A Highly-Scalable Poisson-Coded Retinal Optogenetic Stimulator With Fully-Analog ED-Based Adaptive Spike Detection...

Area of Science:

• Biomedical Engineering
• Neuroscience
• Optogenetics

Background:

• Optogenetic stimulation is a promising tool for neural prosthetics, but challenges remain in achieving high channel counts, energy efficiency, and precise control.
• Current systems often struggle with scalability and adapting to individual patient variations.

Purpose of the Study:

• To present a fully implantable, inductively powered optogenetic stimulator designed for enhanced prosthetic vision.
• To improve stimulation efficacy, pathway specificity, energy efficiency, and channel-count scalability.
• To develop a closed-loop system for adaptive light intensity control based on neural feedback.

Main Methods:

• Leveraged opsin photon integration properties with raster scanning and Poisson-coded stimulation for uniform power and reduced wiring.
• Implemented a compact, power-efficient, SNR-boosted, ADC-less spike detection circuit for real-time feedback.
• Fabricated a 3x3 mm IC in 180nm CMOS coupled with a 100-channel custom optrode array using InGaN on sapphire.

Main Results:

• Demonstrated a scalable system supporting more stimulation channels without compromising safety or functionality.
• Achieved adaptive control of LED light intensity based on retinal ganglion cell (RGC) spiking activity.
• Validated circuit-level performance, system-level efficacy, and in-vitro performance, showing advantages over existing systems.

Conclusions:

• The developed optogenetic stimulator offers significant improvements for prosthetic vision applications.
• Closed-loop adaptivity ensures consistent and effective stimulation, enhancing visual perception quality and energy efficiency.
• The system's scalability and efficiency represent a substantial advancement in implantable neural stimulation technology.