Masoud Roham

A wireless IC for time-share chemical and electrical neural recording

Neurons communicate both electrically and chemically [1]. Extensive effort has been directed at monitoring these signals in awake animals to investigate the neural basis of behavior. While various measurement strategies have been employed in the past, electrophysiology (EPHYS) for single-unit recording [2] and voltammetry for neurotransmitter sensing [3] are established as the two best methods for probing neurotransmission at microscopic scales in real time.

Wireless Amperometric Neurochemical Monitoring Using an Integrated Telemetry Circuit

An integrated circuit for wireless real-time monitoring of neurochemical activity in the nervous system is described. The chip is capable of conducting high-resolution amperometric measurements in four settings of the input current. The chip architecture includes a first-order DeltaSigma modulator (DeltaSigmaM) and a frequency-shift-keyed (FSK) voltage-controlled oscillator (VCO) operating near 433 MHz. It is fabricated using the AMI 0.5 mum double-poly triple-metal n -well CMOS process, and requires only one off-chip component for operation. Measured dc current resolutions of ~ 250 fA, ~ 1.5 pA, ~ 4.5 pA, and ~ 17 pA were achieved for input currents in the range of plusmn5, plusmn37, plusmn150, and plusmn600 nA, respectively. The chip has been interfaced with a diamond-coated, quartz-insulated, microneedle, tungsten electrode, and successfully recorded dopamine concentration levels as low as 0.5 muM wirelessly over a transmission distance of ~ 0.5 m in flow injection analysis experiments.

Wireless Amperometric Neurochemical Monitoring Using an Integrated FSK Telemetry Circuit

A low-power integrated circuit for real-time wireless monitoring of neurochemical activity in the central nervous system is described. The chip is capable of conducting high-resolution amperometric measurements in four input-current settings. The chip architecture includes a current-based, first-order, sigma-delta analog-to-digital converter (LA ADC) and a frequency-shift-keyed (FSK) voltage-controlled oscillator (VCO) operating near 433MHz. It is fabricated using the AMI 0.5mum double-poly triple-metal n-well CMOS process, and requires only one off-chip component for operation. In a truly wireless fashion, measured dc current resolutions of 250fA, ~1.5pA, ~4.5pA and ~17pA were achieved for input currents in the range of plusmn5nA, plusmn 37nA, plusmn 150nA and plusmn 600nA, respectively, at a decimated sampling rate of 100Hz for all ranges. The ADC core and the VCO consume 21.7muA and 400muA from a 2.6-V power supply, respectively.

Diamond Microelectrodes and CMOS Microelectronics for Wireless Transmission of Fast-Scan Cyclic Voltammetry

This paper reports on technology development at the sensor and circuit levels for wireless transmission of fast- scan cyclic voltammetry (FSCV) in neurochemical detection. Heavily conductive, boron-doped diamond is selectively deposited onto the polished tip of a tungsten microelectrode to fabricate versatile, implantable, micro-needle microprobes capable of neurochemical sensing in the brain. In addition, an integrated circuit is fabricated in a 0.5-mum CMOS technology for processing and wireless transmission of the electrochemical signals corresponding to extracellular concentration changes of various neurotransmitters. The chip consists of a current-based, second-order, front-end SigmaDelta ADC and an on-chip, RF-FSK transmitter at the back-end. The ADC core and the transmitter consume 22 muA and 400 muA, respectively, from a 2.6-V power supply. Major electroactive neurotransmitters such as serotonin and dopamine in micromolar concentration have been wirelessly recorded at 433 MHz using 300-V/s FSCV in flow injection analysis experiments.

A miniaturized device for wireless FSCV monitoring of dopamine in an ambulatory subject

This paper reports on a miniaturized device for wireless monitoring of extracellular dopamine levels in the brain of an ambulatory rat using fast-scan cyclic voltammetry at a carbon-fiber microelectrode. The device comprises integrated circuitry for neurochemical recording fabricated in 0.5-µm double-poly triple-metal CMOS technology, which is assembled and packaged on a miniature rigid-flex substrate together with a few external components for supply generation, biasing, and chip programming. The device operates from a single 3-V battery, weighs 2.3 g (including the battery), and upon implantation successfully captures the effects of the psychostimulant amphetamine on electrically and non-electrically evoked dopamine neurotransmission in the caudateputamen region of an ambulatory rats forebrain.

A reconfigurable IC for wireless monitoring of chemical or electrical neural activity

A reconfigurable integrated circuit for single-channel wireless monitoring of chemical or electrical neural activity is described. It can perform both amperometry and fast-scan cyclic voltammetry (FSCV) when configured for neurochemical sensing, and can record extracellular action potentials as well as local field potentials (LFPs) when configured for electrophysiological studies. The chip architecture employs a third-order DeltaSigma modulator (DeltaSigmaM) and a frequency-shift-keyed (FSK) transmitter operating near 433 MHz. It also incorporates a programmable arbitrary waveform generator for FSCV measurements. The chip is fabricated using the AMI 0.5 mum 2P/3M n-well CMOS process, and achieves a measured current resolution of 94.1 pArms in a 5-kHz bandwidth for 300-V/s FSCV and an input-referred noise voltage of 4.69 muVrms in a bandwidth of 1.1-5 kHz. The modulator core, FSCV waveform generator, and RF transmitter draw ~28 muA, ~40 muA, and ~400 muA from a 2.5-V power supply, respectively.

A Wireless IC for Wide-Range Neurochemical Monitoring Using Amperometry and Fast-Scan Cyclic Voltammetry

An integrated circuit for real-time wireless monitoring of neurochemical activity in the nervous system is described. The chip is capable of conducting measurements in both fast-scan cyclic voltammetry (FSCV) and amperometry modes for a wide input current range. The chip architecture employs a second-order DeltaSigma modulator (DeltaSigmaM) and a frequency-shift-keyed transmitter operating near 433 MHz. It is fabricated using the AMI 0.5-mum double-poly triple-metal n-well CMOS process, and requires only one off-chip component for operation. A measured current resolution of 12 pA at a sampling rate of 100 Hz and 132 pA at a sampling rate of 10 kHz is achieved in amperometry and 300-V/s FSCV modes, respectively, for any input current in the range of plusmn430 nA. The modulator core and the transmitter draw 22 and 400 muA from a 2.6-V power supply, respectively. The chip has been externally interfaced with a carbon-fiber microelectrode implanted acutely in the caudate-putamen of an anesthetized rat, and, for the first time, extracellular levels of dopamine elicited by electrical stimulation of the medial forebrain bundle have been successfully recorded wirelessly using 300-V/s FSCV.

A configurable IC for wireless real-time in vivo monitoring of chemical and electrical neural activity

A 16-channel chip for wireless in vivo recording of chemical and electrical neural activity is described. The 7.83-mm² IC is fabricated using a 0.5-µm CMOS process and incorporates a 71-µW, 3^rd-order, configurable, ∆Σ modulator per channel, achieving an input-referred noise of 4.69 µV<inf>rms</inf> in 4-kHz BW and 94.1 pA<inf>rms</inf> in 5-kHz BW for electrical and fastscan voltammetric chemical neurosensing, respectively. Brain extracellular levels of dopamine elicited by electrical stimulation of the medial forebrain bundle have been recorded wirelessly on multiple channels using 300-V/s fast-scan cyclic voltammetry in the anesthetized rat.

A wireless modular multi-modal multi-node patch platform for robust biosignal monitoring

In this paper a wireless modular, multi-modal, multi-node patch platform is described. The platform comprises low-cost semi-disposable patch design aiming at unobtrusive ambulatory monitoring of multiple physiological parameters. Owing to its modular design it can be interfaced with various low-power RF communication and data storage technologies, while the data fusion of multi-modal and multi-node features facilitates measurement of several biosignals from multiple on-body locations for robust feature extraction. Preliminary results of the patch platform are presented which illustrate the capability to extract respiration rate from three different independent metrics, which combined together can give a more robust estimate of the actual respiratory rate.

Wireless integrated microsystems for monitoring brain chemical and electrical activity

A 16-channel chip for wireless in vivo recording of chemical and electrical neural activity is described. The 7.83-mm2 IC is fabricated using a 0.5-μm CMOS process and incorporates a 71-μW, 3rd-order, reconfigurable, ΔΣ modulator per channel, achieving an input-referred noise of 4.69 μVrms in 4-kHz BW and 94.1 pArms in 5-kHz BW for electrical and fast-scan voltammetric chemical neurosensing, respectively. The chip has been externally interfaced with carbon-fiber microelectrodes implanted acutely in the caudate-putamen of an anesthetized rat, and, for the first time, extracellular levels of dopamine elicited by electrical stimulation of the medial forebrain bundle have been successfully recorded wirelessly across multiple channels using 300-V/s fast-scan cyclic voltammetry.