Sleep and Word Learning Over Time in Adults with Moderate-Severe Traumatic Brain Injury
Morrow, Emily L.
0000-0003-4629-2283
:
2022-03-25
Abstract
Cognitive-communication impairment is among the most common and costly consequences of moderate-severe traumatic brain injury (TBI). Word learning is a central but largely unexamined aspect of cognitive communication that draws on memory systems routinely impaired after TBI and is critical to a person’s ability to succeed in rehabilitation, academic, and vocational settings. Studying word learning over time presents the opportunity to examine how external factors that support learning in neurotypical people, like sleep, affect learning for people with TBI. In this study, we used a randomized within-participant crossover design to assess how people with TBI form memories of new words (encoding) and strengthen those memories over time (consolidation), with a focus on the role of sleep in the learning process. 50 adults in the chronic phase of moderate-severe TBI and 50 demographically matched neurotypical peers learned novel words and were tested on their encoding of those words immediately, then assessed for consolidation of those words over time intervals that did or did not involve sleep. They wore activity monitors assessing their sleep-wake cycles over the two-week experiment period. Participants with TBI exhibited a striking word learning deficit across domains and delays. Critically, this deficit grew over the course of the week, suggesting that individuals with TBI do not consolidate information like their neurotypical peers. Participants with and without TBI remembered more words when they slept after learning. All participants remembered more words at the long-term post-test when they slept more over the course of the week, but there were no differences between people with and without TBI in the amount or variability of sleep, as measured by actigraphy, during the experiment period. These results highlight the importance of identifying people at risk for word learning deficits after TBI and developing word learning interventions to improve functional outcomes. More study is needed to understand how to reduce the gap in long-term consolidation of information for people with TBI and to identify the sleep measures that are most strongly associated with learning in this population.