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.
Significance: Low-frequency oscillations (LFOs) (<0.1 Hz) with respect to cerebral blood flow (CBF) have shown promise as an indicator of altered neurologic activity in the abnormal brain. Portable optical instruments have evolved to offer a noninvasive alternative for continuous CBF monitoring at the bedside compared with many large neuroimaging modalities. However, their utilization for acquiring LFOs of CBF has only been studied to a limited extent.Aim: We aim to optimize an innovative speckle contrast diffuse correlation tomography (scDCT) system for the detection of LFOs within CBF variations. Approach:The scDCT was optimized to achieve a higher sampling rate and a faster image reconstruction using a moving window 3D reconstruction algorithm with parallel computation. Power spectral density (PSD) analysis was performed to investigate altered LFOs during transient global cerebral ischemia in neonatal piglets.Results: Transient global cerebral ischemia resulted in reductions in both CBF and PSD compared with their baseline values.Conclusions: Spontaneous LFOs, combined with CBF, provide a more comprehensive assay with the potential to clarify pathological mechanisms involved in brain injury. These results support scDCT's inclusion and application in the growing area of LFO analysis and demonstrate its inherent advantage for neurological studies in preclinical and clinical settings, such as neonatal intensive care units.
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.
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