CMOS microelectrode array for bidirectional interaction with neuronal networks

A CMOS metal-electrode-based micro system for bidirectional communication (stimulation and recording) with neuronal cells in vitro is presented. The chip overcomes the interconnect challenge that limits today's bidirectional microelectrode arrays. The microsystem has been fabricated in an industrial CMOS technology with several post-CMOS processing steps to realize 128 biocompatible electrodes and to ensure chip stability in physiological saline. The system comprises all necessary control circuitry and on-chip A/D and D/A conversion. A modular design has been implemented, where individual stimulation- and signal-conditioning circuitry units are associated with each electrode. Stimulation signals with a resolution of 8 bits can be sent to any subset of electrodes at a rate of 60 kHz, while all electrodes of the chip are continuously sampled at a rate of 20 kHz. The circuitry at each electrode can be individually reset to its operating point in order to suppress artifacts evoked by the stimulation pulses. Biological measurements from cultured neuronal networks originating from dissociated cortical tissue of fertilized chicken eggs with amplitudes of up to 500 /spl mu/V/sub pp/ are presented.     

微电极阵列检测细胞电生理仿真与设计

测量细胞电生理信号的方法--微电极阵列检测技术,是指在微电极表面首先培养可兴奋性细胞,然后进行电信号的实时监测,该方法具有检测通道数多、无损伤性、响应速度快、制备工艺简单、可长期检测等优点。借助Stern双电层模型阐述了微电极-电解液界面的电化学过程,采用电路仿真软件Multisim构建了完整的细胞-微电极等效电路来定量分析电化学过程;对于等效电路中的物理量取不同的数值进行仿真,研究它们对信号大小的影响程度并基于此给出了具体的微电极参数设计方案;设计检测电路并进行仿真,验证该电路满足检测需求。构建出完整的电生理等效电路,给出微电极阵列参数设计方案,设计出检测电路,为进一步电生理测试中的MEMS加工制造和电路研制提供了参考。     

Chronic neural recording using silicon-substrate microelectrode arrays implanted in cerebral cortex

An important aspect of the development of cortical prostheses is the enhancement of suitable implantable microelectrode arrays for chronic neural recording. The objective of this study was to investigate the recording performance of silicon-substrate micromachined probes in terms of reliability and signal quality. These probes were found to consistently and reliably provide high-quality spike recordings over extended periods of time lasting up to 127 days. In a consecutive series of ten rodents involving 14 implanted probes, 13/14 (93%) of the devices remained functional throughout the assessment period. More than 90% of the probe sites consistently recorded spike activity with signal-to-noise ratios sufficient for amplitudes and waveform-based discrimination. Histological analysis of the tissue surrounding the probes generally indicated the development of a stable interface sufficient for sustained electrical contact. The results of this study demonstrate that these planar silicon probes are suitable for long-term recording in the cerebral cortex and provide an effective platform technology foundation for microscale intracortical neural interfaces for use in humans.     

Aligned microcontact printing of micrometer-scale poly-L-lysine structures for controlled growth of cultured neurons on planar microelectrode arrays

We describe a method for producing high-resolution chemical patterns on surfaces to control the attachment and growth of cultured neurons. Microcontact printing has been extended to allow the printing of micron-scale protein lines aligned to an underlying pattern of planar microelectrodes. Poly-L-lysine (PL) lines have been printed on the electrode array for electrical studies on cultured neural networks. Rat hippocampal neurons showed a high degree of attachment selectivity to the PL and produced neurites that faithfully grew onto the electrode recording sites.     

Avoiding interference in planar arrays through the use of artificial neural networks

This article implements an artificial neural network to find, through computer simulation, the excitations of a square planar array. The array is composed of 52 uniformly spaced subarrays, and has a quasi- in its radiation diagram. This simulation model includes the reduction of any signal interference in the shaped radiating zone after its position has been determined.     

Arbitrary footprint patterns from planar arrays with complexexcitations

Elliott and Stern's (1990) method for synthesising shaped patterns using a circular or elliptical planar aperture or array with a complex excitation distribution is generalised to allow the synthesis of footprints of arbitrary shape. The use of complex excitations allows a given footprint to be synthesised using a smaller array than with real excitations. The procedure is illustrated by synthesising a square footprint using an array with a rectangular grid     

Analysis of planar slot arrays using magnetic currents andmagnetomotive force

An effective approach to the analysis of planar slot arrays constructed on a metal-coated dielectric slab is suggested. In the framework of the method, radiation and scattering characteristics of such arrays are obtained from treating the problem of guided mode diffraction with a finite number of transverse slots cut in metallization. The idea of magnetic currents and magnetomotive force is used to solve the problem; in doing so, mutual relations between the slots are taken into consideration. Some numerical results in the specific case of a uniform finite-periodic array are given. Moreover, the design problem aimed at reduction of sidelobes using nonuniform quasi-periodic slot arrays is considered. Applying the proposed analysis to the designed array, one can determine the deviation of actual radiation characteristics from the desired ones, thus correcting the design procedure if necessary     

Free-space multistage optical interconnection networks using microlens arrays

Optical interconnections suitable for three-dimensional combining of lens arrays are presented. A multistage interconnection network with a self-routing function is described. The number of light paths this network is estimated to be capable of handling roughly ten or more times that of previously reported self-routing networks. Two separate lens arrays were fabricated to construct an 8×8 network of this design. The feasibility of the proposed interconnections was successfully demonstrated     

Inband scattering from arrays with series feed networks

Approximate equations are presented for the radar cross section (RCS) of a phased array antenna with a series feed beamforming network. The incident radar wave is assumed to be at the same frequency as the antenna operating frequency. In deriving the RCS formulas, multiple reflections are neglected, and like devices in the feed are assumed to have identical transmission and reflection coefficients. The approximate results are shown to be in excellent agreement with results obtained using a scattering matrix approach. The behavior of the RCS as a function of several feed design parameters is also investigated     

Null steering in rectangular planar arrays by amplitude control using genetic algorithms

Null steering in rectangular planar arrays has been achieved when only the amplitudes of the array elements are perturbed. Genetic algorithms were employed to solve the problem of null steering in uniform and Chebyshev planar arrays. Mathematical expressions for the planar array factor were derived from the linear array factor expression. The results show that nulls can be accurately steered to the required real space directions with the minimal disturbance to the other array parameters and at the same time achieve any prescribed null depth.     

In-band scattering from arrays with parallel feed networks

Approximate closed-form expressions are derived for in-band scattering from an array antenna with parallel (corporate) feed networks. Multiple reflections are neglected and feed devices of the same type are assumed to have identical electrical characteristics. The model is shown to be in good agreement with results generated using a scattering matrix formulation. Based on computed data, the characteristics of array scattering are discussed     

Analysis of cultured neuronal networks using intraburst firing characteristics

It is an open question whether neuronal networks, cultured on multielectrode arrays, retain any capability to usefully process information (learning and memory). A necessary prerequisite for learning is that stimulation can induce lasting changes in the network. To observe these changes, one needs a method to describe the network in sufficient detail, while stable in normal circumstances. We analyzed the spontaneous bursting activity that is encountered in dissociated cultures of rat neocortical cells. Burst profiles (BPs) were made by estimating the instantaneous array-wide firing frequency. The shape of the BPs was found to be stable on a time scale of hours. Spatiotemporal detail is provided by analyzing the instantaneous firing frequency per electrode. The resulting phase profiles (PPs) were estimated by aligning BPs to their peak spiking rate over a period of 15 min. The PPs reveal a stable spatiotemporal pattern of activity during bursts over a period of several hours, making them useful for plasticity and learning studies. We also show that PPs can be used to estimate conditional firing probabilities. Doing so, yields an approach in which network bursting behavior and functional connectivity can be studied.     

Simultaneous measurement of intracellular calcium and electricalactivity from patterned neural networks in culture

Multisite extracellular electrical activity and intracellular calcium were recorded simultaneously. Electrical signals were measured using microelectrode array substrates. A novel cell positioning technique was combined with a method for controlling neurite outgrowth, which allowed cell-electrode contacts to be established easily, thus facilitating the electrical recording. Intracellular calcium was measured optically using the indicator fluo-3. Under low-magnesium conditions, cultured rat cortical neurons showed periodic transients of fluo-3 fluorescence, which were synchronized with the periodic bursting observed electrically. The intervals between bursts could be determined by electrical stimulation through the substrate electrodes. The results suggest that functional synaptic connections are formed in the culture system     

Antenna far-fields from planar acquisition using micro-genetic algorithms

A method for modelling the radiation of an antenna under test from planar near-field data using equivalent magnetic currents (EMC) is presented. Micro-genetic algorithms are used to optimise each component of the EMC. Numerical results of near-field to far-field transformation are reported and discussed.     

Optimal discrimination and classification of neuronal actionpotential waveforms from multiunit, multichannel recordings usingsoftware-based linear filters

Describes advanced protocols for the discrimination and classification of neuronal spike waveforms within multichannel electrophysiological recordings. The programs are capable of detecting and classifying the spikes from multiple, simultaneously active neurons, even in situations where there is a high degree of spike waveform superposition on the recording channels. The protocols are based on the derivation of an optimal linear filter for each individual neuron. Each filter is tuned to selectively respond to the spike waveform generated by the corresponding neuron, and to attenuate noise and the spike waveforms from all other neurons. The protocol is essentially an extension of earlier work (S. Andreassen et al., 1979; W.M. Roberts and D.K. Hartline, 1975; R.B. Stein et al., 1979). However, the protocols extend the power and utility of the original implementations in two significant respects. First, a general single-pass automatic template estimation algorithm was derived and implemented. Second, the filters were implemented within a software environment providing a greatly enhanced functional organization and user interface. The utility of the analysis approach was demonstrated on samples of multiunit electrophysiological recordings from the cricket abdominal nerve cord     

A dual band-pass amplifier-filter circuit for simultaneous recording of spikes and local field potentials from live neuronal tissue using multielectrode arrays

The paper presents the design and test results of a novel circuit with dual band-pass filter for simultaneous recording of Local Filed Potentials and spikes from individual neurons. Single readout channel is built of an input AC-coupling circuit with the cut-off frequency below 0.1 Hz, a low noise preamplifier and two parallel band-pass filters with nominal bandwidths from 2 Hz to 100 Hz and from 200 Hz to 2 kHz. The design is optimized for low noise, high dynamic range, and low power dissipation. The circuit has been designed and manufactured in a 0.35 μm CMOS process as a multichannel chip comprising also an analog multiplexer for serialization of the analog output signals.     

人工神经网络在金相图像分割中的应用研究

利用多层感知器神经网络和自组织映射神经网络对球墨铸铁、可锻铸铁和灰铸铁的金相图像进行了分割提取.通过对比以上两种方法分割后的图像质量和定量分析样本图像中的石墨结构、珍珠岩/铁氧体结构所占的百分含量后发现,多层感知器网络分割提取的结果与样本实际的结果更加接近,而自组织映射神经网络分割提取的结果则不够理想.据此,可以推断多层感知器网络是实现金属图像分割自动化提取和精确性分析的有效工具.     

EMI reduction from airflow aperture arrays using dual-perforatedscreens and loss

Airflow perforations in shielding enclosures can act as apertures facilitating the coupling from internal sources to external electromagnetic interference (EMI). This EMI radiation for single- and dual-screen configurations was studied herein experimentally and with finite-difference time domain (FDTD) modeling. A general EMI reduction of more than 20 dB was achieved for dual-perforated screens spaced 1 cm apart when compared to EMI for a single perforated screen. However, in the dual-screen case, the space between the screens can act as a thin cavity, which, in turn, can lead to significant radiation at distinct angles. Damping the resonances by loading the space between the screens with lossy material mitigates this problem and achieves more than 20-dB reduction over a single screen     

Investigating the neural correlates of pathological cortical networks in Alzheimer's disease using heterogeneous neuronal models

This paper describes an investigation into the pathophysiological causes of abnormal cortical oscillations in Alzheimer's disease (AD) using two heterogeneous neuronal network models. The effect of excitatory circuit disruption on the beta band power (13-30 Hz) using a conductance-based network model of 200 neurons is assessed. Then, the neural correlates of abnormal cortical oscillations in different frequency bands based on a larger network model of 1000 neurons consisting of different types of cortical neurons are also analyzed. EEG studies in AD patients have shown that beta band power (13-30 Hz) decreased in the early stages of the disease with a parallel increase in theta band power (4-7 Hz). This abnormal change progresses with the later stages of the disease but with decreased power spectra in other fast frequency bands plus an increase in delta band power (1-3 Hz). Our results show that, despite the heterogeneity of the network models, the beta band power is significantly affected by excitatory neural and synaptic loss. Second, the results of modeling a functional impairment in the excitatory circuit shows that beta band power exhibits the most decrease compared with other bands. Previous biological experiments on different types of cultural excitatory neurons show that cortical neuronal death is mediated by dysfunctional ionic behavior that might specifically contribute to the pathogenesis of β-amyloid-peptide-induced neuronal death in AD. Our study also shows that beta band power was the first affected component when the modeled excitatory circuit begins to lose neurons and synapses.     

Low-sidelobe patterns from linear and planar arrays with uniformexcitations except for phases of a small number of elements

The use of genetic algorithms allows synthesis of linear and planar arrays with excitations of uniform amplitude that generate radiation patterns with sidelobe levels closely approaching the recognised minima for phase-only control, in spite of only a small number of elements having non-zero phase