One of the most important things to do before children have epilepsy surgery is identify which areas of the brain are important for functions like speech, language, and memory so that those areas can be avoided during surgery. This is difficult with language since there is more than one area in the brain involved in language processing – our brains need to recognize, understand, and extract meaning from words.

One technique that is often used to study how the brain processes language is electroencephalography, or EEG. This involves placing sensors on the head to record the brain activity underneath. Brain activity recorded by EEG is often analyzed by seeing which areas have a “spike” in brain activity when performing a certain task, such as listening to someone speak. Since language is not processed in a single area, looking at activity across the whole brain is needed to get an accurate picture of how these areas work together. One way to approach this is to look at how quickly brain cells fire. Brain cells can fire at different rates, known as delta, theta, alpha, beta or gamma frequencies (slow to fast). When different regions of the brain fire together at the same time, it suggests that these regions are working together to perform a task.

Drs. Liz Pang, Taufik Valiante and colleagues wanted to study the brain areas responsible for understanding and processing language. To do this, they compared brain activity patterns (waves) in healthy young adults during two different conditions: listening to proper English sentences and listening to nonsensical “gibberish” sentences. They found that during the English sentences, brain cells fired at the highest rate (i.e., there was an increase gamma waves). This increase was not seen with the gibberish sentences, suggesting that firing of faster gamma waves is important for processing the meaning of language. During both types of sentences, the researchers saw more brain cells firing at a slower rate (theta waves), which suggests that this slower brain activity may not be as important for interpreting the meaning of words, but is probably needed to process basic word patterns and speech rhythms, which were common to both sentences.

By looking at which areas of the brain showed these patterns, the team was able to identify a possible network for language. Understanding brain language networks using EEG is a novel approach that will help us understand how surgery affecting parts of a network may impact language function. This understanding will help us achieve better post-operative language outcomes.

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