Understanding how the brain combines sound from two ears

Deafness Research UK is supporting an investigation by Dr Roberta Donato at the UCL Ear Institute in London into the way the brain combines sounds from the two ears to help create an auditory “image” of the world.

[Fellowship: 2008-2009]

Human listeners can detect tiny time differences between the arrival of a sound at one ear compared to the other. The differences can be as small as ten to twenty millionths of a second (microseconds). This extraordinary level of precision underlies the ability to listen in noisy backgrounds (the “cocktail party effect”) and to determine where sound sources are located.

Brain mechanisms that contribute to this exquisite binaural (“two-eared”) hearing have been the subject of extensive investigation, however the cellular mechanisms responsible for binaural hearing remain unclear.

Dr Donato’s research aims to determine what happens at the level of communication between brain cells by making experimental recordings in a key processing centre in the brainstem known as the superior olive. Neurons here are the first in the auditory pathway to respond to sounds presented to both ears.

Understanding binaural processing at the cellular level complements other important studies at the Ear Institute which investigate the auditory system’s sensitivity to binaural sounds.

One potential outcome of these studies will be to find out how to restore normal two-eared hearing for cochlear implant users. While current cochlear implants are very useful for restoring the ability to detect sounds and understand speech there is still more work to be done before they are effective for localising sounds or in noisy backgrounds.