New automated imaging greatly speeds up brain mapping

3-D rendering of coronal section of a mouse brain imaged with STP tomography at 20x at a resolution of half a micron.

GFP-expressing pyramidal neurons in hippocampus and cortex are targeted.

A new technology developed by neuroscientists at Cold Spring Harbor Laboratory (CSHL) transforms the way highly detailed anatomical images can be made of whole brains.

Until now, means of obtaining such images – used in cutting-edge projects to map the mammalian brain -- have been painstakingly slow and available only to a handful of highly specialized research teams.

By automating and standardizing the process in which brain samples are divided into sections and then imaged sequentially at precise spatial orientations in two-photon microscopes, the team, led by Assoc. Prof. Pavel Osten and consisting of scientists from his CSHL lab and the Massachusetts Institute of Technology, has opened the door to making whole-brain mapping routine.

Specifically, says Osten, "the new technology should greatly facilitate the systematic study of neuroanatomy in mouse models of human brain disorders such as schizophrenia and autism."

The new technology, developed in concert with TissueVision of Cambridge, Mass. and reported on in a paper appearing online Jan. 15 in Nature Methods, is called Serial Two-Photon Tomography, or STP tomography.

Tomography refers to any process (including the familiar CAT and PET scans used in medical diagnostics) that images an object section by section, by shooting penetrating waves through it.

Computers powered by mathematical formulae reassemble the results to produce a three-dimensional rendering. Two-photon imaging is a type used in biology laboratories, particularly in conjunction with fluorescent biomarkers, which can be mobilized to illuminate specific cell types or other anatomical features.

The two-photon method allows deeper optical penetration into the tissue being sampled than conventional confocal microscopy.

As Osten explains, STP tomography achieves high-throughput fluorescence imaging of whole mouse brains via robotic integration of the two fundamental steps -- tissue sectioning and fluorescence imaging. In their paper, his team reports on the results of several mouse-brain imaging experiments, which indicate the uses and sensitivity of the new tool.

They conclude that it is sufficiently mature to be used in whole-brain mapping efforts such as the ongoing Allen Mouse Brain Atlas project.

One set of experiments tested the technology at different levels of resolution. At 10x magnification of brain tissue samples, they performed fast imaging "at a resolution sufficient to visualize the distribution and morphology of green-fluorescent protein-labeled neurons, including their dendrites and axons," Osten reports.