Janelle Shane @JanelleCShane Research Scientist in optics. Plays with neural networks. Avid reader, writer, and player of Irish flute. she/her. wandering.shop/@janellecshane Jul. 19, 2019 2 min read

So excited our paper is out! And written up by @carlzimmer! I personally calibrated the device in the picture, a programmable hologram that steers laser beams to zap neurons.

Our collaborators at Stanford eavesdropped on neuron activity while mice were seeing vertical stripe patterns. When they later displayed nothing but activated some of those same neurons by zapping them with laser beams, the mice acted as if they were still seeing stripes.

They don't know if the mice were seeing the original stripe pattern exactly. Maybe they were only seeing something that resembled stripes enough that the mice could figure out that they were supposed to do their pipe-licking thing, just like with real stripes.

What's particularly cool is that though thousands of neurons responded when the mice saw real stripes, our colleagues could recreate the effect by laser-zapping as few as two neurons. Other neurons would light up in response and the mouse would act as if it saw stripes.

This is very much a @justsaysinmice situation, where the mice were genetically engineered to have neurons that light up when they fire, and neurons that can be activated by laser zaps. The mice also had windows implanted in their skulls so the light could get in and out.

In other words, this technique isn't going to be usable on humans. No laser-zappy computer display or immersive reality for us. We can only entertain mice this way. But it will be fascinating to see what we learn about biological neural networks.

Very excited to be a part of this research! I worked on the laser-steering device, a computer-controlled holographic beam steerer called a spatial light modulator (SLM). My colleagues & I spent a ton of time getting them to run fast enough to keep up w/neuron activity.

And the SLMs are HUGE - the one in the picture is a 30.7 x 30.7mm display, ridiculously large for a single silicon chip. That made it extra challenging to get them to run at such high frame rates. Our colleagues interleaved patterns from two SLMs to double the frame rate.

Here's a more-detailed summary by @KellyServick :  https://www.sciencemag.org/news/2019/07/laser-holograms-stimulate-brain-cells-mice-probe-roots-perception-and-hallucination 
and the original paper (paywalled)  https://science.sciencemag.org/content/early/2019/07/17/science.aaw5202 

Clarification: the two-neuron activation is in another paper out last week in CELL from the Yuste group at Columbia:  https://www.cell.com/cell/pdf/S0092-8674(19)30616-6.pdf 
This Science paper activated as few as 10-20 neurons (they weren't trying to push it to its lower limits).


You can follow @JanelleCShane.



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