Know how you identify motorbike from its sound

If you are in a street and hear the sound of an approaching motorbike, you expect to see a motorbike, and not a horse, coming around the corner.

This is because the visual cortex also uses information gleaned from the ears as well as the eyes when viewing the world, the researchers, who studied brain process involved in sight, found.

"Sounds create visual imagery, mental images, and automatic projections," said professor Lars Muckli at the University of Glasgow in Britain.

The study involved conducting five different experiments using functional Magnetic Resonance Imaging (fMRI) to examine the activity in the early visual cortex in 10 participants.

In one experiment they asked the blindfolded volunteers to listen to three different natural sounds - birdsong, traffic noise and a talking crowd.

Using a special algorithm that can identify unique patterns in brain activity, the researchers were able to discriminate between the different sounds being processed in early visual cortex activity.

"This research enhances our basic understanding of how interconnected different regions of the brain are," Muckli noted.

"The early visual cortex has not 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," he explained.

The study appeared in the journal Current Biology.