Close-packed dual-color micro-LEDs enable cortical-layer-specific bidirectional in vivo optogenetic electrophysiology

Optogenetics promises to manipulate the brain circuitry by exciting or inhibiting the same neurons via different colors of light (i.e., bidirectionality), and furthermore, to co-work with electrophysiology for low-crosstalk, high-resolution probing of the brain. Limited by feasible integration methods, though, neural probes with close packed dual-color light sources remain underdeveloped, making high-resolution bidirectional in vivo optogenetic electrophysiology technically challenging. Here, we report, based on heterogeneously stacked III-V epitaxial films, a monolithic neural probe integrated with close-packed dual-color micro-light-emitting diodes (LEDs) and microelectrodes in 20-and 50 -mm pitches, respectively. The resulting devices enable bidirectional in vivo optogenetic electrophysiology across layers IV and V of mouse somatosensory cortex, where dual-color LEDs are observed to excite and inhibit layer -specific brain dynamics. Such interlayer bidirectional in vivo optogenetic studies, to which our scalable probes are well suited, can add to high-resolution interrogation of the brain circuitry and shed light on animal disease models.