A Fully Automated Approach to Spike Sorting

Abstract. This paper introduces a new frequency-domain approach to describe the relationships (direction of information flow) between multivariate time series based on the decomposition of multivariate partial coherences computed from multivariate autoregressive models. We discuss its application and compare its performance to other approaches to the problem of determining neural structure relations from the simultaneous measurement of neural electrophysiological signals. The new concept is shown to reflect a frequency-domain representation of the concept of Granger causality.

Partial directed coherence: a new concept in neural structure determination

For the analysis of neuronal cooperativity, simultaneously recorded extracellular signals from neighboring neurons need to be sorted reliably by a spike sorting method. Many algorithms have been developed to this end, however, to date, none of them manages to fulfill a set of demanding requirements. In particular, it is desirable to have an algorithm that operates online, detects and classifies overlapping spikes in real time, and that adapts to non-stationary data. Here, we present a combined spike detection and classification algorithm, which explicitly addresses these issues. Our approach makes use of linear filters to find a new representation of the data and to optimally enhance the signal-to-noise ratio. We introduce a method called "Deconfusion" which de-correlates the filter outputs and provides source separation. Finally, a set of well-defined thresholds is applied and leads to simultaneous spike detection and spike classification. By incorporating a direct feedback, the algorithm adapts to non-stationary data and is, therefore, well suited for acute recordings. We evaluate our method on simulated and experimental data, including simultaneous intra/extra-cellular recordings made in slices of a rat cortex and recordings from the prefrontal cortex of awake behaving macaques. We compare the results to existing spike detection as well as spike sorting methods. We conclude that our algorithm meets all of the mentioned requirements and outperforms other methods under realistic signal-to-noise ratios and in the presence of overlapping spikes.

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An online spike detection and spike classification algorithm capable of instantaneous resolution of overlapping spikes

Using gel polymer electrolytes (GPEs) for lithium-ion batteries usually encounters the drawback of poor mechanical integrity of the GPEs. This study demonstrates the outstanding performance of a GPE consisting of a commercial membrane (Celgard) incorporated with a poly(ethylene oxide)-co-poly(propylene oxide) copolymer (P(EO-co-PO)) swelled by a liquid electrolyte (LE) of 1 M LiPF6 in carbonate solvents. The proposed GPE stably holds LE with an amount that is three times that of the Celgard-P(EO-co-PO) composite. This GPE has a higher ionic conductivity (2.8 × 10–3 and 5.1 × 10–4 S cm–1 at 30 and −20 °C, respectively) and a wider electrochemical voltage range (5.1 V) than the LE-swelled Celgard because of the strong ion-solvation power of P(EO-co-PO). The active ion-solvation role of P(EO-co-PO) also suppresses the formation of the solid–electrolyte interphase layer. When assembling the GPE in a Li/LiFePO4 battery, the P(EO-co-PO) network hinders anionic transport, producing a high Li+ transference number...

Poly(ethylene oxide)-co-Poly(propylene oxide)-Based Gel Electrolyte with High Ionic Conductivity and Mechanical Integrity for Lithium-Ion Batteries

Significant strides have been recently made to develop highly sensorized cybernetic prostheses aimed at restoring sensorimotor limb functions to those who have lost them because of a traumatic event (amputation). In these cases, one of the main goals is to create a bidirectional link between the artificial devices (e.g., robotic hands, arms, or legs) and the nervous system. Several human-machine interfaces (HMIs) are currently used to this aim. Among them, interfaces with the peripheral nervous system and in particular longitudinal intrafascicular electrodes can be a promising solution able to improve the current situation. In this paper, the potentials and limits of the use of this interface to control robotic devices are presented. Specific information is provided on: 1) the neurophysiological bases for the use peripheral nerve interfaces; 2) a comparison of the potentials of the different peripheral neural interfaces; 3) the possibility of extracting and appropriately interpreting the neural code for motor commands and of delivering sensory feedback by stimulating afferent fibers by using longitudinal intrafascicular electrodes; 4) a preliminary comparative analysis of the performance of this approach with the ones of others HMIs; 5) the open issues which have to be addressed for a chronic usability of this approach.

On the Use of Longitudinal Intrafascicular Peripheral Interfaces for the Control of Cybernetic Hand Prostheses in Amputees

https://nip.sjtu.edu.cn/pdf/Spike%20sorting%20based%20on%20automatic%20template%20reconstruction%20with%20a%20partial%20solution.pdf

Spike sorting based on automatic template reconstruction with a partial solution to the overlapping problem

Spike sorting is the mandatory first step in analyzing multiunit recording signals for studying information processing mechanisms within the nervous system. Extracellular recordings usually contain overlapped spikes produced by a number of neurons adjacent to the electrode, together with unknown background noise, which in turn induce some difficulties in neural signal identification. In this paper, we propose a robust method to deal with these problems, which employs an automatic overlap decomposition technique based on the relaxation algorithm that requires simple fast Fourier transforms. The performance of the presented system was tested at various signal-to-noise ratio levels based on synthetic data that were generated from real recordings.

A robust method for spike sorting with automatic overlap decomposition

Thermal Degradation of Syndiotactic Polypropylene and the Influence of Stereoregularity On the Thermal Degradation Behaviour by In Situ FTIR Spectroscopy

Correlation between spike trains or neurons sometimes indicates certain neural coding rules in the visual system. In this paper, the relationship between spike timing correlation and pattern correlation is discussed, and their ability to represent stimulus features is compared to examine their coding strategies not only in individual neurons but also in population. Two kinds of stimuli, natural movies and checkerboard, are used to arouse firing activities in chicken retinal ganglion cells. The spike timing correlation and pattern correlation are calculated by cross-correlation function and Lempel–Ziv distance respectively. According to the correlation values, it is demonstrated that spike trains with similar spike patterns are not necessarily concerted in firing time. Moreover, spike pattern correlation values between individual neurons’ responses reflect the difference of natural movies and checkerboard; neurons cooperate with each other with higher pattern correlation values which represent spatiotemporal correlations during response to natural movies. Spike timing does not reflect stimulus features as obvious as spike patterns, caused by their particular coding properties or physiological foundation. As a result, separating the pattern correlation out of traditional timing correlation concept uncover additional insight in neural coding.

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Neural coding properties based on spike timing and pattern correlation of retinal ganglion cells.

The conformational analysis of high-density poly(ethylene) (HDPE) during the melting and crystallization processes has been performed by the aid of the time-reserved Fourier transform infrared spectroscopy and multivariate analysis technique Upon heating, the conformational transition of HDPE takes place, gradually, due to the restraint of crystal lattice, and various conformational transformations can be discerned clearly However, during the cooling process, HDPE crystallizes very quickly and only one major conformational transition occurs in the crystallization process The comparison of conformational changes during the melting and crystallization processes exhibits that although the polymer crystallization is the reverse process of polymer melting, there still exist some obvious differences in the conformational transformation between them © 2006 Wiley Periodicals, Inc J Appl Polym Sci 100: 4835–4841, 2006

In situ Fourier transform infrared spectroscopic study of the conformational changes of high‐density poly(ethylene) during the melting and crystallization processes

Pu-Ming Zhang

Papers

Spike sorting based on automatic template reconstruction with a partial solution to the overlapping problem

A robust method for spike sorting with automatic overlap decomposition

Thermal Degradation of Syndiotactic Polypropylene and the Influence of Stereoregularity On the Thermal Degradation Behaviour by In Situ FTIR Spectroscopy

Neural coding properties based on spike timing and pattern correlation of retinal ganglion cells.

In situ Fourier transform infrared spectroscopic study of the conformational changes of high‐density poly(ethylene) during the melting and crystallization processes