Real Time EEG Signal Analysis

Invasive electrophysiological recordings in subcortical structures of nonhuman primates typically involve implanting electrodes into the brain through a skull-mounted chamber. These electrodes may be attached to the chamber temporarily for hours of neural recording, or permanently for long-term studies. Current challenges involve maintaining asepsis and integrating dual-modality monitoring of both electrical and chemical neural activity. We developed an implantable neural interface that provides such dual-modality monitoring in monkeys, while maintaining aseptic conditions for year-long periods. We leveraged osseointegrating materials and hermetic sealing strategies to prevent the transmission of pathogenic species, while preserving the modular functionality of chamber systems, such as sensor depth adjustability. The system also features an aspirating port for culturing chamber fluid to ensure continued asepsis. Our chamber system was shown to provide successful recordings of dopamine and electrical neural activity in two monkeys while maintaining negative bacteria culture results for over a year post-implantation. Sealed chamber systems prevent contamination and reduce the risk of compromising animal health by minimizing the accumulation of pathogenic organisms. Such sealed chambers also eliminate the need for frequent cleaning. However, neurochemical measurements require specialized electrodes with fragile carbon fiber tips and are not compatible with recently developed, sealed chamber systems. This advanced chamber design builds upon traditional chamber protocols to enable chronic measurements of chemical and electrical neural activity. This approach facilitates novel ways to study the brain in behaving primates while prioritizing the long-term health and welfare of the animals.

Validating and improving the correction of ocular artifacts in electro-encephalography

The hyperpolarization-activated cation current, I(h), plays an important role in regulating intrinsic neuronal excitability in the brain. In hippocampal pyramidal neurons, I(h) is mediated by h channels comprised primarily of the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel subunits, HCN1 and HCN2. Pyramidal neuron h channels within hippocampal area CA1 are remarkably enriched in distal apical dendrites, and this unique distribution pattern is critical for regulating dendritic excitability. We utilized biochemical and immunohistochemical approaches in organotypic slice cultures to explore factors that control h channel localization in dendrites. We found that distal dendritic enrichment of HCN1 is first detectable at postnatal day 13, reaching maximal enrichment by the 3rd postnatal week. Interestingly we found that an intact entorhinal cortex, which projects to distal dendrites of CA1 but not area CA3, is critical for the establishment and maintenance of distal dendritic enrichment of HCN1. Moreover blockade of excitatory neurotransmission using tetrodotoxin, 6-cyano-7-nitroquinoxaline-2,3-dione, or 2-aminophosphonovalerate redistributed HCN1 evenly throughout the dendrite without significant changes in protein expression levels. Inhibition of calcium/calmodulin-dependent protein kinase II activity, but not p38 MAPK, also redistributed HCN1 in CA1 pyramidal neurons. We conclude that activation of ionotropic glutamate receptors by excitatory temporoammonic pathway projections from the entorhinal cortex establishes and maintains the distribution pattern of HCN1 in CA1 pyramidal neuron dendrites by activating calcium/calmodulin-dependent protein kinase II-mediated downstream signals.

Hippocampal pyramidal cells and dentate granule cells develop morphologically distinct dendritic arbors, yet also share some common features. Both cell types form a long apical dendrite which extends from the apex of the cell soma, while short basal dendrites are developed only in pyramidal cells. Using quantitative morphometric analyses of mouse hippocampal cultures, we evaluated the differences in dendritic arborization patterns between pyramidal and granule cells. Furthermore, we observed and described the final apical dendrite determination during dendritic polarization by time-lapse imaging. Pyramidal and granule cells in culture exhibited similar dendritic patterns with a single principal dendrite and several minor dendrites so that the cell types were not readily distinguished by appearance. While basal dendrites in granule cells are normally degraded by adulthood in vivo, cultured granule cells retained their minor dendrites. Asymmetric growth of a single principal dendrite harboring the Golgi was observed in both cell types soon after the onset of dendritic growth. Time-lapse imaging revealed that up until the second week in culture, final principal dendrite designation was not stabilized, but was frequently replaced by other minor dendrites. Before dendritic polarity was stabilized, the Golgi moved dynamically within the soma and was repeatedly repositioned at newly emerging principal dendrites. Our results suggest that polarized growth of the apical dendrite is regulated by cell intrinsic programs, while regression of basal dendrites requires cue(s) from the extracellular environment in the dentate gyrus. The apical dendrite designation is determined from among multiple growing dendrites of young developing neurons.

Functional implications of inhibitory synapse placement on signal processing in pyramidal neuron dendrites

Activity-dependent development of the neuromuscular synapse during drosophila embryogenesis

Electroencephalography (EEG) is the electrical neural activity recording modality with high temporal and low spatial resolution. Here we propose a novel technique that we call vibroEEG improving significantly the source localization accuracy of EEG. Our method combines electric potential acquisition in concert with acoustic excitation of the vibrational modes of the electrically active cerebral cortex which displace periodically the sources of the low frequency neural electrical activity. The sources residing on the maxima of the induced modes will be maximally weighted in the corresponding spectral components of the broadband signals measured on the noninvasive electrodes. In vibroEEG, for the first time the rich internal geometry of the cerebral cortex can be utilized to separate sources of neural activity lying close in the sense of the Euclidean metric. When the modes are excited locally using phased arrays the neural activity can essentially be probed at any cortical location. When a single transducer is used to induce the excitations, the EEG gain matrix is still being enriched with numerous independent gain vectors increasing its rank. We show theoretically and on numerical simulation that in both cases the source localization accuracy improves substantially.

In this paper, the electroencephalogram (EEG) signal that consists of the information about neurological activities of the brain has been considered to detect epileptic seizures. In connection with neural electrical activities, there is a very limited study using graph theory for seizure detection. In this work, a complete regular weighted undirected graph has been constructed in which the nodes are selected based on the variance among different channels of EEG signals, whereas weights of the edges are assigned based on the phase synchronization between associated nodes. Further, several properties of the graph have been extracted and used as feature sets to perform classification tasks. The well-known classifier k-NN has been applied for classification. In addition, principal component analysis has been used to reduce the dimension of feature sets that leads to improving the analysis and classification performance. The experimental analysis has been performed using EEG signals from the PhysioNet database for three cases - pre-ictal, ictal, and post-ictal. The results demonstrate that the proposed method achieved classification accuracy by up to 100%. The other two parameters' sensitivity and specificity are approximately 100%. The results demonstrate the usability and reliability of the proposed idea.

Activity-Dependent Control of Neuronal Output by Local and Global Dendritic Spike Attenuation

The design of bioelectronics capable of stably tracking brain-wide, single-cell, and millisecond-resolved neural activities in the developing brain is critical to the study of neuroscience and neurodevelopmental disorders. During development, the three-dimensional (3D) structure of the vertebrate brain arises from a 2D neural plate 1,2 . These large morphological changes previously posed a challenge for implantable bioelectronics to track neural activity throughout brain development 3-9 . Here, we present a tissue-level-soft, sub-micrometer-thick, stretchable mesh microelectrode array capable of integrating into the embryonic neural plate of vertebrates by leveraging the 2D-to-3D reconfiguration process of the tissue itself. Driven by the expansion and folding processes of organogenesis, the stretchable mesh electrode array deforms, stretches, and distributes throughout the entire brain, fully integrating into the 3D tissue structure. Immunostaining, gene expression analysis, and behavioral testing show no discernible impact on brain development or function. The embedded electrode array enables long-term, stable, brain-wide, single-unit-single-spike-resolved electrical mapping throughout brain development, illustrating how neural electrical activities and population dynamics emerge and evolve during brain development.

A selective role for a component of the autophagy pathway in coupling the Golgi apparatus to dendrite polarity in pyramidal neurons

Chronic (−) deprenyl administration increases dendritic arborization in CA3 neurons of hippocampus and AChE activity in specific regions of the primate brain

EEG (Electroencephalograph) recording from the scalp has biological artifacts and external artifacts. Biological artifacts, which are generated, can be EMG (Electromyograph) signal, EOG (Electrooculograph) signal or ECG (Electrocardiograph) signal. These artifacts appear as noise in the recorded EEG signal individually or in a combined manner. Usually physicians are misled by these noisy signals and the EEG analysis can go wrong. This paper presents noise cancellation i.e. removal of noise signal which can be either EMG, ECG or a combination of these two artifacts from the corrupted EEG signal and also signal enhancement both using recurrent learning technique. For this purpose, we have implemented the RTRL (Real Time Recurrent Learning) algorithm, which is the most recent and sophisticated real time neural networks algorithm. This algorithm is coded using C language and is executed on the DSP processor TMS320CV5402. The obtained result is verified using MATLAB. Key words: Electroencephalograph (EEG), Recurrent Multilayer Perceptron (RMLP), Real Time Recurrent Learning (RTRL).

This work describes current-mode electroencephalography amplifiers to record the electrical activity of the tangentially oriented cells. Electroencephalography (EEG) measures the summed electrical activity from pyramidal cells in the brain by using non-invasive electrodes placed on the scalp. Traditional, voltage-based measurements are done with differential amplifiers. Depending on the location of the electrodes used for the differential measurement, EEG can estimate electrical activity from radially (common or average reference) or tangentially (bipolar derivation) oriented neurons. A limitation of the bipolar derivation is that when the electrodes are too close together, the conductive solution used to improve electrode-skin impedance can short-circuit the electrodes. Magnetoencephalography (MEG) also enables measurements from tangentially oriented cells without concerns about short-circuiting the electrodes. However, MEG is a more expensive, and a less available technology. Measuring from both radial and tangential cells can improve the resolution to localize the origin of brain activity; this could be extremely useful for diagnoses and treatment of several neurological disorders. Circuit design from previous implementations was improved and the device was compared to a voltage-based (vEEG) amplifier in a saline phantom and in humans with a steady state visually evoked potentials paradigm. The current-based (cEEG) amplifier satisfied suggested electrical parameters for EEG amplifiers and exhibited higher sensitivity to tangential dipoles in the phantom study. It measured brain activity using the same scalp electrodes as vEEG amplifiers with comparable performance. current-based EEG amplifiers can be comparable to traditional voltage-based amplifiers and offer complementary information.

Electroencephalogram (EEG) is an important medical imaging tool which reflects the electrical activity in the brain. It is recorded over the surface of the brain with respect to time. EEG draws potential from the electrodes which are placed on the scalp, this happens due to the firing of the neurons. These signals are in the order of microvolt shows as low amplitude, which are very much prone to the misrepresentation like overlay of other electrical activities exhibit by eye, muscle, heart etc. The other electrical activities which superimposed on the true EEG signal and forms a cock-tailed signal, the other electrical activity which overlay on the true EEG signal is called as Artifact with respect to the brain electrical activity. Mainly EEG signal gets affected with artifact signal which is near or around the brain like EOG, ECG, EMG, etc. forms their respective artifacts in the EEG signal, this makes the physician to make a wrong analysis of EEG signal and treating the brain activity as abnormal and direct the patient to have diagnosis which causes the serious issue. There are many artifacts that overlay and cause misinterpretation of EEG, like from the side of the patient, machinery and other environmental issues. Among this all causes of the artifacts the Ocular artifact caused from the side of the patient takes a principal position because the Ocular artifact (OA) caused by the eye is very much nearer to the psyche. Hence, in this paper the study of the various methods to remove the Ocular artifacts and their benefits, drawbacks are also stated.