In the early 20th century scientists began to record brain activity using electrodes attached to the scalp. To their surprise, they saw that brain activity is characterized by slow and rapid ascending and descending signals which were subsequently called "brain waves".

It is currently known that brain waves express synchronized activity of tens of thousands of nerve cells (neurons), so a normal increase in wave intensity expresses synchronized activity of different groups of neurons for the purpose of transmitting information. But why and how do these waves contribute to the proper transmission of information in the brain?

A new study conducted by doctoral student Tal Dalal in the laboratory of Prof. Rafi Haddad, of the Gonda (Goldschmied) Multidisciplinary Brain Research Center at Bar-Ilan University, focuses on this key question. In the study, published in Cell Reports, the researchers altered the level of synchronization in the area of the brain that transmits information. They then examined how this affected the transfer of information and how the area of the brain that received the information understood it.

The research focused on brain regions that are part of the olfactory system, or sense of smell, which is characterized by strong brain wave intensity. A particular type of neuron in this region is responsible for creating synchronized brain wave activity. 

The researchers found that increasing synchronization of neurons in the upstream brain region that transmits information led to a significant improvement in transmission and processing of the information in the downstream region. Conversely, when synchronization was decreased, the representation of the information in the downstream region was impaired.

An unexpected discovery also occurred.

We were surprised to find that activating the synchrony-inducing neurons also caused a decrease in the overall activity level in the upstream region, so we would have expected less information to be transferred to the downstream region. But the very fact that the output from the upstream region is synchronized, compensated for the overall reduced activity and even improved the transfer of information.
Tal Dalal



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Bar-Ilan University