sight and sound in the visual cortex
May 26, 2014

Visual Cortex Found To Process Sound As Well As Sight

redOrbit Staff & Wire Reports - Your Universe Online

While analyzing the brain processes associated with sight, researchers from the University of Glasgow have discovered that the visual cortex processes information not just from the eyes, but from the ears as well.

Writing in the journal Current Biology, the study authors explain that the auditory input makes it possible for a person’s visual system to predict incoming information, thus giving them an advantage in potentially dangerous situations.

“Sounds create visual imagery, mental images, and automatic projections,” lead researcher Prof. Lars Muckli of the university’s Institute of Neuroscience and Psychology, said in a statement.

“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,” he added.

Prof. Muckli and his colleagues conducted a total of five different experiments involving 10 volunteers, using functional magnetic resonance imaging (fMRI) to examine the activity in each person’s early visual cortex. The goal was to determine how information originating from both auditory and imagery impacts activity patterns in this part of the brain when there is no forward visual stimuli present.

In one of the experiments, they asked blindfolded study participants to listen to three different sounds: birdsong, traffic-related sounds and a talking crowd. They then used an algorithm capable of identifying unique brain activity patterns to discriminate between various sounds being processed within early visual cortex activity.

In another experiment, they found that even images that were imagined when there was no sight or sound present stimulated activity within the early visual cortex. The research was part of a five-year study funded by a grant from the European Research Council and the Biotechnology and Biological Sciences Research Council.

“This research enhances our basic understanding of how interconnected different regions of the brain are,” Muckli said. “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.”

“In future we will test how this auditory information supports visual processing, but the assumption is it provides predictions to help the visual system to focus on surprising events which would confer a survival advantage,” he added. “This might provide insights into mental health conditions such as schizophrenia or autism and help us understand how sensory perceptions differ in these individuals.”