Dynamics Of Electrical Activity Research Articles

Memristor-Based Neuromodulation Device for Real-Time Monitoring and Adaptive Control of Neuronal Populations.

Neurons are specialized cells for information transmission and information processing. In fact, many neurologic disorders are directly linked not to cellular viability/homeostasis issues but rather to specific anomalies in electrical activity dynamics. Consequently, therapeutic strategies based on the direct modulation of neuronal electrical activity have been producing remarkable results, with successful examples ranging from cochlear implants to deep brain stimulation. Developments in these implantable devices are hindered, however, by important challenges such as power requirements, size factor, signal transduction, and adaptability/computational capabilities. Memristors, neuromorphic nanoscale electronic components able to emulate natural synapses, provide unique properties to address these constraints, and their use in neuroprosthetic devices is being actively explored. Here, we demonstrate, for the first time, the use of memristive devices in a clinically relevant setting where communication between two neuronal populations is conditioned to specific activity patterns in the source population. In our approach, the memristor device performs a pattern detection computation and acts as an artificial synapse capable of reversible short-term plasticity. Using in vitro hippocampal neuronal cultures, we show real-time adaptive control with a high degree of reproducibility using our monitor-compute-actuate paradigm. We envision very similar systems being used for the automatic detection and suppression of seizures in epileptic patients.

Dynamics of Electrical Activity in Epileptic Brain and Induced Changes Due to Interictal Epileptiform Discharges

Dynamics of Electrical Activity in Epileptic Brain and Induced Changes Due to Interictal Epileptiform Discharges

Effect of Lithium Preparations on Cerebral Electrophysiological Activity in Rats.

The study examined the effects of a novel neurotropic medication based on a lithium complex composed of lithium citrate, polymethylsiloxane, and aluminum oxide on electrophysiological parameters of the rat brain. In contrast to lithium carbonate (the reference drug), the novel preparation resulted in a wave-like dynamics of electrical activity in the visual cortex. Rhythmic photic stimulation of the rats treated with lithium carbonate resulted in appearance of the signs attesting to up-regulation of excitability of cerebral cortex in all examined ranges. In contrast, the complex lithium preparation diminished the delta power spectrum, which was the only affected frequency band. It is hypothesized that the complex lithium medication induces milder activation of the cerebral cortex in comparison with lithium carbonate. The novel medication composed of lithium citrate, aluminum oxide, and polymethylsiloxane, is characterized by greater efficacy and safety than the preparation based on inorganic lithium salt (lithium carbonate).

Effect of an autapse on the firing pattern transition in a bursting neuron

On the basis of the Hindmarsh–Rose (HR) neuron model, the dynamics of electrical activity and the transition of firing patterns induced by three types of autapses have been investigated in detail. The dynamic effect of an autapse is detected by imposing a feedback term with a specific time-delay and autaptic intensity. We found that the delayed autaptic feedback connection switches the electrical activities of the HR neuron among quiescent, periodic and chaotic firing patterns. In the case of an electrical autapse, the transition from a periodic to a chaotic state occurs depending on the specific autaptic intensity and the time-delay. The excitatory chemical autapse plays a positive role in generating and enhancing the chaotic state. A time delay could decrease and suppress the chaotic state in the case of inhibitory chemical self-connections with a proper autaptic intensity. The bifurcation diagram vs. time-delay and autaptic intensity has been extensively studied, and the time series of membrane potentials and the distribution of information entropy have also been calculated to confirm the bifurcation analysis.

Guided adhesion and outgrowth of a constrained network on tailormade surfaces

Event Abstract Back to Event Guided adhesion and outgrowth of a constrained network on tailormade surfaces Anke Wörz1*, Steffen Kandler2, Oswald Prucker1, Ulrich Egert3 and Jürgen Rühe1 1 Freiburg University, Department of Microsystems Engineering , Germany 2 Freiburg University, Neurobiology and Biophysics, Germany 3 Freiburg University, Department of Microsystems Engineering - Biomicrotechnology, Germany Planar micro-electrode arrays have now been used for some time to investigate the activity dynamics and response of neural networks to electrical or chemical stimuli. Constructing defined connectivity statistics under cell culture conditions that allow the maturation of the neuronal networks for a long period has not been achieved so far. Such networks would be useful to understand the influence of the composition, connectivity statistics, and plasticity in a neuronal network on the dynamics of electrical activity. Successful reports of constrained neuronal networks have used serum free medium to minimize the masking of the pattern by proteins. Serum free medium, however, impairs glia develop-ment, which has shown to have significant effects on network maturation and long-term vitality of the neurons, whereas serum containing medium may mask the patterned molecular layers (e.g. stamped proteins), which leads to a loss of constrained neuronal networks after several hours. The key issue is the control of the spatial and long-term stability of neuronal cell adhesion and neurite outgrowth by physicochemical surface modifications under cell culture conditions that allow long-term maintenance of these networks on a micro-scale. This can be achieved by using thin polymer coatings, whose cell adhesion property is not affected by serum-proteins. We report a simple way to tailor the surface-chemistry using a photochemical approach, leading to the covalent attachment of polymer layers to glass and MEA surfaces. We examined the biocompatibility of polymer layers with different properties, such as hydrophilicity and charge, and their potential to promote or inhibit neuronal cell adhesion. Finally, patterns with cell attractive domains were obtained using pin printing or -contact printing ( -CP) of polymer solutions. These patterns were able to guide neuronal cells in a constrained network and were stable over several weeks in a serum containing cell culture medium. Conference: Bernstein Symposium 2008, Munich, Germany, 8 Oct - 10 Oct, 2008. Presentation Type: Poster Presentation Topic: All Abstracts Citation: Wörz A, Kandler S, Prucker O, Egert U and Rühe J (2008). Guided adhesion and outgrowth of a constrained network on tailormade surfaces. Front. Comput. Neurosci. Conference Abstract: Bernstein Symposium 2008. doi: 10.3389/conf.neuro.10.2008.01.077 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 17 Nov 2008; Published Online: 17 Nov 2008. * Correspondence: Anke Wörz, Freiburg University, Department of Microsystems Engineering, Freiburg, Germany, woerz@imtek.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Anke Wörz Steffen Kandler Oswald Prucker Ulrich Egert Jürgen Rühe Google Anke Wörz Steffen Kandler Oswald Prucker Ulrich Egert Jürgen Rühe Google Scholar Anke Wörz Steffen Kandler Oswald Prucker Ulrich Egert Jürgen Rühe PubMed Anke Wörz Steffen Kandler Oswald Prucker Ulrich Egert Jürgen Rühe Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

MACRODYNAMICS OF ELECTRICAL ACTIVITY IN THE WHOLE BRAIN

The general problem of brain mechanisms involved in perception can now be studied directly by means of new analysis–methods for the activity of large population of neurons. These methods range from indirect means of measuring changes in cerebral blood flow in local regions of the human cortex (functional magnetic resonance imaging, fMRI), or changes in the electrical activity of the human brain with EEG-recording with topological distributed macroelectrodes, to the use of chronically implanted multiple microelectrodes in primates. f MRI has the disadvantage of low temporal resolution and with multiple microelectrodes long distance measurements cannot yet be properly performed. Accordingly, recording of macro-activity (EEG/ERP or MEG) with a time resolution of millisecond-range is the most possibly adequate method to measure the dynamic properties of memory and the integrative brain function.Since neuroscientists have come to the general conclusion that large numbers of different brain regions have to cooperate for any brain function, the analysis of relationships between different regions of the brain is becoming more and more important.Before new progresses and importance of EEG studies research became clear, scientists working with macrodynamics of the brain had a long way to go, in order to elucidate brain functioning. In this tutorial report we explain in a narrative way the developments leading to the concept of Macrodynamics in search of an integrative brain function. Moreover, elements of a brain theory, which we call neurons-brain theory describing the dynamics of electrical activity in the whole brain, are introduced. The concept of superbinding in integrative brain function, which emerged from experimental data, is a consequence of this theory.

Adaptive regulation of the nonlinear dynamics of electrical activity of the brain

A programmable system was used to provide contingent reinforcement of EEG cycles corresponding to a selected criterion in a dynamic regime. Use of automated reinforcing stimulation of emotionally positive zones of the hypothalamus led to a significant increase in the number of cycles with the characteristics specified by the dynamic regime within the dominant EEG frequency bands. This effect lasted for some time after withdrawal of reinforcing stimulation, and then died down gradually. These changes in the EEG activity structure did not occur in conditions of nonassociated hypothalamic stimulation. Pseudoreinforced background EEG cycles showed complex nonlinear dynamics with competitive interactions between processes in which the large dimensionality of the attractor was difficult to interpret because of indeterminacy in the trends of the dominant process. In contingent hypothalamic stimulation, the form of the correlation integral changed towards a predominance of a single nonlinear process determining all the activity recorded. In fact, a single dominant nonlinear process was formed, which became responsible for the entire dynamics of the system with concordance of its internal structure.

Dynamics of electrical activity of the cortex in rats with neuropathic trigeminal neuralgia

According to the theory of generator and systemic mechanisms of pain syndromes [3,5,131, the appearance of a generator of pathologically enhanced excitation (GPEE) in the corresponding nociceptive structure lies at the basis of any pathological pain, As a result, this structure becomes hyperactivated and assumes the role of a determinant which induces the formation of a pathological algical system involving the higher structures of the nociceptive system, in particular, the brain cortex. The latter is evidenced by the appearance of spontaneous epileptfform activity in the somatosensory zone of the cortex that was demonstrated in a model of trigeminal neuralgia of neuropathic [1] and central [61 origin. The present study was aimed at investigating the dynamics of development of epileptiform activity in the cortex in rats infraorbital nerve compression (the model of trigeminal neuralgia of neuropathic origin).

A mechanism of the diffuse component of the conditioned-reflex reaction

In investigating the dynamics of electrical activity in varous zones of the cerebral cortex it was noted that during the elaboration of defense and food conditioned reflexes in dogs in response to the action of unconditioned (defense and food) stimuli or conditioned sound signal oscillations resembling by their appearance induced potentials observed during the action of rhythmic light stimulation appeared in the cortical end of the visual analyzer. The appearance of electrical oscillations in the visual cortex in response to unconditioned and conditioned sound stimuli, is explained by the redistribution of the tone of muscles of the extremity and body, leading to a change of the position of the head and, consequently, of the eye illumination. The results of the present investigation may point to the fact that the reverse afferentation of the visual analyzer may also serve as the source of diffuse changes.

Electrical activity of the respiratory muscles in man during breath holding

A study was made of the dynamics of electrical activity in the inspiratory and expiratory muscles during voluntary and involuntary breath holding in 4 persons. However it appeared on the pneumogram, voluntary apnea was biphasic. During the first phase the electrical activity was completely suppressed in both the inspiratory and expiratory muscles and action potentials were absent. In some persons investigated the second phase of voluntary apnea was attended by restoration of the rhythmic electrical activity in both the inspiratory and expiratory muscles and involuntary muscular movements appeared. Other persons, investigated during the second phase of apnea, presented disturbed rhythmic automatism of the respiratory center. Its increasing excitation was transmitted simultaneously to the inspiratory and expiratory muscles, being manifested in their static tension.