When we were speech-language pathologists (SLPs) in training—one many years ago, the other mere months ago—we were taught to include questions about sleep in diagnostic interviews. But we were never sure whether reports of sleep problems were meaningful to the clinical decision making at hand. What do sleep problems entail? How does poor sleep affect language learning and use? When is a medical referral needed? This uncertainty prompted us to ask whether individuals with sleep disorders are at higher risk for language learning deficits than healthy sleepers. Our primary goal was to inform clinical protocol.
Two lines of evidence support a link between sleep and language learning. The first involves experimental manipulations of sleep intervals relative to learning intervals in the general population. In these experiments, sleep affected adults’ memory consolidation as demonstrated by enhanced retention of word forms (Drummond et al., 2000; Ficca, Lombardo, Rossi, & Salzarulo, 2000), stabilization of improvement in word recognition (Fenn, Nusbaum, & Margoliash, 2003), and integration of newly-learned words into the mental lexicon (Gaskell & Dumay, 2003). The effect of sleep on verbal learning and memory is not limited to adults nor is it exclusive to the lexical domain. Infants who slept after exposure to an artificial language derived abstract grammatical patterns; those who remained awake did not (Gómez, Bootzin, & Nadel, 2006).