What will happen to a person if he has only half of his brain left? We think the answer is obvious. The organ that is responsible for the most important life processes is complex, and the loss of a significant part of it can lead to terrible and irreparable consequences. However, the capabilities of our brain still amaze even neuroscientists. Biopsychologist Sebastian Ocklenburg shares research findings that sound like the plot of a sci-fi movie.
Sometimes, doctors have to go to extreme measures to save human life. One of the most radical procedures in neurosurgery is hemispherectomy, the complete removal of one of the cerebral hemispheres. This procedure is performed only in very rare cases of intractable epilepsy as a last resort when all other options have failed. When the affected hemisphere is removed, the frequency of epileptic seizures, each of which endangers the patient’s life, is radically reduced or completely disappears. But what happens to the patient?
Biopsychologist Sebastian Ocklenburg knows a lot about how the brain and neurotransmitters influence people’s behavior, thoughts, and feelings. He talks about a recent study that helps to understand how the brain can work when only half of it remains.
The scientists examined brain networks in several patients, each of whom had one hemisphere removed in early childhood. The results of the experiment illustrate the ability of the brain to reorganize even after severe damage, if this damage occurs at a young age.
Even without any specific tasks, the brain is very active: for example, in this state we dream
The authors used the neurobiological technique of functional magnetic resonance imaging (MRI) at rest. In this study, participants’ brains are scanned using an MRI scanner, a machine that many hospitals have these days. An MRI scanner is used to create a series of images of body parts based on their magnetic properties.
Functional MRI is used to create images of the brain during a specific task. For example, the subject speaks or moves his fingers. To create a series of images at rest, the researcher asks the patient to lie still in the scanner and do nothing.
Nevertheless, even without any specific tasks, the brain shows a lot of activity: for example, in this state we dream, and our mind “wanders”. By determining which areas of the brain are active when dormant, the researchers were able to find its functional networks.
The scientists examined the networks at rest in a group of patients who underwent surgery to remove half of their brains in early childhood and compared them with a control group of participants who had both halves of the brain working.
Our incredible brain
The results were truly amazing. One would expect that the removal of half of the brain would seriously disrupt its organization. However, the networks of patients undergoing such an operation looked surprisingly similar to those of the control group of healthy people.
The researchers identified seven different functional networks, such as those associated with attention, visual and motor abilities. In patients with half-brain removed, the connectivity between brain regions within the same functional network was remarkably similar to that of the control group with both hemispheres. This means that the patients showed normal brain development, despite the absence of one half of it.
If the operation is performed at an early age, the patient usually retains normal cognitive functions and intelligence.
However, there was one difference: the patients had a marked increase in the connection between different networks. These enhanced connections seem to reflect the processes of cortical reorganization after the removal of half of the brain. With stronger connections between the rest of the brain, these people seem to be able to cope with the loss of the other hemisphere. If the operation is performed at an early age, the patient usually retains normal cognitive functions and intelligence, and can lead a normal life.
This is even more impressive when you consider that brain damage later in life—for example, with a stroke—can have serious consequences for cognitive ability, even if only small areas of the brain are damaged.
It is obvious that such compensation does not always occur and not at any age. However, the results of the study make a significant contribution to the study of the brain. There are still many gaps in this area of knowledge, which means that neurophysiologists and biopsychologists have a wide field of activity, and writers and screenwriters have room for imagination.
Banyere Ọkachamara: Sebastian Ocklenburg bụ ọkà n'akparamàgwà mmadụ.