Sensitivity to Complex Statistical Regularities in Rat Auditory Cortex

Conducting basic scientific research and making new discoveries in a complex field is like creating a single brick and adding it with mortar to a wall long under construction. The research of Hebrew University neurobiologist Prof. Israel Nelken, who led a team investigating brain activity in the auditory cortex of rat brains, could in the long term lead to the development of better hearing aids in humans. The same basic mechanism of repeated sounds may be involved in all kinds of human psychiatric diseases, including schizophrenia.

The research was funded by the Medical Research Fund of the Chief Scientist’s Office at Israel’s Health Ministry, under that framework of the ERA-NET Neuron.

The team implanted multiple tiny electrodes in rat auditory cortex – the part of cortex that responds to sounds – to study the effects of “surprise sounds” on the mammals’ neuronal activity. “We found that activity of neurons is sensitive to surprise. A sequence of identical tones creates expectations even in anesthetized mammals, and the responses to rare tones tend to be stronger than responses to common ones,” Nelken related.

People who have normal hearing are more sensitive to slight differences between tones. “We showed that sensitivity to surprising tones is much stronger, the brain learns very quickly and the activity is reduced in response to expected sounds. The mechanisms underlying surprise reactions appear very early in life and are present even in the fetus,” he said.

“Our central question was how the senses work to collect information from the past and learn from it how to function better in the world. Sensitivity to surprise is very important. If a rat has greater ability to predict the future events in the world, it will be able to collect more rewards in the form of food, locating a place to live and finding a mate. The more the past can be used to predict future, the easier rewards will be won.”

Neuron, Volume 76, Issue 3, 8 November 2012, Pages 603-615. By Prof. Israel Nelken, Amit Yaron and Itai Hershenhoren, Department of Neurobiology, Institute of Life Sciences, the Interdisciplinary Center for Neural Competition and the Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem.

© Angel Barco