Sleep Spindle Density Predicts the Effect of Prior Knowledge on Memory Consolidation

Abstract

Information that relates to a prior knowledge schema is remembered better and consolidates more rapidly than information that does not. Another factor that influences memory consolidation is sleep and growing evidence suggests that sleep-related processing is important for integration with existing knowledge. Here, we perform an examination of how sleep-related mechanisms interact with schema-dependent memory advantage. Participants first established a schema over 2 weeks. Next, they encoded new facts, which were either related to the schema or completely unrelated. After a 24 h retention interval, including a night of sleep, which we monitored with polysomnography, participants encoded a second set of facts. Finally, memory for all facts was tested in a functional magnetic resonance imaging scanner. Behaviorally, sleep spindle density predicted an increase of the schema benefit to memory across the retention interval. Higher spindle densities were associated with reduced decay of schema-related memories. Functionally, spindle density predicted increased disengagement of the hippocampus across 24 h for schema-related memories only. Together, these results suggest that sleep spindle activity is associated with the effect of prior knowledge on memory consolidation.

Prior knowledge is essential for the beneficial effect of targeted memory reactivation during sleep

“…The earlier theta response to word cues over the parietal cortex might reflect the immediate reinstatement of the memory trace in the brain region of initial storage1617. The later spindle response over frontotemporal regions which predicted the cueing-induced memory benefit might reflect the successful integration of new information into these neocortical networks and their stabilization17181920. Future studies need to experimentally manipulate theta and spindle activity in response to memory cues with different level of prior knowledge in order to empirically test the exact role of these oscillations in the reinstatement and the integration of these memories into the existing memory networks.…”

Rotating waves during human sleep spindles organize global patterns of activity that repeat precisely through the night

“…Spindles have recently been specifically and causally implicated in the sleep-dependent consolidation of long-term memories (Mednick et al, 2013;Hennies et al, 2016). While some memories integrate content from single sensory modalities, requiring consolidation in only single cortical regions (such as motor cortex, Khazipov et al, 2004), many memories integrate multimodal sensory and cognitive information (Gibson and Maunsell, 1997), and require 'global' integration of distributed networks across the cortex.…”

Impact of smartphone use on quality of sleep among medical students

“…7 Episodic memories are gradually assimilated into longterm memory and this process is strongly influenced by sleep & existing memories are spontaneously reactivated and strengthened in the brain during rest periods. 8,9 Sleep problems and sleep deprivation lead to poor academic performance and excessive day time sleepiness in college students. 10,11 Since medical students are required to be alert & attentive during learning period so that they acquire professional level knowledge & skills of patient care, medical students who already have lots of academic burden and sleep problems due to other factors, smartphone overuse/addiction if present may further complicate the things and may lead to significant stress & mental health problems.…”