It’s strange when the senses become confused. For many people, this has happened when picking up a drink, taking a sip, and realizing it’s something totally different than expected. Thankfully, instances like these are few and far between, and the reason they’re so rare is because our senses, and the brain, usually work together to avoid such stumbles. A new study from researchers at the Institute of Neuroscience and Psychology at the University of Glasgow now finds that the brain enlists help from the ears when helping a person see the world.
The reasoning behind this finding is actually pretty simple. The visual cortex, the part of the brain obviously involved with sight, uses the information given with sounds to predict what it’s about to see. In turn, our brains are able to process the visual faster. “Sounds create visual imagery, mental images, and automatic projections,” Professor Lars Muckli, from the Institute, said in a press release. “So, for example, if you are in the 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.”
The researchers learned about the definitive connection between the visual cortex and the ears’ job after performing five experiments with the help of magnetic resonance imaging (MRI). In one experiment, for example, the researchers asked participants to listen to three different sounds, like birds singing, traffic, and a group of people talking. With the MRIs, they were able to see that the brain’s early activity visualized the source of the sounds. In a second experiment, they were able to produce the same results by only imagining the source, sans the sound and sight of it.
“This research enhances our basic understanding of how interconnected different regions of the brain are,” Muckli said in the 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 will also help the researchers better understand sensory perception in people with schizophrenia and autism, both of whom experience either sharpened or dulled senses.
The findings also provide us with a story of our past. The researchers believe that the origin of the connections come from our need to survive. “It provides predictions to help the visual system to focus on surprising events, which would confer a survival advantage,” Muckli said.
Source: Vetter P. Smith F, Muckli L. Decoding Sound and Imagery Content in Early Visual Cortex. Current Biology. 2014.