy (MHE), although cognitive functions affected in early stages of liver disease are mainly allocated in different neocortical structures. Here we used cortical surface-based analysis techniques to investigate if patterns of cortical thinning accompany the mildest form of HE. To aim this goal, cortical thickness obtained from high-resolution 31 magnetic resonance imaging (MRI) was measured in patients with no MHE (NMHE), MHE, and healthy controls. Further correlation analyses were performed to examine whether scores in the critical flicker frequency (CFF) test, and blood ammonia levels accounte…
Effects of Cortical Spreading Depression on Cortical Blood Flow, Impedance, DC Potential, and Infarct Size in a Rat Venous Infarct Model
2000
A cortical venous infarction model has been evaluated as to the degree of regional flow reduction and by studying effects of cortical spreading depression (CSD). Two adjacent cortical veins were occluded photochemically with rose bengal and fiberoptic illumination. Seven rats served to demonstrate effects on regional cortical blood flow using laser Doppler scanning. In 36 rats local CBF, DC potential, and brain tissue impedance were measured continuously for 75 min after vein occlusion. No, 3, or 10 CSD waves were induced by potassium chloride injection during the initial 75 min. Rats were compared for spontaneous CSDs; baseline local CBF, CBF, and impedance response to CSD; and infarct vol…
Refractive changes in nuclear, cortical and posterior subcapsular cataracts. Effect of the type and grade
2015
Purpose: To determine the effect of main morphological types and grades of age-related cataracts on refractive error. Methods: We measured 276 subjects with optical compensation prior to the development of cataract. We evaluated 224 eyes with nuclear cataract, 125 with cortical cataract, and 103 with posterior subcapsular (PSC) cataract classified with LOCSIII. We measured visual acuity (VA) with their spectacles and best-corrected visual acuity (BCVA) with chart in decimal scale to obtain the optimal compensation with cataract. We evaluated the differences between compensations. Results: A significant myopic shift was observed in nuclear cataract from low to mild grade (p = 0.031), the sam…
Calcium and increase excitability promote tolerance against anoxia in hippocampal slices.
1999
We have previously demonstrated that anoxic preconditioning (APC) protects against a subsequent otherwise 'lethal' anoxic insult in hippocampal slices. Tested here are two hypotheses: (a) APC requires calcium to improve electrical recovery in hippocampal slices; and (b) mild excitation promotes preconditioning neuroprotection. Control hippocampal slices were given a single 'test' anoxic insult followed by reoxygenation. Experimental slices were preconditioned by three short anoxic insults of 1 min separated by 10 min of reoxygenation. At 30 min after the third 'conditioning' insult, slices underwent a 'test' anoxic insult [1 min of anoxic depolarization (AD)], and then slices were reoxygena…
Transcranial direct current stimulation improves isometric time to exhaustion of the knee extensors
2016
International audience; Transcranial direct current stimulation (tDCS) can increase cortical excitability of a targeted brain area, which may affect endurance exercise performance. However, optimal electrode placement for tDCS remains unclear. We tested the effect of two different tDCS electrode montages for improving exercise performance. Nine subjects underwent a control (CON), placebo (SHAM) and two different tDCS montage sessions in a randomized design. In one tDCS session, the anodal electrode was placed over the left motor cortex and the cathodal on contralateral forehead (HEAD), while for the other montage the anodal electrode was placed over the left motor cortex and cathodal electr…
Locking plates for corrective osteotomy of malunited dorsally tilted distal radial fractures: a biomechanical study.
2005
The purpose of the study was to compare the biomechanical properties of five different palmar fixation plate designs in a distal radius osteotomy cadaver model. A 1 cm metaphyseal osteotomy gap was made to simulate a corrective osteotomy and the osteotomy plated. Axial load was applied to the distal end of each construct by a material testing machine under control of a motion analysis video system. The specimens were arranged into five implant groups of eight specimens each. No test group developed deformity and movement of the fracture gap greater than 2 mm with a load of 100 N. Increasing the load to 250 N revealed statistically significant differences in stiffness and failure load betwe…
Photo-acoustic excitation and optical detection of fundamental flexural guided wave in coated bone phantoms.
2013
Abstract Photo-acoustic (PA) imaging was combined with skeletal quantitative ultrasound (QUS) for assessment of human long bones. This approach permitted low-frequency excitation and detection of ultrasound so as to efficiently receive the thickness-sensitive fundamental flexural guided wave (FFGW) through a coating of soft tissue. The method was tested on seven axisymmetric bone phantoms, whose 1- to 5-mm wall thickness and 16-mm diameter mimicked those of the human radius. Phantoms were made of a composite material and coated with a 2.5- to 7.5-mm layer of soft material that mimicked soft tissue. Ultrasound was excited with a pulsed Nd:YAG laser at 1064-nm wavelength and received on the s…
Assessment of the cortical bone thickness using ultrasonic guided waves: Modelling and in vitro study
2007
Determination of cortical bone thickness is warranted, e.g., for assessing the level of endosteal resorption in osteoporosis or other bone pathologies. We have shown previously that the velocity of the fundamental antisymmetric (or flexural) guided wave, measured for bone phantoms and bones in vitro, correlates with the cortical thickness significantly better than those by other axial ultrasound methods. In addition, we have introduced an inversion scheme based on guided wave theory, group velocity filtering and 2-D fast Fourier transform, for determination of cortical thickness from the measured velocity of guided waves. In this study, the method was validated for tubular structures by usi…
Measuring guided waves in long bones: Modeling and experiments in free and immersed plates
2005
Guided waves, consistent with the A0 Lamb mode, have previously been observed in bone phantoms and human long bones. Reported velocity measurements relied on line fitting of the observed wave fronts. Such an approach has limited ability to assess dispersion and is affected by interference by other wave modes. For a more robust identification of modes and determination of phase velocities, signal processing techniques using the fast Fourier transform (FFT) were investigated. The limitations of FFT because of spatial resolution were addressed to improve the precision of the measured modes. An inversion scheme was developed for determining the plate thickness from the measured velocity. Experi…