Abstract: Data collected from a tetraplegic who teaches BCI to play Simon showed that the brain reproduces learned information during sleep.
Source: general mass
Why do we sleep? Scientists have been debating the issue for millennia, but a new study by researchers at Massachusetts General Hospital (MGH), conducted in collaboration with colleagues from Brown University, the Department of Veterans Affairs and several other institutions, adds new clues to solving this mystery.
Their findings, published in Journal of Neuroscienceit can help explain how people form memories and learn, and could ultimately help develop assistive tools for people affected by neurological diseases or injuries.
Scientists who have studied laboratory animals have long discovered a phenomenon known as “recurrence” that occurs during sleep, explains neurologist Daniel Rubin, MD, Ph.D., of the MGH Center for Neurotechnology and Neurorecovery, lead author of the study.
Replay is theorized as a strategy that the brain uses to remember new information. If a mouse is trained to find its way through a maze, tracking devices can show that a particular pattern of brain cells or neurons will light up as it passes the correct path.
“Then, later, while the animal is sleeping, you can see that these neurons will restart in the same order,” Rubin says. Scientists believe that this repetition of neural activation during sleep is the way the brain practices newly learned information, allowing memory to be consolidated – that is, transformed from short-term to long-term.
However, the replay was convincingly shown only on laboratory animals.
“There was an open question in the neuroscience community: to what extent is this model for how we learn things true in humans? And is that true for different kinds of learning? ” asks neurologist Sydney S. Cash, MD, Ph.D., co-director of the Center for Neurotechnology and Neurorecovery at MGH and one of the senior authors of the study.
It is important, Cash says, that understanding whether repetition occurs with learning motor skills could help develop new therapies and tools for people with neurological diseases and injuries.
To study whether recurrence occurs in the human motor cortex – the region of the brain that controls movement – Rubin, Cash and their colleagues hired a 36-year-old man with tetraplegia (also called quadriplegia), meaning he cannot move his upper and lower backs. limbs, in his case due to a spinal cord injury.
The man, identified in the study as T11, is a participant in a clinical trial of a brain-computer interface device that allows him to use a computer cursor and on-screen keyboard.
The research device is being developed by the BrainGate consortium, a joint effort involving clinicians, neuroscientists and engineers at several institutions to create technologies to restore communication, mobility and independence for people with neurological diseases, injuries or limb loss. The consortium is managed by Leigh R. Hochberg, MD, Ph.D., with MGH, Brown University, and the Department of Veterans Affairs.
In the study, T11 was asked to perform a memory task similar to the electronic game Simon, in which a player observes a pattern of colored glitter and then has to recall and reproduce that sequence. He controlled the pointer on the computer screen simply by thinking about the movement of his hand.
Sensors built into the T11 motor cortex measured patterns of neural motion, reflecting his intended hand movement, allowing him to move the pointer around the screen and click it in the desired places. These brain signals are recorded and transmitted wirelessly to a computer.
That night, while T11 was sleeping at home, activity was recorded in his motor cortex and transmitted wirelessly to a computer.
“What we found was pretty amazing,” Rubin says. “He mostly played the game overnight in his sleep.”
On several occasions, Rubin says, T11’s patterns of neural activation during sleep matched exactly the patterns that occurred while he was performing a memory comparison game earlier that day.
“This is the most direct evidence of recurrence from the motor cortex that has ever been seen during sleep in humans,” Rubin says.
Most of the recurrences detected in the study occurred during slow sleep, the deep sleep phase. Interestingly, recurrence was much less likely to be detected while T11 was in REM sleep, the phase most commonly associated with dreaming. Rubin and Cash see this work as a foundation for learning more about replay and its role in learning and memory in humans.
“We hope we can use this information to help build better brain-computer interfaces and devise paradigms that help people learn faster and more effectively to regain control after injury,” says Cash, stressing the importance of moving this line of research from animals to People.
“This type of research benefits tremendously from the close interaction we have with our participants,” he adds, with gratitude to T11 and other participants in the BrainGate clinical trial.
Hochberg agrees. “Our amazing BrainGate participants not only provide useful feedback on creating a system to restore communication and mobility, but also give us a rare opportunity to advance basic human neuroscience – to understand how the human brain works at the level of individual assemblies. neurons, ”he says,“ and use that information to build next-generation restorative neurotechnology. ”
About this news about sleep research and learning
Original research: Closed access.
“Learned motor patterns are repeated in the human motor cortex during sleep”Daniel B. Rubin et al. Journal of Neuroscience
Learned motor patterns are repeated in the human motor cortex during sleep
Memory consolidation is believed to involve offline reproduction of neural activity. While it has been sufficiently proven in rodents, the evidence for recurrence in humans, especially in relation to motor memory, is less convincing.
To determine if recurrence occurs after motor learning, we attempted to record from the motor cortex during a new motor task and subsequent sleep during the night. A 36-year-old man with tetraplegia resulting from a cervical spinal cord injury, enrolled in a pilot clinical trial of the BrainGate interface between brain and computer, had two 96-channel intracortical microelectrode arrays placed chronically in the left precentral gyrus.
The activity of one or more units was recorded while playing a memory game in color / sound sequence. Intentional movements were decoded from motor cortical neural activity using a real-time stable Kalman filter in real time that allowed the participant to control the neuronically guided cursor on the screen. Intracortical neural activity from the precentral gyrus and 2-drain EEG of the scalp were noted during the night while sleeping.
When decoded using the same Kalman filter parameters in the steady state, the intracortical neural signals recorded overnight reproduced the target sequence from the memory game at intervals throughout the time at a frequency significantly higher than expected randomly. Recurrence events occurred at speeds ranging from 1 to 4 times faster than the initial execution of the task and were most commonly observed during sleep with slow waves.
These results suggest that the recent acquisition of visuomotor skills in humans may be accompanied by a repetition of appropriate neural activity of the motor cortex during sleep.
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