Image: Lloyd Russell, Hausser lab, UCL

How to Make a Smiley Face out of Living Neurons

It requires some experimental brain stimulation techniques.

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Dec 22 2014, 5:10pm

Image: Lloyd Russell, Hausser lab, UCL

Neuroscience isn't all implant this, stimulate that. Sometimes, you get to make a smiley face out of mouse neurons.

Neuroscientists at University College London (UCL) wanted to simultaneously stimulate individual neurons in living mice and map where those signals traveled. To do this, the team combined two optogenetic brain stimulation techniques to allow them to better probe the brain using light.

The first involves infecting mice brains with a virus carrying a light-sensitive protein found in algae that is only expressed in certain predetermined neurons. By shooting lasers at these neurons, scientists can activate them.

The second technique required the UCL researchers to infect those same neurons with green fluorescent light-sensitive proteins that glow when activated by light. By combining these two techniques, the researchers devised a system where they could activate a mouse's neurons with beams of light and observe how they reacted in concert with surrounding neurons.

A notable aspect of the new paper is that the researchers were able to record those stimulation patterns in living mice using a two-photon dual-beampathresonant scanning microscope. The end result, the researchers wrote in a paper published today in Nature Methods, is a new method for looking at how neural circuits—or pathways—react to cell activation in real time.


Mice in treadmills had their brains stimulated and imaged in real time (A), with neuronal response highlighted using two different proteins (B). Image: Lloyd Russell, Hausser lab, Nature Methods

Neural circuits are interconnected series of neurons that govern different activities. By shooting lasers at specific groups of neurons known to correspond to motor activity, for example, researchers can take a look at how the surrounding neurons light up in different patterns and identify pathways that correspond to various actions.

Or, you know, you could just make a smiley face out of mouse neurons. 

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