The method in a nutshell
Polarized light imaging makes use of birefringence, an optical effect of myelinated nerve fibres which causes a change of the oscillation behaviour (i.e., the polarization state) of an interacting light wave. To achieve high-quality measurements, the integrity of the myelin sheaths needs to be preserved. This requires specific tissue handling and preparation. To preserve myelin sheaths, conserved brain tissue is sectioned at very low temperatures (-50 °C).
During sectioning, en face images of the remaining brain block are acquired (blockface imaging) serving as reference images for later reconstruction of the initial brain shape. The generated unstained histological brain sections are scanned with different types of polarimetric setups, which are generally speaking composed of one linear and one circular polarizer and a green-wavelength light source. High-performance computing and simulation approaches enable reliable interpretation and visualization of the targeted fibre architecture.