PITTSBURGH — People generally assume that our ears help us recognize voices and our eyes do the same when it comes to seeing faces. However, new neurological research by a team at the University of Pittsburgh suggests the relationship between facial and voice recognition is much more interconnected than anyone previously thought. Scientists found that when recognizing a familiar voice, the human brain relies on the very same center that lights up when they see the speaker’s face.
In their experiment, participants had to identify former U.S. presidents based on nothing more than their voice.
All in all, study authors say their findings make a strong case that voice and facial recognition processes within the brain are linked even more intimately than once thought. They believe this work opens up the “intriguing possibility” that both the visual and auditory information needed to correctly identify someone else is fed into the very same brain center, facilitating a more comprehensive recognition by incorporating separate sensation modes simultaneously.
“From behavioral research, we know that people can identify a familiar voice faster and more accurately when they can associate it with the speaker’s face, but we never had a good explanation of why that happens,” says senior study author Taylor Abel, M.D., associate professor of neurological surgery at the University of Pittsburgh School of Medicine, in a university release. “In the visual cortex, specifically in the part that typically processes faces, we also see electrical activity in response to famous people’s voices, highlighting how deeply the two systems are interlinked.”
Which brain region responds to both voices and faces?
While the intricate processes underlying the interplay between the auditory and the visual brain systems has been the focus of many studies by neuroscientists all over the world, scientists considered those systems to be structurally and spatially distinct.
Up until very recently, few studies had even attempted to directly gauge activity within the brain center, which primarily serves to consolidate and process visual information, in order to get a better sense of whether or not this center also activates upon exposure to voice stimuli.
The team at UPitt had a unique opportunity to study this interaction among patients with epilepsy. These patients, as part of their medical care, received a temporary implant using electrodes to measure their brain activity to determine the source of seizures.
A total of five patients took part in the study. Prof. Abel and his team showed these patients photographs of three U.S. presidents — Bill Clinton, George W. Bush, and Barack Obama — or played short recordings of their voices, and then asked participants to identify the president.
Recordings of the electrical activity from the region of the brain responsible for processing visual cues, known as the fusiform gyri (FG), revealed that the very same region became active when participants heard familiar voices. The team notes, however, that this response was lower in magnitude and somewhat delayed.
“This is important because it shows that auditory and visual areas interact very early when we identify people, and that they don’t work in isolation,” Prof. Abel concludes. “In addition to enriching our understanding of the basic functioning of the brain, our study explains the mechanisms behind disorders where voice or face recognition is compromised, such as in some dementias or related disorders.”
The study is published in the Journal of Neurophysiology.