A brain transplant is a possible dream but in science fiction

06/18/2023

There is no organ more complex than the brain. A cubic millimeter of the cerebral cortex contains 27,000 neurons and 1,000 million connections. According to neurologist Luis Alfredo Villa, each nerve cell communicates with others between 1,000 and 10,000 times. Neurons are located in both cerebral hemispheres and extend through the brainstem and spinal cord to nerves, where they innervate (reach) muscles.

Transferring this organ from one body to another, as is the case with the heart or kidneys, is an impossible journey and is a science fiction procedure because “we have more than 100,000 million neurons connected to each other. This means that this organ generates a number of interconnected circuits, so the Transplanting means cutting them off and reconnecting them again, but if they are cut off, the neurons quickly deteriorate and die. This is almost impossible, it has to be reconnecting neurons one by one,” says Villa.

Neurologists are not closed off on the possibility that this may be possible in the distant future with more advanced technological developments, but it is not the case at present. However, there is a question raised by science: What will happen to the feelings and personality of the person being transplanted?

The answer is the key to understanding more about what this procedure is: the donor is the person who survives, not the other way around, as happens with a heart transplant. In the end, it will not be a brain transplant but a body transplant.

“Every person is his own mind. This member brings with it a personality, a demeanor, and a way of expressing and relating. All the information is stored in the organ, so it will actually end up in a body transplant, because that person will have a different body than before,” explained Andres Villegas, professor and neurobank coordinator of the Antioquia Neurosciences Group, associated with the A.V. University School of Medicine.

It is nothing more than science fiction. However, there are other types of procedures that have been explored in animals for decades, such as head and neuron transplants, and the latter have more successful results because they are already being done in humans.

head transplant

Transplanting a brain-only organ is not the same as transplanting a whole head. In this procedure it is not necessary to cut nerve connections. It consists of decapitating a living being to insert its head into the body of another living being. Although it sounds unrealistic, there have actually been some experiments on monkeys, dogs, and rats dating back decades.

The first operation of its kind took 18 hours and took place at a hospital in Cleveland, in the United States, where neurosurgeon Robert G. White transplanted a monkey’s head into the body of another. It was a surgery considered successful at the time, despite the fact that the animal lived for only nine days and was paralyzed from the neck down for not being able to connect the brain to the spinal cord of the recipient body.

The animal was able to hear, smell and even bite. It was considered a major breakthrough and until his death in 2010, a neurosurgeon fancied a human head transplant. In fact, he had a candidate: Caraig Vetovitz, a young quadriplegic with organ failure.

This is not achievable due to its high cost and some TV shows have branded it as “Dr. Frankenstein and his monster”.

But the candidate has always defended him: “He’s not the kind of person who would just change his head, he would do it if there was a good chance of a full recovery. He knows what’s behind the eyes because he sees them all the time and he sees the misery,” he told the Cleveland Scene in 1999.

There is a loss of movement

Head transplantation has not been successful enough because all trials end up with the transplanted organ with no downward motion of the neck. In other words, they were left a quadriplegic.

“The head transplant involves injury to the spinal cord that renders the animal a quadriplegic, and by severing the spinal cord at neck level along with the vagus and phrenic nerves, it was impossible to reconnect it. Now that debate has been fueled and there is some progress in the procedure.

In animal experiments, mechanical respiration has been improved and has a longer lifespan, but it is still not an option for people who need this type of procedure,” admitted Andres Villegas, physician.

The doctor asks: What is the benefit of an implant in which the person remains stationary from the head down? It is an ethical issue that is still discussed at bioethics meetings. For now, the findings could benefit people who are already quadriplegics and who have significant systemic damage but whose brains are still in good shape. Surgery is useless because people experience loss of movement and may have problems with breathing and swallowing, that is, moving food from the mouth to the stomach through the throat.

It may interest you: La 13 reaches into the future: it creates a metaverse inspired by the most famous municipality of Medellín

Neuronal transplantation

The dream of a brain transplant or making a head transplant more viable may take time to be tested in humans, while neuron transplantation is a procedure that is already being done, even in Colombia. Neurologist Villa said that in his work he has transplanted neurons, with successful results, but it’s still an experimental area, too. The operation consists of rebuilding brain circuits after brain damage. In this step, the stem cells responsible for creating new neurons every day are key, even if they only occur in certain areas of the adult brain.

“With stem cells, the possibility of inserting neurons so that the brain can recover from injuries that occur at the neurological level is being explored, but it must be borne in mind that neural communication is complex and occurs when we learn new skills,” said Villegas.

Neurologist Villa says this type of procedure is mainly done for patients suffering from post-traumatic stress disorder and diseases that damage neurons such as Parkinson’s, in which dopamine-producing neurons slowly die and their absence wreaks havoc on brain circuits, causing problems. Motors.

To repair the damage, transplants of neurons that produce dopamine have been performed and there have been successful results because symptoms improve. “This cell therapy benefits diseases such as Parkinson’s, in fact, it can be the best treatment option in some cases,” Villegas added.

The brain also has the ability to recover, it is flexible. This ability is known as plasticity. It modifies the connections between nerve cells and new connections are formed and others are removed allowing the person to recover from a brain injury.

“If a person suffers, for example, from a stroke or a specific lesion in a focal area, the cells involved in that area lose their capabilities and others adopt the functions they lost. It learns again with new cells, ”concluded the doctor.