Learning to associate novel words with motor actions: language-induced motor activity following short training

The Neural Correlates of Embodied L2 Learning: Does Embodied L2 Verb Learning Affect Representation and Retention?

We investigated how naturalistic actions in a highly immersive, multimodal, interactive 3D virtual reality (VR) environment may enhance word encoding by recording EEG in a pre/post-test learning paradigm. While behavior data have shown that coupling word encoding with gestures congruent with word meaning enhances learning, the neural underpinnings of this effect have yet to be elucidated. We coupled EEG recording with VR to examine whether embodied learning improves learning and creates linguistic representations that produce greater motor resonance. Participants learned action verbs in an L2 in two different conditions: specific action (observing and performing congruent actions on virtual objects) and pointing (observing actions and pointing to virtual objects). Pre- and post-training participants performed a match-mismatch task as we measured EEG (variation in the N400 response as a function of match between observed actions and auditory verbs) and a passive listening task while we measured motor activation (mu [8-13 Hz] and beta band [13-30 Hz] desynchronization during auditory verb processing) during verb processing. Contrary to our expectations, post-training results revealed neither semantic nor motor effects in either group when considered independently of learning success. Behavioral results showed a great deal of variability in learning success. When considering performance, low performance learners showed no semantic effect and high performance learners exhibited an N400 effect for mismatch versus match trials post-training, independent of the type of learning. Taken as a whole, our results suggest that embodied processes can play an important role in L2 learning.

Between bodily action and conventionalized structure: The neural mechanisms of constructed action in sign language comprehension

Sign languages (SLs) are expressed through different bodily actions, ranging from re-enactment of physical events (constructed action, CA) to sequences of lexical signs with internal structure (plain telling, PT). Despite the prevalence of CA in signed interactions and its significance for SL comprehension, its neural dynamics remain unexplored. We examined the processing of different types of CA (subtle, reduced, and overt) and PT in 35 adult deaf or hearing native signers. The electroencephalographic-based processing of signed sentences with incongruent targets was recorded. Attenuated N300 and early N400 were observed for CA in deaf but not in hearing signers. No differences were found between sentences with CA types in all signers, suggesting a continuum from PT to overt CA. Deaf signers focused more on body movements; hearing signers on faces. We conclude that CA is processed less effortlessly than PT, arguably because of its strong focus on bodily actions.

The concrete processing of Chinese action metaphors: an ERP study

The present research adopts ERP (Event-Related Potentials) technology to investigate whether there exists a concreteness effect in the processing of Chinese action verbs within metaphorical context. The mean amplitudes of N400 activated by action metaphors were compared with those activated by literal verbs and abstract verbs. The findings indicated that the Met verbs evoked a significantly larger N400 response at frontal brain region compared to the Abs verbs at a time window 200-500 ms, while the Met verbs elicited a notably greater N400 amplitude specifically at the posterior brain region in comparison to the Lit verbs at 300-500 ms time window. These results may be interpreted as indicating that the comprehension of the Met verbs is based on the concrete action semantics.

The Role of the Motor System in L1 and L2 Action Verb Processing for Chinese Learners of English: Evidence from Mu Rhythm Desynchronization

The nature of semantic representation has long been a key question in linguistic research. The Embodied Cognition theory challenges the traditional view of language representation, stating that semantic information stems from the sensory-motor cortex, which is activated automatically during semantic processing. However, most of the evidence comes from monolingual studies; it remains unclear whether second-language (L2) comprehension involves different semantic representations or mirrors the pattern seen in first-language (L1) processing. Therefore, the present study investigated the role of the sensory-motor system in language processing via making Electroencephalography (EEG) recordings during the processing of L1 and L2 action verbs. The results showed that L1 (Chinese) action verbs generated higher mu-event-related desynchronization (ERD) than L1 abstract verbs in the early processing stage (250 ms after verb presentation), and the same phenomenon was also observed for L2 (English). The results also indicated that language modulated the processing of action verbs, with L1 action verbs eliciting stronger ERD than L2 action verbs. These results demonstrate that the sensory-motor cortex plays a crucial role in comprehending both L1 and L2 action verbs.

Ecological Meanings: A Consensus Paper on Individual Differences and Contextual Influences in Embodied Language

Embodied theories of cognition consider many aspects of language and other cognitive domains as the result of sensory and motor processes. In this view, the appraisal and the use of concepts are based on mechanisms of simulation grounded on prior sensorimotor experiences. Even though these theories continue receiving attention and support, increasing evidence indicates the need to consider the flexible nature of the simulation process, and to accordingly refine embodied accounts. In this consensus paper, we discuss two potential sources of variability in experimental studies on embodiment of language: individual differences and context. Specifically, we show how factors contributing to individual differences may explain inconsistent findings in embodied language phenomena. These factors include sensorimotor or cultural experiences, imagery, context-related factors, and cognitive strategies. We also analyze the different contextual modulations, from single words to sentences and narratives, as well as the top-down and bottom-up influences. Similarly, we review recent efforts to include cultural and language diversity, aging, neurodegenerative diseases, and brain disorders, as well as bilingual evidence into the embodiment framework. We address the importance of considering individual differences and context in clinical studies to drive translational research more efficiently, and we indicate recommendations on how to correctly address these issues in future research. Systematically investigating individual differences and context may contribute to understanding the dynamic nature of simulation in language processes, refining embodied theories of cognition, and ultimately filling the gap between cognition in artificial experimental settings and cognition in the wild (i.e., in everyday life).

Brain Signatures of Embodied Semantics and Language: A Consensus Paper

According to embodied theories (including embodied, embedded, extended, enacted, situated, and grounded approaches to cognition), language representation is intrinsically linked to our interactions with the world around us, which is reflected in specific brain signatures during language processing and learning. Moving on from the original rivalry of embodied vs. amodal theories, this consensus paper addresses a series of carefully selected questions that aim at determining when and how rather than whether motor and perceptual processes are involved in language processes. We cover a wide range of research areas, from the neurophysiological signatures of embodied semantics, e.g., event-related potentials and fields as well as neural oscillations, to semantic processing and semantic priming effects on concrete and abstract words, to first and second language learning and, finally, the use of virtual reality for examining embodied semantics. Our common aim is to better understand the role of motor and perceptual processes in language representation as indexed by language comprehension and learning. We come to the consensus that, based on seminal research conducted in the field, future directions now call for enhancing the external validity of findings by acknowledging the multimodality, multidimensionality, flexibility and idiosyncrasy of embodied and situated language and semantic processes.

Learning of new associations invokes a major change in modulations of cortical beta oscillations in human adults

Large-scale cortical beta (β) oscillations were implicated in the learning processes, but their exact role is debated. We used MEG to explore the dynamics of movement-related β-oscillations while 22 adults learned, through trial and error, novel associations between four auditory pseudowords and movements of four limbs. As learning proceeded, spatial-temporal characteristics of β-oscillations accompanying cue-triggered movements underwent a major transition. Early in learning, widespread suppression of β-power occurred long before movement initiation and sustained throughout the whole behavioral trial. When learning advanced and performance reached asymptote, β-suppression after the initiation of correct motor response was replaced by a rise in β-power mainly in the prefrontal and medial temporal regions of the left hemisphere. This post-decision β-power predicted trial-by-trial response times (RT) at both stages of learning (before and after the rules become familiar), but with different signs of interaction. When a subject just started to acquire associative rules and gradually improved task performance, a decrease in RT correlated with the increase in the post-decision β-band power. When the participants implemented the already acquired rules, faster (more confident) responses were associated with the weaker post-decision β-band synchronization. Our findings suggest that maximal beta activity is pertinent to a distinct stage of learning and may serve to strengthen the newly learned association in a distributed memory network.

Spatiotemporal Dynamics of Activation in Motor and Language Areas Suggest a Compensatory Role of the Motor Cortex in Second Language Processing

The involvement of the motor cortex in language understanding has been intensively discussed in the framework of embodied cognition. Although some studies have provided evidence for the involvement of the motor cortex in different receptive language tasks, the role that it plays in language perception and understanding is still unclear. In the present study, we explored the degree of involvement of language and motor areas in a visually presented sentence comprehension task, modulated by language proficiency (L1: native language, L2: second language) and linguistic abstractness (literal, metaphorical, and abstract). Magnetoencephalography data were recorded from 26 late Chinese learners of English. A cluster-based permutation F test was performed on the amplitude of the source waveform for each motor and language region of interest (ROI). Results showed a significant effect of language proficiency in both language and motor ROIs, manifested as overall greater involvement of language ROIs (short insular gyri and planum polare of the superior temporal gyrus) in the L1 than the L2 during 300-500 ms, and overall greater involvement of motor ROI (central sulcus) in the L2 than the L1 during 600-800 ms. We interpreted the over-recruitment of the motor area in the L2 as a higher demand for cognitive resources to compensate for the inadequate engagement of the language network. In general, our results indicate a compensatory role of the motor cortex in L2 understanding.

The Link Between Action Verb Processing and Action Observation: A Developmental Study

In this work we aimed to assess the typical link in human development between action observation and language. For this, we studied, in 68 children aged 5-11 years of age, how action verbs can prime action representation. While children 7-8 years of age benefited from a congruent action verb prime when they had to judge an image representing an action, this effect was not present in 5-6-year-olds. Thus, the link between language and action observation changes during development at about age 7. We discussed these findings in consideration of current theories proposed to account for the action-language link.

Semantic Grounding of Novel Spoken Words in the Primary Visual Cortex

Embodied theories of grounded semantics postulate that, when word meaning is first acquired, a link is established between symbol (word form) and corresponding semantic information present in modality-specific—including primary—sensorimotor cortices of the brain. Direct experimental evidence documenting the emergence of such a link (i.e., showing that presentation of a previously unknown, meaningless word sound induces, after learning, category-specific reactivation of relevant primary sensory or motor brain areas), however, is still missing. Here, we present new neuroimaging results that provide such evidence. We taught participants aspects of the referential meaning of previously unknown, senseless novel spoken words (such as “Shruba” or “Flipe”) by associating them with either a familiar action or a familiar object. After training, we used functional magnetic resonance imaging to analyze the participants’ brain responses to the new speech items. We found that hearing the newly learnt object-related word sounds selectively triggered activity in the primary visual cortex, as well as secondary and higher visual areas.These results for the first time directly document the formation of a link between the novel, previously meaningless spoken items and corresponding semantic information in primary sensory areas in a category-specific manner, providing experimental support for perceptual accounts of word-meaning acquisition in the brain.

Why Language Processing Recruits Modality Specific Brain Regions: It Is Not About Understanding Words, but About Modelling Situations

Whether language comprehension requires the participation of brain structures that evolved for perception and action has been a subject of intense debate. While brain-imaging evidence for the involvement of such modality-specific regions has grown, the fact that lesions to these structures do not necessarily erase word knowledge has invited the conclusion that language-induced activity in these structures might not be essential for word recognition. Why language processing recruits these structures remains unanswered, however. Here, we examine the original findings from a slightly different perspective. We first consider the 'original' function of structures in modality-specific brain regions that are recruited by language activity. We propose that these structures help elaborate 'internal forward models' in motor control (c.f. emulators). Emulators are brain systems that capture the relationship between an action and its sensory consequences. During language processing emulators could thus allow accessing associative memories. We further postulate the existence of a linguistic system that exploits, in a rule-based manner, emulators and other nonlinguistic brain systems, to gain complementary (and redundant) information during language processing. Emulators are therefore just one of several sources of information. We emphasize that whether a given word-form triggers activity in modality-specific brain regions depends on the linguistic context and not on the word-form as such. The role of modality-specific systems in language processing is thus not to help understanding words but to model the verbally depicted situation by supplying memorized context information. We present a model derived from these assumptions and provide predictions and perspectives for future research.

Feeling better: Tactile verbs speed up tactile detection

Embodiment of action-related language into the motor system has been extensively documented. Yet the case of sensory words, especially referring to touch, remains overlooked. We investigated the influence of verbs denoting tactile sensations on tactile perception. In Experiment 1, participants detected tactile stimulations on their forearm, preceded by tactile or non-tactile verbs by one of three delays (170, 350, 500 ms) reflecting different word processing stages. Results revealed shorter reaction times to tactile stimulations following tactile than non-tactile verbs, irrespective of delay. To ensure that priming pertained to tactile, and not motor, verb properties, Experiment 2 compared the impact of tactile verbs to both action and non-tactile verbs, while stimulations were delivered on the index finger. No priming emerged following action verbs, therefore not supporting the motor-grounded interpretation. Facilitation by tactile verbs was however not observed, possibly owing to methodological changes. Experiment 3, identical to Experiment 2 except that stimulation was delivered to participants' forearm, replicated the priming effect. Importantly, tactile stimulations were detected faster after tactile than after both non-tactile and action verbs, indicating that verbs' tactile properties engaged resources shared with sensory perception. Our findings suggest that language conveying tactile information can activate somatosensory representations and subsequently promote tactile detection.

The role of motor system in action-related language comprehension in L1 and L2: An fMRI study

The framework of embodied cognition has challenged the modular view of a language-cognition divide by suggesting that meaning-retrieval critically involves the sensory-motor system. Despite extensive research into the neural mechanisms underlying language-motor coupling, it remains unclear how the motor system might be differentially engaged by different levels of linguistic abstraction and language proficiency. To address this issue, we used fMRI to quantify neural activations in brain regions underlying motor and language processing in Chinese-English speakers' processing of literal, metaphorical, and abstract language in their L1 and L2. Results overall revealed a response in motor ROIs gradually attenuating in intensity from literal to abstract via metaphorical language in both L1 and L2. Furthermore, contrast analyses between L1 and L2 showed overall greater activations of motor ROIs in the L2. We conclude that motor involvement in language processing is graded rather than all-or-none and that the motor system has a dual-functional role.

Physical and observational practices of unusual actions prime action verb processing

Numerous studies have highlighted a strong relationship between language and sensorimotor processes, showing, for example, that perceiving an action influences subsequent language processing. Moreover, previous studies have demonstrated that the context in which actions are perceived is crucial to enable this action-language relationship. In particular, action verb processing is facilitated when an action is perceived in its usual context (e.g., someone watering a plant) but not in an unusual context (e.g., someone watering a computer). This difference could be explained in terms of experience; because people always practice actions in accordance with the context, they have no (visual or motor) experience related to the unusual context. The aim of the present study was to test this assumption by assessing and comparing the effect of physical practice and observational learning on the action-language relationship. The results of two experiments showed a facilitation effect of both training methods. Whereas usual actions systematically prime action verb processing, the link between action and language appears for unusual actions only after training by practicing (experiment 1, physical practice) or observing (experiment 2, observational learning). Overall, these findings support the role of experience in the activation of sensorimotor representations during action verb processing.

Motor resonance during linguistic processing as shown by EEG in a naturalistic VR environment

Embodied cognition studies have shown motor resonance during action language processing, indicating that linguistic representations are at least partially multimodal. However, constraints of this activation linked to linguistic and extra-linguistic context, function and timing have not yet been fully explored. Importantly, embodied cognition binds social and physical contexts to cognition, suggesting that more ecologically valid contexts will yield more valid measures of cognitive processing. Herein, we measured cortical motor activation during language processing in a fully immersive Cave automatic virtual environment (CAVE). EEG was recorded while participants engaged in a Go/No-Go task. They heard action verbs and, for Go trials, performed a corresponding action on a virtual object. ERSP (event-related spectral perturbation) was calculated during verb processing, corresponding to the pattern of power suppression (event-related desynchronization - ERD) and enhancement (event-related synchronization - ERS) relative to the reference interval. Significant ERD emerged during verb processing in both the µ (8-13 Hz) and beta band (20-30 Hz) for both Go and No-Go trials. µ ERD emerged in the 400-500 msec time window, associated with lexical-semantic processing. Greater µ ERD emerged for Go compared to No-Go trials. The present results provide compelling evidence in a naturalistic setting of how motor and linguistic processes interact.

Embodied Semantics in a Second Language: Critical Review and Clinical Implications

The role of the sensorimotor system in second language (L2) semantic processing as well as its clinical implications for bilingual patients has hitherto been neglected. We offer an overview of the issues at stake in this under-investigated field, presenting the theoretical and clinical relevance of studying L2 embodiment and reviewing the few studies on this topic. We highlight that (a) the sensorimotor network is involved in L2 processing, and that (b) in most studies, L2 is differently embodied than L1, reflected in a lower degree or in a different pattern of L2 embodiment. Importantly, we outline critical issues to be addressed in order to guide future research. We also delineate the subsequent steps needed to confirm or dismiss the value of language therapeutic approaches based on embodiment theories as a complement of speech and language therapies in adult bilinguals.

Neuronal correlates of label facilitated tactile perception

It is a long-standing question in neurolinguistics, to what extent language can have a causal effect on perception. A recent behavioural study reported that participants improved their discrimination ability of Braille-like tactile stimuli after one week of implicit association training with language stimuli being co-presented redundantly with the tactile stimuli. In that experiment subjects were exposed twice a day for 1 h to the joint presentation of tactile stimuli presented to the fingertip and auditorily presented pseudowords. Their discrimination ability improved only for those tactile stimuli that were consistently paired with pseudowords, but not for those that were discordantly paired with different pseudowords. Thereby, a causal effect of verbal labels on tactile perception has been demonstrated under controlled laboratory conditions. This raises the question as to what the neuronal mechanisms underlying this implicit learning effect are. Here, we present fMRI data collected before and after the aforementioned behavioral learning to test for changes in brain connectivity as the underlying mechanism of the observed behavioral effects. The comparison of pre- and post-training revealed a language-driven increase in connectivity strength between auditory and secondary somatosensory cortex and the hippocampus as an association-learning related region.

Event-related desynchronization of mu and beta oscillations during the processing of novel tool names

According to the embodied cognition framework, the formation of conceptual representations integrates the type of experience during learning. In this electroencephalographic study, we applied a linguistic variant of a training paradigm, in which participants learned to associate novel names to novel tools while either manipulating or visually exploring them. The analysis focused on event-related desynchronization (ERD) of oscillations in the mu and beta frequency range, which reflects activation of sensorimotor brain areas. After three training sessions, processing names of manipulated tools elicited a stronger ERD of the beta (18-25 Hz, 140-260 ms) and the lower mu rhythm (8-10 Hz, 320-440 ms) than processing names of visually explored tools, reflecting a possible reactivation of experiential sensorimotor information. Given the unexpected result that familiarized pseudo-words elicited an ERD comparable to names of manipulated tools, our findings could reflect a suppression of sensorimotor activity during the processing of objects with exclusively visual features.

Response Hand Differentially Affects Action Word Processing

Recent approaches in the tradition of theories of semantic and conceptual “grounding” emphasize the role of perceptual and motor knowledge in language as well as action understanding. However, the role of the two cerebral hemispheres in integrating action-motor and language processes is not clear yet. The present study looked at the influence of a simultaneous motor tapping task on word processing. In a lexical decision task, uni-manual and bi-manual hand-related, and foot-related action verbs were presented in the left and right visual half-field. A group of healthy participants performed tapping with the left hand and lexical decisions with their right hand. In a second group of participants, the reversed hand response pattern was applied. The results showed that response hand had an influence on functional lateralization of word processing when responses were executed with the non-dominant hand. Projecting words to the ipsilateral hemisphere relative to the hemisphere performing lexical decisions led to significantly decreased performance. The results showed that left hand responses led to an increased accuracy for hand-related in contrast to foot-related action verbs. The findings suggest an influence of response hand on action word processing.

EEG beta-power changes reflect motor involvement in abstract action language processing

Brain oscillations in the α- and β-range become suppressed during motor processing and motor imagery. It has recently been discussed that such power changes also occur during action language processing. In our study, we compared β₂-oscillations (16-25Hz) during the observation of prototypical arm movements (revealed via motion tracking) as well as during semantic processing of concrete and abstract sentences containing arm-related action verbs. Whereas we did find a strong desynchronization in the β₂-range during action observation, the processing of action sentences evoked a rather weak desynchronization. However, this desynchronization occurred for action verbs in both concrete and abstract contexts. These results might indicate a tendency for abstract action language to be processed similar to concrete action language rather than abstract sentences. The oscillation patterns reflect the close relationship between language comprehension and motor functions - one of the core claims of current theories on embodied cognition.

Assessing human mirror activity with EEG mu rhythm: A meta-analysis

A fundamental issue in cognitive neuroscience is how the brain encodes others' actions and intentions. In recent years, a potential advance in our knowledge on this issue is the discovery of mirror neurons in the motor cortex of the nonhuman primate. These neurons fire to both execution and observation of specific types of actions. Researchers use this evidence to fuel investigations of a human mirror system, suggesting a common neural code for perceptual and motor processes. Among the methods used for inferring mirror system activity in humans are changes in a particular frequency band in the electroencephalogram (EEG) called the mu rhythm. Mu frequency appears to decrease in amplitude (reflecting cortical activity) during both action execution and action observation. The current meta-analysis reviewed 85 studies (1,707 participants) of mu that infer human mirror system activity. Results demonstrated significant effect sizes for mu during execution (Cohen's d = 0.46, N = 701) as well as observation of action (Cohen's d = 0.31, N = 1,508), confirming a mirroring property in the EEG. A number of moderators were examined to determine the specificity of these effects. We frame these meta-analytic findings within the current discussion about the development and functions of a human mirror system, and conclude that changes in EEG mu activity provide a valid means for the study of human neural mirroring. Suggestions for improving the experimental and methodological approaches in using mu to study the human mirror system are offered.

Language-motor interference reflected in MEG beta oscillations

The involvement of the brain's motor system in action-related language processing can lead to overt interference with simultaneous action execution. The aim of the current study was to find evidence for this behavioural interference effect and to investigate its neurophysiological correlates using oscillatory MEG analysis. Subjects performed a semantic decision task on single action verbs, describing actions executed with the hands or the feet, and abstract verbs. Right hand button press responses were given for concrete verbs only. Therefore, longer response latencies for hand compared to foot verbs should reflect interference. We found interference effects to depend on verb imageability: overall response latencies for hand verbs did not differ significantly from foot verbs. However, imageability interacted with effector: while response latencies to hand and foot verbs with low imageability were equally fast, those for highly imageable hand verbs were longer than for highly imageable foot verbs. The difference is reflected in motor-related MEG beta band power suppression, which was weaker for highly imageable hand verbs compared with highly imageable foot verbs. This provides a putative neuronal mechanism for language-motor interference where the involvement of cortical hand motor areas in hand verb processing interacts with the typical beta suppression seen before movements. We found that the facilitatory effect of higher imageability on action verb processing time is perturbed when verb and motor response relate to the same body part. Importantly, this effect is accompanied by neurophysiological effects in beta band oscillations. The attenuated power suppression around the time of movement, reflecting decreased cortical excitability, seems to result from motor simulation during action-related language processing. This is in line with embodied cognition theories.

Differentiating Semantic Categories during the Acquisition of Novel Words: Correspondence Analysis Applied to Event-related Potentials

Growing evidence suggests that semantic knowledge is represented in distributed neural networks that include modality-specific structures. Here, we examined the processes underlying the acquisition of words from different semantic categories to determine whether the emergence of visual- and action-based categories could be tracked back to their acquisition. For this, we applied correspondence analysis (CA) to ERPs recorded at various moments during acquisition. CA is a multivariate statistical technique typically used to reveal distance relationships between words of a corpus. Applied to ERPs, it allows isolating factors that best explain variations in the data across time and electrodes. Participants were asked to learn new action and visual words by associating novel pseudowords with the execution of hand movements or the observation of visual images. Words were probed before and after training on two consecutive days. To capture processes that unfold during lexical access, CA was applied on the 100–400 msec post-word onset interval. CA isolated two factors that organized the data as a function of test sessions and word categories. Conventional ERP analyses further revealed a category-specific increase in the negativity of the ERPs to action and visual words at the frontal and occipital electrodes, respectively. The distinct neural processes underlying action and visual words can thus be tracked back to the acquisition of word-referent relationships and may have its origin in association learning. Given current evidence for the flexibility of language-induced sensory-motor activity, we argue that these associative links may serve functions beyond word understanding, that is, the elaboration of situation models.

Training of manual actions improves language understanding of semantically related action sentences

Conceptual knowledge accessed by language may involve the reactivation of the associated primary sensory-motor processes. Whether these embodied representations are indeed constitutive to conceptual knowledge is hotly debated, particularly since direct evidence that sensory-motor expertise can improve conceptual processing is scarce. In this study, we sought for this crucial piece of evidence, by training naive healthy subjects to perform complex manual actions and by measuring, before and after training, their performance in a semantic language task. Nineteen participants engaged in 3 weeks of motor training. Each participant was trained in three complex manual actions (e.g., origami). Before and after the training period, each subject underwent a series of manual dexterity tests and a semantic language task. The latter consisted of a sentence-picture semantic congruency judgment task, with 6 target congruent sentence-picture pairs (semantically related to the trained manual actions), 6 non-target congruent pairs (semantically unrelated), and 12 filler incongruent pairs. Manual action training induced a significant improvement in all manual dexterity tests, demonstrating the successful acquisition of sensory-motor expertise. In the semantic language task, the reaction times (RTs) to both target and non-target congruent sentence-picture pairs decreased after action training, indicating a more efficient conceptual-semantic processing. Noteworthy, the RTs for target pairs decreased more than those for non-target pairs, as indicated by the 2 × 2 interaction. These results were confirmed when controlling for the potential bias of increased frequency of use of target lexical items during manual training. The results of the present study suggest that sensory-motor expertise gained by training of specific manual actions can lead to an improvement of cognitive-linguistic skills related to the specific conceptual-semantic domain associated to the trained actions.

Grip force reveals the context sensitivity of language-induced motor activity during "action words" processing: evidence from sentential negation

BACKGROUND

Studies demonstrating the involvement of motor brain structures in language processing typically focus on time windows beyond the latencies of lexical-semantic access. Consequently, such studies remain inconclusive regarding whether motor brain structures are recruited directly in language processing or through post-linguistic conceptual imagery. In the present study, we introduce a grip-force sensor that allows online measurements of language-induced motor activity during sentence listening. We use this tool to investigate whether language-induced motor activity remains constant or is modulated in negative, as opposed to affirmative, linguistic contexts.

METHODOLOGY/PRINCIPAL FINDINGS

Participants listened to spoken action target words in either affirmative or negative sentences while holding a sensor in a precision grip. The participants were asked to count the sentences containing the name of a country to ensure attention. The grip force signal was recorded continuously. The action words elicited an automatic and significant enhancement of the grip force starting at approximately 300 ms after target word onset in affirmative sentences; however, no comparable grip force modulation was observed when these action words occurred in negative contexts.

CONCLUSIONS/SIGNIFICANCE

Our findings demonstrate that this simple experimental paradigm can be used to study the online crosstalk between language and the motor systems in an ecological and economical manner. Our data further confirm that the motor brain structures that can be called upon during action word processing are not mandatorily involved; the crosstalk is asymmetrically governed by the linguistic context and not vice versa.