What is this study about?
In this study, we focused on REM Behavior Disorder (RBD), a disorder that causes people to move and act out their dreams during deep sleep (specifically, rapid eye movement (REM) sleep).
In healthy individuals, there isn't a lot of movement during sleep. Our brains "turn off" motor control while we are sleeping, so that we do not thrash around in bed. However, in individuals with RBD, the brain is not able to "turn off" motor control, and so they run, jump, punch, or do whatever it is that they are doing in their dream, in real life.
To study this disorder, we used a technique called lesion network mapping. To understand what this is, it is important to understand brain networks.
What are brain networks?
In the brain, different regions work together. For example, eating is not just controlled by one area of the brain but instead includes a combination of areas, such as regions that control movement in the hands and jaw, regions that handle depth perception, your senses of smell and taste, and so on. This is true of other tasks, as well.
Groups of regions in the brain that work together are called brain "networks", and, if one region in the network is injured, all the other regions in the network are also affected, meaning that the network will work differently than it did before.
What is the historical context?
Historically, when studying the brain, scientists would study individuals with brain injuries to see how these injuries affect the brain. The idea was that if one person received an injury in one area of the brain, and, as a result, developed a new neurological symptom, then scientists could know that the area of the brain that was injured was responsible for that symptom. However, sometimes researchers would discover that one symptom could be caused by injuries in different areas, and so there was not a direct relationship between the location of the injury and the symptom they developed.
Later, we learned that many areas of the brain do not perform complex tasks on their own, but rather work in networks. Therefore, if any area of the network is injured, then an individual could develop a symptom related to that network. This was true even if different individuals were injured in different parts of that one network.
Lesion network mapping is a technique where we look at brain injuries that cause RBD, and then compare the location of the injury to what we know of brain networks to see what other areas of the brain will be affected besides just the injury location.
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