Chances are you probably won't hear every breath you take today, or every creaking sound your joints make. A new study in fish explains how the brain has to "turn off" certain sensory information so it can understand the rest of the outside world.
Everything we see, hear or taste is a perception of the outside world created for us by our brain. It has to distinguish information from within our bodies, like sounds made by some of our organs, from external information.
Our brain collects all that information from within our bodies to create something scientists call a "negative image." Once it knows if the information is coming from our own bodies, the brain can filter it out and fill in the rest of our perceived world with the external signals it picks up.
Scientists tested how this works in fish. Some fish send out electrical pulses to explore their surroundings, similar to the way human senses work. Researchers found the brain has to complete its negative image before it can process information from the outside. If scientists disrupted this order, the fish could no longer tell which signals were coming from their own bodies or from outside. They had lost the ability to perceive the world.
Learning more about how and when the brain processes information could help us test new treatments for disorders like tinnitus. The condition causes constant ringing in the ears, and scientists think it may be because the brain is misinterpreting signals from the body's senses.