Opto-μECoG Array: A Hybrid Neural Interface With Transparent μECoG Electrode Array and Integrated LEDs for Optogenetics

Abstract

Electrocorticogram (ECoG) recordings, taken from electrodes placed on the surface of the cortex, have been successfully implemented for control of brain machine interfaces (BMIs). Optogenetics, direct optical stimulation of neurons in brain tissue genetically modified to express channelrhodopsin-2 (ChR2), enables targeting of specific types of neurons with sub-millisecond temporal precision. In this work, we developed a BMI device, called an Opto- μECoG array, which combines ECoG recording and optogenetics-based stimulation to enable multichannel, bi-directional interactions with neurons. The Opto- μECoG array comprises two sub-arrays, each containing a 4 × 4 distribution of micro-epidural transparent electrodes ( ∼ 200 μm diameter) and embedded light-emitting diodes (LEDs) for optical neural stimulation on a 2.5 × 2.5 mm² footprint to match the bilateral hemispherical area of the visual cortex in a rat. The transparent electrodes were fabricated with indium tin oxide (ITO). Parylene-C served as the main structural and packaging material for flexibility and biocompatibility. Optical, electrical, and thermal characteristics of the fabricated device were investigated and in vivo experiments were performed to evaluate the efficacy of the device.

Silicon-Integrated High-Density Electrocortical Interfaces

“…(j) Flexible active electrode array with two integrated transistors on each pixel for ECoG signal buffering and column multiplexing for high channel count [30]. (k) Flexible ECoG array with embedded light-emitting diodes for optogenetics-based stimulation [31].…”

“…Recently, transparent electrode arrays with integrated light path for simultaneous ECoG recording and optogenetic stimulation have been demonstrated as shown in Fig. 4(k) [31]. The active development of novel electrode interfaces has not only improved conventional ECoG recording, but also generated new applications and therapeutic opportunities.…”

Transparent, conformable, active multielectrode array using organic electrochemical transistors

“…In the following experiment, w and p are set to be 3 and 18 μm, respectively. In this design, T c is 69%, which is compared with that of the ITO MEA for optogenetic applications (32), whereas the sheet resistance is 3 Ω/sq, which is low enough to operate OECTs.…”

“…Because thin metal cannot achieve high transmittance and high conductance simultaneously, fully transparent conductors are needed. From this viewpoint, indium-tin-oxide (ITO) (32) and graphene (30,33) were used to realize a highly transparent MEA comprising transparent electrodes and transparent wires. Such a high transparency is needed particularly for MEA with the large number of multiple electrodes, because wirings occupy most of the area.…”

Flexible electronics for bio-signal monitoring in implantable applications

“…The LEDs have 1:0 mm  0:5 mm  0:5 mm size and 120°directivity. The LEDs have 1.58-mW/mm 2 irradiance at 2.89-V and 5-mA power consumption, which can induce action potentials [33]. All methods of animal care and use were performed by medical doctors with approval from the Institutional Animal Care and Use Committee of Osaka University.…”