Intertwined-pulse modulation for compressive data telemetry.

This paper presents a novel approach for anisochronous pulse-based modulation. In the proposed approach, referred to as the intertwined-pulse modulation (IPM), every pair of consecutive symbols overlap in time. This allows for shortening the time allocated for the transmission of the symbols, hence achieving temporal compaction while the data goes through the line encoding step in a digital communication system.

Data Transformation in the Processing of Neuronal Signals: A Powerful Tool to Illuminate Informative Contents.

Neuroscientists seek efficient solutions for deciphering the sophisticated unknowns of the brain. Effective development of complicated brain-related tools is the focal point of research in neuroscience and neurotechnology. Thanks to today's technological advancements, the physical development of high-density and high-resolution neural interfaces has been made possible.

Wireless, miniaturized, semi-implantable electrocorticography microsystem validated in vivo.

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.

Hardware and Power-Efficient Compression Technique Based on Discrete Tchebichef Transform for Neural Recording Microsystems.

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.

Spatial Redundancy Reduction in Multi-Channel Implantable Neural Recording Microsystems.

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.

Spike Detection Technique Based on Spike Augmentation with Low Computational and Hardware Complexity.

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.

A framework for on-implant spike sorting based on salient feature selection.

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.

Modeling and Characterization of Capacitive Elements With Tissue as Dielectric Material for Wireless Powering of Neural Implants.

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.

Fully-implantable, multi-channel, microstimulator with tracking supply ribbon and energy recovery.

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.

Versatile Stimulation Back-End With Programmable Exponential Current Pulse Shapes for a Retinal Visual Prosthesis.

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.

Visual prostheses: the enabling technology to give sight to the blind.

Millions of patients are either slowly losing their vision or are already blind due to retinal degenerative diseases such as retinitis pigmentosa (RP) and age-related macular degeneration (AMD) or because of accidents or injuries. Employment of artificial means to treat extreme vision impairment has come closer to reality during the past few decades. Currently, many research groups work towards effective solutions to restore a rudimentary sense of vision to the blind.

Operationalizing Cognitive Science and Technologies' Research and Development; the "Brain and Cognition Study Group (BCSG)" Initiative from Shiraz, Iran.

Recent advances in brain and cognitive science studies have revolutionized concepts in neural dynamics, regulating mechanisms, coding systems and information processing networks which govern our function and behavior. Hidden aspects of neurological and psychiatric diseases are being understood and hopes for their treatment are emerging. Although the two comprehensive mega-projects on brain mapping are in place in the United States and Europe; the proportion of science contributed by the developing countries should not be downsized.

A method for compression of intra-cortically-recorded neural signals dedicated to implantable brain-machine interfaces.

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.

Data compression in brain-machine/computer interfaces based on the Walsh-Hadamard transform.

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.

Nonlinear Signal-Specific ADC for Efficient Neural Recording in Brain-Machine Interfaces.

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.

Wearable, battery-powered, wireless, programmable 8-channel neural stimulator.

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.

Programmable high-output-impedance, large-voltage compliance, microstimulator for low-voltage biomedical applications.

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.

A 64-channel neural signal processor/ compressor based on Haar wavelet transform.

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.

Design of double layer printed spiral coils for wirelessly-powered biomedical implants.

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.

Flexible PET/ITO electrode array for implantable biomedical applications.

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.

New architecture for wireless implantable neural recording microsystems based on frequency-division multiplexing.

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.

Adaptive spike detection method based on capacitor arrays dedicated to implantable neural recording microsystems.

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.

A low-power noncoherent BPSK demodulator and clock recovery circuit for high-data-rate biomedical applications.

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%.

A neural amplifier with high programmable gain and tunable bandwidth.

A neural recording amplifier having programmable gain and bandwidth is presented. The gain can be digitally programmed using 6 bits from 100x to 1100x in steps of 100x. The low-frequency cutoff can be varied from less than 10Hz to above 100Hz to accept or reject field potentials while the high-frequency cutoff is fixed at 9kHz.