👤 Kristof Strijkers

In this functional magnetic resonance imaging study, we investigated whether language production and understanding recruit similar phoneme-specific networks. We did so by comparing the brain's response to different phoneme categories in minimal pairs: Bilabial-initial words (eg "monkey") were contrasted to alveolar-initial words (eg "donkey") in 37 participants performing both language production and comprehension tasks. Individual-specific region-of-interest analyses showed that the same sensorimotor networks were activated across the language modalities. In motor regions, word production and comprehension elicited the same phoneme-specific topographical activity patterns, with stronger haemodynamic activations for alveolar-initial words in the tongue cortex and stronger activations for bilabial-initial words in the lip cortex. In the posterior and middle superior temporal cortex, production and comprehension likewise resulted in similar activity patterns, with enhanced activations to alveolar- compared to bilabial-initial words. These results disagree with the classical asymmetry between language production and understanding in neurobiological models of language, and instead advocate for a cortical organization where phonology is carried by similar topographical activations in motor cortex and distributed activations in temporal cortex across the language modalities. Show less

The motor system is known to process temporal information, and moving rhythmically while listening to a melody can improve auditory processing. In three interrelated behavioural experiments, we demonstrate that this effect translates to speech processing. Motor priming improves the efficiency of subsequent naturalistic speech-in-noise processing under specific conditions. (i) Moving rhythmically at the lexical rate (~1.8 Hz) significantly improves subsequent speech processing compared to moving at other rates, such as the phrasal or syllabic rates. (ii) The impact of such rhythmic motor priming is not influenced by whether it is self-generated or triggered by an auditory beat. (iii) Overt lexical vocalization, regardless of its semantic content, also enhances the efficiency of subsequent speech processing. These findings provide evidence for the functional role of the motor system in processing the temporal dynamics of naturalistic speech. Show less

This study aimed to assess the extent to which human participants co-represent the lexico-semantic processing of a humanoid robot partner. Specifically, we investigated whether participants would engage their speech production system to predict the robot's upcoming words, and how they would progressively adapt to the robot's verbal behaviour. In the experiment, a human participant and a robot alternated in naming pictures of objects from 15 semantic categories, while the participant's electrophysiological activity was recorded. We manipulated word frequency as a measure of lexical access, with half of the pictures associated with high-frequency names and the other half with low-frequency names. In addition, the robot was programmed to provide semantic category labels (e.g., "tool" for the picture of a hammer) instead of the more typical basic-level names (e.g., "hammer") for items in five categories. Analysis of the stimulus-locked activity revealed a comparable event-related potential (ERP) associated with word frequency both when it was the participant's and the robot's turn to speak. Analysis of the response-locked activity showed a different pattern for the category and basic-level responses in the first but not in the second part of the experiment, suggesting that participants adapted to the robot's lexico-semantic patterns over time. These findings provide empirical evidence for two key points: (1) participants engage their speech production system to predict the robot's upcoming words and (2) partner-adaptive behaviour facilitates comprehension of the robot's speech. Show less

Standard models of lexical production assume that speakers access representations of meaning, grammar, and different aspects of sound in a roughly sequential manner (whether or not they admit cascading or interactivity). In contrast, we review evidence for a parallel activation model in which these representations are accessed in parallel. According to this account, word learning involves the binding of the meaning, grammar, and sound of a word into a single representation. This representation is then activated as a whole during production, and so all linguistic components are available simultaneously. We then note that language comprehension involves extensive use of prediction and argue that comprehenders use production mechanisms to determine (roughly) what they would say next if they were speaking. So far, theories of prediction-by-production have assumed sequential lexical production. We therefore reinterpret such evidence in terms of parallel lexical production. Show less