Multiple Simultaneous Recordings Research Articles

Slow-Wave Recordings From Micro-Sized Neural Clusters Using Multiwell Type Microelectrode Arrays.

The use of microelectrode array (MEA) recordings is a very effective neurophysiological method because it is able to continuously and noninvasively obtain the spatiotemporal information of electrical activity from many neurons constituting a neural network. Very recently, studies have been published that used MEAs for the measurement of a low-frequency component of electrical activity as an indicator of diverse activity of cultured neurons. The occurrence of low-frequency activities has electrophysiological information that does not include the information from fast spikes. However, there is no in vitro experimental model suitable for measuring the low-frequency activities (slow-waves) for further study. Neural clusters consisting of dozens of neurons were placed directly onto each electrode of an MEA from which fast spikes and slow-waves were measured. We obtained sufficient data on the early development patterns of the slow-waves and the spikes measured from many independent neural clusters confirming that the slow-waves occurred first before the emergence of the spikes in the neural clusters. We also showed that changes in the occurrence frequency of the slow-waves for synaptic blockers were measured from a large number of independent cultures. Microsized neural cluster arrays, which can be combined with conventional MEAs, are suitable for multiple simultaneous recordings of slow-waves. Our technology provides a simple but useful method to study the generation of a low-frequency component of the electrical activity in cultured neural networks that are not yet well known as well as to expand the use of conventional MEAs.

(Invited) Chip Based Electrochemical Imaging of Neuron Transmitters Expression at Single PC12 Cell and 3-D Spheroids Level

Understanding and controlling the interface between neuronal cells and neuronal network and electrical devices is vital to both biological science and technology. Recent developments in the field of in vitro neuron mapping focus on the development of optical and electrochemical strategies for either single neuron cell/neuron measurement or artificial neuronal networks/brain slices mapping. To mimic in vivo neuronal networks and to elucidate the mechanisms of computation, spontaneous and elicited electrical activity need to be monitored, and multiple simultaneous recordings are required for monitoring individual unit and collective network activity. In this way, both individual cells and cell networks can be scrutinized in order to understand how changes in single unit activity and functionality. In the present study, we developed a large-scale integration -based amperometric sensor array system for electrochemical bioimaging and throughput sensing of dopamine expression from three-dimensional (3D)-cultured PC12 cells upon dopaminergic drugs exposure. It has been shown that individual cells behave differently from the population even under the identical conditions, as a complementary study, we also explore the possibility of single cell-on-chip based analytical technique which can collect real-time change in cell physiology by measurement of cell exocytosis, i.e., release of neurotransmitters, in a neuronal model cell line, i.e. PC12 cells. The study of single cell dynamics could help us better understand the complex processes, such as, neurotransmitter kinetics, ion channel functions, and cell communications, single cell analysis can be an equivalent and complementary strategy to existing approaches.

Advanced target identification in STN-DBS with beta power of combined local field potentials and spiking activity

BackgroundIn deep brain stimulation of the subthalamic nucleus (STN-DBS) for Parkinson's Disease (PD), often microelectrode recordings (MER) are used for STN identification. However, for advanced target identification of the sensorimotor STN, it may be relevant to use local field potential (LFP) recordings. Then, it is important to assure that the measured oscillations are coming from the close proximity of the electrode. New methodThrough multiple simultaneous recordings of LFP and neuronal spiking, we investigated the temporal relationship between local neuronal spiking and more global LFP. We analyzed the local oscillations in the LFP by calculating power only over specific frequencies that show a significant coherence between LFP and neuronal spiking. Using this ‘coherence method’, we investigated how well measurements in the sensorimotor STN could be discriminated from measurements elsewhere in the STN. Results/comparison with existing methodsThe ‘sensorimotor power index’ (SMPI) of beta frequencies, representing the ability to discriminate sensorimotor STN measurements based on the beta power, was significantly larger using the ‘coherence method’ for LFP spectral analysis compared to other methods where either the complete LFP beta spectrum or only the prominent peaks in the LFP beta spectrum were used to calculate beta power. ConclusionsThe results suggest that due to volume conduction of beta frequency oscillations, proper localization of the sensorimotor STN with only LFP recordings is difficult. However, combining recordings of LFP and neuronal spiking and calculating beta power over the coherent parts of the LFP spectrum can be beneficial in discriminating the sensorimotor STN.

Assignment of Empirical Mode Decomposition Components and Its Application to Biomedical Signals.

Empirical mode decomposition (EMD) is a frequently used signal processing approach which adaptively decomposes a signal into a set of narrow-band components known as intrinsic mode functions (IMFs). For multi-trial, multivariate (multiple simultaneous recordings), and multi-subject analyses the number and signal properties of the IMFs can deviate from each other between trials, channels and subjects. A further processing of IMFs, e.g. a simple ensemble averaging, should determine which IMFs of one signal correspond to IMFs from another signal. When the signal properties have similar characteristics, the IMFs are assigned to each other. This problem is known as correspondence problem. From the mathematical point of view, in some cases the correspondence problem can be transformed into an assignment problem which can be solved e.g. by the Kuhn-Munkres algorithm (KMA) by which a minimal cost matching can be found. We use the KMA for solving classic assignment problems, i.e. the pairwise correspondence between two sets of IMFs of equal cardinalities, and for pairwise correspondences between two sets of IMFs with different cardinalities representing an unbalanced assignment problem which is a special case of the k-cardinality assignment problem. A KMA-based approach to solve the correspondence problem was tested by using simulated, heart rate variability (HRV), and EEG data. The KMA-based results of HRV decomposition are compared with those obtained from a hierarchical cluster analysis (state-of-the-art). The major difference between the two approaches is that there is a more consistent assignment pattern using KMA. Integrating KMA into complex analysis concepts enables a comprehensive exploitation of the key advantages of the EMD. This can be demonstrated by non-linear analysis of HRV-related IMFs and by an EMD-based cross-frequency coupling analysis of the EEG data. The successful application to HRV and EEG analysis demonstrates that our solutions can be used for automated EMD-based processing concepts for biomedical signals.

Re‐emerging microneurography

Re‐emerging microneurography

On the analysis of single versus multiple channels of electromagnetic brain signals

When extracting information from electromagnetic (EM) brain function through recordings such as the electroencephalogram (EEG) it is often assumed that signal processing techniques must be applied to multiple simultaneous recordings in order to obtain useful results. However, sometimes only a single channel of EEG recording is available or desirable. In this paper we objectively assess a novel methodology which exploits only a single measurement channel to extract information of interest relatively independent of channel location (relative to the source of interest). The method relies on a combination of a matrix of delay vectors constructed from the single channel measurement, along with constrained independent component analysis, which incorporates prior information into the process. Here, we use synthetically generated seizure EEG, composed of real, normal multi-channel EEG onto which is superimposed synthetic epileptic "seizure-like" activity, at different signal-to-noise (SNR) levels, through an equivalent current dipole model. We show that the method can extract desired information from single channels with a reasonable accuracy even at very small SNR and from channels distant from the focus of the activity. This provides a powerful technique capable of extracting multiple sources underlying single channel recordings and will be useful in situations where only single channel EM recordings of brain function are desirable, such as would be the case in wearable or implantable recording devices.

Application of Direction of Arrival for Slow Wave Propagation in Isolated Duodenum

The technique of multiple simultaneous recordings from a large number of extracellular electrodes (>100) is currently used in the study of normal and abnormal electrical conduction in the heart and the genesis of cardiac arrhythmias. To investigate whether such a system could also be applied in gastrointestinal electrophysiology, several studies were performed with this technique on segments of isolated rabbit duodenum. A multiple electrode assembly consisting of 240 silver wires was positioned on the serosal surface of the duodenum and the recorded signals were, after suitable processing, stored. Thereafter, analysis of all simultaneously recorded slow waves during a selected period of time was performed to reconstruct the pattern of conduction in the duodenum. The first method based on isochrine contours shows considerable pattern through which the pacemaker(s) location(s) would be determined as well as the main direction of propagation. Its output results are sensitive to signal conversion and quantization error and it will show noticeable error if signal-to-noise ratio increases. Moreover, it assumes the homogenous characteristic of the tissue. On the other hand, the second method based on Multiple Signal Classification (MUSIC) technique overcomes the sources of errors mentioned with the first method. It gives the spatial variation of Direction of Arrival (DOA) which is confirmed with the inhomogenity of the tissue.This property is very helpful to follow up the variation of conduction velocity over the sample.

Slow and fast (gamma) neuronal oscillations in the perirhinal cortex and lateral amygdala.

Most lesion studies emphasize the distinct contributions of the amygdala and perirhinal cortex to memory. Yet, the presence of strong reciprocal excitatory projections between these two structures suggests that they are functionally coupled. To gain some insight into this issue, the present study examined whether the close anatomical ties existing between perirhinal and lateral amygdala (LA) neurons are expressed in their spontaneous activity. To this end, multiple simultaneous recordings of single unit discharges and local field potentials were performed in the LA and perirhinal cortex in ketamine-xylazine anesthetized cats. The perirhinal cortex and LA exhibited a similar pattern of spontaneous activity. Recordings at both sites were dominated by a slow focal oscillation at 1 Hz onto which was superimposed a faster rhythm (approximately 30 Hz) whose amplitude fluctuated cyclically. Computing crosscorrelograms between focal waves recorded simultaneously in the perirhinal cortex and LA revealed a close relationship between their spontaneous activity. Even when recording sites were separated by as much as 8 mm, the slow focal oscillation remained highly correlated (r > or = 0.7). In contrast, the correlation between fast oscillations was usually lower (r approximately 0.3). Perievent histograms of neuronal discharges revealed that the firing probability of most LA and perirhinal neurons increased during the depth-negative component of the slow oscillation. In addition, respectively, 47 and 64% of LA and perirhinal neurons exhibited a significant modulation of firing probability in relation to the fast oscillations. Finally, crosscorrelating unit discharges simultaneously recorded in the LA and perirhinal cortex confirmed the presence of phase-related oscillatory events in both structures. In summary, our results suggest that the interconnections existing between the perirhinal cortex and LA can support the genesis of coherent neuronal activities at various frequencies. These results imply that cooperative interactions must be taking place between these structures.

How to map and ablate atrial scar macroreentrant tachycardia of the right atrium

A special form of macroreentrant atrial tachycardia (MRAT), due to reentrant activation around surgical scars, can occur in patients after cardiac surgery. Scar MRAT occurs usually after correction of congenital defects, such as atrial or ventricular septal defects, and especially after Mustard, Senning or Fontan procedures, but it can occur also after myxoma, valvular or coronary bypass surgery. The simplest form of scar MRAT is reentry around a lateral right atrial surgical scar. A basic mapping array with multiple simultaneous recordings from the anterior and septal right atrium is very useful to make the electrophysiological diagnosis. A line of double electrograms can be mapped in the centre of the circuit and a fragmented electrogram usually marks the pivoting point between the inferior end of the scar and the inferior vena cava (IVC). Extension of the scar toward the closest fixed obstacle, usually the IVC, by means of radiofrequency ablation, can interrupt the tachycardia and make it non-inducible. Typical atrial flutter usually coexists with scar MRAT and flutter isthmus ablation is probably indicated in all cases. In patients having undergone baffle atrial surgery it can be impossible to map the whole circuit and entrainment-mapping is helpful to localize critical isthmuses in the circuit. After the Fontan operation the right atrium can be severely dilated and scarred, and multiple, complex reentry circuits can be found. Left atrial MRAT based on large areas of scar has been described, but there is still too little experience with these to propose general rules for diagnosis and management.

Atrial flutter ablation: electrophysiological landmarks.

Understanding the configuration of the whole flutter circuit is for us the only valid parameter allowing the design of an ablation strategy. Fragmented or double electrograms may have different meanings in different parts of the circuit, and full activation mapping is the best clue to their interpretation. Correlation of anatomy with activation sequence will mark the best ablation target (isthmus) in each case. Multiple simultaneous recordings from the septum and right atrial anterior wall are very helpful to rapidly diagnose circular activation of the right atrium. In cases without this type of activation, coronary sinus recordings and the study of postentrainment cycles are helpful to localize the reentry circuit.

Multielectrode mapping of slow-wave activity in the isolated rabbit duodenum

The technique of multiple simultaneous recordings from a large number of extracellular electrodes (> 100) is currently used in the study of normal and abnormal electrical conduction in the heart and the genesis of cardiac arrhythmias. To investigate whether such a system could also be applied in gastrointestinal electrophysiology, several studies were performed with this technique on segments of isolated rabbit duodenum. A multiple-electrode assembly consisting of 240 silver wires was positioned on the serosal surface of the duodenum, and the recorded signals were, after suitable processing, stored. Thereafter, analysis of all simultaneously recorded slow waves during a selected period of time was performed to reconstruct the pattern of conduction in the duodenum. The first results show that there is a considerable variation in conduction pattern, which is determined by the site of the natural pacemaker. Several experiments were performed to rule out possible deleterious effects of positioning the multiple-electrode assembly on the duodenum. Furthermore, prolonged periods of recording did not influence propagation speed and pattern provided that the positioning of the multiple electrode assembly was performed with care. Entrainment of the natural pacemaker was possible by applying electrical stimuli through 2 of the 240 extracellular electrodes during simultaneous recordings. In conclusion, multisite extracellular mapping of gastrointestinal smooth muscle is possible and can be used to study origin and spread of slow-wave activity.

Coordination of electrical activities in muscle layers of the pig colon

Simultaneous recording of electrical activities from the circular and longitudinal muscle layers of the pig colon was performed in vitro to study possible coordination of activities. The electrical activity of both muscle layers consisted of electrical oscillations with superimposed spikes. The frequency range of the electrical oscillations in the circular muscle was 0.5-3.5 cycles per minute (cpm) and in the longitudinal muscle 24-42 cpm. Coordination of the activities of both muscle layers occurred consistently only after stretch or cholinergic stimulation. Then it occurred in a unique fashion. Each oscillation in the circular muscle layer occurred at the same time as the onset of a burst of oscillations in the longitudinal muscle. In addition, multiple simultaneous recordings of the electrical activities from each muscle layer were obtained showing that within the circular muscle layer electrical oscillations were phase locked in the circumferential direction and along the long axis of the colon. They appeared to propagate in either the oral or aboral direction. In tetrodotoxin (with stretch as stimulus) and also in presence of carbachol, bursts of oscillations in the longitudinal muscle layer were phase locked circumferentially (in the different taeniae) and longitudinally. This study shows that the muscle layers in the colon, which have different myogenic electrical activities, can obtain a high level of coordination.

CONTROLLED CLINICAL STUDY OF THE CARDIOVASCULAR EFFECTS OF THE NEW LOCAL ANAESTHETIC MY 33—7, USING A SYSTEM OF MULTIPLE SIMULTANEOUS RECORDINGS

With the aid of a non-invasive system of multiple simultaneous recordings a study was carried out in two groups of ten patients free from circulatory disorders, to compare the effects on the circulatory system of MY 33—7, a new local anaesthetic, with those of lignocaine. The two drugs were administered subcutaneously in 20–ml doses and in equi-active concentrations, 0.5 per cent for MY 33—7 and 2 per cent for lignocaine. The multiple records were read before and 30 minutes after administration of the anaesthetics. It is concluded that: (1) The stroke volume is lowered by both anaesthetics. (2) Lignocaine reduces the voltage of the T wave in the electrocardiogram, and depresses the conduction mechanisms of the heart; this does not occur with MY 33—7. (3) MY 33—7 might therefore be safer than lignocaine for use in patients suffering from disorders of conduction