Keywords:

Electrocorticogram (ECoG): type of electrophysiological monitoring that uses electrodes placed directly on the surface of the brain to record electrical activity from cerebral cortex

Optogenetics: biological technique used to control neuron activity with light

Signal to Noise Ratio (SNR): ratio between desired information and undesired signal (background noise) ⇒ high SNR means high desired output relative to noise

Transmittance: ratio of light energy falling on a body to that transmitted through it

Sheet Resistance: $R = ρ/t * 1/w$

Poly Methyl Methacrylate (PMMA): synthetic resin

Photoresist (PR): organic layer sensitive to light that is used to single out portions of a substrate through exposure to light (positive PR or negative PR)

Photoelectric Effect: the absorption of incident light causing ejection of electrons from surface

Goal: Make implantable neural interface that can map neural activity during simultaneous optical stimulation

Why optogenetics?

• optogenetics offers highest spatial resolution through cell-type-specific transfection
• sub-microsecond temporal resolution
• versatile control of activation and inhibition

Challenges:

1. mechanical stability of micro-electrodes

   1. prevent mechanical damage due to repetitive attaching/detaching

2. conformal contact

   1. flexibility

3. minimizing photoelectric artifact

   When sufficiently energetic photon falls on the microelectrode during light stimulation, electrons gain sufficient energy and are ejected resulting in an additional current.

Previous ECoG neural interfaces

Trade-off between mechanical stability & photoelectric artifact