1A-4 Acoustoelectric Detection of Current Flow in a Neural Recording Chamber

Acoustic pressure (P) traveling in a biologic fluid or tissue generates a local change in electrical conductivity. This acoustoelectric interaction (AE) induces a voltage modulation that depends on local current, resistance, and pressure. We explore the AE signal as a way to enhance traditional electrophysiology or surface recording of neural signals. A thin stretch tube mimicking an enlarged axon and an abdominal segment of a fresh lobster nerve cord were used as test structures for AE detection in a tri-compartment neural recording chamber. Stimulating electrodes passed low frequency current through the structures, while a pair of recording electrodes detected the high frequency AE signal. Ultrasound transducers from 0.5 to 7.5 MHz delivered P up to 2 MPa. The differentially-recorded AE signal was captured on a fast data acquisition board and saved for post processing. In the lobster nerve cord, the AE signal was linear between the tested range of current densities of 9 to 86 mA/cM2 [18 dB/log(J), r 2=0.96] and P of 0.5 to 2 MPa [21 dB/log(P), r 2 =0.96]. In addition, a transverse scan of the structures produced cross-sectional AE images of current flow with remote detection by the recording electrodes. Results were consistent with AE simulations. This study demonstrates that the AF signal can be used to detect and image current flow in a biologic environment with physiologically relevant current densities and acoustic pressures on par with clinical ultrasound imaging