Ross Walker

HermesE: A 96-Channel Full Data Rate Direct Neural Interface in 0.13

A power and area efficient sensor interface consumes 6.4 mW from 1.2 V while occupying 5 mm × 5 mm in 0.13 μm CMOS. The interface offers simultaneous access to 96 channels of broadband neural data acquired from cortical microelectrodes as part of a head-mounted wireless recording system, enabling basic neuroscience as well as neuroprosthetics research. Signals are conditioned with a front-end achieving 2.2 μVrms input-referred noise in a 10 kHz bandwidth before conversion at 31.25 kSa/s by 10-bit SAR ADCs with 60.3 dB SNDR and 42 fJ/conv-step. Switched-capacitor filtering provides a well-controlled frequency response and utilizes windowed integrator sampling to mitigate noise aliasing, enhancing noise/power efficiency.

\mu

Ovarian cancer is the fifth leading cause of cancer death in women, in part because of the limited knowledge about early stage disease. We develop a novel rat model of ovarian cancer and perform a pilot study to examine the harvested ovaries with complementary optical imaging modalities. Rats are exposed to repeated daily dosing (20 days) with 4-vinylcyclohexene diepoxide (VCD) to cause early ovarian failure (model for postmenopause), and ovaries are directly exposed to 7,12-dimethylbenz(a)anthracene (DMBA) to cause abnormal ovarian proliferation and neoplasia. Harvested ovaries are examined with optical coherence tomography (OCT) and light-induced fluorescence (LIF) at one, three, and five months post-DMBA treatment. VCD causes complete ovarian follicle depletion within 8 months after onset of dosing. DMBA induces abnormal size, cysts, and neoplastic changes. OCT successfully visualizes normal and abnormal structures (e.g., cysts, bursa, follicular remnant degeneration) and the LIF spectra show statistically significant changes in the ratio of average emission intensity at 390:450 nm between VCD-treated ovaries and both normal cycling and neoplastic DMBA-treated ovaries. Overall, this pilot study demonstrates the feasibility of both the novel animal model for ovarian cancer and the ability of optical imaging techniques to visualize ovarian function and health.

m CMOS

OBJECTIVE Motor neuroscience and brain-machine interface (BMI) design is based on examining how the brain controls voluntary movement, typically by recording neural activity and behavior from animal models. Recording technologies used with these animal models have traditionally limited the range of behaviors that can be studied, and thus the generality of science and engineering research. We aim to design a freely-moving animal model using neural and behavioral recording technologies that do not constrain movement. APPROACH We have established a freely-moving rhesus monkey model employing technology that transmits neural activity from an intracortical array using a head-mounted device and records behavior through computer vision using markerless motion capture. We demonstrate the flexibility and utility of this new monkey model, including the first recordings from motor cortex while rhesus monkeys walk quadrupedally on a treadmill. MAIN RESULTS Using this monkey model, we show that multi-unit threshold-crossing neural activity encodes the phase of walking and that the average firing rate of the threshold crossings covaries with the speed of individual steps. On a population level, we find that neural state-space trajectories of walking at different speeds have similar rotational dynamics in some dimensions that evolve at the step rate of walking, yet robustly separate by speed in other state-space dimensions. SIGNIFICANCE Freely-moving animal models may allow neuroscientists to examine a wider range of behaviors and can provide a flexible experimental paradigm for examining the neural mechanisms that underlie movement generation across behaviors and environments. For BMIs, freely-moving animal models have the potential to aid prosthetic design by examining how neural encoding changes with posture, environment and other real-world context changes. Understanding this new realm of behavior in more naturalistic settings is essential for overall progress of basic motor neuroscience and for the successful translation of BMIs to people with paralysis.

Dual modality imaging of a novel rat model of ovarian carcinogenesis

This paper proposes high speed wireline communication over FDA-cleared implantable leads and connectors. It presents the electrical characterization of a clinically-used implantable extension lead, and discusses issues related to utilizing this type of interconnect for high-speed communication. S-parameters and TDR measurements are presented for a complete wireline link constructed with commercial-off-the-shelf FPGA boards, which achieves low BER communication at 200 Mbps with LVCMOS and LVDS signaling. The study highlights new avenues of research in circuits and systems for next generation prosthetics, neuromodulation, and large scale neural interfacing.

A freely-moving monkey treadmill model.

Electronic interfaces to the nervous system are increasingly important for experimental neuroscience as well as medical diagnostics and therapies. Existing neural interfaces are limited, however, by the use of passive recording and stimulation devices that are connected to active electronics on separate physical platforms through large amounts of passive wiring. This manuscript proposes a new approach to integrate active electronics directly with neural recording and stimulation devices using state-of-the-art silicon processing, assembly, and packaging techniques. System concepts are described for fully wireless operation as well as wireline interfacing through FDA-cleared implantable leads and connectors. The approach offers a more modular paradigm of neural interface design, which is greatly needed as the demand for higher channel counts grows.

Wireline communication over an implantable lead

Field-Effect Transistors (FETs) with Three Independent Gates (TIG) can achieve different modes of operation according to the bias of the gate terminals. In particular, TIG FETs were recently shown capable of (i) device-level polarity control, (ii) dynamic threshold modulation and (iii) subthreshold slope tuning down to ultra-steep-slope operation. Experimentally demonstrated using both contemporary FinFETs and emerging silicon nanowires channel technologies, TIGFETs unlock several design opportunities. In this paper, we comment on the digital, analog and RF design capabilities offered by this new class of transistors.

Integrated neural interfaces

Ovarian cancer is relatively rare but is the fifth leading cause of death from cancer in women. Little is known about the precursors and early stages of ovarian cancer partially due to the lack of a realistic animal model. A cohesive model that incorporates ovarian cancer induction into a menopausal rodent would be well suited for comprehensive studies of ovarian cancer, and non-destructive imaging would allow carcinogenesis to be followed. Optical Coherence Tomography (OCT) and Light-Induced Fluorescence (LIF) are minimally invasive optical modalities that allow both structural and biochemical changes to be noted. Rat ovaries were exposed to 4-vinylcyclohexene diepoxide (VCD) for 20 days in order to destroy the primordial follicles. Sutures coated with 7,12-dimethylbenz(a)anthracene (DMBA) were implanted in the right ovary, in order to produce epithelial based ovarian cancers. Rats were sacrificed at 1, 3, and 5 months and ovaries were harvested and imaged with a combined OCT/LIF system. Histology was preformed on the harvested ovaries and any pathology determined. OCT was able to visualize follicle loss and DMBA-induced abnormalities. LIF spectra were also different between cycling, follicle deplete, and DMBA-exposed ovaries. Overall this pilot study demonstrated the feasibility of both the animal model and optical imaging.

Digital, analog and RF design opportunities of three-independent-gate transistors

Neural recording systems that interface with implanted microelectrodes are used extensively in experimental neuroscience and neural engineering research. Interface electronics that are needed to amplify, filter, and digitize signals from multichannel electrode arrays are a critical bottleneck to scaling such systems. This paper presents the design and testing of an electronic architecture for intracortical neural recording that drastically reduces the size per channel by rapidly multiplexing many electrodes to a single circuit. The architecture utilizes mixed-signal feedback to cancel electrode offsets, windowed integration sampling to reduce aliased high-frequency noise, and a successive approximation analog-to-digital converter with small capacitance and asynchronous control. Results are presented from a 180 nm CMOS integrated circuit prototype verified using in vivo experiments with a tungsten microwire array implanted in rodent cortex. The integrated circuit prototype achieves <0.004 mm2 area per channel, 7 µW power dissipation per channel, 5.6 µVrms input referred noise, 50 dB common mode rejection ratio, and generates 9-bit samples at 30 kHz per channel by multiplexing at 600 kHz. General considerations are discussed for rapid time domain multiplexing of high-impedance microelectrodes. Overall, this work describes a promising path forward for scaling neural recording systems to numbers of electrodes that are orders of magnitude larger.

Optical coherence tomography imaging and fluorescence spectroscopy of a novel rat model of ovarian cancer

This paper provides a comprehensive review of Three-Independent-Gate Field-Effect Transistors (TIGFETs). In parallel to the focus on transistor scaling, an alternative approach to push further the performance of computing systems consists in increasing the functionalities of the basic transistors by means of additional gate controls. TIGFETs belong to this category of devices and can achieve different modes of operation according to the bias of the gate terminals. In particular, these devices are capable of (i) device-level polarity control, (ii) dynamic threshold modulation and (iii) subthreshold slope tuning down to ultra-steep-slope operation. The functionality increase at the device level leads to several design opportunities for digital, analog and RF applications.

Acquisition of Neural Action Potentials Using Rapid Multiplexing Directly at the Electrodes

Ovarian cancer is not a common cancer-approximately 25,000 new cases in 2004-but it is the fifth leading cause of death from cancer in women (over 16,000 in 2004). Little is known about the precursors and early stages of ovarian cancer partially due to the lack of human samples at the early stages. A cohesive model that incorporates ovarian cancer induction into a menopausal rodent would be well suited for comprehensive studies of ovarian cancer. Non-destructive imaging would allow carcinogenesis to be followed. Optical Coherence Tomography (OCT), Optical Coherence Microscopy (OCM) and Light-Induced Fluorescence (LIF) are minimally invasive optical modalities that allow both structural and biochemical changes to be noted. Rat ovaries were exposed to 4-vinylcyclohexene diepoxide (VCD) for 20 days in order to destroy the primordial follicles. Plain sutures and sutures coated with 7,12-dimethylbenz(a)anthracene (DMBA) were implanted in the right ovary, in order to produce epithelial based ovarian cancers (a plain suture was inserted in the control). Rats were sacrificed at 4 weeks and ovaries were harvested and imaged with a combined OCT/LIF system and with the OCM. Histology was preformed on the harvested ovaries and any pathology determined. Two of the ovaries were visually abnormal; the OCT/LIF imaging confirmed these abnormalities. The normal ovary OCM and OCT images show the organized structure of the ovary, the follicles, bursa and corpus lutea are visible. The OCM images show the disorganized structure of one of the abnormal ovaries. Overall this pilot study demonstrated the feasibility of both the animal model and optical imaging.