Nanosecond pulsed electric field (nsPEF) is a new modality for neuromodulation, with unique capabilities
qualitatively different from the conventional electrostimulation. The potential benefits of nsPEF include but are
not limited to prolonged stimulation with little or no electrochemical side effects; excitation at lower thresholds;
selectivity based on cell charging time constant; the capability of choosing between stimulation, inhibition, and
ablation; and achieving these effects non-invasively, either for outpatient deep brain stimulation or for tumor
ablation.
The primary effect of nsPEF is a rapid build-up of cell membrane potential (MP). Real-time measurements
of MP kinetics are a key to predicting the outcomes of nsPEF stimulation. They are also a key to understanding
bipolar cancellation, a unique feature that enables interference targeting of nsPEF for non-invasive
neuromodulation. However, membrane charging by nsPEF occurs on a nanosecond time scale, much faster
than could be resolved by the existing electrophysiological and imaging methods.
We have addressed this challenge by implementing strobe pulsed laser microscopy for MP imaging with
better than 50 ns accuracy. In this one-of-a-kind set-up, cells loaded with a fast voltage-sensitive fluorescence
dye are exposed to high-power momentary laser flashes (5 kW, 6 ns). The flashes are dynamically
synchronized with nsPEF stimulation of target cells. Photos of fluorescence taken at different times during and
after nsPEF show the real-time dynamics of MP changes and how these changes culminate in downstream
effects, such as opening of voltage gated ion channels, initiation of action potentials, and nanoelectroporation.
We will employ this all-new set-up for understanding fine mechanisms and principles how neurons respond
to the nanosecond electric stress. We will characterize nsPEF parameters needed to evoke the desired
neuromodulation effect and tune the interference targeting protocols to achieve this effect at a distance from
stimulating electrodes. We will perform finite element modeling of the electric field thresholds and use our in
vitro results to define the feasibility and nsPEF requirements for non-invasive deep brain stimulation.
This project will generate new basic knowledge of neuronal function, including nanosecond-scale
biophysics of the cell membrane and ion channels. We will systematically characterize nsPEF neuromodulation
effects and link them to dielectric and physiological properties of neurons and to nsPEF stimulation
parameters. This in vitro project will utilize R21 “high risk, high reward” concept to collect mechanistic and
quantitative data necessary for animal and human studies of nsPEF neuromodulation.