The episodic context account (Gaskell et al., 2019) proposes that the act of language comprehension gives rise to an episodic discourse representation, and that this representation is prone to sleep-related memory effects. In three experiments, we tested this prediction by asking participants to read/listen to naturalistic stories before their memory was tested after a 12-hr interval, which included either daytime wakefulness or overnight sleep. To assess discourse memory, we used sentence recognition (Experiment 1; N = 386), free story recall (Experiment 2; N = 96), and cued recall (Experiments 2 and 3; N = 192). We found no evidence of sleep-related effects in sentence recognition or free recall, but cued recall (aka fill-in-the-blank) showed that the degree of time-dependent distortion, as indexed by both a subjective categorisation measure and Latent Semantic Analysis, was lower after sleep than after wake. Our experiments suggest that the effect of sleep on discourse memory may [1] be constrained by the retrieval processes (recollection vs. familiarity & associative vs. item), [2] lie on a qualitative level that is difficult to detect in an all-or-nothing scoring metric, and [3] primarily situate in the textbase level of the tripartite model of discourse processing. Overall, in line with the episodic context account, our findings highlight a specific role of declarative memory and sleep in day-to-day language comprehension, but with limitations on their impact depending on the nature of the retrieval processes.

Familiar words come with a wealth of associated knowledge about their variety of usage, accumulated over a lifetime. How do we track and adjust this knowledge as new instances of a word are encountered? A recent study (Gaskell, Cairney & Rodd, 2019, Cognition) found that, for homonyms (e.g., bank), sleep-associated consolidation facilitates the updating of meaning dominance. Here, we tested the generality of this finding by exposing participants to (Experiment 1; N = 125) non-homonyms (e.g., bathtub) in sentences that biased their meanings towards a specific interpretation (e.g., bathtub-slip vs. bathtub-relax), and (Experiment 2; N = 128) word-class ambiguous words (e.g., loan) in sentences where the words were used in their dispreferred word class (e.g., “He will loan me money”). Both experiments showed that such sentential experience influenced later interpretation and usage of the words more after a night’s sleep than a day awake. We interpret these results in relation to an episodic context account of language comprehension in which new episodic memories are formed every time a sentence is comprehended, and these memories contribute to lexical processing next time the word is encountered and potentially the fine-tuning of long-term lexical knowledge.

Familiar words come with a wealth of associated knowledge about their variety of usage, accumulated over a lifetime. How do we track and adjust this knowledge as new instances of a word are encountered? A recent study (Cognition) found that, for homonyms (e.g., bank), sleep-associated consolidation facilitates the updating of meaning dominance. Here, we tested the generality of this finding by exposing participants to (Experiment 1; N = 125) nonhomonyms (e.g., bathtub) in sentences that biased their meanings toward a specific interpretation (e.g., bathtub-slip vs. bathtub-relax), and (Experiment 2; N = 128) word-class ambiguous words (e.g., loan) in sentences where the words were used in their dispreferred word class (e.g., "He will loan me money"). Both experiments showed that such sentential experience influenced later interpretation and usage of the words more after a night's sleep than a day awake. We interpret these results as evidence for a general role of episodic memory in language comprehension such that new episodic memories are formed every time a sentence is comprehended, and these memories contribute to lexical processing next time the word is encountered, as well as potentially to the fine-tuning of long-term lexical knowledge. Public Significance StatementOur research adds to the growing body of evidence that language and memory, which have historically been studied as distinct cognitive abilities, are heavily intertwined. We tested the notion that episodic memory-memories for specific events-is involved in the maintenance of discourse representations during language comprehension. We showed that these representations, presumably binding words and concepts together, capture context-specific lexical information such as the precise meaning (e.g., relaxing vs. slipping in a bathtub) and their word class (e.g., loan as a noun vs. verb). We showed that (a) these representations can prime subsequent lexical processing, and (b) as in other newly acquired episodic memories, these representations may be prone to sleep-related memory consolidation such that their effects on lexical processing was more robust after sleep (vs. wakefulness). Our findings highlighted how episodic memory and sleep may contribute to the updating of lexical memory, providing some degree of malleability to our mental lexicon.

When a homonym (e.g., bark) is encountered in a sentential context that biases its interpretation towards a less frequent meaning, subsequent interpretations of the word are more likely to favour that subordinate meaning. Such word-meaning priming effects have been shown to be maintained via sleep-related consolidation, leading some to suggest that declarative memory systems play a crucial role in language comprehension, providing a relatively enduring contextually bound memory trace for the ambiguous word. By this account, word-meaning priming effects should be observable for all words, not just homonyms. In three experiments, participants were exposed to non-homonym targets (e.g., “balloon”) in sentences that biased interpretation toward a specific aspect of the word’s meaning (e.g., balloon-helium vs. balloon-float). After a ~10-30 min delay, the targets were presented in relatedness judgement and associate production tasks to assess whether the sentential contexts enhanced access to the primed aspect of the word’s meaning. The results reveal that word-meaning priming effects do extend to non-homonyms. Indeed, there was also some evidence of a more generalized priming that did not rely on prior presentation of the non-homonym itself. We argue that context-specific interpretations of words are maintained during recognition in order to facilitate comprehension over longer periods.