Measurement and visualization of stimulus-evoked tissue dynamics in mouse barrel cortex using phase-sensitive optical coherence tomography.

Peijun Tang,Adiya Rakymzhan,Zhiying Xie,Ruikang K Wang,Yuandong Li

doi:10.1364/boe.381332

Abstract

We describe a method to measure tissue dynamics in mouse barrel cortex during functional activation via phase-sensitive optical coherence tomography (PhS-OCT). The method measures the phase changes in OCT signals, which are induced by the tissue volume change, upon which to localize the activated tissue region. Phase unwrapping, compensation and normalization are applied to increase the dynamic range of the OCT phase detection. To guide the OCT scanning, intrinsic optical signal imaging (IOSI) system equipped with a green light laser source (532 nm) is integrated with the PhS-OCT system to provide a full field time-lapsed images of the reflectance that is used to identify the transversal 2D localized tissue response in the mouse brain. The OCT results show a localized decrease in the OCT phase signal in the activated region of the mouse brain tissue. The decrease in the phase signal may be originated from the brain tissue compression caused by the vasodilatation in the activated region. The activated region revealed in the cross-sectional OCT image is consistent with that identified by the IOSI imaging, indicating the phase change in the OCT signals may associate with the changes in the corresponding hemodynamics. In vivo localized tissue dynamics in the barrel cortex at depth during whisker stimulation is observed and monitored in this study.

Highlights

Optical detection of the neural activity in brain is gaining increasing interests in the field of neuroscience in recent years, because several physiological changes associated with neuronal activity can be observed by the optical methods with high spatiotemporal resolution and without requiring the use of labeling tools and invasive procedures
The previous studies of optical neural activity imaging mainly use the optical methods such as laser speckle contrast imaging (LSCI) [1,2,3,4,5], laser doppler flowmetry (LDF) [6,7,8], near-infrared (NIR) spectroscopy [9,10], and optical coherence tomography [11,12,13,14,15,16,17,18] to detect the vascular responses to brain such as the changes in cerebral blood flow (CBF) [1,5], cerebral blood volume (CBV) [3,4], deoxyhemoglobin concentration (HbR) and oxyhemoglobin (Hb-O2) [1,2,4]
We first present the intrinsic optical signal imaging (IOSI) result that maps the hemodynamic changes in the mouse barrel cortex during whisker stimulation as an indication of neural activity

Summary

Introduction

Optical detection of the neural activity in brain is gaining increasing interests in the field of neuroscience in recent years, because several physiological changes associated with neuronal activity can be observed by the optical methods with high spatiotemporal resolution and without requiring the use of labeling tools and invasive procedures. One of the interesting findings is that the change in neural tissue volume induced by the neuronal activation can modulate the optical properties of the tissue [23,24,25,26] This phenomenon has been observed by several techniques such as traditional microscopy imaging [26], dark-field microscope [23,25] and organic photodetector (OPD) [24]. These optical techniques can only provide one-dimensional (1-D) signals or two-dimensional (2-D) brain-slice images in vitro, and they do not enable depth resolution

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Discussion

Conclusion