Silicon probes are small, scalable devices that allow high-quality extracellular in vivo recordings from multiple neurons simultaneously. These probes can be mass-produced at low cost, and while they have been widely adopted for acute recordings in small laboratory animals, their application in chronic implants has been lagging. Implant-induced astrogliosis and a degradation in signal quality and neuron yield are thought to severely limit the use of silicon probes as chronic recording implants, but actual data on the brain's response has been scarce.
The Bonin lab set out to evaluate in vivo the response to a multisite silicon probe that is rigidly implanted in the mouse neocortex. In the study, the team tested a light-weight implant made of a CMOS-compatible titanium nitride silicon probe and a cranial window for cellular imaging.
Katrien Mols, PhD student in the Bonin lab: "We found that with a standard electrophysiological protocol, the local astrocytic response to a rigidly implanted multisite silicon probe is limited and shows little change from the second week up to the tenth week after probe implantation. We also did not observe an increase in noise amplitude or a degradation in signal amplitude of extracellular multiunit recordings for at least 10 weeks post-implantation."
Since the team observed little degradation in the quality of multiunit recordings over the 10-week observation period, Vincent Bonin is convinced that rigidly implanted silicon probes can provide good short-to-medium term chronic recordings with a limited astrocyte inflammatory response.
The results have been published in Cell Reports this week.
Katrien Mols, Silke Musa, Bart Nuttin, Liesbet Lagae & Vincent Bonin. In vivo characterization of the electrophysiological and astrocytic responses to a silicon neuroprobe implanted in the mouse neocortex. Scientific Reports 7, Article number: 15642 (2017) doi:10.1038/s41598-017-15121-1