For people who have epilepsy surgery, it is important for doctors to know which areas of the brain are involved in critical functions, such as understanding language, so they can avoid these areas during surgery. One way to study these functions is by using electroencephalography, or EEG, a technique where sensors are placed on top of the head to record the brain activity underneath. When researchers look at recordings of brain activity during speech, they can analyze the data in different ways to try and understand how the brain processes language. EEG can show which regions of the brain are most active when processing speech. If different brain areas are active, showing similar patterns of activity at the same time, it may mean that these areas are working together (as part of a network) to accomplish a task. Drs. Liz Pang, Taufik Valiante, and colleagues wanted to study what these patterns of activity look like during language processing.
EEGs were recorded from 20 young, healthy adults while they watched a series of 7-minute cartoon videos featuring “Pingu” the penguin. Each video presented spoken sentences that were either fully correct or contained errors in meaning or grammar. For example, a sentence with an error in meaning would be “Pingu is eating pants for breakfast”. An example of a sentence with an error in grammar would be “Pingu is eating jam with this those hands”. The researchers then looked at the different patterns of brain activity that were seen for each type of sentence. They found that although both types of sentences activated different brain areas, both types of errors produced a similar pattern of brain activity. This suggests that the brain processes language errors in a similar way whether they are errors in meaning or in grammar. The results also showed that the connections between brain areas are strong when listening to correct sentences, and that these connections are disrupted when an error occurs. Importantly, these results show that multiple brain regions work together to help us understand language. Identifying these regions before epilepsy surgery is essential for preserving language function following surgery.
In the coming weeks, find out how Drs. Pang and Valiante and their team are using these techniques to map language networks in the brain and how they can be used in epilepsy surgery.