In the introduction of the brain-computer interface, we talked about open-loop systems and closed-loop systems. If you are interested, you can go back and review it again.
Many people may have wondered how can the signal be sent back to the human brain.
We call the method of artificially generating brain signals neuromodulation
There are many different ways, both invasive and non-invasive
Today we will introduce one of the methods, Deep Brain Stimulation (DBS)
How Does DBS Work?
DBS basically inserts an electrode into the brain. Of course, a more precise and safer medical method has to be used in order for the treatment to be effective. When passing a high-frequency current into the brain, the signal can inhibit the abnormal discharge of the nerves nearby.
There are three points to insert electrical currents, the subthalamus nucleus (STN), the internal pallidum, and the ventrolateral thalamus.
Although it is very irresponsible to say this, the actual working principle behind this technology is still unknown. Scientists speculate that a disease like Parkinson's disease is caused by the abnormal discharge of the brain nerves. The low-frequency abnormal discharge can be overwritten by the high-frequency current inflow. The body tremor can be relieved or reduced. As for why this can be overwritten, we do not know.
Method
The operation will be performed while the patient is conscious. Local anesthesia would be done, and the device will be implanted according to the doctor's instructions. Why do patients need to be awake? Because only in this way can the doctor make sure the location of the implant is accurate. The doctor directs the location of the implant according to the patient's physiological responses.
If the patient's symptoms are on both sides of the body, two electrodes will be implanted on the left and right sides respectively. After implantation, the patient will need to carry a portable device, which will provide a specific frequency of the electrical current. When the device is operating, the patient's symptoms would be significantly reduced
Structure of DBS Electrodes
I’ll just put the picture
Baniasadi, M., Proverbio, D., Gonçalves, J., Hertel, F., & Husch, A. (2020). FastField: An open-source toolbox for efficient approximation of deep brain stimulation electric fields. NeuroImage, 223, 117330. https://doi.org/10.1016/j.neuroimage.2020.117330
The darker part is the lead, which is the place where the electrical current is carried out. According to the different places where the current is required, there are different types of electrodes.
Source
This is what the device looks like. It's not really big, it’s a little smaller than your palm. It usually has a sleeve that hangs around the neck so that the patient can carry it around.
DBS Demonstration
We can see, at the beginning of the video, the patient's hands trembled a lot. After the device was turned on, the tremor was greatly reduced. Although it was not completely eliminated, patients would be able to live a normal life with that level of tremor. Additional medical treatment can be used to better control the conditions. The only issue is that the battery needs to be replaced or recharged periodically.
My Point of View
Although this seems to have nothing to do with what we wanted to say at the beginning, which is to have feedback from the machine we are manipulating. After all, what we want to achieve is to make the brain feel external stimulation. This technology actually reflects our lack of understanding of the mechanism of the brain to some extent. We know it can reduce tremors in the hands of patients, but we don't know exactly why. It's just that it's not bad that he can achieve what we want it to achieve.
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