Simultaneous high-density 512-channel SiNAPS electrical recordings and optogenetics.

The experimental use of CMOS high-density neural probes enables the wide field observation of the electrical activity of neural circuits at the resolution of single neurons. Optogenetic light stimulation allows to control and modulate the activity of neural cells, in a genetically selective manner. The combination of these techniques can be a powerful approach for investigating mechanisms of brain diseases and of information processing in the brain. The main obstacle to combining such techniques, however, is the photosensitivity of CMOS circuits and consequent photoelectric artefacts affecting electrophysiological recordings. This paper presents a CMOS based high-density SiNAPS neural implant which was designed to be combined with a tapered optical fiber. A photoelectric shield was created on a 512-channel probe, where the electrodes are arranged in 4 columns with 29.5 μm electrode pitch. Results show the light sensitivity of the probe with and without the photoelectric shield and the capability of recording light-evoked responses in vivo. More than 180 neurons were recorded without any light-induced distortion of the electrophysiological signals.