July 27, 2022 – Feeling forgetful? Having trouble matching names to faces lately? It doesn’t necessarily mean you’re not well or that your thinking skills are fading. You may just not have enough sleep.
Researchers have long known that sleep is vital for relational memory, the brain’s ability to make connections between objects, places, people and events. What they didn’t pinpoint was what happens during sleep to help memory make the right connections.
To find out, two researchers at the University of California, San Diego built computer models of the brain’s thalamus and cortex and studied activity in those regions during an artificial version of an awake state. and deep sleep.
During the computer modeling exercise, the researchers strengthened or weakened the connections between neurons, depending on how active they were. First, they trained the modeled network during waking mode to directly associate one thing with another, like A+B and B+C.
Then, during deep sleep, they observed how the network made indirect associations, such as A+C, on its own. They published their findings this month in The Journal of Neuroscience.
Maxim Bazhenov, PhD, one of the researchers, explained that the indirect links occur because the neurons linked to A, B and C all fire in a close order, called sleep replay, which creates a connection between the three neurons.
“Therefore, after sleep, activation of one group, such as A, activated all other related groups, such as B and C,” he said in a Prepared statement.
The thalamus is the part of the brain that takes in sensory signals and gives them meaning, and the cortex is essential for memory, learning, and decision-making. Our neurons receive sensory information when they are awake, but it is during deep sleep that the cortex makes sense of information from the day. During this time, the brain repeats an electrical activity called slow waves.
Sleep replay triggers synaptic plasticity, the activity between neurons that allows them to communicate with each other and the main way the brain creates, modifies or suppresses memories.
The computer model has primarily helped researchers understand how relational memory works in the brain, that is, how the brain connects seemingly unrelated information. But it also sheds light on what might not work in people with certain neurological or psychiatric conditions that affect memory, such as schizophrenia or autism spectrum disorder.
Their results suggest that finding ways to improve slow-wave sleep in people with these conditions can help their brains make these connections and improve their general memory and association-making problems.