It’s a noisy world out there. Whether it’s the sound of traffic, a crowded office with phones ringing and printers clacking, or a busy restaurant, the amount of auditory stimuli in normal every day environments can make it hard to focus. How does the brain filter out the noise we don’t need to hear, and allow in the important noises like a honking horn to alert us to an oncoming car, or a siren that lets us know to give way to an emergency vehicle?
In new research from Johns Hopkins University, published recently
the journal Proceedings of the National Academy of Sciences, a team of neuroscientists and biologists looked at how bats determine what sounds they need to pay attention to, and which they can safely ignore or filter out.
Bats are nocturnal, hunting at night since more insects are around after sunset and there far less predators. Since there isn’t normally much ambient light, bats are often flying through the air in total darkness. To keep from bashing into trees or other obstacles bats use echolocation
to navigate their environment. Much like sonar pings used in submarines, they will chirp as they fly around and those sounds are echoed off trees, rocks, mountains etc. coming back to them in distinct patterns depending on the surroundings.
Bats too have much to discern in these patterns and in other noises. In the research at Johns Hopkins, the team monitored the mid-brain activity of bats to see which sounds would evoke a response and which could be ignored. They played recorded sounds of the bats own chirping noises as well as white noise and other random sounds. All of the sounds were played for the same duration and the same volume. In the mid-brain of bats, all of the sensorimotor neurons reacted to all of the sounds in some way. However, the specific neurons that are involved in stimulus selection and that guide the bats navigation patterns only responded to natural chirping sounds. The white noise and other sounds were effectively ignored by the bats so they could focus on the sounds they needed to guide them.
In a press release
from Johns Hopkins Department of Psychological and Brain Sciences, lead author for the study Melville J. Wohlgemuth said, “With so many stimuli in the world, the brain needs a filter to determine what’s important. The bat brain has developed special sensitivities that allow it to pick out sounds from the environment that are pertinent to the animal. We were able to uncover these sensitivities because we used the perfect stimulus — the bat’s own vocalizations.”
Check out the video below to see more about the study and how bat echolocation might show us how the human brain filters noise to stay focused.