scholarly journals Subspace based Multiple Constrained Minimum Variance (SMCMV) Beamformers

2021 ◽  
Author(s):  
Alexander Moiseev ◽  
Anthony T Herdman ◽  
Urs Ribary
Keyword(s):  
Rap Music ◽  
Minimum Variance ◽  
Correlated Sources ◽  
Advantages And Disadvantages ◽  
Noise Measurements ◽  
Imaging Research ◽  
Noise Covariance ◽  
Modeling Data ◽  
The Brain ◽  
Focal Task

In MEG and EEG brain imaging research two popular approaches are often used for spatial localization of focal task- or stimuli-related brain activations. One is a so called MUSIC approach applied in the form of RAP or TRAP MUSIC algorithms. Another one is the beamformer approach, specifically multiple constrained minimum variance (MCMV) beamformer when dealing with significantly correlated activations. Either method is using its own source localizer functions. Considering simplicity, accuracy and computational efficiency both approaches have their advantages and disadvantages. In this study we introduce a novel set of so called Subspace MCMV (or SMCMV) beamformers whose localizer functions combine MUSIC and MCMV localizers. We show that in ideal situations where forward modeling, data recording and noise measurements are error-free, SMCMV localizers allow precise identification of n arbitrarily correlated sources irrespective to their strength in just n scans of the brain volume using RAP MUSIC type algorithm. We also demonstrate by extensive computer simulations that with respect to source localization errors and the total number of identified sources SMCMV outperforms both the TRAP MUSIC and MIA MCMV (which is the most accurate MCMV algorithm to our knowledge) in non-ideal practical situations, specifically when the noise covariance cannot be estimated precisely, signal to noise ratios are small, source correlations are significant and larger numbers of sources are involved.

Implantable neural interfaces

2018 ◽  
Author(s):  
Stefano Vassanelli
Keyword(s):  
Brain Function ◽  
Large Scale ◽  
Ionic Channels ◽  
Patch Clamp Technique ◽  
Advantages And Disadvantages ◽  
Optogenetic Stimulation ◽  
Physical Interfaces ◽  
The Brain

Establishing direct communication with the brain through physical interfaces is a fundamental strategy to investigate brain function. Starting with the patch-clamp technique in the seventies, neuroscience has moved from detailed characterization of ionic channels to the analysis of single neurons and, more recently, microcircuits in brain neuronal networks. Development of new biohybrid probes with electrodes for recording and stimulating neurons in the living animal is a natural consequence of this trend. The recent introduction of optogenetic stimulation and advanced high-resolution large-scale electrical recording approaches demonstrates this need. Brain implants for real-time neurophysiology are also opening new avenues for neuroprosthetics to restore brain function after injury or in neurological disorders. This chapter provides an overview on existing and emergent neurophysiology technologies with particular focus on those intended to interface neuronal microcircuits in vivo. Chemical, electrical, and optogenetic-based interfaces are presented, with an analysis of advantages and disadvantages of the different technical approaches.

scholarly journals Modeling temperature- and Cav3 subtype-dependent alterations in T-type calcium channel mediated burst firing

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Fernando R. Fernandez ◽  
Mircea C. Iftinca ◽  
Gerald W. Zamponi ◽  
Ray W. Turner
Keyword(s):  
Calcium Channel ◽  
Neuronal Excitability ◽  
Neuronal Firing ◽  
Mammalian Brain ◽  
Peripheral Tissues ◽  
Window Current ◽  
Modeling Data ◽  
The Brain ◽  
Firing Neuron ◽  
Cav3 Channel

AbstractT-type calcium channels are important regulators of neuronal excitability. The mammalian brain expresses three T-type channel isoforms (Cav3.1, Cav3.2 and Cav3.3) with distinct biophysical properties that are critically regulated by temperature. Here, we test the effects of how temperature affects spike output in a reduced firing neuron model expressing specific Cav3 channel isoforms. The modeling data revealed only a minimal effect on baseline spontaneous firing near rest, but a dramatic increase in rebound burst discharge frequency for Cav3.1 compared to Cav3.2 or Cav3.3 due to differences in window current or activation/recovery time constants. The reduced response by Cav3.2 could optimize its activity where it is expressed in peripheral tissues more subject to temperature variations than Cav3.1 or Cav3.3 channels expressed prominently in the brain. These tests thus reveal that aspects of neuronal firing behavior are critically dependent on both temperature and T-type calcium channel subtype.

scholarly journals Developing a Multi-channel Beamformer by Enhancing Spatially Constrained ICA for Recovery of Correlated EEG Sources

2018 ◽  
Author(s):  
N Samadzadehaghdam ◽  
B MakkiAbadi ◽  
E Eqlimi ◽  
F Mohagheghian ◽  
H Khajehpoor ◽  
...  
Keyword(s):  
Mean Squared Error ◽  
Partial Information ◽  
Minimum Variance ◽  
Point Of View ◽  
The Body ◽  
Correlated Sources ◽  
Source Imaging ◽  
Neuron Populations ◽  
Eeg Data ◽  
Robust Beamformer

Background: Brain source imaging based on electroencephalogram (EEG) data aims to recover the neuron populations’ activity producing the scalp potentials. This procedure is known as the EEG inverse problem. Recently, beamformers have gained a lot of consideration in the EEG inverse problem.Objective: Beamformers lack acceptable performance in the case of correlated brain sources. These sources happen when some regions of the brain have simultaneous or correlated activities such as auditory stimulation or moving left and right extremities of the body at the same time. In this paper, we have developed a multichannel beamformer robust to correlated sources. Material and Methods: We have looked at the problem of brain source imaging and beamforming from a blind source separation point of view. We focused on the spatially constraint independent component analysis (scICA) algorithm, which generally benefits from the pre-known partial information of mixing matrix, and modified the steps of the algorithm in a way that makes it more robust to correlated sources. We called the modified scICA algorithm Multichannel ICA based EEG Beamformer (MIEB).Results: We evaluated the proposed algorithm on simulated EEG data and compared its performance quantitatively with three algorithms: scICA, linearly-constrained minimum-variance (LCMV) and Dual-Core beamformers; it is considered that the latter is specially designed to reconstruct correlated sources.Conclusion:The MIEB algorithm has much better performance in terms of normalized mean squared error in recovering the correlated/uncorrelated sources both in noise free and noisy synthetic EEG signals. Therefore, it could be used as a robust beamformer in recovering correlated brain sources. 

Brain Tumor Reporting and Data System: A Pictorial Review

Neurographics ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 175-185
Author(s):  
B. Rao ◽  
I. Ikuta ◽  
A. Mahajan ◽  
A.A. Karam ◽  
V.M. Zohrabian
Keyword(s):  
Brain Tumor ◽  
Brain Tumors ◽  
Response To Therapy ◽  
Data System ◽  
Imaging Features ◽  
New Paradigm ◽  
Advantages And Disadvantages ◽  
Pictorial Review ◽  
Almost All ◽  
The Brain

Brain tumors are a diverse group of neoplasms that are a source of substantial morbidity and mortality worldwide. Primary gliomas constitute almost all malignant brain tumors, with the most aggressive as well as most common form in adults, grade IV glioma or glioblastoma multiforme, carrying an especially poor prognosis. Neuroimaging is critical not only in the identification of CNS tumor but also in treatment-planning and assessing the response to therapy. Structured reporting continues to gain traction in radiology by reducing report ambiguity and improving consistency, while keeping referring clinicians and patients informed. The Brain Tumor Reporting and Data System (BT-RADS) is a relatively new paradigm that attempts to simplify and maximize consistency in radiologic reporting. BT-RADS incorporates MR imaging features, clinical assessment, and timing of therapy to assign each study a score or category, which is, in turn, linked to a management suggestion. The purpose of this pictorial review article is to familiarize radiologists and nonradiology neurologic specialists alike with BT-RADS, highlighting both advantages and limitations, in the hope that adoption of this system might ultimately facilitate more effective communication and improve consistency among reports.Learning Objective: To describe the features and underscore the advantages and disadvantages of the Brain Tumor Reporting and Data System (BT-RADS), a relatively new classification system that attempts to simplify and maximize consistency in radiologic reporting

Imaging

2017 ◽  
Author(s):  
Robert Laureno
Keyword(s):  
Resonance Imaging ◽  
Cross Sectional ◽  
Advantages And Disadvantages ◽  
Mri Scans ◽  
Cross Sectional Imaging ◽  
Magnetic Resonance Imaging Mri ◽  
Cellular Pathology ◽  
Brain And Spinal Cord ◽  
The Brain

This chapter on “Imaging” examines the relative advantages and disadvantages of computed tomography (CT) and magnetic resonance imaging (MRI) scans. It compares the modalities to each other and to gross neuropathology. For several decades, neurologists have been able to view cross-sectional images of living patients. Analogous to gross neuropathology, cross-sectional imaging displays the brain as an entire organ but does not demonstrate microscopic tissue or cellular pathology. By allowing practitioners to view sections of brain and spinal cord in vivo, imaging has improved neurologic practice and facilitated clinical research. This chapter deals with imaging topics that are important to the neurologist. The timing of scans, the effects of gravity, and the importance of plane of section are considered. Imaging is compared to gross neuropathology, and MRI is compared to CT.

On the consequences of bilingualism: We need language and the brain to understand cognition

2014 ◽  
Vol 18 (1) ◽  
pp. 32-34 ◽  
Author(s):  
JUDITH F. KROLL
Keyword(s):  
Neural Networks ◽  
Learning Environments ◽  
Language Use ◽  
Neural Systems ◽  
Language Experience ◽  
Advantages And Disadvantages ◽  
The Mind ◽  
The Brain

In the last two decades there has been an explosion of research on bilingualism and its consequences for the mind and the brain (e.g., Kroll & Bialystok, 2013). One reason is that the use of two or more languages reveals interactions across cognitive and neural systems that are often obscured in monolingual speakers of a single language (e.g., Kroll, Dussias, Bogulski & Valdes Kroff, 2012). From this perspective, the interest in bilingualism is about developing a platform to ask questions about the ways that cognitive and neural networks are engaged during language use, in different learning environments, and across the lifespan. Another reason is that an emerging body of research on the consequences of bilingualism suggests that language experience changes cognition and the brain (e.g., Abutalebi, Della Rosa, Green, Hernandez, Scifo, Keim, Cappa & Costa, 2012; Bialystok, Craik, Green, & Gollan, 2009). Some of these changes have been claimed to produce cognitive advantages (see Bialystok et al., for a review of bilingual advantages and disadvantages).

scholarly journals Metode Pengukuran Volume Perdarahan Pemeriksaan MSCT Kepala pada Kasus Intraserebral Hemmorhage

2021 ◽  
Vol 7 (1) ◽  
pp. 1-7
Author(s):  
Siti Masrochah ◽  
Rinda Yuliana Lestar ◽  
Luthfi Rusyadi
Keyword(s):  
Qualitative Research ◽  
Intracerebral Hemorrhage ◽  
Brain Parenchyma ◽  
Slice Thickness ◽  
Manual Method ◽  
Advantages And Disadvantages ◽  
Bleeding Volume ◽  
Irregular Bleeding ◽  
Volume Method ◽  
The Brain

Background: Intracerebral hemorrhage is bleeding in the brain parenchyma. An accurate measurement of bleeding volume to determine the appropriate medical action. This study to determine the method of measuring the volume of intracerebral hemorrhage in MSCT examination of the head and determine the advantages and disadvantages between the manual method (Broderick, ABC's, Ellipsoid) and the software method (automatic volume, otsu).Methods: This type of descriptive qualitative research with the Literature Review. Data obtained by identifying problems then searching for keywords, looking for several journals sourced from databases such as Google Scholar, Science Direct, Springer. Data analysis by studying theoretically the method of measuring the volume of bleeding methods manually (Broderick, ABC’s, ellipsoid) and using software methods (automatic volume, otsu).Results: The results of measuring the volume of bleeding in the same patient with the manual method (Broderick) produce more bleeding volume (overestimate) that is 8750 mm3 from the 7960 mm3 automatic volume method. The manual method (Broderick, ABC’s, Ellipsoid) uses the ABC / 2 formula and uses 5 mm slice thickness, the automatic volume software method uses 1 mm slice thickness segmentation and technique, while the otsu software method uses 2.5 mm segmentation and slice thickness techniques.Conclusion: The advantages of the manual method (Broderick, ABC’s, ellipsoid) take approximately 1 minute to determine the estimated outcome of the bleeding volume, the weakness is higher in irregular bleeding. The advantages of the software method (automatic volume, otsu) in the use of precise segmentation techniques for accurate volume results, weaknesses are too long in determining the estimated bleeding volume results.

In vivo measurements of mitochondrial function and cell death following hypoxic/ischaemic damage to the new-born brain

1999 ◽  
Vol 66 ◽  
pp. 123-140 ◽  
Author(s):  
Chris E. Cooper
Keyword(s):  
Cell Death ◽  
Magnetic Resonance ◽  
Mitochondrial Function ◽  
Apoptotic Cell ◽  
Cellular Damage ◽  
Resonance Spectroscopy ◽  
Advantages And Disadvantages ◽  
Non Invasive ◽  
The Brain

Critically impaired gas exchange to the brain due to decreased oxygen (hypoxia) or reduced blood flow (ischaemia) is a major cause of brain injury in the perinatal period. There is an accumulating body of evidence suggesting that the irreversible cellular damage in the neonatal brain that occurs subsequent to an hypoxic/ischaemic insult is at the level of the mitochondria. Much of this evidence has been obtained by novel non-invasive measurements of mitochondrial function in vivo. This review focuses on four techniques: near-infrared spectroscopy, magnetic resonance spectroscopy, magnetic resonance imaging and electron paramagnetic resonance spectroscopy. The advantages and disadvantages of these in vivo methods are described in patients and animal models. The picture that emerges is of a slow (1-2 day) energy failure, occurring at the level of the brain mitochondria and leading to a primarily apoptotic cell death. Moderate post-insult hypothermia prevents this damage by an unknown mechanism. It is stressed that isolated cell studies alone are not sufficient to understand the processes occurring at the biochemical and physiological levels. The use of the non-invasive techniques described to understand the biochemistry occurring in vivo is therefore an invaluable aid in integrating cellular and organismal studies of the role of mitochondria in cell death.

scholarly journals Sensory Reweighting in Targeted Reaching: Effects of Conscious Effort, Error History, and Target Salience

2010 ◽  
Vol 103 (1) ◽  
pp. 206-217 ◽  
Author(s):  
Hannah J. Block ◽  
Amy J. Bastian
Keyword(s):  
Minimum Variance ◽  
The Body ◽  
The Other ◽  
Proprioceptive Information ◽  
Sensory Reweighting ◽  
Sensorimotor Processing ◽  
Important Principle ◽  
Conscious Effort ◽  
Visual Error ◽  
The Brain

When both visual and proprioceptive information are available about the position of a part of the body, the brain weights and combines these sources to form a single estimate, often modeled by minimum variance integration. These weights are known to vary with different circumstances, but the type of information causing the brain to change weights (reweight) is unknown. Here we studied reweighting in the context of estimating the position of a hand for the purpose of reaching it with the other hand. Subjects reached to visual (V), proprioceptive (P), or combined (VP) targets in a virtual reality setup. We calculated weights for vision and proprioception by comparing endpoints on VP reaches with endpoints on P and V reaches. Endpoint visual feedback was manipulated to control completely for the error history seen by subjects. In different experiments, we manipulated target salience, conscious effort, or statistics of the visual error history to see if these cues could cause reweighting. Most subjects could reweight strongly by conscious effort. Changes in target salience reliably caused reweighting, but seen error history alone did not. We also found that experimental weights can be predicted by minimizing the variance of visual and proprioceptive estimates, supporting the idea that minimum variance integration is an important principle of sensorimotor processing.

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