Multi-array Electrodes Research Articles

Research and development of taste sensors as a novel analytical tool.

Gustatory and olfactory receptors receive multiple chemical substances of different types simultaneously, but they can barely discriminate one chemical species from others. In this article, we describe a device used to measure taste, i.e., taste sensors. Toko and colleagues developed a taste sensor equipped with multiarray electrodes using a lipid/polymer membrane as the transducer in 1989. This sensor has a concept of global selectivity to decompose the characteristics of a chemical substance into taste qualities and to quantify them. The use of taste sensors has spread around the world. More than 600 examples of taste-sensing system have been used, while providing the first "taste scale" in the world. This article explains the principle of taste sensors and their application to foods and medicines, and also a novel type of taste sensor using allostery. Taste-sensor technology, the underlying principle of which is different from that of conventional analytical instruments, markedly affects many aspects including social economy as well as the food industry.

Different coding characteristics between flight and freezing in dorsal periaqueductal gray of mice during exposure to innate threats.

Flight and freezing are two vital defensive behaviors that mice display to avoid natural enemies. When they are exposed to innate threats, visual cues are processed and transmitted by the visual system into the emotional nuclei and finally transmitted to the periaqueductal gray (PAG) to induce defensive behaviors. However, how the dorsal PAG (dPAG) encodes the two defensive behaviors is unclear. Multi-array electrodes were implanted in the dPAG nuclei of C57BL/6 mice. Two kinds of visual stimuli (looming and sweeping) were used to induce defensive behaviors in mice. Neural signals under different defense behaviors were recorded, and the encoding characteristics of the two behaviors were extracted and analyzed from spike firing and frequency oscillations. Finally, synchronization of neural activity during the defense process was analyzed. The neural activity between flight and freezing behaviors showed different firing patterns, and the differences in the inter-spike interval distribution were mainly reflected in the 2-10ms period. The frequency band activities under both defensive behaviors were concentrated in the theta band; the active frequency of flight was ~8 to 10Hz, whereas that of freezing behavior was ~6 to 8Hz. The network connection density under both defense behaviors was significantly higher than the period before and after defensive behavior occurred, indicating that there was a high synchronization of neural activity during the defense process. The dPAG nuclei of mice have different coding features between flight and freezing behaviors; during strong looming stimulation, fast neuro-instinctive decision making is required while encountering weak sweeping stimulation, and computable planning late behavior is predicted in the early stage. The frequency band activities under both defensive behaviors were concentrated in the theta band. There was a high synchronization of neural activity during the defense process, which may be a key factor triggering different defensive behaviors.

The Effect of the Partial Pressure of H2S and CO2 on the Permeation of Hydrogen in Carbon Steel by Using Pressure Buildup Techniques

There are concerns in the industry about using an electrochemical technique for actual hydrogen permeation measurements where charging current is not a field condition. The objective of this work is to use pressure buildup techniques to study the influence of H2S and CO2 partial pressure on the relationship between hydrogen permeation and corrosion rate measured by different techniques. Sulfide films formed on carbon steel in a solution containing 5 wt% NaCl and 0.5 wt% acidic acid at various H2S and CO2 partial pressures were characterized, and the effect of the film on hydrogen permeation was also investigated. Field conditions were included in this study for comparison purposes. The relationship was modeled at the steady state of both hydrogen flux and corrosion rate. The results confirmed by use of two hydrogen flux measurement techniques (eudiometer and high-pressure buildup probe) and two corrosion measurement methods (weight loss coupons and coupled multiarray electrode system), that there is no direct correlation between hydrogen flux and corrosion rate. Therefore, the hydrogen permeation rate in H2S and CO2 environments was found to be more controlled by partial pressure of H2S than corrosion rate. The amount of descent in hydrogen flux, after reaching maximum of hydrogen permeation rate and before reaching a steady state, depends on the morphology and structure of corrosion films which are mainly controlled by concentration of H2S.

The translationally relevant mouse model of the 15q13.3 microdeletion syndrome reveals deficits in neuronal spike firing matching clinical neurophysiological biomarkers seen in schizophrenia.

AimTo date, the understanding and development of novel treatments for mental illness is hampered by inadequate animal models. For instance, it is unclear to what extent commonly used behavioural tests in animals can inform us on the mental and affective aspects of schizophrenia.MethodsTo link pathophysiological processes in an animal model to clinical findings, we have here utilized the recently developed Df(h15q13)/+ mouse model for detailed investigations of cortical neuronal engagement during pre‐attentive processing of auditory information from two back‐translational auditory paradigms. We also investigate if compromised putative fast‐spiking interneurone (FSI) function can be restored through pharmacological intervention using the Kv3.1 channel opener RE1. Chronic multi‐array electrodes in primary auditory cortex were used to record single cell firing from putative pyramidal and FSI in awake animals during processing of auditory sensory information.ResultsWe find a decreased amplitude in the response to auditory stimuli and reduced recruitment of neurones to fast steady‐state gamma oscillatory activity. These results resemble encephalography recordings in patients with schizophrenia. Furthermore, the probability of interneurones to fire with low interspike intervals during 80 Hz auditory stimulation was reduced in Df(h15q13)/+ mice, an effect that was partially reversed by the Kv3.1 channel modulator, RE1.ConclusionThis study offers insight into the consequences on a neuronal level of carrying the 15q13.3 microdeletion. Furthermore, it points to deficient functioning of interneurones as a potential pathophysiological mechanism in schizophrenia and suggests a therapeutic potential of Kv3.1 channel openers.

근막통증증후군의 통증유발점 치료를 위한 멀티어레이 전극과 프로그램 가능한 다채널 전기자극기 개발

Abstract: In this study, Multi-Array Electrodes (MAE) and Programmable Multi-channel Electrical Stimulator(PMES) were implemented for firing Trigger Points (TPs) of the patient with Myofascial Pain Syndrome (MPS). MAEhas 25 Ag/AgCl electrodes arranged in the form of array (5×5) fabricated with flexible pad, which are applicable tobe easy-attached to curved specific region of the human body. PMES consisted of 25 channels. Each channel wasto generate various electric stimulus patterns (ESPs) by changing the mono-phasic or bi-phasic of ESP, On/Off dura-tion of ESP, the interval between ESP, and amplitude of ESP. PMES hardware was composed of Host PC, StimulationPattern Editing Program (SPEP), and Multi-channel Electrical Stimulator (MES). Experiments were performed usingMAE and PMES as the following. First experiment was performed to evaluate the function for each channel of Sub-Micro Controller Unit (SMCU) in MES. Second experiment was conducted on whether ESP applied from each chan-nel of SMCU in PMES was focused to the electrode set to the ground, after applying ESP being output from eachchannel of SMCU in PMES to MAE.Key words: programmable, stimulator, trigger point, multi-array, multi-channel

In vivo real-time monitoring system of electroporation mediated control of transdermal and topical drug delivery

Electroporation (EP) is a physical method for the delivery of molecules into cells and tissues, including the skin. In this study, in order to control the degree of transdermal and topical drug delivery, EP at different amplitudes of electric pulses was evaluated. A new in vivo real-time monitoring system based on fluorescently labeled molecules was developed, for the quantification of transdermal and topical drug delivery. EP of the mouse skin was performed with new non-invasive multi-array electrodes, delivering different amplitudes of electric pulses ranging from 70 to 570V, between the electrode pin pairs. Patches, soaked with 4kDa fluorescein-isothiocyanate labeled dextran (FD), doxorubicin (DOX) or fentanyl (FEN), were applied to the skin before and after EP. The new monitoring system was developed based on the delivery of FD to and through the skin. FD relative quantity was determined with fluorescence microscopy imaging, in the treated region of the skin for topical delivery and in a segment of the mouse tail for transdermal delivery. The application of electric pulses for FD delivery resulted in enhanced transdermal delivery. Depending on the amplitude of electric pulses, it increased up to the amplitude of 360V, and decreased at higher amplitudes (460 and 570V). Topical delivery steadily enhanced with increasing the amplitude of the delivered electric pulses, being even higher than after tape stripping used as a positive control. The non-invasive monitoring of the delivery of DOX, a fluorescent chemotherapeutic drug, qualitatively and quantitatively confirmed the effects of EP at 360 and 570V pulse amplitudes on topical and transdermal drug delivery. Delivery of FEN at 360 and 570V pulse amplitudes verified the observed effects as obtained with FD and DOX, by the measured physiological responses of the mice as well as FEN plasma concentration. This study demonstrates that with the newly developed non-invasive multi-array electrodes and with the varying electric pulse amplitude, the amount of topical and transdermal drug delivery to the skin can be controlled. Furthermore, the newly developed monitoring system provides a tool for rapid real-time determination of both, transdermal and topical delivery, when the delivered molecule is fluorescent.

Heterotopic low-frequency stimulation induces nociceptive LTD within the same central receptive field in man

Electrical low-frequency stimulation (LFS) evokes long-term depression (LTD) of nociception. Human studies suggested a strictly homotopic organization. This study hypothesizes that even heterotopic LFS evokes LTD within the same receptive field (RF). In 33 healthy volunteers, painful electrical test stimulation and LFS were applied to the low back by a concentric electrode (ExpBack) and to the forearm by a multiarray electrode (ExpArm). Volunteers rated pain perception during test stimulation that was applied before and after LFS. In ExpBack, test stimuli were administered within the right T12 dermatome. LFS was applied heterotopically within the same RF or remote in dermatome T8. In ExpArm, test stimulation was carried out in the center of the RF whereas LFS was applied to the center, margin, or outside the RF. In ExpBack (n=20), pain ratings decreased significantly stronger in T12 than in T8 dermatome (P<0.01). In ExpArm (n=20), LFS to the center of the RF induced a stronger pain reduction than LFS applied outside the RF (P<0.001). This study demonstrates a heterosynaptic organization of LTD within the same RF. Profound knowledge about RF involvement on LTD seems crucial in order to judge the quality of LFS as a possible neuromodulatory treatment of pain.

A model for transcutaneous current stimulation: simulations and experiments

Complex nerve models have been developed for describing the generation of action potentials in humans. Such nerve models have primarily been used to model implantable electrical stimulation systems, where the stimulation electrodes are close to the nerve (near-field). To address if these nerve models can also be used to model transcutaneous electrical stimulation (TES) (far-field), we have developed a TES model that comprises a volume conductor and different previously published non-linear nerve models. The volume conductor models the resistive and capacitive properties of electrodes, electrode-skin interface, skin, fat, muscle, and bone. The non-linear nerve models were used to conclude from the potential field within the volume conductor on nerve activation. A comparison of simulated and experimentally measured chronaxie values (a measure for the excitability of nerves) and muscle twitch forces on human volunteers allowed us to conclude that some of the published nerve models can be used in TES models. The presented TES model provides a first step to more extensive model implementations for TES in which e.g., multi-array electrode configurations can be tested.

A multiarray electrode mapping method for percutaneous thermocoagulation as treatment of trigeminal neuralgia. Technical note on a series of 178 consecutive procedures

Background We describe our method and mapping technique of the trigeminal nerve using a quadripolar electrode to minimize morbidity of percutaneous thermocoagulation as treatment of trigeminal neuralgia. Method Of 381 patients selected for postgasserian thermocoagulation, 178 consecutive procedures were carried out using, in most cases, our painless and ambulatory method and technique. All patients were preoperatively subjected to 3-dimensional constructive interference in steady-state magnetic resonance and magnetic resonance angiography. Transgasserian introduction of our quadripolar multiarray electrode under constant fluoroscopic monitoring is used with systematic recording of radiologic angles at, in front of, and behind the clivus profile, always below the selar floor. The individual's somatotopic map based on the verbal responses of 34 facial subsegments in lieu of the usual 3 is carefully established. Lesions are aimed at the trigger of pain and restricted to fibers with the lowest thresholds. Maximal lesions are one third the size used in conventional thermocoagulation. Lesions attempt to avoid damage to the first division, uninvolved fibers, and the motor division. Results Pre- and postoperatory thresholds demonstrate that trigger-aimed small lesions do not extend to unwanted subsegments. The described technique can minimize unnecessary complications from percutaneous thermocoagulation.

Real-time detection of neurotransmitter release and its spatial distribution

Neurotransmitters have been well known as information carriers for a long time. Recently, some of the research indicated their neurotoxicity, while some indicated their neurotrophic actions. It is very important to understand the role of neurotransmitters. Glutamate is one of the most important excitatory neurotransmitter in the brain. We developed a novel measurement method for glutamate. The method we describe here is based on the enzyme-mediated electrochemical detection. Glutamate oxidase and horseradish peroxidase were deposited together with polymer-mediator on the electrode. We applied this idea on ITO multi-array electrode and developed a 64 channel multi-array sensor. The sensor permits us to detect glutamate release from multiple regions simultaneously in real time. As it is possible to illustrate the distribution of glutamate release, the sensor could be used not only in the pharmacological field, but also in medical treatment in the near future.

Hippocampal LTP observed by Multi-Array-Electrodes

Hippocampal LTP, well known as the learning model, is induced by tetanic stimulation to CA1 region in the hippocampus. The microelectrode techniques is advantageous in temporal resolution, while that of optical probing by functional dyes has advantage to spatial resolution. For long period observation from wider area, the recording by multi-array-electrode (MAE) is desirable. We applied MAE to the hippocampal slice to analyze the signal transudation property at the cellular level.