A drivable optrode for use in chronic electrophysiology and optogenetic experiments

Combining optogenetic tools with behaving electrophysiology is a powerful approach for investigating the neural mechanisms underlying behavior. A traditional approach to ensure viable recordings during chronic long-term electrophysiological experiments is the use of drivable electrodes. However, few options exist for drivable optrodes.

Here, we describe the design and construction of an economical drivable optrode for chronic experiments in behaving rodents, which allows for the simultaneous photo-stimulation and recording of distinct neuronal populations.

We demonstrate the utility of the drivable optrode by recording light-evoked modulation in awake behaving rats over multiple recording sessions and across different depths. Using a virus to drive expression of channelrhodopsin-2 (ChR2) in the anterior piriform cortex, the drivable optrode was used to record consistent light-evoked modulation of neural activity in the gustatory cortex during photo-activation of the axonal projections from anterior piriform cortex in behaving rats.

Although sophisticated optrodes have been developed, many are expensive, unmodifiable, require advanced engineering techniques, and/or lack drivability. The drivable optrode uses relatively inexpensive materials, requires no machined parts, and can be fabricated with tools available in most labs. In addition, it can be easily modified to accommodate different experimental parameters.

In summary, we believe that the cost-effective and relatively simple-to-prepare design makes this drivable optrode a practical option for researchers using optogenetic and electrophysiological tools to investigate network and circuit function.