Continuous long‐term recording and triggering of brain neurovascular activity and behaviour in freely moving rodents

Abstract

support-information-section).A minimally invasive, microchip-based approach enables continuous long-term recording of brain neurovascular activity, heart rate, and head movement in freely behaving rodents. This approach can also be used for transcranial optical triggering of cortical activity in mice expressing channelrhodopsin. The system uses optical intrinsic signal recording to measure cerebral blood volume, which under baseline conditions is correlated with spontaneous neuronal activity. The arterial pulse and breathing can be quantified as a component of the optical intrinsic signal. D. N. Yousef Yengej and others

Different characteristics of cortical spreading depression in the sleep and wake states

“…With green illumination the OIS primarily indicates CBV 10 (i.e., tissue gets darker/lighter as arteries dilate/constrict and CBV increases/decreases, respectively). CSD in rodents is associated with a dramatic multiphasic change in OIS that is 100% correlated with the classical electrophysiological changes of CSD 11,14 …”

“…Microchips were permanently glued to the skull in a short (<30 min) surgical procedure, as previously described 14 . Carpofen (5 mg/kg sc) and topical 2% lidocaine were administered as analgesics at the time of the procedure.…”

“…The custom‐made chip system (Syrinx Industrial Electronics) comprises an optical sensor and green light‐emitting diodes (LEDs) for illumination and OIS measurements, a blue LED for optical stimulation of channelrhodopsin, and a movement sensor. Implants were connected via recording wires to a micro‐computer (Raspberry Pi Foundation), running custom software 14 . Data was continuously sampled at 128 Hz.…”

“…If a baseline threshold was well determined, stimulations were started three to four steps before that baseline for subsequent CSDs. CSD triggered under isoflurane anesthesia was performed as previously described 14 …”

“…We have developed a minimally invasive microchip‐based recording and stimulation method to continuously quantify cerebral blood volume (CBV) and motor activity in mice over extended time periods, and to intermittently trigger brain activity, including CSD 14 . We showed that CSD triggered under anesthesia versus the awake state in the same mouse has remarkably different characteristics 14 . Now, we hypothesized that the characteristics of CSD would be different when triggered in the awake versus sleep states in the same animals.…”