In vivo measurements with robust silicon-based multielectrode arrays with extreme shaft lengths

In this paper, manufacturing and in vivo testing of extreme-long Si-based neural microelectrode arrays are presented. Probes with different shaft lengths (15–70 mm) are formed by deep reactive ion etching and have been equipped with platinum electrodes of various configurations. In vivo measurements on rats indicate good mechanical stability, robust implantation, and targeting capability. High-quality signals have been recorded from different locations of the cerebrum of the rodents. The accompanied tissue damage is characterized by histology

Intracranial neuronal ensemble recordings and analysis in epilepsy

Pathological neuronal firing was demonstrated 50 years ago as the hallmark of epileptically transformed cortex with the use of implanted microelectrodes. Since then, microelectrodes remained only experimental tools in humans to detect unitary neuronal activity to reveal physiological and pathological brain functions. This recording technique has evolved substantially in the past few decades; however, based on recent human data implying their usefulness as diagnostic tools, we expect a substantial increase in the development of microelectrodes in the near future. Here, we review the technological background and history of microelectrode array development for human examinations in epilepsy, including discussions on of wire-based and microelectrode arrays fabricated using micro-electro-mechanical system (MEMS) techniques and novel future techniques to record neuronal ensemble. We give an overview of clinical and surgical considerations, and try to provide a list of probes on the market with their availability for human recording. Then finally, we briefly review the literature on modulation of single neuron for the treatment of epilepsy, and highlight the current topics under examination that can be background for the future development

Revealing the distribution of transmembrane currents along the dendritic tree of a neuron from extracellular recordings.

Revealing the current source distribution along the neuronal membrane is a key step on the way to understanding neural computations, however, the experimental and theoretical tools to achieve sufficient spatiotemporal resolution for the estimation remain to be established. Here we address this problem using extracellularly recorded potentials with arbitrarily distributed electrodes for a neuron of known morphology. We use simulations of models with varying complexity to validate the proposed method and to give recommendations for experimental applications. The method is applied to in vitro data from rat hippocampus

Physiological sharp wave-ripples and interictal events in vitro: What’s the difference?

Sharp wave-ripples and interictal events are physiological and pathological forms of transient high activity in the hippocampus with similar features. Sharp wave-ripples have been shown to be essential in memory consolidation, while epileptiform (interictal) events are thought to be damaging. It is essential to grasp the difference between physiological sharp wave-ripples and pathological interictal events in order to understand the failure of control mechanisms in the latter case. We investigated the dynamics of activity generated intrinsically in the CA3 region of the mouse hippocampus in vitro, using four different types of intervention to induce epiletiform activity. As a result, sharp wave-ripples spontaneously occurring in CA3 disappeared, and following an asynchronous transitory phase, activity reorganized into a new form of pathological synchrony. During epileptiform events, all neurons increased their firing rate compared to sharp wave-ripples. Different cell types showed complementary firing: parvalbumin-positive basket cells and some axo-axonic cells stopped firing due to a depolarization block at the climax of the events in high potassium, 4-aminopyridine and zero magnesium models, but not in the gabazine model. In contrast, pyramidal cells started firing maximally at this stage. To understand the underlying mechanism we measured changes of intrinsic neuronal and transmission parameters in the high potassium model. We found that the cellular excitability increased and excitatory transmission was enhanced, whereas inhibitory transmission was compromised. We observed a strong short-term depression in parvalbumin-positive basket cell to pyramidal cell transmission. Thus, the collapse of pyramidal cell perisomatic inhibition appears to be a crucial factor in the emergence of epileptiform events

Deep comparisons of Neural Networks from the EEGNet family

Most of the Brain-Computer Interface (BCI) publications, which propose artificial neural networks for Motor Imagery (MI) Electroencephalography (EEG) signal classification, are presented using one of the BCI Competition datasets. However, these databases contain MI EEG data from less than or equal to 10 subjects . In addition, these algorithms usually include only bandpass filtering to reduce noise and increase signal quality. In this article, we compared 5 well-known neural networks (Shallow ConvNet, Deep ConvNet, EEGNet, EEGNet Fusion, MI-EEGNet) using open-access databases with many subjects next to the BCI Competition 4 2a dataset to acquire statistically significant results. We removed artifacts from the EEG using the FASTER algorithm as a signal processing step. Moreover, we investigated whether transfer learning can further improve the classification results on artifact filtered data. We aimed to rank the neural networks; therefore, next to the classification accuracy, we introduced two additional metrics: the accuracy improvement from chance level and the effect of transfer learning. The former can be used with different class-numbered databases, while the latter can highlight neural networks with sufficient generalization abilities. Our metrics showed that the researchers should not avoid Shallow ConvNet and Deep ConvNet because they can perform better than the later published ones from the EEGNet family

A megismerési folyamatok pszichofiziológiája: agyi elektromos tevékenység = Psychophysiology of cognitive processes: brain electric activity

A pályázat fő feladataként összefoglaló monográfiák készültek a figyelem pszichológiája (Czigler István) és a fejlődés-neuropszichológia (Csépe Valéria) területén. A tudományos iskola alapjában az agyi elektromos változások elemzése állt (eseményhez kötött potenciál módszerek, frekvencia-elemzések, nem-lineáris módszerek), melyet a klasszikus kognitív pszichológia teljesítmény-elemző módszereivel együtt, és esetenként a vegetatív idegrendszeri aktivitás elemzésével kiegészítve végeztünk. Kutatásaink fő eredményei az automatikus és figyelmi információfeldolgozási folyamatokhoz (változás-detekció, orientáció, reorientáció), fejlődés-pszichofiziológiai kutatásokban az olvasás és számolás jellemzőihez és ezek zavaraihoz, agyi érbetegségek agyi elektromos jellemzőihez, epilepsziás agyi működések mikro-szerkezetének elemzéséhez, valamint állatkísérletes információfeldolgozási modellek kutatásához kapcsolódtak. A tudományos iskola pályázat lehetővé tette fiatal munkatársak bevonását e kutatásokba, melyek tematikus támogatását OTKA, NKFP, FIRCA, Informatikai - és Egészséügyi Minisztériumi pályázatok tették lehetővé. | As the main task, comprehensive books were written on psychology of attention (I. Czigler) and developmental neuropsychology (V. Csépe) respectively. In the research projects we concentrated on the methods of brain electric activity analyses (event-related potentials, frequency analyses, non-linear methods). Electrophysiologyical methods were conducted together with the analyses of behavioral performance (reaction time, error measures), and in some occasions with the investigations of autonomic changes. Our main results concentrated on the automatic and attentional processes of human information processing (change detection, orientation, re-orientation), within the field of developmental neuropsychology on reading and arithmetic development (and the impairment of these activities). We obtained results on stroke-related activity, and on the micro-processes of epileptic activity. In the comparative research animal models of perceptual activity were investigated. The grant supported the involvement of young scientists into our research projects. The research projects were supported by thematic OTKA grants, NKFP, FIRCA grants, and supports from Ministries of Healh and Informatic

A Multimodal, SU-8-Platinum - Polyimide Microelectrode Array for Chronic In Vivo Neurophysiology

Utilization of polymers as insulator and bulk materials of microelectrode arrays (MEAs) makes the realization of flexible, biocompatible sensors possible, which are suitable for various neurophysiological experiments such as in vivo detection of local field potential changes on the surface of the neocortex or unit activities within the brain tissue. In this paper the microfabrication of a novel, all-flexible, polymer-based MEA is presented. The device consists of a three dimensional sensor configuration with an implantable depth electrode array and brain surface electrodes, allowing the recording of electrocorticographic (ECoG) signals with laminar ones, simultaneously. In vivo recordings were performed in anesthetized rat brain to test the functionality of the device under both acute and chronic conditions. The ECoG electrodes recorded slow-wave thalamocortical oscillations, while the implanted component provided high quality depth recordings. The implants remained viable for detecting action potentials of individual neurons for at least 15 weeks