Can Sound Help Us to See?

If you have ever watched Marvel’s Daredevil, then you must have appreciated the fantastic ability of Matt Murdock- his heightened senses. With the exception of being blind, developing an extraordinary spacial awareness is quite an impressive superpower one could wish for.

(Source: welshdragon on Deviantart)

Although hearing is not considered a superpower in reality, research carried out by a team of neurobiologists earlier in 2008 suggests that sound and the ability to hear it, in fact can enhance visual perception of low contrast visualisations, i.e. when the object of focus is relatively similar to its background.

And this is actually quite a big deal in neuroscience, as one of the group’s neurobiologists, Pascal Barone states, “our results argue against a strict hierarchical model of sensory integration in the brain”. The model that Barone is referring to, sensory integration, is a standard model in neurobiology of how the brain organises various incoming stimuli from the environment and uses that information to coordinate the body appropriately.

Before the discovery, it was accepted that incoming multi-sensory stimuli (stimuli detected by different organ systems) are carried along brain nerve cells separately, never meeting until reaching one of the deeper centres of the brain, like the superior colliculus, a multi-layered structure which receives impulses from multiple organ systems to produce motor commands in response.

However, in their study of visuo-auditory interactions, Barone and his colleagues claim to have discovered that in fact the multi-sensory stimuli from both the visual and auditory systems actually interact before reaching a region of the brain like the superior colliculus. In their investigation, researchers trained two macaques to locate flashes of light on a screen. In brief, it was measured that monkeys easily traced the bright, high contrast flashes of light and, as expected, took longer to locate dimmer, low contrast flashes of light.

But the investigation became more interesting when researchers added some noise to the visuals. When the macaques were shown low contrast, dim light in sync with a distinct sound, they were able to trace the light quicker by 5-10% in comparison to locating the same, low contrast light without sound.

Ye Wang, one of the team’s researchers, explained the reason for why sound allowed the monkeys to trace the light much faster than expected; within the brain exists a direct neuronal connection between the brain regions that individually process sound and vision. This means that the brain has special multisensory neurons that can integrate information from more than one sensory stimuli, and Barone declares their research is the first to confirm such a phenomenon.

A more recent study published in 2011, also supports the existence of direct neural connections between the visual and auditory brain regions, but on a behavioural level. The investigation involving 63 people uncovered something even more interesting about the perception of auditory and visual stimuli; when uninformative noise, i.e. noise containing zero useful information, was added in a task requesting to decide horizontal movement of multiple dots, it was found that uninformative sound actually improved participants’ ability to perceive the movement of dots.

As Robyn Kim, a neuroscientist involved in the later study says, “even at a non-conscious level, visual and auditory processes are not so straightforward,” and “perception is actually a very complex thing affected by many factors.” Hear hear.

References:

http://www.livescience.com/5045-scientists-sound.html

http://phys.org/news/2008-08-visual-perception.html

http://www.psychologicalscience.org/index.php/news/releases/even-unconsciously-sound-helps-us-see.html

#SintijaJurkevica #Biology #Neuroscience