See with Your Ears: The Human Brain's Visual Cortex Processes Auditory Information

The visual cortex doesn't only glean information for your eyes; it turns out that it also takes sensory information from your ears when viewing the world. The findings reveal a bit more about auditory input that the brain processes that determine how we sense the world.

"Sounds create visual imagery, mental images, and automatic projections," said Lars Muckli, one of the researchers, in a news release. "So, for example, if you are in a street and you hear the sound of an approaching motorbike, you expect to see a motorbike coming around the corner. If it turned out to be a horse, you'd be very surprised."

In order to learn a bit more about the visual cortex, the scientists conducted five different experiments using functional Magnetic Resonance Imaging (fMRI). This allowed them to examine the activity in the early visual cortex in 10 volunteers.

The first experiment involved asking blindfolded participants to listen to birdsong, traffic noise and a talking crowd. Using an algorithm, the researchers identified unique patterns in brain activity and discriminated between the different sounds being process. In the second experiment, scientists found that even imagined images in the absence of both sight and sound evoked activity in the early visual cortex.

"This research enhances our basic understanding of how interconnected different regions of the brain are," said Muckli in a news release. "The early visual cortex hasn't previously been known to process auditory information, and while there is some anatomical evidence of interconnectedness in monkeys, our study is the first to clearly show a relationship in humans."

The findings are important for better understanding how our brain functions. In the future, the scientists plan to test how this auditory information supports visual processing. This could provide the researchers with insights into mental health conditions and see how sensory perceptions differ in these individuals.

The findings are published in the journal Current Biology.