An affordable solution for investigating zebra finch intracranial electroencephalography (iEEG) signals

The Zebra finch is a well-studied animal for studying neural mechanisms of speech, and electrophysiology is the primary technique for understanding the song system in them. Most of the studies on zebra finches have focused on intracerebral recordings. However, these methods are only affordable for limited laboratories. Recently, different open-source hardware for acquiring EEG signals has been developed. It is unclear whether these solutions suit zebra finch studies as they have not been evaluated. Electrocorticography signals can provide a preliminary guide for more in-depth inquiries and also aid in understanding the global behavior of the bird's brain, as opposed to the more common localized approach. We provide a detailed protocol for acquiring iEEG data from zebra finches with an open-source device. We implemented stainless steel electrodes on the brain's surface and recorded the brain signals from two recording sites. To validate our method, we ran two different experiments. In the first experiment, we recorded neural activity under various concentrations of isoflurane and extracted the suppression duration to measure anesthesia depth. In the second experiment, we head-fixed the birds and presented them with different auditory stimuli to evaluate event-related potential (ERP). Results showed a significant increase in the suppression duration by increasing the anesthesia depth and evident ERP response to auditory stimuli. These findings indicate that by our methodology, we can successfully collect iEEG signals from awake and anesthetized birds. These findings pave the way for future studies to use iEEG to investigate bird cognition.