Scientists think that they have found a way to enable humans to see in the dark by harnessing an in-built attribute that they have identified.
Few animals like cats can see in the dark. That is so because they have a well-developed infrared vision which is adept in detecting thermal imprints. Every hot-blooded animal, of which a human is one, give off heat, which manifests as infrared radiation. To enable the ocular faculty of cats and other night-vision enabled animals and snakes like the rattlesnake to be activated, there must be a discernible temperature differential between the objects. But these rays remain altogether invisible to the human eye.
Humans are completely blind in the dark. They can see in the darkness only if there is a faint light source say like a moonlight. And even in these low-light conditions, humans will need ten to thirty seconds to acclimatize. Though there are night goggles to convey the infrared radiation to the brain but that vision lacks the clarity of daylight visuals.
But now, if some scientists are to be believed humans can see even in the complete absence of light! And apparently we humans had this faculty all along. These scientists have identified that the retinal circuits that were previously thought to be inflexible and strictly programmed for specific day-time tasks only are actually adaptive to other light conditions as well. It means that the retina has within itself the wherewithal to reprogram itself for low visibility conditions.
As per a paper published in Neuron, a biweekly peer-reviewed scientific journal that covers neuroscience and related biological processes, the reprogramming can happen in retinal cells which are sensitive to motion.
As such, recognising the presence and direction of moving objects, even in broad daylight is a key survival criteria for most animals. But detecting motion with a singular point of reference isn’t easy. That’s why retinas of vertebrates need to employ four types of purpose-built directional cells which are: up, down, right or left. These motion-sensitive neurons comprise about only 4 percent of the cells that send signals from the retina to the brain, in humans.
A study conducted on mice revealed that the retinal cells connected to the ‘up’ movement changed their behaviour in a lesser light environment. The brain sensed the movement by coalescing a weak motion signal from the ‘up’ neurons with another similarly weak signal from any one of the other directional cells.
Taking a cue, scientists believe that if relevant neurons could be controlled remotely, then it could revolutionise human biology. Implantable retinal prosthetic could be designed to mimic the adaptability of retinal neurons to help humans see in the dark, in the near future.