Relational memory is the ability to remember arbitrary or indirect associations between objects, people or events, such as names with faces, where you left your car keys and whether you turned off the stove after cooking but before you left the house.
Previous research has established that animal and human memory benefits from sufficient, quality sleep. In a new study, published May 25, 2022 in the Journal of Neuroscience, Maxim Bazhenov, PhD, professor of medicine at University of California San Diego School of Medicine, and Timothy Tadros, a graduate student in his lab, describe the underlying mechanisms that strengthen or create new relational memories during sleep.
Sleep and the Brain
The authors developed an artificial model of two regions of the brain: the thalamic (involved in earlier sensory processing) and the cortical (involved in memory, learning and decision-making). The model was capable of simulating two major brain states: awake when neurons are spontaneously active and optimized to process sensory input and deep sleep when intrinsic oscillations of electrical activity are generated, such as slow-waves. The properties of the network model could be changed to promote transitions between awake and asleep activity, similar to what the biological brain does every day.
“We modelled the cortex after visual processing, with one cortical layer representing primary visual cortex and another cortical layer representing associative cortex,” said Tadros. “Every time one sees the same object, roughly the same neurons in the visual cortex would be active. If a person sees two objects in the same context, then these associations might be learned in the associative cortex by strengthening connections between neurons that represent each of the two objects.”
The scientists trained the network in its awake mode to learn such direct associations, such as A+B or B+C but not A+C, then discovered that in the sleep mode, the model formed indirect associations: A+C.
“This happened because during sleep the neurons representing all three related items (A, B and C) spontaneously fired in close temporal order, a phenomenon called sleep replay, which triggered synaptic plasticity and led to formation of strong synaptic connections between all these neurons,” said Bazhenov. “Therefore, after sleep, activating any one group, such as A, activated all other related groups, such as B and C.”
Improving Slow-Wave Sleep
While primarily conceptual, the researchers said the work has real-world implications. “One important real-world impact of the study is in informing future studies of disease, such as schizophrenia and autism spectrum disorder,” said Bazhenov.
“Studies have shown that people with these conditions perform worse on relational memory tasks and also have disrupted sleep, specifically slow-wave sleep.
The authors also noted that memory function and sleep quality decline with age, but current or new technologies that augment sleep oscillations may help protect and improve memory function in older adults.
This important research shows again how important sleep is for learning. Specifically, this article shows the importance of deep sleep for helping us consolidate our relational memory. Our relational memory is our ability to look at “pieces of information” (for example: numbers: 2,4,6,8,10…) and to “see” (visualize) the “patterns of information.” We can’t memorize all the math facts from one to 1 million, but by seeing the “patterns of information” in the numbers, we have the power to do any math problem.
The ability to go from pieces to patterns underlies our ability visualize or “see” the meaning of number patterns in math and of word patterns in language. Processing speed (fluency) is the brain skill that enables us to put pieces of information together into patterns. The StepUp program exercises give us daily practice in fluently seeing patterns of information within and among the numbers and letters that are the building blocks of learning.
Reposted from University of California San Diego
Note by Nancy W Rowe, M.S., CCC/A