Language processing recruits a core fronto-temporal cortical network, which is complemented by a distributed network of modality-specific areas (such as the motor cortex) to encode referential aspects of meaning. Since most studies typically focus on already fully-formed adult vocabulary, it remains unclear how and when exactly modality-specific areas become involved in language processing. Here, we addressed this question using a 3D virtual environment game to teach adult participants new action verbs and object nouns. To test the role of primary motor cortex (M1) in selectively encoding aspects of action verb meaning early on in the process of word learning, we delivered theta-burst stimulation to three groups of participants prior to learning: M1 TMS, active control TMS, and sham TMS. Our results show that TMS of M1 (but not active or sham controls) interferes with the learning process, as indexed by measures of movement kinematics and a higher number of errors during training. Thus, TMS disruption of M1 degrades learning outcomes when motor information is an integral part of lexico-semantic encoding. This effect was corroborated in a subsequent lexical decision task, which showed significant group- and word-category RT differences, suggesting category-specific effects of TMS on word learning. Overall, our study demonstrates the M1’s causal involvement in the earliest phases of word learning and rapid encoding of semantic motor information.

How do we communicate our pain to others? The challenge of conveying such a highly individual experience in words is faced daily by many sufferers of chronic pain and their doctors. Moreover, such linguistic strategies are especially relevant in situations where no obvious reference to physical injuries or tissue damage can be made. Neurolinguistically, this question is directly linked to understanding the brain mechanisms behind the encoding, storage, and comprehension of word meanings. An influential view posits that comprehension involves mentally simulating sensorimotor experiences which words refer to. Here, we test the hypothesis that both pain word comprehension and first-hand experiences of pain rely on a common neural substrate, leading to a prediction that word processing should modulate the perception of noxious stimuli. We used a priming task and asked neurotypical and chronic pain participants to read sentences containing literal or metaphoric pain descriptors, and then rate the intensity of thermal pain stimuli. We found that pain language comprehension modulated participants’ ratings of pain intensity. Furthermore, this effect depended on linguistic context as well as individual pain history. We discuss our findings within the larger theoretical debate on the nature of semantic representations, and point to their potential relevance for clinical practice.

Among various questions pertinent to grounding human cognitive functions in a neurobiological substrate, the association between language and motor brain structures is a particularly debated one in neuroscience and psychology. While many studies support a broadly distributed model of language and semantics grounded, among other things, in the general modality-specific systems, theories disagree as to whether motor and sensory cortex activity observed during language processing is functional or epiphenomenal. Here, we assessed the role of motor areas in linguistic processing by investigating the responses of 28 healthy volunteers to different word types in semantic and lexical decision tasks, following repetitive transcranial magnetic stimulation (rTMS) of primary motor cortex. We found that early rTMS (delivered within 200 ms of word onset) produces a left-lateralised and meaning-specific change in reaction speed, slowing down behavioural responses to action-related words, and facilitating abstract words – an effect present only during semantic, but not lexical, decision. We interpret these data in light of action-perception theory of language, bolstering the claim that motor cortical areas play a functional role in language comprehension.

The Val66Met polymorphism of the Brain-Derived Neurotrophic Factor (BDNF) gene is known to alter brain structure and plasticity mechanisms. Although at the behavioral level Met carriers show differences in memory performance, little is known about the underlying neural mechanisms. Since previous studies with neuro-typical populations showed the critical role of the dorsolateral prefrontal cortex (DLPFC) in episodic memory processes, here we used repetitive Transcranial Magnetic Stimulation (rTMS) to causally address the role of left and right DLPFC in episodic retrieval in relation to the BDNF Val66Met polymorphism. To achieve this goal, we adopted a classical deep and shallow memory task. Participants encoded visually presented words while performing a semantic (living/non-living) or perceptual (letter judgment) task, followed by an incidental recognition memory task. Whereas encoding was free of stimulation, 10 Hz rTMS was delivered at retrieval over the left and right DLPFC. Vertex (active site) and no rTMS were included as control conditions. We found a significant drop of memory performance for the ValVal group during left DLPFC stimulation: the effect was specific for recognition of deeply encoded items. Conversely, rTMS had no impact on Met-carriers' memory performance. Our results represent the first causal evidence of rTMS modulatory effects during a cognitive task in relation to the Val66Met polymorphism. These findings highlight possible differences across the cortical memory network and plasticity mechanisms between the two BDNF genotypes, and might represent a step towards the development of genetically-based brain stimulation therapies in patients with memory impairments.

To help us live in the three-dimensional world, our brain integrates incoming spatial information into reference frames, which are based either on our own body (egocentric) or independent from it (allocentric). Such frames, however, may be crucial not only when interacting with the visual world, but also in language comprehension, since even the simplest utterance can be understood from different perspectives. While significant progress has been made in elucidating how linguistic factors, such as pronouns, influence reference frame adoption, the neural underpinnings of this ability are largely unknown. Building on the neural reuse framework, this study tested the hypothesis that reference frame processing in language comprehension involves mechanisms used in navigation and spatial cognition. We recorded EEG activity in 28 healthy volunteers to identify spatiotemporal dynamics in (1) spatial navigation, and (2) a language comprehension task (sentence-picture matching). By decomposing the EEG signal into a set of maximally independent activity patterns, we localised and identified a subset of components which best characterised perspective-taking in both domains. Remarkably, we find individual co-variability across these tasks: people's strategies in spatial navigation are also reflected in their construction of sentential perspective. Furthermore, a distributed network of cortical generators of such strategy-dependent activity responded not only in navigation, but in sentence comprehension. Thus we report, for the first time, evidence for shared brain mechanisms across these two domains - advancing our understanding of language's interaction with other cognitive systems, and the individual differences shaping comprehension.

The factors that contribute to perceptual simulation during sentence comprehension remain underexplored. Extant research on perspective taking in language has largely focused on linguistic constraints, such as the role of pronouns in guiding perspective adoption. In the present study, we identify preferential usage of egocentric and allocentric reference frames in individuals, and test the two groups on a standard sentence-picture verification task. Across three experiments, we show that individual biases in spatial reference frame adoption observed in non-linguistic tasks influence visual simulation of perspective in language. Our findings suggest that typically reported grand-averaged effects may obscure important between-subject differences, and support proposals arguing for representational pluralism, where perceptual information is integrated dynamically and in a way that is sensitive to contextual and especially individual constraints.

Understanding neurocognitive mechanisms supporting the use of multiple languages is a key question in language science. Recent neuroimaging studies in monolinguals indicated that core language areas in human neo-cortex together with sensorimotor structures form a highly interactive system underpinning native language comprehension. While the experience of a native speaker promotes the establishment of strong action–perception links in the comprehension network, this may not necessarily be the case for L2 where, as it has been argued, the most a typical L2 speaker may get is a link between an L2 wordform and its L1 translation equivalent. Therefore, we investigated, whether the motor cortex of bilingual subjects shows differential involvement in processing action semantics of native and non-native words. We used high-density EEG to dynamically measure changes in the cortical motor system's activity, indexed by event-related desynchronisation (ERD) of the mu-rhythm, in response to passively reading L1 (German) and L2 (English) action words. Analysis of motor-related EEG oscillations at the sensor level revealed an early (starting ~150 ms) and left-lateralised coupling between action and semantics during both L1 and L2 processing. Crucially, source-level activation in the motor areas showed that mu-rhythm ERD, while present for both languages, is significantly stronger for L1 words. This is the first neurophysiological evidence of rapid motor-cortex involvement during L2 action–semantic processing. Our results both strengthen embodied cognition evidence obtained previously in monolinguals and, at the same time, reveal important quantitative differences between L1 and L2 sensorimotor brain activity in language comprehension.

Research supports the claim that, when understanding language, people perform mental simulation using those parts of the brain which support sensation, action, and emotion. A major criticism of the findings quoted as evidence for embodied simulation, however, is that they could be a result of conscious image generation strategies. Here we exploit the well-known fact that bilinguals routinely and automatically activate both their languages during comprehension to test whether this automatic process is, in turn, modulated by embodied simulatory processes. Dutch participants heard English sentences containing interlingual homophones and implying specific distance relations, and had to subsequently respond to pictures of objects matching or mismatching this implied distance. Participants were significantly slower to reject critical items when their perceptual features matched said distance relationship. These results suggest that bilinguals not only activate task-irrelevant meanings of interlingual homophones, but also automatically simulate these meanings in a detailed perceptual fashion. Our study supports the claim that embodied simulation is not due to participants' conscious strategies, but is an automatic component of meaning construction.