We can hear the light and feel it in our hearts. It's not just terrible poetry - it might be fact. Scientists have shown that infrared light can stimulate the muscles in your heart and inner ear.
Researchers at the University of Utah have been spending long hours shooting infrared lasers at mouse heart cells and toadfish inner-ear cells. They did this not just for fun (though it has to be fun) but for science. The heart cells were muscles cells called cardiomyocytes, which are also found in humans. The inner ear cells were the tiny hairs that line the inner ear, and oyster toadfish inner ear cells have been used for quite some time as a model for human ear and balance responses. When the scientists saw that the cells responded to the laser, several new medical possibilities opened up.
One common misconception about infrared is it's the same as heat. Often hot bodies, such as heaters, put off both regular heat and infrared radiation, but heat is the random motion of atoms within a substance. The faster the atoms are moving, the hotter the substance is. Infrared radiation is an electromagnetic wave just like regular light - it's just too low-energy to be picked up by human eyes. Infrared light can cause objects to heat the same way regular light causes them to heat - light is energy and when substances absorb energy they heat up. But it's not heat, it's light.
And so it's very strange that something in our ears and hearts might be light-sensitive. The small hair cells of the inner ear are usually stimulated by mechanical changes. Vibrating air causes them to vibrate. Gravity can tug them one way or the other, which is where the human sense of balance comes from - if people tip their heads sideways they feel it in their ears. It's not like the inner ear gets a lot of optical stimulation. (And if all goes well, the heart doesn't see light very often either.) Why would they respond to infrared?
The hair cells of the inner ear, and the cardiomyocites are full of mitochondria. These are the little organs that act as cellular power stations, producing the molecule that serves as chemical energy for the cell. During the course of their operations, they let calcium ions flow in and out of them. Infrared light affects that flow. Calcium ions trigger the nerve cells to release neurotransmitters and the muscles cells to contract.
The ability of these cells to sense infrared radiation has a lot of medical professionals excited. Optical, instead of electrical, pacemakers are a possibility, although a remote one since current pacemakers work very well. Cochlear implants, devices that convert sound to electrical signals to help deaf people hear, could be much improved by the use of infrared signals. Balance disorders, or the natural loss of balance due to aging, could also be ameliorated with pulses of infrared in the ear. Plus, these infrared devices wouldn't be as invasive as current ones. Infrared can penetrate into the body a certain distance, which would eliminate the need to give the devices direct contact with nerve cells.
They could be a boon to people losing their sight as well. Certain diseases cause people to lose the rods and cones in their eyes that receive optical signals but not the underlying nerve cells. Obviously, these people can't send electrical impulse directly into their eyeballs, but they can use infrared signals to trigger the nerve cells. It looks like this discovery can restore any number of senses to people currently going without.
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