Scalable Labeling for Cytoarchitectonic Characterization of Large Optically Cleared Human Neocortex Samples

Area of Science:

• Neuroscience
• Histology
• Optical Imaging

Background:

• Optical clearing and light sheet microscopy have advanced rodent brain imaging.
• Labeling and clearing thick human cortical tissue, especially formalin-fixed adult samples, remains challenging.
• Existing methods struggle with deep penetration and cellular resolution in large human brain samples.

Purpose of the Study:

• To develop a simple, fast, and low-cost method for cytoarchitectonic labeling of optically cleared human cortex.
• To enable deep volume imaging and detailed 3D characterization of human cortical architecture.
• To facilitate investigation of large-scale human cortical systems at cellular resolution.

Main Methods:

• Developed Multiscale Architectonic Staining of Human cortex (MASH) for large (up to 5 mm thick) formalin-fixed adult human brain samples.
• Utilized small-molecule fluorescent nuclear and cytoplasmic dyes combined with novel refractive index matching solutions.
• Applied MASH to archival samples of human visual areas for 3D architectural analysis.

Main Results:

• MASH allows for efficient cytoarchitectonic labeling and deep volume imaging of cleared human cortical tissue.
• The method enables classification of cytoarchitectonic layers across the full cortical depth.
• Demonstrated characterization of cortical architecture in 3D, from area to single-cell scales.

Conclusions:

• MASH significantly reduces the time and cost of imaging human cortical cytoarchitecture in thick samples.
• This technique allows for detailed 3D analysis of human brain architecture at cellular resolution.
• MASH, coupled with light sheet imaging and analysis, can advance the study of large human cortical systems.