Publications

Abstract

Retrieval from semantic memory of conceptual and lexical information is essential for producing speech. It is unclear whether there are differences in the neural mechanisms of conceptual and lexical retrieval when spreading activation through semantic memory is initiated by verbal or nonverbal settings. The same twenty participants took part in two EEG experiments. The first experiment examined conceptual and lexical retrieval following nonverbal settings, whereas the second experiment was a replication of previous studies examining conceptual and lexical retrieval following verbal settings. Target pictures were presented after constraining and nonconstraining contexts. In the nonverbal settings, contexts were provided as two priming pictures (e.g., constraining: nest, feather; nonconstraining: anchor, lipstick; target picture: BIRD). In the verbal settings, contexts were provided as sentences (e.g., constraining: “The farmer milked a...”; nonconstraining: “The child drew a...”; target picture: COW). Target pictures were named faster following constraining contexts in both experiments, indicating that conceptual preparation starts before target picture onset in constraining conditions. In the verbal experiment, we replicated the alpha-beta power decreases in constraining relative to nonconstraining conditions before target picture onset. No such power decreases were found in the nonverbal experiment. Power decreases in constraining relative to nonconstraining conditions were significantly different between experiments. Our findings suggest that participants engage in conceptual preparation following verbal and nonverbal settings, albeit differently. The retrieval of a target word, initiated by verbal settings, is associated with alpha-beta power decreases. By contrast, broad conceptual preparation alone, prompted by nonverbal settings, does not seem enough to elicit alpha-beta power decreases. These findings have implications for theories of oscillations and semantic memory.

Abstract

Foreign language attrition (FLA) appears to be driven by interference from other, more recently-used languages (Mickan et al., 2020). Here we tracked these interference dynamics electrophysiologically to further our understanding of the underlying processes. Twenty-seven Dutch native speakers learned 70 new Italian words over two days. On a third day, EEG was recorded as they performed naming tasks on half of these words in English and, finally, as their memory for all the Italian words was tested in a picture-naming task. Replicating Mickan et al., recall was slower and tended to be less complete for Italian words that were interfered with (i.e., named in English) than for words that were not. These behavioral interference effects were accompanied by an enhanced frontal N2 and a decreased late positivity (LPC) for interfered compared to not-interfered items. Moreover, interfered items elicited more theta power. We also found an increased N2 during the interference phase for items that participants were later slower to retrieve in Italian. We interpret the N2 and theta effects as markers of interference, in line with the idea that Italian retrieval at final test is hampered by competition from recently practiced English translations. The LPC, in turn, reflects the consequences of interference: the reduced accessibility of interfered Italian labels. Finally, that retrieval ease at final test was related to the degree of interference during previous English retrieval shows that FLA is already set in motion during the interference phase, and hence can be the direct consequence of using other languages.

Abstract

One of the challenges in speech perception is that listeners must deal with considerable
segmental and suprasegmental variability in the acoustic signal due to differences between talkers. Most previous studies have focused on how listeners deal with segmental variability.
In this EEG experiment, we investigated whether listeners track talker-specific usage of suprasegmental cues to lexical stress to recognize spoken words correctly. In a three-day training phase, Dutch participants learned to map non-word minimal stress pairs onto different object referents (e.g., USklot meant “lamp”; usKLOT meant “train”). These non-words were
produced by two male talkers. Critically, each talker used only one suprasegmental cue to signal stress (e.g., Talker A used only F0 and Talker B only intensity). We expected participants to learn which talker used which cue to signal stress. In the test phase, participants indicated whether spoken sentences including these non-words were correct (“The word for lamp is…”).
We found that participants were slower to indicate that a stimulus was correct if the non-word was produced with the unexpected cue (e.g., Talker A using intensity). That is, if in training Talker A used F0 to signal stress, participants experienced a mismatch between predicted and perceived phonological word-forms if, at test, Talker A unexpectedly used intensity to cue
stress. In contrast, the N200 amplitude, an event-related potential related to phonological
prediction, was not modulated by the cue mismatch. Theoretical implications of these
contrasting results are discussed. The behavioral findings illustrate talker-specific prediction of prosodic cues, picked up through perceptual learning during training.