A recent scientific study has shed new light on how our brain functions during sleep, particularly during Non-Rapid Eye Movement (NREM) sleep, and how this affects our cognitive and behavioural performance. This groundbreaking research, conducted by a team from Rice University, Houston Methodist’s Center for Neural Systems Restoration and Weill Cornell Medical College, could revolutionize our understanding of how sleep enhances brain functionality.
The study, published in Science, highlights how NREM sleep – the lighter stage of sleep often experienced during a nap – promotes brain synchronization and enhances the brain’s ability to encode information. The team was able to replicate these effects through invasive stimulation, indicating potential future applications for neuromodulation therapies. These findings could lead to innovative treatments for sleep disorders and even methods to improve cognitive performance.
The research involved analysing the neural activity in different brain areas of macaques during a visual discrimination task before and after a 30-minute NREM sleep session. The team used multielectrode arrays to monitor the neurons’ activity in three brain regions associated with visual processing and executive functions. They confirmed the animals were in NREM sleep using polysomnography, a type of sleep study, and video analysis.
The results revealed that sleep enhanced the macaques’ ability to distinguish rotated images with increased accuracy, with this improvement only seen in those who actually fell asleep. The quiet wakefulness group that did not fall asleep showed no such enhancement in performance.
“Sleep led to an increase in low-frequency delta wave activity and synchronized firing of neurons across different cortical areas,” said Dr. Natasha Kharas, lead author of the study. “Post-sleep, neuronal activity became more independent, leading to improved information processing and task performance.”
In addition to monitoring natural sleep, the researchers also artificially simulated the neural effects of sleep by applying low-frequency electrical stimulation to the visual cortex of the awake macaques. This stimulation, which mimicked the delta frequency observed during NREM sleep, generated the same desynchronization effect seen post-sleep and similarly improved the animals’ task performance.
“This suggests that some cognitive benefits of sleep might be achievable without actual sleep,” said co-author Valentin Dragoi. “The ability to replicate sleep-like neural desynchronization while awake opens up possibilities for enhancing cognitive and perceptual performance in situations where sleep is not possible.”
By creating a large neural network model, the team discovered that during sleep, both excitatory and inhibitory connections in the brain weaken asymmetrically, with inhibitory connections weakening more than excitatory ones, resulting in increased excitation.
Dragoi explained, “We’ve found a surprising solution where after sleep, despite receiving synchronizing inputs during sleep, the brain reduces the level of synchrony in neural populations involved in the task.”
This understanding of how NREM sleep enhances brain performance and how this process can be artificially replicated offers hope for the development of therapeutic brain stimulation techniques to improve cognitive function and memory.
“Our study not only deepens our understanding of sleep’s role in cognitive function but also shows that specific patterns of brain stimulation could substitute for some benefits of sleep,” Dragoi concluded. “This points towards a future where we might boost brain function independently of sleep itself.”
This research received support from National Eye Institute grants 5R01EY026156 (V.D.) and 5F31EY029993 (N.K.).
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