"Embodied" language processing: Mental motor imagery aptitude predicts word-definition skill for high but not for low imageable words in adolescents.

Our study was designed to test a recent proposal by Cayol and Nazir (2020), according to which language processing takes advantage of motor system "emulators". An emulator is a brain mechanism that learns the causal relationship between an action and its sensory consequences. Emulators predict the outcome of a motor command in terms of its sensory reafference and serve monitoring ongoing movements. For the purpose of motor planning/learning, emulators can "run offline", decoupled from sensory input and motor output. Such offline simulations are equivalent to mental imagery (Grush, 2004). If language processing can profit from the associative-memory network of emulators, mental-imagery-aptitude should predict language skills. However, this should hold only for language content that is imageable. We tested this assumption in typically developing adolescents using two motor-imagery paradigms. One that measured participant's error in estimating their motor ability, and another that measured the time to perform a mental simulation. When the time to perform a mental simulation is taken as measure, mental-imagery-aptitude does indeed selectively predict word-definition performance for high imageable words. These results provide an alternative position relative to the question of why language processes recruit modality-specific brain regions and support the often-hypothesized link between language and motor skills.

A simple technique to study embodied language processes: the grip force sensor.

Research in cognitive neuroscience has shown that brain structures serving perceptual, emotional, and motor processes are also recruited during the understanding of language when it refers to emotion, perception, and action. However, the exact linguistic and extralinguistic conditions under which such language-induced activity in modality-specific cortex is triggered are not yet well understood. The purpose of this study is to introduce a simple experimental technique that allows for the online measure of language-induced activity in motor structures of the brain. This technique consists in the use of a grip force sensor that captures subtle grip force variations while participants listen to words and sentences. Since grip force reflects activity in motor brain structures, the continuous monitoring of force fluctuations provides a fine-grained estimation of motor activity across time. In other terms, this method allows for both localization of the source of language-induced activity to motor brain structures and high temporal resolution of the recorded data. To facilitate comparison of the data to be collected with this tool, we present two experiments that describe in detail the technical setup, the nature of the recorded data, and the analyses (including justification about the data filtering and artifact rejection) that we applied. We also discuss how the tool could be used in other domains of behavioral research.

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.

Simultaneous action execution and observation optimise grasping actions.

Action observation and execution share overlapping neural resonating mechanisms. In the present study, we sought to examine the effect of the activation of this system during concurrent movement observation and execution in a prehension task, when no a priori information about the requirements of grasping action was available. Although it is known that simultaneous activation by observation and execution influences motor performance, the importance of the delays of these two events and the specific effect of movement observation itself (and not the prediction of the to-be-observed movement) on action performance are poorly known. Fine-grained kinematic analysis of both the transport and grasp components of the movement should provide knowledge about the influence of movement observation on the precision and the performance of the executed movement. The experiment involved two real participants who were asked to grasp a different side of a single object that was composed of a large and a small part. In the first experiment, we measured how the transport component and the grasp component were affected by movement observation. We tested whether this influence was greater if the observed movement occurred just before the onset of movement (200 ms) or well before the onset of movement (1 s). In a second experiment, to reproduce the previous experiment and to verify the specificity of the grasping movements, we also included a condition consisting of pointing towards the object. Both experiments showed two main results. A general facilitation of the transport component was found when observing a simultaneous action, independent of its congruency. Moreover, a specific facilitation of the grasp component was present during the observation of a congruent action when movement execution and observation were nearly synchronised. While the general facilitation may arise from a competition between the two participants as they reached for the object, the specific facilitation of the grasp component seems to be directly related to mirror neuron system activity induced by action observation itself. Moreover, the time course of the events appears to be an essential factor for this modulation, implying the transitory activation of the mirror neuron system.

Improving the acceptability of social robots: Make them look different from humans.

The social robots market will grow considerably in the coming years. What the arrival of these new kind of social agents means for society, however, is largely unknown. Existing cases of robot abuse point to risks of introducing such artificial social agents (ASAs) without considerations about consequences (risks for the robots and the human witnesses to the abuse). We believe that humans react aggressively towards ASAs when they are enticed into establishing dominance hierarchies. This happens when there is a basis for skill comparison. We therefore presented pairs of robots on which we varied similarity and the degree of stimulatability of their mechanisms/functions with the human body (walking, jumping = simulatable; rolling, floating = non-simulatable). We asked which robot (i) resembled more a human, (ii) possessed more "essentialized human qualities" (e.g. creativity). To estimate social acceptability, participants had also (iii) to predict the outcome of a situation where a robot approached a group of humans. For robots with simulatable functions, rating of essentialized human qualities decreased as human resemblance decreased (jumper < walker). For robots with non-simulable functions, the reversed relation was seen: robots that least resembled humans (floater) scored highest in qualities. Critically, robot's acceptability followed ratings of essentialized human qualities. Humans respond socially to certain morphological (physical aspects) and behavioral cues. Therefore, unless ASAs perfectly mimic humans, it is safer to provide them with mechanisms/functions that cannot be simulated with the human body.

Factives at hand: When presupposition mode affects motor response.

It is well established that the processing of hand-, mouth-, and foot-related action terms can activate areas of the motor cortex that are involved in the planning and execution of the described actions. In the present study, the sensitivity of these motor structures to language processes was exploited to test linguistic theories on information layering. Human languages possess a variety of linguistic devices, so-called presupposition triggers, that allow us to convey background information without asserting it. A statement such as "Marie stopped smoking" presupposes, without asserting it, that Marie used to smoke. How such presupposed information is represented in the brain is not yet understood. Using a grip-force sensor that allows capturing motor brain activity during language processing, we investigated effects of information layering by comparing asserted information that is known to trigger motor activity ("In the living room, Peter irons his shirt") with information embedded under a presuppositional factive verb construction ("Louis knows that Peter irons his shirt"; Experiment 1) and a nonfactive verb construction ("Louis believes that Peter irons his shirt"; Experiment 2). Furthermore, we examined whether the projection behavior of a factive verb construction modulates grip force under negation ("Louis does not know that Peter irons his shirt"; Experiment 3). The data show that only the presupposed action verb in affirmative contexts (Experiment 1) triggers an increase in grip force comparable to the one of asserted action verbs, whereas the nonfactive complement and projection structure show a weaker response (Experiments 2 and 3). While the first two experiments seem to confirm the sensitivity of the grip-force response to the construction of a plausible situation or event model, in which the motor action is represented as taking place, the third one raises the question of how robust this hypothesis is and how it can take the specificity of projection into account. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The left ventral occipito-temporal response to words depends on language lateralization but not on visual familiarity.

The sensitivity of the left ventral occipito-temporal (vOT) cortex to visual word processing has triggered a considerable debate about the role of this region in reading. One popular view is that the left vOT underlies the perceptual expertise needed for rapid skilled reading. Because skilled reading breaks down when words are presented in a visually unfamiliar format, we tested this hypothesis by analyzing vOT responses to horizontally presented words (familiar format) and vertically presented words (unfamiliar format). In addition, we compared the activity in participants with left and right cerebral dominance for language generation. Our results revealed 1) that the vOT activity during reading is lateralized to the same side as the inferior frontal activity during word generation, 2) that vertically and horizontally presented words triggered the same amount of activity in the vOT of the dominant hemisphere, but 3) that there was significantly more activity for vertically presented words in the vOT of the nondominant hemisphere. We suggest that the reading-related activity in vOT reflects the integration of general perceptual processes with language processing in the anterior brain regions and is not limited to skilled reading in the familiar horizontal format.

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.

Word processing in Parkinson's disease is impaired for action verbs but not for concrete nouns.

Recent studies have demonstrated that processing of action words recruits cortical motor regions that are also involved in the planning and execution of the actions words refer to. The functional role of these regions in word understanding remains, however, to be clarified. The present study investigates this issue by examining the impact of Parkinson's disease (PD) on lexical decision performance for action words, relative to concrete nouns, in a masked priming paradigm. Priming effects for the two word categories were measured in non-demented PD patients off and on dopaminergic treatment, and in healthy participants. Our results revealed that although overall performances did not differ between verbs and nouns, priming effects showed a clear dissociation between word categories. While priming for concrete nouns was not affected by Levodopa intake, it dissociated as a function of treatment for action verbs. No priming was actually obtained for action verbs in PD patients off dopaminergic treatment. Following Levodopa intake, this deficit recovered, however, because priming effects for verbs became comparable to those for concrete nouns and similar to performance of healthy participants. Overall, this study thus brings compelling evidence that processing lexico-semantic information about action words depends on the integrity of the motor system.

Subliminal display of action words interferes with motor planning: a combined EEG and kinematic study.

Recent evidence has shown that processing action-related language and motor action share common neural representations to a point that the two processes can interfere when performed concurrently. To support the assumption that language-induced motor activity contributes to action word understanding, the present study aimed at ruling out that this activity results from mental imagery of the movements depicted by the words. For this purpose, we examined cross-talk between action word processing and an arm reaching movement, using words that were presented too fast to be consciously perceived (subliminally). Encephalogram (EEG) and movement kinematics were recorded. EEG recordings of the "Readiness potential" ("RP", indicator of motor preparation) revealed that subliminal displays of action verbs during movement preparation reduced the RP and affected the subsequent reaching movement. The finding that motor processes were modulated by language processes despite the fact that words were not consciously perceived, suggests that cortical structures that serve the preparation and execution of motor actions are indeed part of the (action) language processing network.

Differential effects of age-of-acquisition for concrete nouns and action verbs: evidence for partly distinct representations?

There is growing evidence that words that are acquired early in life are processed faster and more accurately than words acquired later, even by adults. As neuropsychological and neuroimaging studies have implicated different brain networks in the processing of action verbs and concrete nouns, the present study was aimed at contrasting reaction times to early and later-acquired action verbs and concrete nouns, in order to determine whether effects of word learning age express differently for the two types of words. Our results show that while word frequency affected both types of words in the same way, distinct learning age effects were observed for action verbs and concrete nouns. A further experiment specified that this difference was observed for verbs describing actions belonging to the human motor repertoire, but not for verbs denoting actions past this repertoire (e.g., to neigh). We interpret these data within a recently emerging framework according to which language processing is associated with sensory motor programs.

How odgcrnwi becomes crowding: stimulus-specific learning reduces crowding.

Processes underlying crowding in visual letter recognition were examined by investigating effects of training. Experiment 1 revealed that training reduces crowding mainly for trained strings. This was corroborated in Experiment 2, where no training effects were obvious after 3 days of training when strings changed from trial to trial. Experiment 3 specified that after a short amount of training, learning effects remained specific to trained strings and also to the trained retinal eccentricity and the interletter spacing used in training. Transfer to other than trained conditions was observed only after further training. Experiment 4 showed that transfer occurred earlier when words were used as stimuli. These results thus demonstrate that part of crowding results from the absence of higher level representations of the stimulus. Such representations can be acquired through learning visual properties of the stimulus.

Dynamics of Social Interaction: Kinematic Analysis of a Joint Action.

Non-verbal social interaction between humans requires accurate understanding of the others' actions. The cognitivist approach suggests that successful interaction depends on the creation of a shared representation of the task, where the pairing of perceptive and motor systems of partners allows inclusion of the other's goal into the overarching representation. Activity of the Mirror Neurons System (MNS) is thought to be a crucial mechanism linking two individuals during a joint action through action observation. The construction of a shared representation of an interaction (i.e., joint action) depends upon sensorimotor cognitive processes that modulate the ability to adapt in time and space. We attempted to detect individuals' behavioral/kinematic change resulting in a global amelioration of performance for both subjects when a common representation of the action is built using a repetitive joint action. We asked pairs of subjects to carry out a simple task where one puts a base in the middle of a table and the other places a parallelepiped fitting into the base, the crucial manipulation being that participants switched roles during the experiment. We aimed to show that a full comprehension of a joint action is not an automatic process. We found that, before switching the interactional role, the participant initially placing the base orientated it in a way that led to an uncomfortable action for participants placing the parallelepiped. However, after switching roles, the action's kinematics by the participant who places the base changed in order to facilitate the action of the other. More precisely, our data shows significant modulation of the base angle in order to ease the completion of the joint action, highlighting the fact that a shared knowledge of the complete action facilitates the generation of a common representation. This evidence suggests the ability to establish an efficient shared representation of a joint action benefits from physically taking our partner's perspective because simply observing the actions of others may not be enough.

PURE ALEXIA AND THE VIEWING POSITION EFFECT IN PRINTED WORDS.

In the present article, we investigated the reading ability of CP, a pure alexic patient, using an experimental paradigm that is known to elicit the viewing position effect in norm al readers. The viewing position effect consists of a systematic variation of word recognition performance as a function of fixation location w ithin a word: Word recognition is best when the eyes fixate slightly left from the word centre and decreases when the eyes deviate from this optimal viewing position. A mathematical model (Nazir, O'Regan, & Jacobs, 1991), which provides a good description and quantification of the prototypical shape of the viewing position effect, served to interpret CP's reading performance. The results show ed that, like normal readers, CP was able to process all letters of a w ord in one fixation. However, in contrast to normal readers, reading performance was optimal when CP w as fixating the right half of the word. This somewhat abnormal pattern of performance was due to (1) poor perceptual processing in the right visual field, and (2) poor processing of letters situated towards the end of the word, independent of visual field presentation. A similar pattern of perform ance w as obtained with normal readers under experimental conditions in which lexical know ledge was of restricted use. We suggest that CP's reading impairment stems from a dysfunction in the coupling between incoming visual information and stored lexical information. This dysfunction is thought to uncover a prelexical level of word processing, where letter information is weighted differently as a function of letter position in a word-centred space.

Reading habits, perceptual learning, and recognition of printed words.

The present work aims at demonstrating that visual training associated with the act of reading modifies the way we perceive printed words. As reading does not train all parts of the retina in the same way but favors regions on the side in the direction of scanning, visual word recognition should be better at retinal locations that are frequently used during reading. In two studies that probed word and letter discriminations we provided evidence for a correlation between eye fixation pattern during reading and performance. We showed that effects of reading-related visual training were stimulus-specific in the sense that it affected the perception of words but not that of visually unfamiliar non-words. This stimulus specificity was also evident in the legibility of individual characters of the Roman and the Hebrew scripts-two scripts that are read in opposing directions. When displayed within a sequence of homogenous letters (e.g., xxexx) the legibility of a target character varied with the location of the sequence in the visual field and with the serial position of the target within the sequence. This retinal location- and context-dependency differed between Roman and Hebrew characters. These results seem to indicate that reading modifies the functional structure of early stages in the visual pathway. The cortical network that supports reading seems to comprise components of the visual cortex of both hemispheres before it lateralizes to the left hemisphere. Expanding the reading network to include these visual regions will shed a different light on the potential role of the visual word form area (e.g., ) in word recognition and on the organization of the reading system in general.

Action relevance in linguistic context drives word-induced motor activity.

Many neurocognitive studies on the role of motor structures in action-language processing have implicitly adopted a "dictionary-like" framework within which lexical meaning is constructed on the basis of an invariant set of semantic features. The debate has thus been centered on the question of whether motor activation is an integral part of the lexical semantics (embodied theories) or the result of a post-lexical construction of a situation model (disembodied theories). However, research in psycholinguistics show that lexical semantic processing and context-dependent meaning construction are narrowly integrated. An understanding of the role of motor structures in action-language processing might thus be better achieved by focusing on the linguistic contexts under which such structures are recruited. Here, we therefore analyzed online modulations of grip force while subjects listened to target words embedded in different linguistic contexts. When the target word was a hand action verb and when the sentence focused on that action (John signs the contract) an early increase of grip force was observed. No comparable increase was detected when the same word occurred in a context that shifted the focus toward the agent's mental state (John wants to sign the contract). There mere presence of an action word is thus not sufficient to trigger motor activation. Moreover, when the linguistic context set up a strong expectation for a hand action, a grip force increase was observed even when the tested word was a pseudo-verb. The presence of a known action word is thus not required to trigger motor activation. Importantly, however, the same linguistic contexts that sufficed to trigger motor activation with pseudo-verbs failed to trigger motor activation when the target words were verbs with no motor action reference. Context is thus not by itself sufficient to supersede an "incompatible" word meaning. We argue that motor structure activation is part of a dynamic process that integrates the lexical meaning potential of a term and the context in the online construction of a situation model, which is a crucial process for fluent and efficient online language comprehension.

Neural correlates of non-verbal social interactions: a dual-EEG study.

Successful non-verbal social interaction between human beings requires dynamic and efficient encoding of others' gestures. Our study aimed at identifying neural markers of social interaction and goal variations in a non-verbal task. For this, we recorded simultaneously the electroencephalogram from two participants (dual-EEG), an actor and an observer, and their arm/hand kinematics in a real face-to-face paradigm. The observer watched "biological actions" performed by the human actor and "non-biological actions" performed by a robot. All actions occurred within an interactive or non-interactive context depending on whether the observer had to perform a complementary action or not (e.g., the actor presents a saucer and the observer either places the corresponding cup or does nothing). We analysed the EEG signals of both participants (i.e., beta (~20 Hz) oscillations as an index of cortical motor activity and motor related potentials (MRPs)). We identified markers of social interactions by synchronising EEG to the onset of the actor's movement. Movement kinematics did not differ in the two context conditions and the MRPs of the actor were similar in the two conditions. For the observer, however, an observation-related MRP was measured in all conditions but was more negative in the interactive context over fronto-central electrodes. Moreover, this feature was specific to biological actions. Concurrently, the suppression of beta oscillations was observed in the actor's EEG and the observer's EEG rapidly after the onset of the actor's movement. Critically, this suppression was stronger in the interactive than in the non-interactive context despite the fact that movement kinematics did not differ in the two context conditions. For the observer, this modulation was observed independently of whether the actor was a human or a robot. Our results suggest that acting in a social context induced analogous modulations of motor and sensorimotor regions in observer and actor. Sharing a common goal during an interaction seems thus to evoke a common representation of the global action that includes both actor and observer movements.

Motor resonance facilitates movement execution: an ERP and kinematic study.

Action observation, simulation and execution share neural mechanisms that allow for a common motor representation. It is known that when these overlapping mechanisms are simultaneously activated by action observation and execution, motor performance is influenced by observation and vice versa. To understand the neural dynamics underlying this influence and to measure how variations in brain activity impact the precise kinematics of motor behavior, we coupled kinematics and electrophysiological recordings of participants while they performed and observed congruent or non-congruent actions or during action execution alone. We found that movement velocities and the trajectory deviations of the executed actions increased during the observation of congruent actions compared to the observation of non-congruent actions or action execution alone. This facilitation was also discernible in the motor-related potentials of the participants; the motor-related potentials were transiently more negative in the congruent condition around the onset of the executed movement, which occurred 300 ms after the onset of the observed movement. This facilitation seemed to depend not only on spatial congruency but also on the optimal temporal relationship of the observation and execution events.

Grasp it loudly! Supporting actions with semantically congruent spoken action words.

Evidence for cross-talk between motor and language brain structures has accumulated over the past several years. However, while a significant amount of research has focused on the interaction between language perception and action, little attention has been paid to the potential impact of language production on overt motor behaviour. The aim of the present study was to test whether verbalizing during a grasp-to-displace action would affect motor behaviour and, if so, whether this effect would depend on the semantic content of the pronounced word (Experiment I). Furthermore, we sought to test the stability of such effects in a different group of participants and investigate at which stage of the motor act language intervenes (Experiment II). For this, participants were asked to reach, grasp and displace an object while overtly pronouncing verbal descriptions of the action ("grasp" and "put down") or unrelated words (e.g. "butterfly" and "pigeon"). Fine-grained analyses of several kinematic parameters such as velocity peaks revealed that when participants produced action-related words their movements became faster compared to conditions in which they did not verbalize or in which they produced words that were not related to the action. These effects likely result from the functional interaction between semantic retrieval of the words and the planning and programming of the action. Therefore, links between (action) language and motor structures are significant to the point that language can refine overt motor behaviour.