We present a fully implantable, chronic system for untethered neuroscience research in freely behaving animals. The system infrastructure provides an experimental toolkit for recording electrical signals and activating neural tissues via a neurostimulator. This system provides the ability to investigate the dynamic behavior of neural circuits without the limitations of typical acute laboratory environments, tethered links, or the confounds of anesthesia that may undermine data interpretation. The engineering behind this device is briefly discussed with an emphasis on system considerations for chronic use. We describe here an implant in a black bear, Ursus americanus, to demonstrate system capabilities and provide a report of brain activity during bear hibernation.