After falling asleep, our brains go offline, turn on Replay mode, re-create the experience of waking up, and the memory is consolidated. Previously, scientists have only observed this process in non-human animals such as rodents, and in a pilot clinical trial of brain-computer interfaces, a team of researchers at Massachusetts General Hospital, Harvard Medical School, Brown University, University of California, San Diego and other institutions observed for the first time the replayed process of the acquired nerve-triggered sequence in the brain motor cortex of two human participants.
On May 5, 2020, the journal Cell Reports published the team’s paper, “Replay Of Learned Neural Firing Sin Sin Human Motor Cortex” (Replaying of neuro-stimulating sequences acquired in the motor cortex of the human brain during sleep).
Place the sensor in the cerebral cortex
Our brains are the most advanced part of the human nervous system, with a layer of gray matter on the surface of the left and right hemispheres, what we call the “cerebral cortex.”
The position of the cerebral cortex is not to be underestimated. There are about 14 billion nerve cells in the cerebral cortex, which is the organ of the mind, which dominates all the processes of activity in the body and plays a role in regulating the balance between the body and the surrounding environment, so the cerebral cortex is the material basis of advanced neuroactivity in humans.
In the cerebral cortex, there is an area involved in planning, controlling, and performing autonomous movements, known as the Motor cortex.
The team’s brain-machine interface pilot clinical trial was conducted from the motor cortex as an entry point , with the researchers placing two 1.5 mm 96-channel silicon microelectrode arrays (96-channel silicon microelectrode arrays) in each of the participants’ brains.
In fact, beata Jarosiewicz, one of the paper’s co-authors, said:
The electrodes used to treat conditions such as Parkinson’s disease are too large to track the peak activity of individual neurons. But the electrode arrays used in our clinical trials are the first to allow such detailed neural recordingin in the human brain. It is only at this point that our research is unprecedented.
It is understood that both participants are quadriplegic and currently need to live on a ventilator, but are still able to speak. Of these, participants T9 implanted a silicon microelectrode array for 11 months prior to participating in the study, and T10 implanted a silicon microelectrode array for 3 months before participating in the study.
Using the discharge activity of the brain’s motor cortex in both participants, the researchers attempted to find “direct evidence of offline replay of the sequence of neurodischarge rate associated with specific learning.
The trial is called BrainGate2, also known as the BrainGate2 sensor, according to ClinicalTrials, a US clinical trial database. The trial aims to advance the development of brain-machine interface technology so that quadriplegic patients can use their neural activity to control computers, robotic arms, and other devices, with the primary endpoint being to determine the safety of the BrainGate2 neural interface system, the secondary endpoint to determine the feasibility of Gate Brain2 and to establish parameters for subsequent large-scale clinical studies.
As can be seen from the figure below, the trial began in May 2009 and is expected to be completed in December 2022. The researchers recorded the participants’nerves at least once a week for at least a year.
Participate in the game in the way you think
In fact, the process of the experiment can be graphically represented by the picture below.
Specifically, the two participants participated in a “sequence-copying game”, similar to a memory game from the 1980s called “REPEAT”, in which four colored plates were lit in a different order, and the player needed to repeat a specific order and light the color block again.
What’s special about the game in the experiment is that it doesn’t require participants to move their arms, just use their minds to imagine them moving quickly with their hands and the right color blocks in the order of memory.
The researchers were reported to have asked participants to take a nap before and after playing the game (about 20 minutes) (20-30 minutes each), and during the break-play-rest, the researchers used the BrainGate2 sensor to record the peak activity of a large number of neurons in the participants’ brains.
Based on the above characteristics, to determine whether BrainGate2 is reliable, the number of repeat and control sequences is an important measure. According to the paper, there were 66 duplicate sequences and 22 control sequences throughout the process.
Experiments showed that repeated sequence correlations increased more than control sequence correlations, from pregame rest to post-game rest, and that the brain discharge patterns of participants during games and post-game breaks were the same, which is direct evidence of “offline replay” during sleep in the human brain.
As Beata Jarosiewicz says:
This is the first direct evidence that humans play back when awake during sleep, which may help to consolidate memory. We’ve studied memory consolidation mechanisms associated with brain playback in other animals for decades, and that actually applies to humans.
Notably, the research team comes from BrainGate, an academic research alliance focused on the development of restorative neural interfaces in science and medicine, whose members include Brown University, Massachusetts General Hospital, Case Western Reserve University and Stanford University, along with NeuraLink, founded by Musk, and Kernel, the top echelon of research in invasive brain interface sufcus interfaces in the United States.
In terms of future research directions, the team hopes to explore the potential link between brain reproduction mechanisms and memory formation.