Polarized light imaging of the human brain: a new approach to the data analysis of tilted sections

Abstract

3D-Polarized Light Imaging (3D-PLI) is a unique technique that enables high-resolution three-dimensional mapping of the nerve fiber architecture in unstained histological sections of the human brain. 3D-PLI is based on the detection of the intrinsic tissue birefringence caused by the nerve fibers. The measured birefringent signals comprise entangled information on both spatial fiber orientation and the local fiber density. In this study, we introduce a novel approach to effectively and unambiguously unravel this interrelation, for providing a reliable estimation of fiber orientations in the entire human brain. The method relies on an in-house developed polarimetric device equipped with a tiltable specimen stage. Each brain section is measured from different perspectives and the obtained data sets are processed with a dedicated Fourier analysis optimized for fast computation and shot noise stability. For the first time it is demonstrated, that the prevailing orientations of cortical fibers can be quantified in the three-dimensional space and traced back into the white matter. Moreover, the approach provides descriptions of variances in fiber density. Hence, the method presented here opens new perspectives for the neuroanatomical study of the human cortex.