Continuous and longitudinal monitoring of cerebral blood flow (CBF) in animal models provides information for studying the mechanisms and interventions of various cerebral diseases. Since anesthesia may affect brain hemodynamics, researchers have been seeking wearable devices for use in conscious animals. We present a wearable diffuse speckle contrast flowmeter (DSCF) probe for monitoring CBF variations in mice. The DSCF probe consists of a small low-power near-infrared laser diode as a point source and an ultra-small low-power CMOS camera as a 2D detector array, which can be affixed on a mouse head. The movement of red blood cells in brain cortex (i.e., CBF) produces spatial fluctuations of laser speckles, which are captured by the camera. The DSCF system was calibrated using tissue phantoms and validated in a human forearm and mouse brains for continuous monitoring of blood flow increases and decreases against the established technologies. Significant correlations were observed among these measurements (R2 ≥ 0.80, p < 10−5). This small fiberless probe has the potential to be worn by a freely moving conscious mouse. Moreover, the flexible source-detector configuration allows for varied probing depths up to ~8 mm, which is sufficient for transcranially detecting CBF in the cortices of rodents and newborn infants.

No 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, O 2 and CO 2 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 CO 2induced 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.

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.

No abstract