Some of the most exciting medical research these days involves light. Light therapy for cancer, in which a tumor-seeking dye becomes toxic as soon as a light is switched on, manages to avoid slaughtering nearby healthy cells. Optogenetics—using light to turn on or off the expression of neurons—has advanced researchers’ understanding of neurological diseases.
Now, a recent paper is a reminder that light might someday be used for exquisitely tailored drug delivery: in this paper, tiny packages bearing all the molecular machinery to build a protein are idle when injected into mice, but spring into action when exposed to UV light.
With optogenetics, a technique that uses beams of light to control the activity of particular cells, researchers have already flicked on clusters of neurons that trigger aggressive behavior and ramped up insulin production in mice. Now, scientists are applying the technique to the heart, working towards a cardiac pacemaker driven by light, Courtney Humphries reports in Technology Review.
The burgeoning field of optogenetics—using shot of light on neurons to control behavior—has already produced some intruiging and peculiar results. Now add one more: Scientists can use it to make mice angry and aggressive.
With a pulse of light, Dayu Lin from New York University can turn docile mice into violent fighters – it’s Dr Jekyll’s potion, delivered via fibre optic cable. The light activates a group of neurons in the mouse’s brain that are involved in aggressive behaviour. As a result, the mouse attacks other males, females, and even inanimate objects.
Lin focused on a primitive part of the brain called the hypothalamus that keeps our basic bodily functions ticking over. It lords over body temperature, hunger, thirst, sleep and more. In particular, Lin found that a small part of this area – the ventrolateral ventromedial hypothalamus (VMHvl) – acts as a hub for both sex and violence.
Read plenty more about this study in the rest of Ed’s post at Not Exactly Rocket Science.
80beats: Zapping Worm Brains With Lasers Reveals the Duty of Each Neuron
80beats: Star Trek-Style “Phaser” Paralyzes Worms With a UV Blast
80beats: Shiny New Neuroscience Technique (Optogenetics) Verifies a Familiar Method (fMRI)
80beats: Researchers Flip Brain Cells On and Off With Light Pulses
Taking advantage of the emerging technique of optogenetics, Harvard researchers report in the journal Nature Methods that they can target any individual neuron of the tiny transparent worm C. elegans, whether the creature is moving or at rest, and zap it with a laser to see what the particular cell does—move the worm to the left or right, or even cause it to lay eggs.
The whole process, from finding the cell to light hitting its target, takes about 20 milliseconds. As the worm’s position changes, that information is fed back into the computer program, and the laser is adjusted. If the worm crawls too far, a motorized microscope stage brings the animal back. One of the biggest benefits of the new method, [biologist William] Ryu says, is that it works in a roving animal. “The worms are not held down in any way — they’re freely moving. There aren’t many systems where you can look at such truly free organisms.” [Science News]
After a quarter-million scientific papers, you’d better hope your methodology was solid.
Most of the studies you’ve probably heard of that try to tie a specific region of the brain to an action or feeling probably relied on a functional MRI technique that tracks the flow of oxygenated blood–so when you see a region “light up” on an fMRI image, that’s not the fMRI picking up the actual neurons firing. Rather, it watches for small changes in blood oxygen levels in the region. This method, called blood oxygenation level-dependence (BOLD), presumes that active neurons use more energy and thus require more oxygen. Now, in a study in Nature, researchers at Stanford Medical Center have provided direct evidence that the inference is correct.
Lead researcher Karl Deisseroth employed a technique called optogenetics to prove the point. He and his colleagues engineered brain cells that respond to a flash of blue light; when they did this trick on cells in the motor cortex of rats, the flash of light acted as a trigger to active the neurons there. The idea was that they would examine these rats with fMRI at the same time they stimulated those motor neurons with the blue light. If the fMRI lit up in the same places where the researchers knew they were stimulating neurons, they could be confident that fMRI was really picking up brain activation.
Sure enough, when the neurons were turned on with a pulse of blue light, the researchers detected a strong BOLD signal emanating from the motor cortex neurons’ neighborhood. The BOLD signals were exactly what was expected. “It was very compelling and reassuring,” Deisseroth says. “Everyone can breathe a sigh of relief” [Science News].
Scientists have figured out a way to switch brain cells on and off like light bulbs, but instead of using a clapper, they’re using microbial proteins and lasers. Ed Boyden, a neuroscientist at the Massachusetts Institute of Technology, has developed a way to shut down parts of a brain just by shining light on them. When the light is turned off, the brain switches back on [Forbes].
The research team says their technology will help neuroscientists probe the brain’s circuitry by silencing certain regions and studying the effects. The technique, which was described in the journal Nature, could one day be used to shut down overactive regions of the brain often found in people with epilepsy, depression, Parkinson’s disease, and blindness.