Research
Closed-Loop Neuromodulation
Neuromodulation has seen widespread adoption for the treatment of disorders such as Parkinson's disease and epilepsy. To improve the therapeutic efficacy and battery lifetime of neuromodulators, researchers have begun using closed-loop stimulation protocols that rely on sensing neural biomarkers of disease or brain state. However, electrical stimulation can create artifactual signals up to 100dB greater than the biomarker of interest. The NMIC (neuromodulation IC) is an integrated circuit that enables concurrent sensing and stimulation. A pair of NMICs is the key enabler for WAND (wireless artifact-free neuromodulation device), a neurotechnology research platform that has been used in non-human primate studies.
Implantable Bioelectronic Medicine
Implantable peripheral nerve stimulators are a class of bioelectronic medicine (a.k.a. electroceuticals) that offer a promising alternative to traditional systemic pharmaceutical treatments. Electrically modulating the peripheral nervous system has been shown to help regulate aberrant physiological conditions, such as epilepsy, blood pressure, rheumatoid arthritis, and more.
StimDust (stimulating neural dust) is a mm-scale, batteryless implant that is wirelessly powered and controlled through ultrasound. Ultrasonic energy can easily propagate through tissue allowing StimDust to be implanted deep in the body (>5cm). A low-power IC interprets the incoming ultrasound and generates controlled stimulation patterns to activate (or inhibit) the nerve.
Lab on a Chip
Microelectrode Arrays
In dense neural tissue, the isolation of single unit activity (spiking) is extremely difficult with a single recording site, meaning densely-packed (cellular scale), multi-site recording arrays are required for cell localization and sorting. Microelectrode arrays (MEAs) simultaneously acquire electric field activity across relatively large areas of neural tissue. Increasing the number of electrodes allows for more simultaneous single-cell recordings as well as spatially broad analysis of local field potentials (LFPs) that provide insight into how and under what conditions neuronal ensembles synchronize activity. The channel count of active CMOS MEAs can be drastically increased relative to passive arrays (fanout-constrained) by locally multiplexing channels onto fewer wires.
Neural Circuits
Oscillatory (coherent) neural activity within and between brain structures are ubiquitous, present in both normal and aberrant brain function. For sensory processing in the olfactory bulb, these oscillations are implicated as a "clock" for robust, timing-sensitive computation of multi-dimensional inputs. While gamma-band activity is intrinsic to the olfactory bulb in mammals, the circuitry that drives these oscillations is unclear. Using slices on MEAs, we discovered the presence of independent, intracolumnar (i.e. local) oscillators. We induced persistent (minutes) gamma oscillations using neurochemical activation and optogenetic stimulation of olfactory sensory neuron axons.
CMOS Imagers
Our imager work has focused on lens-less, lab-on-chip applications. Applications include a single photon avalanche diode array for 3D fluorescence lifetime imaging and a high-speed 'circular' imager that performs rotation invariant measurement for calibrating intertial MEMS sensors.
