Blue Laser Could Lead to Autism Cure

Eric Bland, Discovery News

Triggering Brain Waves

Triggering Brain Waves | Discovery News Video

April 29, 2009 — Lasers could one day cure, or at least aid in the search for drugs that treat diseases ranging from autism to schizophrenia, according to two new studies from the Massachusetts Institute of Technology and Stanford University and published in the online issue of the journal Nature.

A blue laser shined into a live mouse brain triggered gamma waves, which are a kind of brain wave necessary for concentration and cognition that people with autism and schizophrenia often lack.

"There are lots of theories about why [gamma wave oscillation] is impaired," said Li-Huei Tsai, a professor at MIT and a co-author on one of the Nature papers.

"This is the first proof that a specific set of neurons are responsible for gamma waves."

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The specific neurons that trigger gamma waves are called fast-spiking interneurons. Connected to hundreds of other neurons, interneurons regulate which neurons fire and which neurons remain silent. The coordinated firing of these neurons creates a variety of brain waves, from ten waves per second of alpha waves to 40 waves per second of gamma waves.

Scientists have known about gamma waves for decades. Using techniques that measure the brain’s electrical activity, like EEG, scientists detect gamma waves when subjects concentrate during activities like test-taking.

One characteristic of people with autism, attention deficit disorder and schizophrenia, is that they either don’t have gamma waves at all, or that the gamma waves they do have are irregular. Triggering gamma waves in people with these psychiatric conditions, might, the thinking goes, alleviate symptoms.

For decades scientists have suspected that fast-spiking interneurons trigger gamma waves, but lacked the means to prove their theory. Two different technologies, detailed in the two Nature studies, gave scientists the tools to prove their suspicion.

First scientists genetically engineered mice by splicing a gene, originally isolated by algae, that responds to blue light. Next they activated the gene by injecting a genetically engineered virus into a specific region of the brain known as the somatosensory cortex.

The fast-spiking neurons were now primed and ready to fire. All they needed was a spark, and the blue laser was that spark. When the scientists shined a blue laser onto fast-spiking interneurons infected with the engineered virus, they began to fire in sequence, 40 times each second, just like the scientists expected.

The neurons fired as long as the light shined on them, from a few seconds to a few minutes. The neurons continued to fire after the laser was removed, but scientists didn’t measure how long the effect lasted. The mice were anesthetized during the procedure, so the induced gamma waves didn’t change how the mice behaved.

"This is really powerful technology," said Edward Scolnick, Director of the Psychiatric Disease Program at the Broad Institute. "It allows you to turn on and off specific circuits inside the brain."

This is still basic research, caution scientists, limited to the lab and years away from any clinical or therapeutic use.

But Konstantinos Meletis, another MIT co-author, believes that the blue laser could directly treat autism, schizophrenia or attention deficient disorder.

A much more likely use for the combination of laser and genetic engineering is to indirectly treat psychiatric diseases by helping researchers identify drugs that induce gamma waves, as well as just learning more about how fast-spiking interneurons work, all of which future studies at MIT will examine.

"This is the first type of work addressing these cells, and theoretically you could expect that within years or decades this could be applied to human brains, but there is still plenty of work that needs to be done," said Meletis.

Blue Laser Could Lead to Autism Cure: Discovery News

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