Brain captures vision, sound differently yet perfectly

In a crowded room, where so many conversations are on, your brain still captures the one you are involved with - simultaneously relying on lip-reading, looking at gestures to gauge the exact mood.

This visual-sound coordination does not happen in one brain command, as was thought earlier.

In fact, Duke University researchers have found the opposite - neurons in a particular brain region respond differently, not similarly, based on whether the stimuli is visual or auditory.

To link these sights and sounds, the brain has to know where each stimulus is located so it can coordinate processing of related visual and auditory aspects of the scene.

"The neurons respond to nearly all sound locations. But how vigorously they respond depend on where the sound is coming from," said lead author Jennifer Groh, a professor of psychology and neuroscience at Duke University.

The findings provide fresh insight into how vision captures the location of perceived sound.

The new finding also opens up a mystery. If neurons respond differently to visual and auditory stimuli at similar locations in space, then the underlying mechanism of how vision captures sound is now somewhat uncertain, said the study published in the journal PLOS ONE.

For their research, the scientists assessed the responses of neurons, located in front part of the superior colliculus - a paired formation on the roof of the midbrain - of two Nazuri monkeys as they moved their eyes to visual and auditory targets.

The researchers measured the monkey's responses to noise bursts and illuminating of the lights.

"How the brain takes raw input of one form and converts it into something else may be broadly useful for more cognitive processes," said Groh.

"Both of these kinds of signals can be used to control behaviour - like eye movements - but it is trickier to envision how one type of signal might directly influence the other," Groh added.

"It's still teamwork, but a different kind. It's pretty cool that the neurons can use two different strategies, play two different games, at the same time," she said.

Neurons are cells that process and transmit information through electrical and chemical signals in the brain.