Telling voices Friday Review

Light for the brain

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American neuroscientist Ed Boyden’s ideas have revolutionised the way brain science thinks and hold much hope for the cure of several diseases, notes Sudhamahi Regunathan

Ed Boyden has been recognised as one who has changed the way brain science thinks. The ideas have not really been completely translated into medical practice but hold out much hope.

It is definitely not reassuring when Boyden begins by saying, “…a significant fraction of us in this room, if we live long enough, will encounter, perhaps, a brain disorder.” Not just that. Boyden adds, “Already, a billion people have had some kind of brain disorder that incapacitates them, and the numbers don’t do justice to it though. These disorders —schizophrenia, Alzheimer’s, depression, addiction — they not only steal our time to live, they change who we are. They take our identity and change our emotions and change who we are as people.”

Indeed. They change who we are. But who are we? We are defined primarily by the brain about which Boyden says, “…the brain…an incredibly complicated circuit made out of hundreds of billions of cells called neurons…They come in different shapes; they’re made out of different molecules. And they project and connect to different brain regions, and they also change different ways in different disease states.”

Boyden, a synthetic neuroscientist, says we could use light and not drugs to modify/correct/explore the workings of the brain and keep ourselves as we know ourselves.

Says Boyden, “I had trained as an electrical engineer and a physicist, and the first thing I thought about was, if these neurons are electrical devices, all we need to do is to find some way of driving those electrical changes at a distance. If we could turn on the electricity in one cell, but not its neighbours, that would give us the tool we need to activate and shut down these different cells, figure out what they do and how they contribute to the networks in which they're embedded. And also it would allow us to have the ultra-precise control we need in order to fix the circuit computations that have gone awry. Now how are we going to do that?”

Boyden finds there are many molecules that exist in nature, which are able to convert light into electricity. They are like little proteins that are like solar cells.

In 2004 Boyden and his team took a certain alga that swims in the wild, and needs to navigate towards light in order to photosynthesise optimally and found, “…it senses light with a little eye-spot, which works not unlike how our eye works. In its membrane, or its boundary, it contains little proteins that indeed can convert light into electricity. So these molecules are called channelrhodopsins. And each of these proteins acts just like a solar cell...”

When these channelrhodopsins are installed in neurons, Boyden says, “The neuron uses its natural protein-making machinery to fabricate these little light-sensitive proteins and install them all over the cell, like putting solar panels on a roof, and the next thing you know, you have a neuron which can be activated with light. So this is very powerful…If we can install these molecules in neurons somehow, then these neurons would become electrically drivable with light. And their neighbours, which don't have the molecule, would not,” says Boyden claiming that we can get them into the brain just as we lay optical fibres in the ground.

A small but interesting statement he makes is that the brain does not feel pain!

Of course the next question would be how would select just those cells you want to be activated. Boyden says, “…you can tweak the viruses so they hit just some cells and not others. This field has now come to be known as optogenetics. And just as one example of the kind of thing you can do, you can take a complex network, use one of these viruses to deliver the gene just to one kind of cell in this dense network. And then when you shine light on the entire network, just that cell type will be activated.”

Boyden says one can control seizures or epilepsy, Parkinsons, schizophrenia and all such with light instead of drugs. Even blindness.

sudhamahi@gmail.com

Web link:

http://www.ted.com/talks/ed_boyden

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Printable version | Dec 8, 2019 11:47:03 AM | https://www.thehindu.com/features/friday-review/Light-for-the-brain/article14628609.ece

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