, from now on your world more science~
Everyone is at the forefront of science and technology
Tao Hu
Researcher and deputy director of the Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences
Deputy Director of the State Key Laboratory of Sensing Technology, Founding Director of the 2020 Frontier Laboratory
Where is the boundary of your body? Some people say that my skin demarcates the boundary between me and the world.
But we always feel that our boundaries are bigger, for example, when a stranger is less than 1 meter away from you, you will feel uncomfortable, if it is only half a meter, you will even feel uncomfortable, at this time, your boundary is no longer your skin.
Imagine you're driving your car home from work, thinking about what you're going to have for dinner, and looking up in the rearview mirror from time to time to make sure you don't collide with other cars. There will always be a moment when you feel that the car and your body are one, commonly known as "the integration of people and vehicles", and then your boundaries extend to the whole car.
The expansion of the above boundaries is mostly innate or passive, so is it possible for us to actively expand the boundaries of our bodies? Of course we can.
Brain-computer interfaces are one such technology that expands your physical and mental boundaries. Fixing the degraded senses, stretching the space that the limbs reach, and even making the situations depicted in the movie "Avatar" come true, these are all things that brain-computer interfaces have been or are making possible.
Boundary repair
Rebuild neural connections
Our perception of the world comes from the brain, our nervous system, and the biggest difference between this system and all other body systems is that it is malleable.
As a simple example, a child's brain changes plasticity before and after they learn to speak. Swap "plasticity" for brain science terminology: "Fire together, wire together".
A single word contains almost all the wisdom of the human world. Let's expand on the English expression above. The brain is made up of neurons and glial cells, the latter of which is the main supporter, and the former is the main carrier of information transmission. Neurons have a special appearance because they have many antennae that help them make connections with other neurons around them, where information is transmitted through electrical signals.
Thus, "Fire together, wire together" can be understood in such a way that when neuronal A continuously and repeatedly engages in the activity that evokes neuron B, the connection between A and B is strengthened.
There are two key points in the above expression: one is repetition, that is, it occurs multiple times, and the other is that there is a temporal sequence, that is, the activity of A must occur before B.
Discharge together, connect together
So what does neuroplasticity have to do with brain-computer interfaces? It's so much that we can use brain-computer interfaces to reshape the nervous system. For example, many paralyzed patients have severed the connections between the "instructional" neurons in their brains and the motor neurons distributed in the limbs. At this point, we can place electrodes on the patient's head to record the activity that is happening in his brain in real time. At the same time, the patient is asked to do motor imagination, imagine that he wants to lift his hands or feet, and once these "imaginary signals" are monitored, the limb corresponding to the signal is immediately stimulated, so as to simulate the limb receiving the instructions of the brain and acting. As long as we ensure that each instruction is followed by a corresponding action, repeated enough times, we can hopefully rebuild the neural connections of the paralyzed patients.
At the forefront of exploring the mysteries of the brain, scientists are working to develop a completely new technology – ultrasound neuromodulation. This technology uses ultrasound as a non-invasive tool to work directly on specific areas of the brain through precise frequency control. Ultrasound plays a similar role as a "commander" in this process, directing the activity of neurons and achieving fine regulation of brain function.
The potential of ultrasound neuromodulation is enormous, and it offers new hope for the treatment of a range of neurological diseases. For example, it may help reduce tremor symptoms in people with Parkinson's disease, relieve chronic pain, and may even have a positive impact on the treatment of depression. In the future, ultrasound neuromodulation may be a powerful tool for us to regulate brain states and help people achieve a higher level of cognitive and emotional balance. Research in this area is not only important for medicine, but may also have a profound impact on the depth and breadth of human self-understanding.
Cochlear implants
Let's take a look at another more mature BCI application – cochlear implants. In the 60s of the 20th century, scientists first proposed the concept of cochlear implants. In 1972, the first commercial cochlear implant was implanted into the human body. As of 2017, the global cochlear implant market reached $1.3 billion.
Many people with hearing loss have lesions in the inner ear, the cochlea, and the neurons in the brain that are responsible for interpreting sounds do not have organic lesions. As a result, the idea of treating such hearing-impaired patients has become - to replace the diseased cochlea with artificial organs. A typical cochlear implant consists of at least three parts:
Sound receivers, sound processors, and auditory cortex stimulators. The sound receiver is a small microphone that needs to be converted into more familiar electrical signals by the nervous system by the sound processor, and finally the auditory cortex is stimulated by a stimulator implanted under the skin behind the ear, so that the sound is perceived by the brain again.
For people with paralysis and hearing impairment, brain-computer interface technology has helped them regain their physical boundaries.
See the world with your tongue
"I saw a beautiful view" is a common expression, and "I have tasted a beautiful view" becomes a sentence that uses the rhetoric of synaesthesia. Synaesthesia, also known as synesthesia in the field of brain science, is a real phenomenon in which a stimulus from one sense triggers a sensation or experience from another sense.
Hearing, sight, smell, and touch, which are common sensations, tend to correspond to specific areas in the cerebral cortex. Generally speaking, the visual cortex "cheers" the moment you see a brilliant color, while the auditory cortex and olfactory cortex do not react. But if at some point, the brilliant colors make your auditory cortex "flicker" as well, then you will feel the colors become pleasant and sounding, and at that moment, synesthesia happens.
Now, with the help of brain-computer interface technology, humans can create synesthesia experiences anytime, anywhere, such as seeing the world with their tongues.
In fact, there are already medical device companies in the United States that have launched mature brain-computer interface products to help blind people "regain sight" with their tongues. Once again, these products use the plasticity of the nervous system: a special glasses are placed in front of your eyes to capture images of the world, which can "read" information such as the size, depth and angle of the external image, which is turned into electrical signals through a signal converter, and then directed the electrical signals to electrodes placed on the tongue with the help of another device, repeating the above steps many times, and you can basically "taste" the world.
For most blind people, their visual cortex is always there, but there are very few visual signals projected from the retina. If the electrodes connected to the glasses are placed on their tongue, the sensory cortex corresponding to the tongue will receive nerve electrical signals intensively, and the visual cortex and the corresponding sensory cortex of the tongue are not far away.
Thus, a strange phenomenon arises, the tongue of a blind person receives an electrical stimulus, and the visual cortex responds to it. At this point, the sensory cortex completely "encroaches" on the territory of the visual cortex, and what is more interesting is that the visual cortex remembers its own identity - to establish a cognition of external images in the brain. In other words, with the help of brain-computer interface technology, blind friends have successfully expanded the boundaries of their tongues.
Boundary expansion
Sixth finger
Let's ask that question again: where exactly are the boundaries of your body?
Let's take a look at the classic experiment: the rubber hand illusion. The experimenter has the subject sit at a table with one hand on the table and the other under the table (preferably in a position where the subject's gaze is directly in front of the table). At the same time, a realistic rubber prosthetic hand is placed on the table, with the focus on repeatedly adjusting the position of the prosthetic hand so that it looks like the subject's hand under the table is on the table. Immediately after, the experimenter stroked both the real and the fake hand with a brush.
Now imagine that you are the subject, do you think you can tell the difference between your real hand and your fake hand?" Can I still tell the difference?"
At the moment when the subject was distracted, the experimenter took out a huge hammer and slammed it into the prosthetic hand. Whenever this happens, the subjects are horrified. After the hammer was dropped, some subjects even reported that they experienced significant pain, and regardless of how they explained afterwards, their fear and pain neurons did not lie, and they reacted violently before and after the hammer was dropped.
That is, at that moment, the prosthetic hand was also incorporated within the boundaries of the body.
Similarly, we can control exoskeletons with the help of brain-computer interfaces. Scientists at University College London gave the subjects a mechanical finger attached to their little finger and then taught them to use their feet to control the finger, and the force of their big toe picking at the ground was converted into the opening and closing of the sixth finger. The nervous system is the most "afraid" of repetition, after 5 days of continuous training, most subjects can skillfully use this extra finger, some can even complete the action of opening the bottle cap with one hand, playing cards with one hand, and some people have achieved the feat of playing the guitar with six fingers. Obviously, this extra bloodless finger was also incorporated into the boundaries of the body.
Iron Man at the World Cup
Almost all of what we discussed above is a one-way input of instructions or sensations to the brain, which is the final link in generalized brain-computer interface technology. More often, scientists need to obtain high-quality EEG signals, then decode them, and finally transmit artificially generated feedback back to the brain according to the decoding results, thus forming a complete closed loop of brain-computer interfaces.
When the 2014 World Cup was held in Brazil, Miguel Nicolelis, a Brazilian-born brain-computer interface expert, vowed to make the event on his doorstep go down in history. At the opening ceremony of this World Cup, 29-year-old Brazilian Juliano Pinto (Juliano Pinto) once again felt the joy of playing football after six years. And this time, Pinto puts on a heavy exoskeleton and becomes a realistic version of Iron Man.
Pinto in Iron Man's exoskeleton
Let's start with the first part - EEG acquisition and decoding, with the help of electrodes placed on the surface of the scalp, the experimenter can monitor Pinto's EEG activity in real time, which contains a variety of complicated thoughts and wills. In order to make the EEG signals and motor imagination correspond to each other, Pinto completed thousands of trainings, trying to imagine those few actions, don't underestimate the word "imagination", in order to capture the "pure" EEG signals, Pinto must be free of distractions when imagining each action, maybe when imagining the foot lifting action, the mind drifts to Maradona's celebratory action, which will make this EEG signal collection fall short.
Next, we move on to the next step - exoskeleton control and sensory feedback. First, the EEG signals are converted into clear motor instructions, and the exoskeleton is directed to pull the paralyzed limb to complete the action. After that, Pinto needed feedback. Feedback is extremely important, the instructions given by the brain at the beginning are not necessarily accurate, they need to be adjusted in real time, and the adjustment comes from feedback, that is, the completion of each action requires multiple interactions between the brain and the peripheral sensory nerves. Returning to Pinto, the touch of the turf on the green field on the day of the opening ceremony, the temperature and humidity of the outside world and most importantly, the touch of the ball, all need to be transmitted back to Pinto's brain with the help of sensors attached to the exoskeleton. With the help of an exoskeleton, Pinto has managed to push the boundaries of his body.
Realistic version of "Avatar"
At this point, our discussion of brain-computer interfaces is limited to the surroundings of one's own body, and the machinery controlled is relatively simple. Can we lie at home and manipulate complex bodies thousands of miles away, like in the movie "Avatar"? Professor Miguel realized this idea with a monkey named Idoya.
As a monkey, Idoya is more accustomed to four-legged walking, but if you put it on a treadmill and hold it delicious fruit after each upright walk, then bipedal walking is perfectly acceptable. The point is that when Idoya walked, Miguel's team recorded the electrical activity of hundreds of neurons in its cortex, and then they decoded these electrical activities, that is, to find the correlation between the different firing patterns of these neurons and walking movements, and once the strong correlation was found, we could use EEG signals to predict Idoa's movements.
Realistic version of "Avatar"
The above experiments, as long as the monkeys cooperate, can be completed by most electrophysiology laboratories around the world. Professor Miguel was clearly not satisfied, and wanted Idoa to complete a more sci-fi set of actions - using its cortical EEG to control the movement of a robot thousands of miles away.
At the beginning of the experiment, Idoya once again stood on a treadmill, his right hip, knee, and ankle were coated with fluorescent paint, and as he moved his lower limbs to walk, the camera on the ceiling captured the light reflected by the fluorescent paint. With the help of this set of equipment, every subtle movement of Idoya's leg will be accurately recorded, and can be quantitatively described, and then using the linear regression equation, the discharge signal of hundreds of cortical neurons can be converted into the predicted value of the three-dimensional spatial position of Idoya's leg, and constantly adjust the coefficient of the linear equation, so that the predicted value and the actual value are constantly approximated, and finally the coefficient of the linear equation is stable at a certain specific value, and the determination of the value marks the success of the decoding model.
Next, before each of Idoya's walks, the "intention" in his mind will be accurately translated into movement commands, which will be transmitted to another robot on the other side of the ocean.
As an aside, although Idoya performed the same walking action every time, the model for each experiment needed to be adjusted and even retrained. This is due to the degeneracy of the nervous system, i.e. in the brain, there is much more than one set of "neuronal solutions" for any action or thought to be characterized. In other words, even if the action and environment are exactly the same, Idoa may use a different set of neurons to do so.
Returning to the experiment, the robot's movement will be transmitted back to the display in front of Idoya, and as soon as the thought of his left leg is moved, the robot will lift its left leg without missing a beat. What's even more amazing is that with the help of high-speed cables, the time interval between Idoya's heart and seeing the robot start to move is even less than the time it takes for Idoya to control his own legs, and perhaps in Idoya's opinion, the robot's legs are more "obedient" than its own.
In order to further verify whether Idoya realized that he had "avatar"-like superpowers, Miguel's team stopped the running mechanism under its feet, and immediately followed, an exciting moment appeared, the robot's legs did not stop, but continued to walk smoothly, which means that Idoya is actively using his own brain to control the steel body in the distance. In Miguel's words, this is "a small step for robots, a giant step for primates".
In this way, the boundaries of our bodies can be extended to any place where electrical signals can reach.
Spiritual boundaries expand
The boundaries of physics are tangible after all, and tangible means that there are boundaries, but the spiritual world of human beings can be infinite, and in terms of expanding the spiritual world, brain-computer interface technology is making more sci-fi scenarios come true.
You must have had the experience of picking up a novel and reading it on a sunny afternoon, and when you look up again, it's dark, yes, it's the feeling of time slipping away. Brain scientists have come up with a nice name for this state of distraction – flow.
Flow is a beautiful state, but it's also a state of being extremely efficient, can we actively create it? Brain-computer interfaces are making this happen.
Those who are in a state of flow have brain waves between the α and theta bands – around 8 Hz – and we can induce this characteristic EEG with the help of external inputs, actively entering the flow state. This is a very cutting-edge and highly imaginative technology.
"Consume less energy, transmit more information" is always one of the main axes of the development of the human world, which coincides with the ultimate picture of brain-computer interface: what we want to connect most is not computers, but people, and "machines" are just a carrier. As a result, brain-brain interfaces are also on the agenda.
You must have had times when you couldn't express what you meant, sometimes it's a matter of expression skills, but more often than not, it's the meaning itself that can only be understood and difficult to convey. Trisolarans will not be bothered by this, because their thoughts are transparent, and with the help of brain-brain interface, we humans also have the hope of entering a world where the efficiency of information communication has been greatly improved, and misunderstandings and embarrassments no longer exist. Scientists have already made some progress in this matter, such as in 2018, when researchers at the University of Washington succeeded in getting three subjects to tacitly play a game of Tetris with only EEG communication.
Furthermore, the brain-brain interface can not be real-time, and if the electrical activity in the brain is uploaded or stored in a USB stick, it will completely erase the communication cost. Furthermore, we can even upload our consciousness to achieve immortality on a digital level, at which point the physical and spiritual boundaries of the individual will be completely broken.
Back to the electrodes
Let's pause our imagination for a moment and refocus our attention on the first interface where the device and brain tissue come into contact – the neural electrode. It is not only the initiation point of various stimuli, but also the starting point of EEG signal acquisition, so it is not an exaggeration to say that electrodes are the key to brain-computer interfaces. However, the choice of material for this key is related to the safety and efficiency of the entire system. While traditional metal electrodes can do the job in the short term, in the long run, they will inevitably harm the fragile brain tissue, triggering the body's inflammatory response. It's like putting a rough stone into a delicate clock, which not only affects the operation of the clock, but can also cause irreversible damage.
Some people say that the theory of evolution is the most reliable success on this earth, and the contact with biological tissues also depends on biological materials, which is the heart of Brain Tiger Technology to develop silk protein electrodes. Silk, an ancient material, not only carries a thousand-year-old culture, but also has become an excellent "key" to open the brain-computer interface with its unique biocompatibility and mechanical properties.
Silk proteins are able to persist stably in the brain for long periods of time without eliciting an immune response. What's more, silk protein has controlled degradability, which means that it is able to be gradually absorbed by the body after completing its mission, leaving no traces. In addition to good biocompatibility, the mechanical properties of silk protein are excellent. In practice, the implantation process of silk protein electrodes is very gentle, which can reduce the damage to blood vessels and reduce the risk of bleeding. At the same time, its soft texture also reduces cutting damage to brain tissue.
Final words
The rapid development of brain-computer interface technology has allowed us to see a new era full of infinite possibilities. Brain-computer interfaces not only expand our physical capabilities, but also deepen our understanding of the spiritual world. In the face of this historic opportunity, we should maintain humility and awe, move forward cautiously, and hope that we can witness the bright future that brain-computer interfaces open up for the human world.
-This article is based on the author's report at the "Maritime Science Popularization Forum" hosted by the Shanghai Science and Technology Popularization Volunteer Association-
END
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