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1.
Sci Rep ; 10(1): 21261, 2020 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-33277523

RESUMO

This paper reports on the design, development, and test of a multi-channel wireless micro-electrocorticography (µECoG) system. The system consists of a semi-implantable, ultra-compact recording unit and an external unit, interfaced through a 2.4 GHz radio frequency data telemetry link with 2 Mbps (partially used) data transfer rate. Encased in a 3D-printed 2.9 cm × 2.9 cm × 2.5 cm cubic package, the semi-implantable recording unit consists of a microelectrode array, a vertically-stacked PCB platform containing off-the-shelf components, and commercially-available small-size 3.7-V, 50 mAh lithium-ion batteries. Two versions of microelectrode array were developed for the recording unit: a rigid 4 × 2 microelectrode array, and a flexible 12 × 6 microelectrode array, 36 of which routed to bonding pads for actual recording. The external unit comprises a transceiver board, a data acquisition board, and a host computer, on which reconstruction of the received signals is performed. After development, assembly, and integration, the system was tested and validated in vivo on anesthetized rats. The system successfully recorded both spontaneous and evoked activities from the brain of the subject.

2.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3489-3492, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018755

RESUMO

In this paper a new compression technique based on the discrete Tchebichef transform is presented. To comply with strict on-implant hardware implementation requirements, such as low power dissipation and small silicon area consumption, the discrete Tchebichef transform is modified and truncated. An algorithm is proposed to generate approximate transform matrices capable of truncation without suffering from destructive energy leakage among the coefficients. This is achieved by preserving orthogonality of the basis functions that convey majority portion of the signal energy. Based on the presented algorithm, a new truncated transformation matrix is proposed, which reduces the hardware complexity by up to 74% compared to that of the original transform. Hardware implementation of the proposed neural signal compression technique is prototyped using standard digital hardware. With pre-recorded neural signals as the input, compression rate of 26.15 is achieved while the root-mean-square of error is kept as low as 1.1%.Clinical Relevance- This paper proposes a technique for data compression in high-density neural recording brain implants, along with a power- and area-efficient hardware implementation. From among clinical applications of such implants one can point to neuro-prostheses, and brain-machine interfaces for therapeutic purposes.


Assuntos
Interfaces Cérebro-Computador , Compressão de Dados , Algoritmos , Computadores , Registros
3.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 894-897, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018128

RESUMO

In this paper, a method for the detection and subsequently extraction of neural spikes in an intra-cortically recorded neural signal is proposed. This method distinguishes spikes from the background noise based on the natural difference between their time-domain amplitude variation patterns. According to this difference, a spike mask is generated, which takes on large values over the course of spikes, and much smaller values for the background noise. The "high" part of this mask is designed to be wide enough to contain a complete spike. By multiplying the input neural signal with the spike mask, spikes are amplified with a large factor while the background noise is not. The result is a spike-augmented signal with significantly larger signal-to-noise ratio, on which spike detection is performed much more easily and accurately. According to this detection mechanism, spikes of the original neural signal are extracted.Clinical Relevance-This paper presents an automatic spike detection technique, dedicated to brain-implantable neural recording devices. Such devices are developed for clinical applications such as the treatment of epilepsy, neuro-prostheses, and brain-machine interfacing for therapeutic purposes.


Assuntos
Interfaces Cérebro-Computador , Processamento de Sinais Assistido por Computador , Potenciais de Ação , Algoritmos , Razão Sinal-Ruído
4.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 898-901, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018129

RESUMO

This paper introduces a lossless approach for data reduction in multi-channel neural recording microsystems. The proposed approach benefits from eliminating the redundancy that exists in the signals recorded from the same space in the brain, e.g., local field potentials in intra-cortical recording from neighboring recording sites. In this approach, a single baseline component is extracted from the original neural signals, which is treated as the component all the channels share in common. What remains is a set of channel-specific difference components, which are much smaller in word length compared to the sample size of the original neural signals. To make the proposed approach more efficient in data reduction, length of the difference component words is adaptively determined according to their instantaneous amplitudes. This approach is low in both computational and hardware complexity, which introduces it as an attractive suggestion for high-density neural recording brain implants. Applied on multi-channel neural signals intra-cortically recorded using 16 multi-electrode array, the data is reduced by around 48%. Designed in TSMC 130-nm standard CMOS technology, hardware implementation of this technique for 16 parallel channels occupies a silicon area of 0.06 mm2, and dissipates 6.4 µW of power per channel when operates at VDD=1.2V and 400 kHz.Clinical Relevance- This paper presents a lossless data reduction technique, dedicated to brain-implantable neural recording devices. Such devices are developed for clinical applications such as the treatment of epilepsy, neuro-prostheses, and brain-machine interfacing for therapeutic purposes.


Assuntos
Interfaces Cérebro-Computador , Procedimentos Cirúrgicos Reconstrutivos , Encéfalo , Próteses e Implantes , Registros
5.
Nat Commun ; 11(1): 3278, 2020 06 30.
Artigo em Inglês | MEDLINE | ID: mdl-32606311

RESUMO

On-implant spike sorting methods employ static feature extraction/selection techniques to minimize the hardware cost. Here we propose a novel framework for real-time spike sorting based on dynamic selection of features. We select salient features that maximize the geometric-mean of between-class distances as well as the associated homogeneity index effectively to best discriminate spikes for classification. Wave-shape classification is performed based on a multi-label window discrimination approach. An external module calculates the salient features and discrimination windows through optimizing a replica of the on-implant operation, and then configures the on-implant spike sorter for real-time online operation. Hardware implementation of the on-implant online spike sorter for 512 channels of concurrent extra-cellular neural signals is reported, with an average classification accuracy of ~88%. Compared with other similar methods, our method shows reduction in classification error by a factor of ~2, and also reduction in the required memory space by a factor of ~5.


Assuntos
Potenciais de Ação/fisiologia , Algoritmos , Encéfalo/fisiologia , Modelos Neurológicos , Neurônios/fisiologia , Processamento de Sinais Assistido por Computador/instrumentação , Encéfalo/citologia , Eletrofisiologia/instrumentação , Eletrofisiologia/métodos , Humanos , Neuroestimuladores Implantáveis
6.
IEEE Trans Neural Syst Rehabil Eng ; 26(5): 1093-1099, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29752245

RESUMO

This paper reports on the modeling and characterization of capacitive elements with tissue as the dielectric material, representing the core building block of a capacitive link for wireless power transfer to neural implants. Each capacitive element consists of two parallel plates that are aligned around the tissue layer and incorporate a grounded, guarded, capacitive pad to mitigate the adverse effect of stray capacitances and shield the plates from external interfering electric fields. The plates are also coated with a biocompatible, insulating, coating layer on the inner side of each plate in contact with the tissue. A comprehensive circuit model is presented that accounts for the effect of the coating layers and is validated by measurements of the equivalent capacitance as well as impedance magnitude/phase of the parallel plates over a wide frequency range of 1 kHz-10 MHz. Using insulating coating layers of Parylene-C at a thickness of and Parylene-N at a thickness of deposited on two sets of parallel plates with different sizes and shapes of the guarded pad, our modeling and characterization results accurately capture the effect of the thickness and electrical properties of the coating layers on the behavior of the capacitive elements over frequency and with different tissues.


Assuntos
Próteses Neurais , Desenho de Prótese , Tecnologia sem Fio , Algoritmos , Capacitância Elétrica , Eletrodos , Humanos , Polímeros , Próteses e Implantes , Xilenos
7.
IEEE Trans Neural Syst Rehabil Eng ; 24(11): 1243-1253, 2016 11.
Artigo em Inglês | MEDLINE | ID: mdl-27046904

RESUMO

This paper reports on the design, implementation, and test of a stimulation back-end, for an implantable retinal prosthesis. In addition to traditional rectangular pulse shapes, the circuit features biphasic stimulation pulses with both rising and falling exponential shapes, whose time constants are digitally programmable. A class-B second generation current conveyor is used as a wide-swing, high-output-resistance stimulation current driver, delivering stimulation current pulses of up to ±96 µA to the target tissue. Duration of the generated current pulses is programmable within the range of 100 µs to 3 ms. Current-mode digital-to-analog converters (DACs) are used to program the amplitudes of the stimulation pulses. Fabricated using the IBM 130 nm process, the circuit consumes 1.5×1.5 mm2 of silicon area. According to the measurements, the DACs exhibit DNL and INL of 0.23 LSB and 0.364 LSB, respectively. Experimental results indicate that the stimuli generator meets expected requirements when connected to electrode-tissue impedance of as high as 25 k Ω. Maximum power consumption of the proposed design is 3.4 mW when delivering biphasic rectangular pulses to the target load. A charge pump block is in charge of the upconversion of the standard 1.2-V supply voltage to ±3.3V.


Assuntos
Fontes de Energia Elétrica , Terapia por Estimulação Elétrica/instrumentação , Processamento de Sinais Assistido por Computador/instrumentação , Terapia Assistida por Computador/instrumentação , Próteses Visuais , Tecnologia sem Fio/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento
8.
Annu Int Conf IEEE Eng Med Biol Soc ; 2016: 1818-1821, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28268680

RESUMO

This paper proposes a novel energy-efficient approach dedicated to high-density implantable stimulators such as visual prostheses. Energy efficiency of the approach proposed in this work is achieved through two ideas: the `tracking supply ribbon' technique, and `reverse charge pumping'. The proposed approach is implemented, in the multichannel case, in such a way that power efficiency of each stimulation channel is enhanced according to its specific voltage/current condition and independently from other channels. Based on the proposed approach, a 16-channel stimulation backend for a visual prosthesis was designed and simulated in the transistor level in a low-voltage 0.18µm triple-well CMOS technology, occupying 1 mm2 of silicon area. According to post-layout simulation results, power savings of up to 74.9% are achieved compared to the conventional output stage with a constant supply voltage.


Assuntos
Próteses Visuais
9.
IEEE Trans Neural Syst Rehabil Eng ; 23(3): 485-97, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25222949

RESUMO

This paper proposes an efficient data compression technique dedicated to implantable intra-cortical neural recording devices. The proposed technique benefits from processing neural signals in the Discrete Haar Wavelet Transform space, a new spike extraction approach, and a novel data framing scheme to telemeter the recorded neural information to the outside world. Based on the proposed technique, a 64-channel neural signal processor was designed and prototyped as a part of a wireless implantable extra-cellular neural recording microsystem. Designed in a 0.13- µ m standard CMOS process, the 64-channel neural signal processor reported in this paper occupies ∼ 0.206 mm(2) of silicon area, and consumes 94.18 µW when operating under a 1.2-V supply voltage at a master clock frequency of 1.28 MHz.


Assuntos
Interfaces Cérebro-Computador , Encéfalo/fisiologia , Córtex Cerebral/fisiologia , Próteses Neurais , Algoritmos , Simulação por Computador , Compressão de Dados , Fenômenos Eletrofisiológicos , Desenho de Equipamento , Humanos , Microcomputadores , Próteses e Implantes , Processamento de Sinais Assistido por Computador , Razão Sinal-Ruído , Análise de Ondaletas
10.
IEEE Trans Biomed Circuits Syst ; 8(1): 129-37, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-24681926

RESUMO

This paper reports on the application of the Walsh-Hadamard transform (WHT) for data compression in brain-machine/brain-computer interfaces. Using the proposed technique, the amount of the neural data transmitted off the implant is compressed by a factor of at least 63 at the expense of as low as 4.66% RMS error between the signal reconstructed on the external host and the original neural signal on the implant side. Based on the proposed idea, a 128-channel WHT processor was designed in a 0.18- µm CMOS process occupying 1.64 mm(2) of silicon area. The circuit consumes 81 µW (0.63 µW per channel) from a 1.8-V power supply at 250 kHz. A prototype of the proposed processor was implemented and successfully tested using prerecorded neural signals.


Assuntos
Algoritmos , Interfaces Cérebro-Computador , Compressão de Dados/métodos , Processamento de Sinais Assistido por Computador , Próteses Neurais
11.
IEEE Trans Biomed Circuits Syst ; 8(3): 371-81, 2014 06.
Artigo em Inglês | MEDLINE | ID: mdl-23925374

RESUMO

A nonlinear ADC dedicated to the digitization of neural signals in implantable brain-machine interfaces is presented. Benefitting from an exponential quantization function, effective resolution of the proposed ADC in the digitization of action potentials is almost 2 bits more than its physical number of bits. Hence, it is shown in this paper that the choice of a proper nonlinear quantization function helps reduce the outgoing bit rate carrying the recorded neural data. Another major benefit of digitizing neural signals using the proposed signal-specific ADC is the considerable reduction in the background noise of the neural signal. The 8-b exponential ADC reported in this paper digitizes large action potentials with maximum resolution of 10.5 bits , while quantizing the small background noise is performed with a resolution of as low as 3 bits. Fully-integrated version of the circuit was designed and fabricated in a 0.18-µm CMOS process, occupying 0.036 mm(2) silicon area. Designed based on a two-step successive-approximation register ADC architecture, the proposed ADC employs a piecewise-linear approximation of the target exponential function for quantization. Operating at a sampling frequency of 25 kS/s (typical for intra-cortical neural recording) and with a supply voltage of 1.8 V, the entire chip, including the ADC and reference circuits, dissipates 87.2 µW. According to the experiments, Noise-Content-Reduction Ratio (NCRR) of the ADC is 41.1 dB.


Assuntos
Potenciais de Ação , Interfaces Cérebro-Computador , Neurofisiologia/instrumentação , Próteses e Implantes , Animais , Córtex Auditivo/fisiologia , Desenho de Equipamento , Cobaias , Neurônios/fisiologia
12.
13.
Artigo em Inglês | MEDLINE | ID: mdl-23366029

RESUMO

This paper reports on the design of a programmable, high output impedance, large voltage compliance microstimulator for low-voltage biomedical applications. A 6-bit binary-weighted digital to analog converter (DAC) is used to generate biphasic stimulus current pulses. A compact current mirror with large output voltage compliance and high output resistance conveys the current pulses to the target tissue. Designed and simulated in a standard 0.18µm CMOS process, the microstimulator circuit is capable of delivering a maximum stimulation current of 160µA to a 10-kΩ resistive load. Operated at a 1.8-V supply voltage, the output stage exhibits a voltage compliance of 1.69V and output resistance of 160MΩ at full scale stimulus current. Layout of the core microelectrode circuit measures 25.5µm×31.5µm.


Assuntos
Terapia por Estimulação Elétrica/instrumentação , Impedância Elétrica , Humanos , Microeletrodos
14.
Artigo em Inglês | MEDLINE | ID: mdl-23367325

RESUMO

In this paper, a wearable, battery-powered, low-power, low-size, cost-efficient, fully programmable neural stimulator is presented. The system comprises a wearable stimulator module and an external controller. To receive the settings required for the operation of the system, the wearable module is programmed through wireless connection to the external controller. Implemented using off-the-shelf components, the wearable neural stimulator weighs 60 g and measures 9 cm × 5 cm × 2 cm. The system is capable of generating independent biphasic stimulations on 8 channels with programmable amplitudes and timings. The neural stimulator consumes about 1.5 mW in the power-down mode and about 51.2 mW in the active mode when all the 8 channels are active. For in-vivo experiments, the system was used to stimulate motor cortex of an anesthetized rat fixed in a stereotaxic instrument.


Assuntos
Fontes de Energia Elétrica , Estimulação Elétrica , Ondas de Rádio , Humanos
15.
Artigo em Inglês | MEDLINE | ID: mdl-22254942

RESUMO

Flexible PET/ITO (PolyEthylene Terephthalate/ Indium Tin Oxide) implantable electrode array for spinal cord stimulation and retina prosthesis have been developed. The electrode array is fabricated on a thin PET/ITO substrate and encapsulated with insulating material, SU-8. The PET substrate made electrodes flexible so that they could shape to contoured tissues. A layer of gold on the stimulation sites served to reduce the electrode/tissue interface impedance. Prototypes of 1 × 8 and 3 × 8 electrode arrays are fabricated for monophasic and biphasic stimulation of spinal cord respectively. The exposed electrode dimensions are 3 mm² for monophasic and 6 mm² for biphasic stimulation with 100 µm of interconnection paths. The prototype of 4 × 4 electrode arrays were also fabricated with the same process for retinal prosthesis with exposed electrode diameter of 125 µm. To verify the functionality of the subdural electrodes, the electrochemical impedance spectroscopy was measured. The electrode/tissue impedance was 500 Ω at 1KHz for 3 mm² area.


Assuntos
Eletrodos Implantados , Polietilenoglicóis/química , Compostos de Estanho/química , Espectroscopia Dielétrica
16.
Artigo em Inglês | MEDLINE | ID: mdl-22254943

RESUMO

In this paper employing double layer printed spiral coils (PSCs) is proposed for wireless power transmission in implantable biomedical applications. Detailed modeling of this type of PSCs is presented. Both calculations and measurements of fabricated double layer PSCs indicate that this structure can decrease the size of typical single layer PSCs without any change in the most important parameters of the coils, such as quality factor. Also, it is shown that with equal PSC dimensions and design parameters, double layer PSCs achieve significantly higher inductances and quality factors. Ultimately, a pair of double layer PSCs with a distance of 5 mm in air is used in an inductive link. The power transfer efficiency of this link is about 79.8% with a carrier frequency of 5 MHz and coupling coefficient of 0.189.


Assuntos
Desenho de Equipamento , Próteses e Implantes , Ondas de Rádio , Modelos Teóricos
17.
Artigo em Inglês | MEDLINE | ID: mdl-22255805

RESUMO

A signal processor/compressor dedicated to implantable neural recording microsystems is presented. Signal compression is performed based on Haar wavelet. It is shown in this paper that, compared to other mathematical transforms already used for this purpose, compression of neural signals using this type of wavelet transform can be of almost the same quality, while demanding less circuit complexity and smaller silicon area. Designed in a 0.13-µm standard CMOS process, the 64-channel 8-bit signal processor reported in this paper occupies 113 µm x 110 µm of silicon area. It operates under a 1.8-V supply voltage at a master clock frequency of 3.2 MHz.


Assuntos
Neurônios/fisiologia , Processamento de Sinais Assistido por Computador , Análise de Ondaletas , Algoritmos , Engenharia Biomédica/instrumentação , Engenharia Biomédica/métodos , Computadores , Desenho de Equipamento , Humanos , Teste de Materiais , Microcomputadores , Modelos Estatísticos , Modelos Teóricos , Neurônios/metabolismo , Reprodutibilidade dos Testes , Silício/química , Software , Fatores de Tempo
18.
Artigo em Inglês | MEDLINE | ID: mdl-21096714

RESUMO

An analog spike detector circuit is presented, which adaptively generates a threshold level for spike detection based on hard-thresholding. Operation of the circuit was tested not only with a neural signal obtained from real in-vivo recording from a live animal, but also with a large sinusoidal baseline variation intentionally added to examine the capability of the circuit to track baseline variations as large as 50mV. The circuit runs at 3.3V supply voltage and dissipates 270 microW.


Assuntos
Eletrônica Médica/métodos , Neurociências/métodos , Próteses e Implantes , Eletrônica Médica/instrumentação , Neurociências/instrumentação
19.
Artigo em Inglês | MEDLINE | ID: mdl-21096715

RESUMO

This paper investigates the use of a new architecture for implantable microsystems for multi-channel intra-cortical neural recording. The proposed architecture performs frequency-division multiplexing (FDM) to wirelessly transfer multiple neural channels to an external setup. Based on the proposed idea, an 8-channel wireless neural recording system was designed. As a result of FDM, preconditioned neural signals are placed in the frequency domain with 100kHz spacing, occupying a approximately 800-kHz bandwidth starting from 10MHz. The entire band is then shifted to within the traditional frequency modulation (FM) band. The system, designed in a 0.18-microm standard CMOS process, consumes 4.7mW@1.8V.


Assuntos
Eletrônica Médica/métodos , Neurociências/métodos , Próteses e Implantes , Eletrônica Médica/instrumentação , Desenho de Equipamento , Humanos , Neurociências/instrumentação
20.
Artigo em Inglês | MEDLINE | ID: mdl-19963861

RESUMO

A novel noncoherent BPSK demodulator is presented for inductively powered biomedical devices. Differential Manchester encoding technique is used and data demodulation is based on pulse width measurement method. In addition to ultra low power consumption, high data rate without increasing the carrier frequency is achieved with the outstanding data-rate-to-carrier-frequency ratio of 100%. The proposed demodulator is especially appropriate for biomedical applications where high speed data transfer is required, e.g., cochlear implants and visual prostheses. The circuit is designed in a 0.18-mum standard CMOS technology and consumes as low as 232 microW@1.8V at a data rate of 10 Mbps.


Assuntos
Eletrônica Médica/instrumentação , Eletrônica Médica/métodos , Próteses e Implantes , Desenho de Equipamento , Humanos
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