A Guide to In vivo Single-unit Recording from Optogenetically Identified Cortical Inhibitory Interneurons

The overall goal of the following experiment is to obtain high quality extracellular single unit recordings from cortical inter neurons in mice expressing channel rootin two. This is achieved by advancing a high impedance recording electrode through the tissue to identify inter neurons from spiking responses to blue light pulses. The electrical signal is monitored for changes that indicate the appropriate rate of advance and likelihood of obtaining a stable well isolated recording.

If good single unit isolation cannot be achieved or conversely light responsive neurons are rarely encountered, replace the recording electrode. The results show the reliability of light evokes responses from optically identified into neurons and the typical signal to noise ratio obtained with this strategy. The photo stimulation approach is an accessible and inexpensive way to target genetically identified cell types using a standard extracellular amplifier and blue light.