Scientists Discover a New Daily Rhythm Providing Insight Into How Brain Activity is Fine-Tuned

Researchers Kunwei Wu, Wenyan Han, and Wei Lu at the National Institute of Neurological Disorders and Stroke (NINDS) have found a new daily rhythm in a type of brain synapse. It is referred to as an inhibitory synapse and it helps to dampen brain activity and is rebalanced during sleep to consolidate new memories.

The study, published in PLOS Biology, aims to understand how sleep and wakefulness regulate the plasticity of these synapses, which are important for various brain functions, but have not been widely studied. The researchers examined inhibitory synapses in mice during sleep and wakefulness using electrical recordings from neurons in the hippocampus, a brain region involved in memory formation. They found that during wakefulness, steady "tonic" inhibitory activity increased but fast "phasic" inhibition decreased. Additionally, they found a larger activity-dependent enhancement of inhibitory electrical responses in awake mouse neurons, suggesting that wakefulness may strengthen these synapses more than sleep.

Inhibitory neurons use the neurotransmitter gamma-aminobutyric acid (GABA) to reduce nervous system activity by releasing GABA molecules into the synaptic cleft, the space between neurons, at inhibitory synapses. These molecules bind to GABAA receptors on the surface of neighboring excitatory neurons, reducing their firing. The changes in synapses during wakefulness were driven by an increased number of α5-GABAA receptors, which may be key to building stronger, more efficient inhibitory synapses through a process called synaptic plasticity.

Due to the similarities between the neural circuits involved in memory and cognition for humans and mice, this research provides insight on how the human brain performs fine-tuned, cognitive tasks. In the future, the team plans to study the molecular basis of GABAA receptor trafficking to inhibitory synapses. This research may help scientists to better understand sleep-wake cycles and neurological disorders linked to abnormal brain rhythms.

References:

National Institute of Neurological Disorders and Stroke. (2022, December 20). Scientists Discover a New Daily Rhythm Providing Insight Into How Brain Activity Is Fine-Tuned. SciTechDaily. Retrieved December 21, 2022, from https://scitechdaily.com/scientists-discover-a-new-daily-rhythm-providing-insight-into-how-brain-activity-is-fine-tuned/

“Sleep and wake cycles dynamically modulate hippocampal inhibitory synaptic plasticity” by Kunwei Wu, Wenyan Han and Wei Lu, 1 November 2022, PLOS Biology. DOI: 10.1371/journal.pbio.3001812