We may not spend a lot of time thinking about our ears, but we should probably take better care of them, because they are essential in making sense of the world around us. In fact, they are so sensitive and complex that scientists are still discovering new things about how the ears communicate with the brain and how this affects our environment.
We already know how the brain performs the horizontal localization of sound thanks to what we call interaural time difference between ears (DIT). This DTI is basically a stereophonic system, where an infinitesimal but perceptible delay, between the moment when the sound waves reach the left ear and the right ear, tells the brain if the source of that sound is located to our left or to our left. right.
But what happens vertically? This part is not so well understood, but a recent study led by neuroscientist Régis Trapeau of the University of Montreal (Canada) sheds light on how we differentiate the sounds in the vertical panel.
The experts conducted an experiment. 16 volunteers took turns sitting on a Dyson sphere, in which the researchers made sounds from different points around the dome while observing the participants’ brain activity through functional magnetic resonance imaging scanners.
The scans revealed that as the source of the sounds increased, neural activity decreased. It is not known exactly why this occurs, but scientists believe it could be some kind of evolutionary adaptation to the sounds emanating from below us, rather than above us.
However, the answer can change subtly, if the shape of the ear changes. Thus, in the experiments, the insertion of thin silicone molds in the ears of the participants deviated their vertical sound location, making them think that the sounds were coming from places where they were not.
After a period of time – during which the volunteers continued to wear the silicone ear molds – the participants adjusted to the new artificial contours of their outer ears and regained control of their vertical orientation.
This shows how something as subtle as the shape of the ear radically affects our perception of the world around us.
Quite strange, but it still doesn’t help us to explain some of the more curious things associated with the science of the ear , such as why there is a mysterious link between smoking and hearing loss, or how one in five people can ” hearing “things that don’t actually make any sound, a phenomenon called an auditory response evoked by a visual stimulus.”
Ears are clearly a rather unusual part of our bodies, but also fantastic ones, with untapped potential for doing things that almost seem like superpowers, like learning to mimic the echolocation abilities of animals.
Reference: The encoding of sound source elevation in the human auditory cortex. Régis Trapeau and Marc Schönwiesner Journal of Neuroscience 2018, 2530-17; DOI: https://doi.org/10.1523/JNEUROSCI.2530-17.2018
