Neurovascular coupling investigated by simultaneous optical coherence tomography and electrophysiology

Abstract

A comprehensive understanding of the neurovascular coupling relationship requires the simultaneous measurement of neuronal and vascular responses and the capability to probe all layers of the cerebral cortex. Current macroscopic imaging techniques like laser Doppler imaging, diffuse optical tomography, fMRI, and PET lack spatial resolution. While two-photon microscopy is widely used in imaging the brain, it suffers from a lack of depth penetration and imaging speed. Optical coherence tomography (OCT) provides a platform for imaging the brain that potentially overcomes all of the above disadvantages, providing high-resolution cross-sectional images of light backscattered from cortical tissue. Here, we outline the experimental methods involved in simultaneous OCT (hemodynamic) and electrophysiological (neuronal) measurements to investigate neurovascular coupling in the rat somatosensory cortex. Using a spectral/ Fourier domain OCT system, changes in cerebral blood flow and scattering were measured from multiple cortical layers. Simultaneous neuronal responses from layer IV using a tungsten microelectrode and surface potentials from a fire-polished ball electrode were also measured. This chapter provides details on animal preparation, instrumental setup, and data acquisition methods, and, finally, discusses potential limitations and pitfalls.