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Poster D46, Thursday, November 9, 6:15 – 7:30 pm, Harborview and Loch Raven Ballrooms

Brain oscillation signatures of learning new meanings for known words and novel words

Xiaoping Fang1,2, Charles Perfetti1,2;1Learning Research and Development Center, University of Pittsburgh, 2Center for the Neural Basis of Cognition

In addition to learning new words, people refine and add new meanings to words they already know. For example, one might learn that “skate” is a kind of fish long after knowing its most common meaning. This type of learning involves strong interactions between new information and prior knowledge and is relatively less studied, compared to the learning of novel words. The current study tracked the two types of learning by recording EEGs throughout the learning phase. Twenty-one native English speakers learned new meanings for known words (e.g., “plenty” means “causing fever”) and novel words (e.g., “tasdite” means “having a tight schedule”) in an associative learning paradigm in which a word and its meaning were presented consecutively. Each word was presented once in each of six learning blocks. Following the first block of study trials, blocks two through six were test-study trials, requiring participants to attempt to recall the new meanings before viewing them and assessing their recall success. To observe oscillation indicators of learning, we compared early-phase learning trials (the second and third learning blocks) with late-phase learning trials (the last two learning blocks). Self-assessed recall increased from early to late phases, and in both phases the performance for known words was better than for novel words, a pattern also found in a post-learning multiple-choice test. Brain oscillations on the trained words showed different patterns for the two types of learning. In late learning, novel words showed decreased synchronization at alpha band (9-12 HZ) but not at other frequency bands. In contrast, known words showed decreased synchronization in alpha, upper beta (21-29 HZ), and lower gamma (30-59 HZ) bands from early to late learning phases. We interpret the decreased beta synchronization observed in the frontal regions to reflect the suppression of original meanings that comes as a new meaning is learned well enough to evoke competition from a word’s original meaning. Theta synchronization did not change over learning phases on either known or novel words, suggesting that neural communications between the hippocampus and neocortex during the retrieval of new meanings were maintained during the 90-120 minutes of learning within the session. This interpretation is consistent with the assumption that episodic learning continues across trials within a single session for both novel and real worlds, with the main difference being the need for suppression of original meanings in the case of real words.

Topic Area: Meaning: Lexical Semantics

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