Scientists Get Clearer Picture Of The Brain With Multiphoton Microscopy

Scientists Get Clearer Picture Of The Brain With Multiphoton Microscopy

24 January 2013

Scientists at Cornell University have inched closer to solving the mysteries of the brain, showing a new way of taking 3D images of the most complex organ with an optical resolution 100 to 1,000 times higher than MRI that allows a clear visualization of individual neurons.

The researchers, led by Chris Xu, associate professor of applied and engineering physics, have demonstrated high-resolution, 3D imaging of the subcortical area of a live, intact mouse brain, through a three-fold improvement in the depth limits of multiphoton microscopy, a fluorescence-based imaging technique with Cornell origin.

The scientists have pushed the fundamental depth limit of two-photon microscopy, the standard imaging technology invented in 1990 by Winfried Denk and Watt Webb at Cornell. The three-photon fluorescence imaging was first demonstrated in 1995 by Xu and Webb, but its advantages were not fully recognized.

The new paper, published in Nature Photonics, describes three-photon fluorescence, combined with a longer excitation wavelength of the laser pulse, to remove obstacles such as tissue scattering and absorption, thus enabling high-resolution imaging deep within biological tissues.

With the three-photon microscopy operating at a wavelength of 1,700 nm and the new laser specifically created for three-photon excitation, the researchers were able to perform high-resolution imaging of neurons at unprecedented depths within a mouse brain.

In the mouse model, the scientists used dyes and transgenic mice to test their multiphoton microscope on different fluorescent signals. If three-photon microscopy can be used to map the whole mouse brain it could help understand the intricate inner workings of the human brain, leading to major advancements in neuroscience and other clinically relevant areas, according to Xu.

Subcortical neural imaging could help find cures for diseases associated with changes deep inside the human brain such as Alzheimer's, Parkinson's and depression, Xu says, adding that brain mapping could be the main challenge in the next decade.