Department: Electrical & Computer Engineering
Faculty Advisor(s): Shadi A. Dayeh

Primary Student
Name: Mehran Ganji
Email: mganji@ucsd.edu
Phone: 949-537-9178
Grad Year: 2020

The increased role of single unit recordings in our understanding and translation of brain signals in normal and diseased subjects requires direct interface with single neurons at high spatial resolution (Ám scale) and temporal resolutions (100Ás-1 ms). To achieve this goal, dramatic improvement over the traditional clinical electrocorticography (ECoG) arrays is needed with higher sensor densities and lower electrochemical interface impedances at the sensor/tissue interface. Poly(3,4-ethylenenedioxythiophene), commonly known as PEDOT, is vowed as a serious candidate for alternative neuronal electrode material owing to its permeability to charge ions in the electrophysiological medium resulting in about two orders of magnitude lower impedances than conventional metal electrodes. The fabrication of PEDOT doped with poly (styrenesulfonate) (PSS), known as PEDOT:PSS, on parylene can marry the excellent electrical characterization of PEDOT:PSS with the outstanding mechanical flexibility, compliancy and conformity of parylene for high performance neural recording and stimulation. Here, we demonstrated the development of high density, brain-conformal PEDOT:PSS arrays in three different configurations for electrophysiology studies in animal models and human subjects at UCSD. Our multi-cortical 2-Fin flexible electrode was placed epiduraly on the surface of the dorsal retrosplenial cortex of a urethane-anesthetized rat. Electrophysiological recordings revealed strong theta-2 (4Hz) spectral power, known to evolve in urethane-anesthetized rats. Additionally, strong correlation between the theta-2 activity between left and right hemispheres was observed. This validated the electrophysiological recording capability of our electrodes. For clinical translation, we demonstrated compatibility of our electrodes with autoclave sterilization in steam at 121 oC. The devices were then implanted for ECoG recording through an awake craniotomy study at UCSD?s Thornton hospital. Recorded data with observation of delta, theta and alpha oscillations and Power spectral densities with a clear distinction for two different states (performing task state and unconscious state due to anesthesia) demonstrated the operation of our platform in clinical settings. Overall, the results offer significant potential for decoding neuronal activity from the brain surface in diagnostic and therapeutic configurations and have implications for transforming the density and resolution of brain-machine interfaces.

Industry Application Area(s)
Electronics/Photonics | Life Sciences/Medical Devices & Instruments | Materials

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