Implantable nanophotonic neural probes for integrated patterned photostimulation and electrophysiological recording

Abstract Optogenetics enables precise neural circuit manipulation with light. However, optical attenuation poses a challenge to deliver spatially shaped light that controls the stimulation volume into deep brain regions. Here, we overcome this challenge with foundry-fabricated implantable silicon neural probes with microelectrodes and nanophotonic circuits. The probes emit engineered beam profiles with sufficiently high powers to excite neural activity ranging from cellular spikes to network-wide responses. Our in vivo experiments evaluated probes emitting low-divergence beams or planar sheets, both of which could selectively stimulate neurons at different depths. Comparisons of their evoked spiking responses showed that the light sheet probes induced greater firing rate fatigue at lower optical intensities than the low-divergence probes. Light sheets can also induce seizures in the hippocampus of an epilepsy mouse model while keeping the temperature rise ≲ 1 °C. Integrating additional devices, such as wavelength multiplexers and photodetectors, will lead to versatile implants for multimodal brain activity mapping.