scholarly journals Electrical Fields Induced Inside the Rat Brain with Skin, Skull, and Dural Placements of the Current Injection Electrode

2018 ◽  
Author(s):  
Ahmet S. Asan ◽  
Sinan Gok ◽  
Mesut Sahin
Keyword(s):  
White Matter ◽  
Rat Brain ◽  
Electric Fields ◽  
Gray Matter ◽  
Animal Experiments ◽  
Field Measurements ◽  
Transcranial Electrical Stimulation ◽  
Clinical Tool ◽  
Electrical Fields ◽  
The Brain

AbstractTranscranial electrical stimulation (tES) is rapidly becoming an indispensable clinical tool with its different forms. Animal data are crucially needed for better understanding of the underlying mechanisms of tES. For reproducibility of results in animal experiments, the electric fields (E-Fields) inside the brain parenchyma induced by the injected currents need to be predicted accurately. In this study, we measured the electrical fields in the rat brain perpendicular to the brain surface, i.e. vertical electric field (VE-field), when the stimulation electrode was placed over the skin, skull, or dura mater through a craniotomy hole. The E-field attenuation through the skin was a few times larger than that of the skull and the presence of skin substantially reduced the VE-field peak at the cortical surface near the electrode. The VE-field declined much quicker in the gray matter underneath the pial surface than it did in the white matter, and thus the large VE-fields were contained mostly in the gray matter. The transition at the gray/white matter border caused a significant peak in the VE-field, as well as at other local inhomogeneties. A conductivity value of 0.57 S/m is predicted as a global value for the whole brain by matching our VE-field measurements to the field profile given by analytical equations for volume conductors. Finally, insertion of the current return electrode into the shoulder, submandibular, and hind leg muscles had virtually no effects on the measured E-field amplitudes in the cortex underneath the epidural electrodes.

scholarly journals The Transfer Coefficients for L-Valine and the Rate of Incorporation of L-[1-14C] Valine into Proteins in Normal Adult Rat Brain

1988 ◽  
Vol 8 (4) ◽  
pp. 598-605 ◽  
Author(s):  
M. Kirikae ◽  
M. Diksic ◽  
Y. L. Yamamoto
Keyword(s):  
White Matter ◽  
Rat Brain ◽  
Inferior Colliculus ◽  
Gray Matter ◽  
Transfer Coefficients ◽  
Brain Proteins ◽  
Adult Rat ◽  
Adult Rat Brain ◽  
Normal Rat ◽  
The Brain

An autoradiographic method for the measurement of the rate of valine incorporation into brain proteins is described. The transfer coefficients for valine into and out of the brain and the rate of valine incorporation into normal rat brain proteins are given. The valine incorporation and the transfer constants of valine between different biological compartments are provided for 14 gray matter and 2 white matter structures of an adult rat brain. The rate of valine incorporation varies between 0.52 ± 0.19 nmol/g/min in white matter and 1.94 ± 0.47 in inferior colliculus (gray matter). Generally, the rate of valine incorporation is about three to four times higher in the gray matter than in the white matter structures.

Segmentation of Rat Brain MR Images Using Artificial Neural Network Classifier

2013 ◽  
Author(s):  
K. N. Magdoom ◽  
Thomas H. Mareci ◽  
Malisa Sarntinoranont
Keyword(s):  
Neural Network ◽  
White Matter ◽  
Rat Brain ◽  
Gray Matter ◽  
Computational Models ◽  
Chemotherapeutic Agents ◽  
Mr Images ◽  
Artificial Neural Network Classifier ◽  
Brain Mr Images ◽  
The Brain

Recently MR image based computational models are being developed to assist targeted drug delivery in the brain by helping determine appropriate catheter position, drug dose among others to achieve the desired drug distribution [1–3]. Such a planning might be important to prevent damaging healthier tissues because many of the drugs (e.g. chemotherapeutic agents) are usually toxic and needs to be concentrated in specific regions of interest (e.g. tumor). However, for the image based model to make accurate predictions, it is important to segment the image and assign appropriate tissue properties such as hydraulic conductivity which are known to vary significantly within the brain. For example, it has been experimentally found that drugs injected into brain parenchyma get preferentially transported along the white matter tracts compared to the gray matter regions [4]. Segmenting MR images is a challenging task since the pixel intensities between different regions often overlap, hence traditional approaches based on thresholds might not provide reliable results. In this study, we used multi-layered perceptron (MLP) neural network to segment rat brain MR images into 3 different regions namely white matter (WM), gray matter (GM) and cerebrospinal fluid (CSF).

MR Brain Image Segmentation to Detect White Matter, Gray Matter, and Cerebro Spinal Fluid Using TLBO Algorithm

2021 ◽  
pp. 2150034
Author(s):  
Sandhya Gudise ◽  
Giri Babu Kande ◽  
T. Satya Savithri
Keyword(s):  
White Matter ◽  
Gray Matter ◽  
Population Based ◽  
Spinal Fluid ◽  
Brain Image ◽  
Tlbo Algorithm ◽  
Wide Range ◽  
Skull Stripping ◽  
The Brain ◽  
Mr Brain

This paper proposes an advanced and precise technique for the segmentation of Magnetic Resonance Image (MRI) of the brain. Brain MRI segmentation is to be familiar with the anatomical structure, to recognize the deformities, and to distinguish different tissues which help in treatment planning and diagnosis. Nature’s inspired population-based evolutionary algorithms are extremely popular for a wide range of applications due to their best solutions. Teaching Learning Based Optimization (TLBO) is an advanced population-based evolutionary algorithm designed based on Teaching and Learning process of a classroom. TLBO uses common controlling parameters and it won’t require algorithm-specific parameters. TLBO is more appropriate to optimize the real variables which are fuzzy valued, computationally efficient, and does not require parameter tuning. In this work, the pixels of the brain image are automatically grouped into three distinct homogeneous tissues such as White Matter (WM), Gray Matter (GM), and Cerebro Spinal Fluid (CSF) using the TLBO algorithm. The methodology includes skull stripping and filtering in the pre-processing stage. The outcomes for 10 MR brain images acquired by utilizing the proposed strategy proved that the three brain tissues are segmented accurately. The segmentation outputs are compared with the ground truth images and high values are obtained for the measure’s sensitivity, specificity, and segmentation accuracy. Four different approaches, namely Particle Swarm Optimization (PSO), Genetic Algorithm (GA), Bacterial Foraging Algorithm (BFA), and Electromagnetic Optimization (EMO) are likewise implemented to compare with the results of the proposed methodology. From the results, it can be proved that the proposed method performed effectively than the other.

scholarly journals Effects of Temperature on Evoked Electrical Activity and Anoxic Injury in CNS White Matter

1992 ◽  
Vol 12 (6) ◽  
pp. 977-986 ◽  
Author(s):  
Peter K. Stys ◽  
Stephen G. Waxman ◽  
Bruce R. Ransom
Keyword(s):  
White Matter ◽  
Optic Nerve ◽  
Functional Outcome ◽  
Gray Matter ◽  
Functional Recovery ◽  
Temperature Sensitive ◽  
Anoxic Injury ◽  
Intracellular Ca ◽  
Effects Of Temperature ◽  
The Brain

Temperature is known to influence the extent of anoxic/ischemic injury in gray matter of the brain. We tested the hypothesis that small changes in temperature during anoxic exposure could affect the degree of functional injury seen in white matter, using the isolated rat optic nerve, a typical CNS white matter tract (Foster et al., 1982). Functional recovery after anoxia was monitored by quantitative assessment of the compound action potential (CAP) area. Small changes in ambient temperature, within a range of 32 to 42°C, mildly affected the CAP of the optic nerve under normoxic conditions. Reducing the temperature to <37°C caused a reversible increase in the CAP area and in the latencies of all three CAP peaks; increasing the temperature to >37°C had opposite effects. Functional recovery of white matter following 60 min of anoxia was strongly influenced by temperature during the period of anoxia. The average recovery of the CAP, relative to control, after 60 min of anoxia administered at 37°C was 35.4 ± 7%; when the temperature was lowered by 2.5°C (i.e., to 34.5°C) for the period of anoxic exposure, the extent of functional recovery improved to 64.6 ± 15% ( p < 0.00001). Lowering the temperature to 32°C during anoxic exposure for 60 min resulted in even greater functional recovery (100.5 ± 14% of the control CAP area). Conversely, if temperature was increased to >37°C during anoxia, the functional outcome worsened, e.g., CAP recovery at 42°C was 8.5 ± 7% ( p < 0.00001). Hypothermia (i.e., 32°C) for 30 min immediately following anoxia at 37°C did not improve the functional outcome. Many processes within the brain are temperature sensitive, including O2 consumption, and it is not clear which of these is most relevant to the observed effects of temperature on recovery of white matter from anoxic injury. Unlike the situation in gray matter, the temperature dependency of anoxic injury cannot be related to reduced release of excitotoxins like glutamate, because neurotransmitters play no role in the pathophysiology of anoxic damage in white matter (Ransom et al., 1990 a). It is more likely that temperature affects the rate of ion transport by the Na+–Ca2+ exchanger, the transporter responsible for intracellular Ca2+ loading during anoxia in white matter, and/or the rate of some destructive intracellular enzymatic mechanism(s) activated by pathological increases in intracellular Ca2+.

scholarly journals Brain imaging in myotonic dystrophy type 1

Neurology ◽  
2017 ◽  
Vol 89 (9) ◽  
pp. 960-969 ◽  
Author(s):  
Kees Okkersen ◽  
Darren G. Monckton ◽  
Nhu Le ◽  
Anil M. Tuladhar ◽  
Joost Raaphorst ◽  
...  
Keyword(s):  
White Matter ◽  
Brain Imaging ◽  
Longitudinal Studies ◽  
Myotonic Dystrophy ◽  
Gray Matter ◽  
Myotonic Dystrophy Type 1 ◽  
Myotonic Dystrophy Type ◽  
Pooled Prevalence ◽  
The Brain

Objective:To systematically review brain imaging studies in myotonic dystrophy type 1 (DM1).Methods:We searched Embase (index period 1974–2016) and MEDLINE (index period 1946–2016) for studies in patients with DM1 using MRI, magnetic resonance spectroscopy (MRS), functional MRI (fMRI), CT, ultrasound, PET, or SPECT. From 81 studies, we extracted clinical characteristics, primary outcomes, clinical-genetic correlations, and information on potential risk of bias. Results were summarized and pooled prevalence of imaging abnormalities was calculated, where possible.Results:In DM1, various imaging changes are widely dispersed throughout the brain, with apparently little anatomical specificity. We found general atrophy and widespread gray matter volume reductions in all 4 cortical lobes, the basal ganglia, and cerebellum. The pooled prevalence of white matter hyperintensities is 70% (95% CI 64–77), compared with 6% (95% CI 3–12) in unaffected controls. DTI shows increased mean diffusivity in all 4 lobes and reduced fractional anisotropy in virtually all major association, projection, and commissural white matter tracts. Functional studies demonstrate reduced glucose uptake and cerebral perfusion in frontal, parietal, and temporal lobes, and abnormal fMRI connectivity patterns that correlate with personality traits. There is significant between-study heterogeneity in terms of imaging methods, which together with the established clinical variability of DM1 may explain divergent results. Longitudinal studies are remarkably scarce.Conclusions:DM1 brains show widespread white and gray matter involvement throughout the brain, which is supported by abnormal resting-state network, PET/SPECT, and MRS parameters. Longitudinal studies evaluating spatiotemporal imaging changes are essential.

scholarly journals Diffusion tensor imaging analysis of the brain in the canine model of Krabbe disease

2016 ◽  
Vol 29 (6) ◽  
pp. 417-424 ◽  
Author(s):  
Allison Bradbury ◽  
David Peterson ◽  
Charles Vite ◽  
Steven Chen ◽  
N Matthew Ellinwood ◽  
...  
Keyword(s):  
Diffusion Tensor Imaging ◽  
White Matter ◽  
Mr Imaging ◽  
Gray Matter ◽  
Diffusion Tensor ◽  
Ex Vivo ◽  
Small Animal ◽  
Krabbe Disease ◽  
Adc Values ◽  
The Brain

Purpose The goal of this study was to compare the diffusion tensor imaging (DTI) metrics from an end-stage canine Krabbe brain evaluated by MR imaging ex vivo to those of a normal dog brain. We hypothesized that the white matter of the canine Krabbe brain would show decreased fractional anisotropy (FA) values and increased apparent diffusion coefficient (ADC) and radial diffusivity (RD) values. Methods An 11-week-old Krabbe dog was euthanized after disease progression. The brain was removed and was placed in a solution of 10% formalin. MR imaging was performed and compared to the brain images of a normal dog that was similarly fixed post-mortem. Both brains were scanned using similar protocols on a 7 T small-animal MRI system. For each brain, maps of ADC, FA, and RD were calculated for 11 white-matter regions and five control gray-matter regions. Results Large decreases in FA values, increases in ADC values, and increases in RD (consistent with demyelination) values, were seen in white matter of the Krabbe brain but not gray matter. ADC values in gray matter of the Krabbe brain were decreased by approximately 29% but increased by approximately 3.6% in white matter of the Krabbe brain. FA values in gray matter were decreased by approximately 3.3% but decreased by approximately 29% in white matter. RD values were decreased by approximately 27.2% in gray matter but increased by approximately 20% in white matter. Conclusion We found substantial abnormalities of FA, ADC, and RD values in an ex vivo canine Krabbe brain.

scholarly journals Edited Magnetic Resonance Spectroscopy Detects an Age-Related Decline in Nonhuman Primate Brain GABA Levels

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Xuanzi He ◽  
Bang-Bon Koo ◽  
Ronald J. Killiany
Keyword(s):  
White Matter ◽  
Gray Matter ◽  
Posterior Cingulate Cortex ◽  
Resonance Spectroscopy ◽  
Gamma Aminobutyric Acid ◽  
Gaba Level ◽  
Inhibitory Neurotransmitter ◽  
Independent Variables ◽  
Age Related ◽  
The Brain

Recent research had shown a correlation between aging and decreasing Gamma-aminobutyric acid (GABA), the primary inhibitory neurotransmitter in the brain. However, how GABA level varies with age in the medial portion of the brain has not yet been studied. The purpose of this study was to investigate the GABA level variation with age focusing on the posterior cingulate cortex, which is the “core hub” of the default mode network. In this study, 14 monkeys between 4 and 21 years were recruited, and MEGA-PRESS MRS was performed to measure GABA levels, in order to explore a potential link between aging and GABA. Our results showed that a correlation between age and GABA+/Creatine ratio was at the edge of significance (r=-0.523,p=0.081). There was also a near-significant trend between gray matter/white matter ratio and the GABA+/Creatine ratio (r=-0.518,p=0.0848). Meanwhile, the correlation between age and grey matter showed no significance (r=-0.028,p=0.93). Therefore, age and gray matter/white matter ratio account for different part ofR-squared (adjustedR-squared = 0.5187) as independent variables for predicting GABA levels. AdjustedR-squared is about 0.5 for two independent variables. These findings suggest that there is internal neurochemical variation of GABA levels in the nonhuman primates associated with normal aging and structural brain decline.

scholarly journals Realistic Anatomically Detailed Open-Source Spinal Cord Stimulation (RADO-SCS) Model

2019 ◽  
Author(s):  
Niranjan Khadka ◽  
Xijie Liu ◽  
Hans Zander ◽  
Jaiti Swami ◽  
Evan Rogers ◽  
...  
Keyword(s):  
Spinal Cord ◽  
White Matter ◽  
Open Source ◽  
Electric Fields ◽  
Epidural Space ◽  
Gray Matter ◽  
Spinal Cord Stimulation ◽  
Clinical Trial Design ◽  
Element Model ◽  
Scs Model

AbstractObjectiveComputational current flow models of spinal cord stimulation (SCS) are widely used in device development, clinical trial design, and patient programming. Proprietary models of varied sophistication have been developed. An open-source model with state-of-the-art precision would serve as a standard for SCS simulation.ApproachWe developed a sophisticated SCS modeling platform, named Realistic Anatomically Detailed Open-Source Spinal Cord Stimulation (RADO-SCS) model. This platform consists of realistic and detailed spinal cord and ancillary tissues anatomy derived based on prior imaging and cadaveric studies. Represented tissues within the T9-T11 spine levels include vertebrae, intravertebral discs, epidural space, dura, CSF, white-matter, gray-matter, dorsal and ventral roots and rootlets, dorsal root ganglion, sympathetic chain, thoracic aorta, epidural space vasculature, white-matter vasculature, and thorax. As an exemplary, a bipolar SCS montage was simulated to illustrate the model workflow from the electric field calculated from a finite element model (FEM) to activation thresholds predicted for individual axons populating the spinal cord.Main ResultsCompared to prior models, RADO-SCS meets or exceeds detail for every tissue compartment. The resulting electric fields in white and gray-matter, and axon model activation thresholds are broadly consistent with prior stimulations.SignificanceThe RADO-SCS can be used to simulate any SCS approach with both unprecedented resolution (precision) and transparency (reproducibility). Freely available online, the RADO-SCS will be updated continuously with version control.

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