No abstract

Many of our everyday decisions are based not only on memories of direct experiences, but on memories that are integrated across multiple distinct experiences. Sometimes memory integration between existing memories and newly learnt information occurs rapidly, without requiring inference at the time of a decision. Such fast memory integration is known to be supported by the hippocampus but not the neocortex. In this study, we explore an alternative mechanism of fast memory integration, through related prior knowledge (i.e., schema), which is associated with neocortical learning. Paired associates were selected to be schema consistent or inconsistent, and confirmed with a latent semantic analysis of text corpora. We observed that after enabling fast learning by using material that is consistent with a schema, faster memory integration can occur. This result suggests that the hippocampus-mediated integration of new information is not the only available mechanism that supports fast memory integration.peer-reviewed)

Difficulty perceiving phonological contrasts in a second language (L2) can impede initial L2 lexical learning. Such is the case for English speakers learning tonal languages, like Mandarin Chinese. Given the hypothesized role of reduced neuroplasticity in adulthood limiting L2 phonological perception, the current study examined whether transcutaneous auricular vagus nerve stimulation (taVNS), a relatively new neuromodulatory technique, can facilitate L2 lexical learning for English speakers learning Mandarin Chinese over 2 days. Using a double-blind design, one group of participants received 10 min of continuous priming taVNS before lexical training and testing each day, a second group received 500 msec of peristimulus (peristim) taVNS preceding each to-be-learned item in the same tasks, and a third group received passive sham stimulation. Results of the lexical recognition test administered at the end of each day revealed evidence of learning for all groups, but a higher likelihood of accuracy across days for the peristim group and a greater improvement in response time between days for the priming group. Analyses of N400 ERP components elicited during the same tasks indicate behavioral advantages for both taVNS groups coincided with stronger lexico-semantic encoding for target words. Comparison of these findings to pupillometry results for the same study reported in Pandža, Phillips, Karuzis, O'Rourke, and Kuchinsky (2020) suggest that positive effects of priming taVNS (but not peristim taVNS) on lexico-semantic encoding are related to sustained attentional effort.

In two ERP experiments we examined local (recent text) and global (centrality) text influences on word-to-text integration. Participants read words that appeared across a sentence boundary or in text-final position. In both cases, the word was either related (central) or unrelated (noncentral) to the central theme of the passage. Additionally, words across a sentence boundary had an antecedent in the preceding sentence (local binding) or did not (baseline). Results indicate local-binding processes influence sentence-initial words with no additional effect of centrality, evidenced by a reduced N400 for central and non-central words with a local-binding opportunity relative to baseline. At text-final words, we observed a reduced P600 (Experiment 1) as well as an N400 (Experiment 2) for central relative to non-central words. This pattern suggests that integration across a sentence boundary is supported by local context and that over the course of continued reading, integration begins to reflect global text meaning.

We provide new evidence concerning two opposing views of episodic associations: The independent-association hypothesis posits that associations are unidirectional and separately modifiable links (A→B and A←B); in contrast, the associativesymmetry hypothesis proposes that a single, bidirectional association exists between A and B (A↔B). We used a novel method to demonstrate that whether or not episodic associations are symmetric depends on whether there is a preexisting semantic relationship between A and B. In two experiments, participants studied 30 semantically unrelated and 30 semantically related pairs intermixed in a single list and then performed a series of up to eight cued-recall test cycles. All pairs were tested in each cycle, and the testing direction (A-? or B-?) alternated between cycles. Unrelated pairs exhibited associative symmetry-that is, accuracy and response times improved gradually on each test-suggesting that testing in both directions strengthened the same association. In contrast, semantically related pairs exhibited a stair-like pattern, in which performance did not change from odd to even tests when the test direction changed; it only improved between tests in the same direction. We concluded that episodic associations can have either a single bidirectional representation or separate directional representations, depending on the semantic relatedness of their constituent items.