# Chronically implantable μLED arrays for optogenetic cortical surface stimulation in mice

## TL;DR

Researchers developed a high-resolution, implantable microLED device to study brain activity in mice using optogenetics.

## Contribution

A stable, chronically implantable μLED array enables high-resolution optogenetic stimulation of cortical circuits in freely-behaving mice.

## Key findings

- The μLED arrays remained stable for over 300 hours of continuous in vivo operation.
- Low drive currents (<5 mA) produced robust neuronal responses with minimal thermal effects.
- The device successfully drove behavioral outcomes via spatiotemporal optogenetic stimulation of the auditory cortex.

## Abstract

Cortical implants are a proven clinical neurotechnology with the potential to transform our understanding of cognitive processes. These processes rely on complex neuronal networks that are difficult to selectively probe or stimulate. Optogenetics offers cell-type specificity, but achieving the density and coverage required for chronic, high-resolution modulation remains a challenge. We fabricated 100-element μLED arrays (200 μm pixel pitch, 2 × 2 mm2 footprint) coupled into chronically implantable systems for optogenetic stimulation of the mouse cortex. The μLEDs remain stable for over 300 hours continuous operation time in vivo, allowing for months-long chronic experiments. Simultaneous electrophysiology recordings confirmed robust neuronal responses at low μLED drive currents (< 5 mA), minimising thermal effects. Here we show that our device can be chronically implanted in freely-behaving mice and drive behavioural outcomes from spatiotemporal, patterned, optogenetic stimulation of auditory cortical circuits.

Achieving high resolution with optical neural interfaces is challenging. Here, the authors developed and chronically implanted 100-pixel microLED arrays on the surface of the mouse auditory cortex for optogenetic behavioural experiements.