A new technique will allow us to watch hundreds of neurons in 3D, in real time, at a resolution that’s 50 times greater than before.
The technology, known as digital holographic microscopy (DHM), was imported into neuroscience from materials science. It measures differences in the wavelengths of harmless lasers as they travel through a certain region of the brain – and this allows a computer system to construct precise 3D models of neurons at work.
Since individual neurons are transparent, scientists used to use various kinds of chemical stains in order to study them. The cells have to be extracted and placed in a Petri dish before being stained, which causes all kinds of hangups: it takes time, it changes the chemical composition of the cells, and (obviously) it physically damages them.
Patch clamps and other electrodes allow scientists to study the electrochemical activity of neurons without removing them, but even these techniques tend to be damaging – and they’re really only helpful for studying small groups of neurons.
But DHM blasts all these problems away – with lasers.
DHM [images cells] with a laser beam, by pointing a single wavelength at an object, collecting the distorted wave on the other side, and comparing it to a reference beam. A computer then numerically reconstructs a 3D image of the object — in this case, neurons — using an algorithm developed by the authors. In addition, the laser beam travels through the transparent cells and important information about their internal composition is obtained.
And all this happens without chemically disrupting the cells, physically damaging them, or even moving them at all. Even cooler, it can record high-resolution images of hundreds of neurons at a time – giving us a much clearer picture of the brain’s patterns of chemical and electrical activity, and the relationships between the two.
In fact, the Journal of Neuroscience reports, a team led by Pierre Magistretti of Switzerland’s Brain Mind Institute showed off DHM’s awesomeness by using it to track some neurotransmitter chemicals in real-time 3D:
In a recent study, we showed that the quantitative monitoring of the phase signal by DHM was a simple label-free method to study the effects of glutamate on neuronal optical responses … DHM is the first imaging technique able to monitor dynamically and in situ the activity of these cotransporters [a certain kind of neurotransmitters] during physiological and/or pathological neuronal conditions.
A genuine Real Genius moment for neuroscience.
The team hope this new technology will lead to quicker and more accurate diagnoses of neurodegenerative diseases like Alzheimer’s and Parkinson’s – and even to the development of more precisely targeted drugs to combat the exact kinds of damage those diseases cause:
What normally would take 12 hours in the lab can now be done in 15 to 30 minutes, greatly decreasing the time it takes for researchers to know if a drug is effective or not.
It’s also exciting to think about the potential of integrating DHM data with information gathered in fMRI scans – it could give us a much more detailed understanding of how larger activation patterns in the brain are created by the interactions between individual neurons. In short, this could be a major boost for connectomics research.
Sometimes, you’ve got to take a step back and think, “You know, we’re actually using lasers and holograms for real scientific purposes.” Living in the future’s pretty cool, isn’t it?