A Wearable Fiber-free Optical Sensor for Continuous Monitoring of Cerebral Blood Flow in Freely Behaving Mice

Abstract

Wearable technologies for functional brain monitoring in freely behaving subjects would advance our understanding of cognitive processing and adaptive behavior. Existing technologies are lacking in this capability or need procedures which are invasive and/or otherwise impede brain assessments during social behavioral conditions, exercise, and sleep. In response we developed a complete system combining cerebral blood flow (CBF) measurement, O2 and CO2 supplies, and behavior recording for use on conscious, freely behaving mice. An innovative diffuse speckle contrast flowmetry (DSCF) device and associated hardware were miniaturized and optimized for small subject applications. The installation and use of this wearable, fiber-free, near-infrared DSCF head-stage/probe required no craniotomy, invasive probe implantation, or restraints of awake animals. Significant correlations were found between measurements with the new DSCF design and an optical standard. The system successfully and repeatedly detected CBF responses to CO2-induced hypercapnia in both anesthetized and moving mice. Collecting CBF and activity information together during natural behaviors provides realistic physiological results and opens the path to exploring their correlations with pathophysiological conditions.