The fact that there is so little known about the process of hearing is what first drew Yael Bitterman to research this field. Bitterman, a graduate of the Hebrew University, is today a doctoral student in the Jack and Alice Ormut Doctoral Program in Brain Research, Computation and Information Processing at the University’s Interdisciplinary Center for Neural Computation (ICNC), which is an integral part of the new Edmond and Lily Safra Center for Brain Sciences (ELSC). She has already achieved such groundbreaking results that her findings were published in 2009 in the internationally renowned science journal Nature — just a month before the birth of her first child.
Her research provides important insights into the way the brain processes auditory information and could have important ramifications in improving the design of cochlear implants, which are surgically implanted to provide rudimentary hearing fort he profoundly deaf and those severely hard of hearing.
Following her army service in intelligence, Bitterman did her first degree in physics combined with the Amirim program, which provided her with what she sees as the perfect preparation for entering a field of scientific research that keeps its focus on human beings. As an outstanding undergraduate, Bitterman was selected during her first year for the University’s interdisciplinary Amirim program which, for 20 years, has provided its annual intake of 25 carefully selected students with the benefits of a broad-based BA program in humanistic studies in addition to their studies for their other major. “It was brilliant... it was at the highest level and helped feed and develop my intellectual curiosity,” she says.
When she joined the ICNC’s prestigious Ormut Doctoral Program, Bitterman was given the opportunity by the head of the program, Professor Israel Nelken, to work on detailed auditory data that had been acquired in a somewhat fortuitous way.
When trying to answer the question “How do we hear?” scientists are usually faced with the insurmountable problem of not having any direct access to the human brain. But a collaborative project between pioneering Israeli surgeon Professor Itzhak Fried, now at UCLA, and Professor Rafael Malach of the Weizmann Institute of Science, provided a unique opportunity to peep inside the brain. Prior to essential surgery, severe epileptic patients are fitted with electrodes that provide specific information about the precise location of the seizure triggering part of the brain. Several of the patients also agreed to watch a sequence from the Clint Eastwood movie “The Good, The Bad and the Ugly” while responses of unprecedented detail were recorded by the electrodes. Importantly, there was also a rich and varied soundtrack — including background noise, speech and music — to which was added an artificial sequence of random chords. The data collected provided information into how individual neurons in the human brain respond to such a diverse collection of sounds.
The results of Bitterman’s analysis of this data have essentially changed some of the established ideas regarding auditory processing in the brain. Individual neurons in the auditory cortex were found to be “exquisitely tuned” to respond to a very narrow range of frequencies with considerable sensitivity, although they also varied their processing according to the context of the sounds. Moreover, this type of explicit specialization, which exceeds that within the cochlea, was not expected to exist in this region of the brain — indeed, it is unprecedented in any other mammalian species (except bats which, of course, use sound to find their way around). Better understanding of the processing of behaviorally relevant sounds in the human cortex, says Bitterman, could enable cochlear implants to provide improved speech comprehension and music appreciation.