Listening to action-related sentences modulates the activity of the motor system: a combined TMS and behavioral study

Temporal dynamics of the action-sentence compatibility effect

A number of recent studies have demonstrated variants of the action-sentence compatibility effect (ACE), wherein the execution of a motor response is facilitated by the comprehension of sentences that describe actions taking place in the same direction as the motor response (e.g., a sentence about action towards one's body facilitates the execution of an arm movement towards the body). This paper presents an experiment that explores how the timing of the motor response during the processing of sentences affects the magnitude of the ACE that is observed. The results show that the ACE occurs when the motor response is executed at an early point in the comprehension of the sentence, disappears for a time, and then reappears when the motor response is executed right before the end of the sentence. These data help to refine our understanding of the temporal dynamics involved in the activation and use of motor information during sentence comprehension.

Language-induced motor perturbations during the execution of a reaching movement

In a recent study Boulenger et al. (2006) found that processing action verbs assisted reaching movement when the word was processed prior to movement onset and interfered with the movement when the word was processed at movement onset. The present study aimed to further corroborate the existence of such cross-talk between language processes and overt motor behaviour by demonstrating that the reaching movement can be disturbed by action words even when the words are presented delayed with respect to movement onset (50 ms and 200 ms). The results are compared to studies that show language-motor interaction in conditions where the word is presented prior to movement onset and are discussed within the context of embodied theories of language comprehension.

Language comprehension and dominant hand motion simulation

In five experiments participants were presented with pairs of nouns and verbs. They were asked to decide whether the combinations made sense or not. Half of the participants responded "yes" with the dominant hand, half with the left hand. When pairs referred to manual and mouth actions, participants responded faster with the dominant than with the left hand with sensible sentences. When pairs referred to manual and foot actions the result was opposite. Results suggest that language processing activates an action simulation that is sensitive to both the effector involved and the goal expressed by the sentence.

Actions, Words, and Numbers

Recent findings in neuroscience challenge the view that the motor system is exclusively dedicated to the control of actions, and it has been suggested that it may contribute critically to conceptual processes such as those involved in language and number representation. The aim of this review is to address this issue by illustrating some interactions between the motor system and the processing of words and numbers. First, we detail functional brain imaging studies suggesting that motor circuits may be recruited to represent the meaning of action-related words. Second, we summarize a series of experiments demonstrating some interference between the size of grip used to grasp objects and the magnitude processing of words or numbers. Third, we report data suggestive of a common representation of numbers and finger movements in the adult brain, a possible trace of the finger-counting strategies used in childhood. Altogether, these studies indicate that the motor system interacts with several aspects of word and number representations. Future research should determine whether these findings reflect a causal role of the motor system in the organization of semantic knowledge.

Neuroanatomical distribution of five semantic components of verbs: evidence from fMRI

The Simulation Framework, also known as the Embodied Cognition Framework, maintains that conceptual knowledge is grounded in sensorimotor systems. To test several predictions that this theory makes about the neural substrates of verb meanings, we used functional magnetic resonance imaging (fMRI) to scan subjects' brains while they made semantic judgments involving five classes of verbs-specifically, Running verbs (e.g., run, jog, walk), Speaking verbs (e.g., shout, mumble, whisper), Hitting verbs (e.g., hit, poke, jab), Cutting verbs (e.g., cut, slice, hack), and Change of State verbs (e.g., shatter, smash, crack). These classes were selected because they vary with respect to the presence or absence of five distinct semantic components-specifically, ACTION, MOTION, CONTACT, CHANGE OF STATE, and TOOL USE. Based on the Simulation Framework, we hypothesized that the ACTION component depends on the primary motor and premotor cortices, that the MOTION component depends on the posterolateral temporal cortex, that the CONTACT component depends on the intraparietal sulcus and inferior parietal lobule, that the CHANGE OF STATE component depends on the ventral temporal cortex, and that the TOOL USE component depends on a distributed network of temporal, parietal, and frontal regions. Virtually all of the predictions were confirmed. Taken together, these findings support the Simulation Framework and extend our understanding of the neuroanatomical distribution of different aspects of verb meaning.

A case of impaired verbalization but preserved gesticulation of motion events

In most cultures, most of the time, when people talk they gesture. We took advantage of a rare opportunity to explore the relation between the verbalization and gesticulation of motion events by studying Marcel, an English speaker with a unilateral left-hemisphere lesion affecting frontal, parietal, and temporal sectors of the perisylvian cortex. Marcel has intact semantic knowledge of the three major classes of words that are commonly used in English descriptions of motion events - specifically, concrete nouns, action verbs, and spatial prepositions - as well as intact syntactic knowledge of how these word classes are typically combined in the intransitive motion construction (e.g., The ball rolled down the hill). However, his ability to retrieve the lexical-phonological structures of these words is severely impaired. Despite this profound anomia, he is still remarkably skilled at producing iconic manual depictions of motion events, as demonstrated in two experiments involving spontaneous gestures and one experiment involving elicited gestures. Moreover, the structural characteristics of Marcel's gestures are clearly sensitive to the idiosyncratic meanings of English verbs and prepositions, and they may also be sensitive to the way motion events are syntactically packaged in the intransitive motion construction. These findings improve our understanding of how some brain-damaged individuals with severe aphasia but without manual apraxia can successfully employ gesture to augment the semantic content of their speech.

Imagery or meaning? Evidence for a semantic origin of category-specific brain activity in metabolic imaging

Category-specific brain activation distinguishing between semantic word types has imposed challenges on theories of semantic representations and processes. However, existing metabolic imaging data are still ambiguous about whether these category-specific activations reflect processes involved in accessing the semantic representation of the stimuli, or secondary processes such as deliberate mental imagery. Further information about the response characteristics of category-specific activation is still required. Our study for the first time investigated the differential impact of word frequency on functional magnetic resonance imaging (fMRI) responses to action-related words and visually related words, respectively. First, we corroborated previous results showing that action-relatedness modulates neural responses in action-related areas, while word imageability modulates activation in object processing areas. Second, we provide novel results showing that activation negatively correlated with word frequency in the left fusiform gyrus was specific for visually related words, while in the left middle temporal gyrus word frequency effects emerged only for action-related words. Following the dominant view in the literature that effects of word frequency mainly reflect access to lexico-semantic information, we suggest that category-specific brain activation reflects distributed neuronal ensembles, which ground language and concepts in perception-action systems of the human brain. Our approach can be applied to any event-related data using single-stimulus presentation, and allows a detailed characterization of the functional role of category-specific activation patterns.

Grasp Cueing shows Obligatory Attention to Action Goals

To understand the grounding of cognitive mechanisms in perception and action, we used a simple detection task to determine how long it takes to predict an action goal from the perception of grasp postures and whether this prediction is under strategic control. Healthy observers detected visual probes over small or large objects after seeing either a precision grip or a power grip posture. Although the posture was uninformative it induced attention shifts to the grasp-congruent object within 350 ms. When the posture predicted target appearance over the grasp-incongruent object, observers’ initial strategic allocation of attention was overruled by the congruency between grasp and object. These results might help to characterize the human mirror neuron system and reveal how joint attention tunes early perceptual processes toward action prediction.

Processing Abstract Language Modulates Motor System Activity

Embodiment theory proposes that neural systems for perception and action are also engaged during language comprehension. Previous neuroimaging and neurophysiological studies have only been able to demonstrate modulation of action systems during comprehension of concrete language. We provide neurophysiological evidence for modulation of motor system activity during the comprehension of both concrete and abstract language. In Experiment 1, when the described direction of object transfer or information transfer (e.g., away from the reader to another) matched the literal direction of a hand movement used to make a response, speed of responding was faster than when the two directions mismatched (an action–sentence compatibility effect). In Experiment 2, we used single-pulse transcranial magnetic stimulation to study changes in the corticospinal motor pathways to hand muscles while reading the same sentences. Relative to sentences that do not describe transfer, there is greater modulation of activity in the hand muscles when reading sentences describing transfer of both concrete objects and abstract information. These findings are discussed in relation to the human mirror neuron system.

Walking the talk--speech activates the leg motor cortex

Speech may have evolved from earlier modes of communication based on gestures. Consistent with such a motor theory of speech, cortical orofacial and hand motor areas are activated by both speech production and speech perception. However, the extent of speech-related activation of the motor cortex remains unclear. Therefore, we examined if reading and listening to continuous prose also activates non-brachiofacial motor representations like the leg motor cortex. We found corticospinal excitability of bilateral leg muscle representations to be enhanced by speech production and silent reading. Control experiments showed that speech production yielded stronger facilitation of the leg motor system than non-verbal tongue-mouth mobilization and silent reading more than a visuo-attentional task thus indicating speech-specificity of the effect. In the frame of the motor theory of speech this finding suggests that the system of gestural communication, from which speech may have evolved, is not confined to the hand but includes gestural movements of other body parts as well.

Processing nouns and verbs in the left frontal cortex: a transcranial magnetic stimulation study

Neuropsychological and neurophysiological studies suggest that the production of verbs in speech depends on cortical regions in the left frontal lobe. However, the precise topography of these regions, and their functional roles in verb production, remains matters of debate. In an earlier study with repetitive transcranial magnetic stimulation (rTMS), we showed that stimulation to the left anterior midfrontal gyrus disrupted verb production, but not noun production, in a task that required subjects to perform simple morphological alternations. This result raises a number of questions: for example, is the effect of stimulation focal and specific to that brain region? Is the behavioral effect limited to rule-based, regular transformations, or can it be generalized over the grammatical category? In the present study, we used rTMS to suppress the excitability of distinct parts of the left prefrontal cortex to assess their role in producing regular and irregular verbs compared to nouns. We compared rTMS to sham stimulation and to stimulation of homologous areas in the right hemisphere. Response latencies increased for verbs, but were unaffected for nouns, following stimulation to the left anterior midfrontal gyrus. No significant interference specific for verbs resulted after stimulation to two other areas in the left frontal lobe, the posterior midfrontal gyrus and Broca's area. These results therefore reinforce the idea that the left anterior midfrontal cortex is critical for processing verbs. Moreover, none of the regions stimulated was preferentially engaged in the production of regular or irregular inflection, raising questions about the role of the frontal lobes in processing inflectional morphology.

Mirror neurons and the understanding of behavioural symptoms in psychiatric disorders

PURPOSE OF REVIEW

Recent findings show that we can understand other people's actions, intentions and emotions through a mirror mechanism as if we performed the same actions and felt the same intentions or emotions (embodied simulation). The present paper reviews experimental evidence that this mechanism may be broken in some psychiatric disorders.

RECENT FINDINGS

A mirror neuron system has been described in both monkeys and humans that allows one to map an observed action on a correspondent motor representation in the observer's brain. This mechanism has been involved in many higher motor functions ranging from action understanding to imitation and intention coding. A mirror mechanism has also been invoked in empathy, through an embodied simulation.

SUMMARY

A dysfunction of the mirror neuron system may be at the root of the inability to empathize in patients with autism and may play a role in some negative and positive symptoms found in patients with schizophrenia. This opens up new perspectives in the interpretation of psychotic symptoms and possibly in developing therapeutic strategies.

Grounded cognition

Grounded cognition rejects traditional views that cognition is computation on amodal symbols in a modular system, independent of the brain's modal systems for perception, action, and introspection. Instead, grounded cognition proposes that modal simulations, bodily states, and situated action underlie cognition. Accumulating behavioral and neural evidence supporting this view is reviewed from research on perception, memory, knowledge, language, thought, social cognition, and development. Theories of grounded cognition are also reviewed, as are origins of the area and common misperceptions of it. Theoretical, empirical, and methodological issues are raised whose future treatment is likely to affect the growth and impact of grounded cognition.

The time course of action and action-word comprehension in the human brain as revealed by neurophysiology

Numerous previous neuroimaging studies suggest an involvement of cortical motor areas not only in action execution but also in action recognition and understanding. Motor areas of the human brain have also been found to activate during the processing of written and spoken action-related words and sentences. Even more strikingly, stimuli referring to different bodily effectors produced specific somatotopic activation patterns in the motor areas. However, metabolic neuroimaging results can be ambiguous with respect to the processing stage they reflect. This is a serious limitation when hypotheses concerning linguistic processes are tested, since in this case it is usually crucial to distinguish early lexico-semantic processing from strategic effects or mental imagery that may follow lexico-semantic information access. Timing information is therefore pivotal to determine the functional significance of motor areas in action recognition and action-word comprehension. Here, we review attempts to reveal the time course of these processes using neurophysiological methods (EEG, MEG and TMS), in visual and auditory domains. We will highlight the importance of the choice of appropriate paradigms in combination with the corresponding method for the extraction of timing information. The findings will be discussed in the general context of putative brain mechanisms of word and object recognition.

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.

A critical look at the embodied cognition hypothesis and a new proposal for grounding conceptual content

Many studies have demonstrated that the sensory and motor systems are activated during conceptual processing. Such results have been interpreted as indicating that concepts, and important aspects of cognition more broadly, are embodied. That conclusion does not follow from the empirical evidence. The reason why is that the empirical evidence can equally be accommodated by a 'disembodied' view of conceptual representation that makes explicit assumptions about spreading activation between the conceptual and sensory and motor systems. At the same time, the strong form of the embodied cognition hypothesis is at variance with currently available neuropsychological evidence. We suggest a middle ground between the embodied and disembodied cognition hypotheses--grounding by interaction. This hypothesis combines the view that concepts are, at some level, 'abstract' and 'symbolic', with the idea that sensory and motor information may 'instantiate' online conceptual processing.

Putting motor resonance in perspective

Perceiving another person's actions changes the spatial perspective people use to describe objects in a scene, possibly because seeing human action induces people to map the actions, including their spatial context, to their own body and motor representations [Lozano, S. C., Hard, B. M., & Tversky, B. (2007). Putting action in perspective. Cognition 103, 480-490]. If so, then the effect of perceived action on perspective should be modulated by action experience. The present studies tested this prediction by showing participants a photograph and asking them to describe the location of one object relative to another. Across studies, adoption of the actor's perspective increased when participants saw actions that were more familiar or were performed with a limb (hand or foot) that observers had more experience performing actions with themselves. The present findings indicate that observers' experience performing observed actions influences their tendency to engage in self-other mapping, and consequently, their interpretations and descriptions of spatial scenes.

Naming dynamic and static actions: neuropsychological evidence

There has been considerable interest in identifying the neural correlates of action naming, but the bulk of previous work on this topic has utilized static stimuli. Recent research comparing the visual processing of dynamic versus static actions suggests that these two types of stimuli engage largely overlapping neural systems, raising the possibility that the higher-order processing requirements for naming dynamic and static actions might not be very different. To explore this issue in greater depth, we developed the Dynamic Action Naming Test (DANT), which consists of 158 video clips 3-5s in length, for each of which the participant is asked to produce the most appropriate verb. We administered the DANT to 78 brain-damaged patients drawn from our Patient Registry, and to a demographically matched group of 50 normal participants. Out of the 16 patients who performed defectively on the DANT, nearly all (15/16) had damage in the left hemisphere. Lesion analysis indicated that the frontal operculum was the most frequent area of damage in the 15 patients; also, damage to the posterolateral temporal-occipital sector (in and near MT) was specifically related to defective dynamic action naming. Most of the brain-damaged participants (n=71) also received our Static Action Naming Test (SANT), and we found that performances on verb items that were common across the DANT and SANT were highly correlated (R=.91). Moreover, patients who failed the DANT almost invariably also failed the SANT. These findings lend further support to the hypothesis that there is considerable commonality in the neural systems underlying the use of verbs to orally name dynamic and static actions, a conclusion that is in turn compatible with the concept of "representational momentum". Our results also contribute more generally to the rapidly growing field of research on embodied cognition.

Before and below 'theory of mind': embodied simulation and the neural correlates of social cognition

The automatic translation of folk psychology into newly formed brain modules specifically dedicated to mind-reading and other social cognitive abilities should be carefully scrutinized. Searching for the brain location of intentions, beliefs and desires-as such-might not be the best epistemic strategy to disclose what social cognition really is. The results of neurocognitive research suggest that in the brain of primates, mirror neurons, and more generally the premotor system, play a major role in several aspects of social cognition, from action and intention understanding to language processing. This evidence is presented and discussed within the theoretical frame of an embodied simulation account of social cognition. Embodied simulation and the mirror neuron system underpinning it provide the means to share communicative intentions, meaning and reference, thus granting the parity requirements of social communication.

Different strategies do not moderate primary motor cortex involvement in mental rotation: a TMS study

Background

Regions of the dorsal visual stream are known to play an essential role during the process of mental rotation. The functional role of the primary motor cortex (M1) in mental rotation is however less clear. It has been suggested that the strategy used to mentally rotate objects determines M1 involvement. Based on the strategy hypothesis that distinguishes between an internal and an external strategy, our study was designed to specifically test the relation between strategy and M1 activity.

Methods

Twenty-two subjects were asked to participate in a standard mental rotation task. We used specific picture stimuli that were supposed to trigger either the internal (e.g. pictures of hands or tools) or the external strategy (e.g. pictures of houses or abstract figures). The strategy hypothesis predicts an involvement of M1 only in case of stimuli triggering the internal strategy (imagine grasping and rotating the object by oneself). Single-pulse Transcranial Magnetic Stimulation (TMS) was employed to quantify M1 activity during task performance by measuring Motor Evoked Potentials (MEPs) at the right hand muscle.

Results

Contrary to the strategy hypothesis, we found no interaction between stimulus category and corticospinal excitability. Instead, corticospinal excitability was generally increased compared with a resting baseline although subjects indicated more frequent use of the external strategy for all object categories.

Conclusion

This finding suggests that M1 involvement is not exclusively linked with the use of the internal strategy but rather directly with the process of mental rotation. Alternatively, our results might support the hypothesis that M1 is active due to a 'spill-over' effect from adjacent brain regions.

Neural evidence for the interplay between language, gesture, and action: a review

Co-speech gestures embody a form of manual action that is tightly coupled to the language system. As such, the co-occurrence of speech and co-speech gestures is an excellent example of the interplay between language and action. There are, however, other ways in which language and action can be thought of as closely related. In this paper we will give an overview of studies in cognitive neuroscience that examine the neural underpinnings of links between language and action. Topics include neurocognitive studies of motor representations of speech sounds, action-related language, sign language and co-speech gestures. It will be concluded that there is strong evidence on the interaction between speech and gestures in the brain. This interaction however shares general properties with other domains in which there is interplay between language and action.

Putting action in perspective

Embodied approaches to cognition propose that our own actions influence our understanding of the world. Do other people's actions also have this influence? The present studies show that perceiving another person's actions changes the way people think about objects in a scene. In Study 1, participants viewed a photograph and answered a question about the location of one object relative to another. The question either did or did not call attention to an action being performed in the scene. Studies 2 and 3 focused on whether depicting an action in a scene influenced perspective choice. Across all studies, drawing attention to action, whether verbally or pictorially, led observers to encode object locations from the actor's spatial perspective. Study 4 demonstrated that the tendency to adopt the actor's perspective might be mediated by motor experience.

Emotion simulation during language comprehension

We report a novel finding on the relation of emotion and language. Covert manipulation of emotional facial posture interacts with sentence valence when measuring the amount of time to judge valence (Experiment 1) and sensibility (Experiment 2) of the sentence. In each case, an emotion-sentence compatibility effect is found: Judgment times are faster when facial posture and sentence valence match than when they mismatch. We interpret the finding using a simulation account; that is, emotional systems contribute to language comprehension much as they do in social interaction. Because the effect was not observed on a lexical decision task using emotion-laden words (Experiment 3), we suggest that the emotion simulation affects comprehension processes beyond initial lexical access.

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.

Central mechanisms in phantom limb perception: The past, present and future

Phantom limbs provide valuable insight into the mechanisms underlying bodily awareness and ownership. This paper reviews the complexity of phantom limb phenomena (proprioception, form, position, posture and telescoping), and the various contributions of internal constructs of the body, or body schema, and neuromatrix theory in explaining these phenomena. Specific systems and processes that have received little attention in phantom limb research are also reviewed and highlighted as important future directions, These include prosthesis embodiment and extended physiological proprioception (i.e., the extension of the body's "area of influence" that thereby extends one's innate sense of proprioception, mirror neurons and cross-referencing of the phantom limb with the intact limb (and the related phenomena of perceiving referred sensations and mirrored movements in the phantom form the intact limb). The likely involvements of the body schema and the body-self neuromatrix, mirror neurons, and cross-callosal and ipsilateral mechanisms in phantom limb phenomena all suggest that the perception of a "normal" phantom limb (that is, a non-painful phantom that has the sensory qualities of an intact limb) is more than likely an epiphenomenon of normal functioning, action understanding and empathy, and potentially may even be evolutionarily adaptive and perhaps necessary. Phantom pain, however, may be a maladaptive failure of the neuromatrix to maintain global bodily constructs.

Stimulus properties matter more than perspective: an fMRI study of mental imagery and silent reading of action phrases

The role of the primary motor cortex (M1) in tasks involving action words remains controversial. Therefore, we investigated whether the previously reported involvement of M1 in processing of action words results from the semantic representation of action words per se, or if M1 activation may actually depend on whether or not subjects (explicitly or automatically) adopt a strategy of simulating the movements. Subjects silently read short phrases describing a situation which either involved a motor scene or not (STIMULUS: motor, non-motor phrases) and performed a secondary task: either they were explicitly asked to imagine the situation or they performed letter detection preventing them from using a simulation strategy (TASK: imagery vs. letter detection). In addition, phrases were presented both in 1st and 3rd person singular (

PERSPECTIVE

1st vs. 3rd person). This allowed us to investigate the influence of the secondary tasks (letter detection versus explicit motor imagery) on the neural activity in M1 during the processing of motor and non-motor phrases. We found differential left M1 activity in the task by stimulus interaction with enhanced M1 activation for imagery in the presence of motor phrases (vs. non-motor phrases) compared to letter detection of motor vs. non-motor phrases. This M1-activity was not differentially modulated by perspective. Therefore, M1 activation previously found in experiments of silent reading of action words may have resulted from the subjects' strategy to mentally simulate the movements during the processing of action words.

Stimulating language: insights from TMS

Fifteen years ago, Pascual-Leone and colleagues used transcranial magnetic stimulation (TMS) to investigate speech production in pre-surgical epilepsy patients and in doing so, introduced a novel tool into language research. TMS can be used to non-invasively stimulate a specific cortical region and transiently disrupt information processing. These 'virtual lesion' studies offer not only the ability to explore causal relations between brain regions and language functions absent in functional neuroimaging, but also spatial and temporal precision not typically available in patient studies. For instance, TMS has been used to demonstrate functionally distinct sub-regions of the left inferior frontal gyrus; to clarify the relationship between pre-morbid language organization and susceptibility to unilateral lesions and to investigate the contribution of both left and right hemisphere language areas in recovery from aphasia. When TMS is used as a measure of functional connectivity, it demonstrates a close link between action words and motor programmes; it suggests a potential evolutionary link between hand gestures and language and it suggests a role in speech perception for the motor system underlying speech production. In combination with functional neuroimaging, it can elucidate the circuits responsible for this involvement. Finally, TMS may even be useful for enhancing recovery in aphasic patients. In other words, TMS has already become an important tool for studying language at both the cognitive and neural levels, and it is clear that further developments in TMS methodology are likely to result in even greater opportunities for language research.

Action representation of sound: audiomotor recognition network while listening to newly acquired actions

The discovery of audiovisual mirror neurons in monkeys gave rise to the hypothesis that premotor areas are inherently involved not only when observing actions but also when listening to action-related sound. However, the whole-brain functional formation underlying such "action-listening" is not fully understood. In addition, previous studies in humans have focused mostly on relatively simple and overexperienced everyday actions, such as hand clapping or door knocking. Here we used functional magnetic resonance imaging to ask whether the human action-recognition system responds to sounds found in a more complex sequence of newly acquired actions. To address this, we chose a piece of music as a model set of acoustically presentable actions and trained non-musicians to play it by ear. We then monitored brain activity in subjects while they listened to the newly acquired piece. Although subjects listened to the music without performing any movements, activation was found bilaterally in the frontoparietal motor-related network (including Broca's area, the premotor region, the intraparietal sulcus, and the inferior parietal region), consistent with neural circuits that have been associated with action observations, and may constitute the human mirror neuron system. Presentation of the practiced notes in a different order activated the network to a much lesser degree, whereas listening to an equally familiar but motorically unknown music did not activate this network. These findings support the hypothesis of a "hearing-doing" system that is highly dependent on the individual's motor repertoire, gets established rapidly, and consists of Broca's area as its hub.

Action representation of sound: audiomotor recognition network while listening to newly acquired actions

The discovery of audiovisual mirror neurons in monkeys gave rise to the hypothesis that premotor areas are inherently involved not only when observing actions but also when listening to action-related sound. However, the whole-brain functional formation underlying such "action-listening" is not fully understood. In addition, previous studies in humans have focused mostly on relatively simple and overexperienced everyday actions, such as hand clapping or door knocking. Here we used functional magnetic resonance imaging to ask whether the human action-recognition system responds to sounds found in a more complex sequence of newly acquired actions. To address this, we chose a piece of music as a model set of acoustically presentable actions and trained non-musicians to play it by ear. We then monitored brain activity in subjects while they listened to the newly acquired piece. Although subjects listened to the music without performing any movements, activation was found bilaterally in the frontoparietal motor-related network (including Broca's area, the premotor region, the intraparietal sulcus, and the inferior parietal region), consistent with neural circuits that have been associated with action observations, and may constitute the human mirror neuron system. Presentation of the practiced notes in a different order activated the network to a much lesser degree, whereas listening to an equally familiar but motorically unknown music did not activate this network. These findings support the hypothesis of a "hearing-doing" system that is highly dependent on the individual's motor repertoire, gets established rapidly, and consists of Broca's area as its hub.

Intentional attunement: mirror neurons and the neural underpinnings of interpersonal relations

The neural circuits activated in a person carrying out actions, expressing emotions, and experiencing sensations are activated also, automatically via a mirror neuron system, in the observer of those actions, emotions, and sensations. It is proposed that this finding of shared activation suggests a functional mechanism of "embodied simulation" that consists of the automatic, unconscious, and noninferential simulation in the observer of actions, emotions, and sensations carried out and experienced by the observed. It is proposed also that the shared neural activation pattern and the accompanying embodied simulation constitute a fundamental biological basis for understanding another's mind. The implications of this perspective for psychoanalysis are discussed, particularly regarding unconscious communication, projective identification, attunement, empathy, autism, therapeutic action, and transference-countertransference interactions.

Sentence comprehension and action: effector specific modulation of the motor system

The purpose of the paper is to study whether sentence comprehension modulates the motor system. Participants were presented with 24 pairs of nouns and verbs that could be referred to hand and mouth actions (e.g., to unwrap vs. to suck the sweet), in the first block, or, in the second block, to 24 hand and foot actions (e.g., to throw vs. kick the ball). An equal number of non-sensible pairs were presented. Participants' task consisted of deciding whether the combination made sense or not: 20 participants responded by saying yes loudly into a microphone, 20 by pressing a pedal. Results support embodied theories of language comprehension, as they suggest that sentence processing activates an action simulation. This simulation is quite detailed, as it is sensitive to the effector involved. Namely, it leads to a facilitation in responses to 'mouth sentences' and 'foot sentences' compared to 'hand sentences' in case of congruency between the effectors - mouth and foot - involved in the motor response and in the sentence.

Cross-talk between language processes and overt motor behavior in the first 200 msec of processing

A recently emerging view sees language understanding as closely linked to sensory and motor processes. The present study investigates this issue by examining the influence of processing action verbs and concrete nouns on the execution of a reaching movement. Fine-grained analyses of movement kinematics revealed that relative to nouns, processing action verbs significantly affects overt motor performance. Within 200 msec after onset, processing action verbs interferes with a concurrent reaching movement. By contrast, the same words assist reaching movement when processed before movement onset. The cross-talk between language processes and overt motor behavior provides unambiguous evidence that action words and motor action share common cortical representations and could thus suggest that cortical motor regions are indeed involved in action word retrieval.

The role of ventral premotor cortex in action execution and action understanding

The human ventral premotor cortex overlaps, at least in part, with Broca's region in the dominant cerebral hemisphere, that is known to mediate the production of language and contributes to language comprehension. This region is constituted of Brodmann's areas 44 and 45 in the inferior frontal gyrus. We summarize the evidence that the motor related part of Broca's region is localized in the opercular portion of the inferior frontal cortex, mainly in area 44 of Brodmann. According to our own data, there seems to be a homology between Brodmann area 44 in humans and the monkey area F5. The non-language related motor functions of Broca's region comprise complex hand movements, associative sensorimotor learning and sensorimotor integration. Brodmann's area 44 is also a part of a specialized parieto-premotor network and interacts significantly with the neighbouring premotor areas. In the ventral premotor area F5 of monkeys, the so called mirror neurons have been found which discharge both when the animal performs a goal-directed hand action and when it observes another individual performing the same or a similar action. More recently, in the same area mirror neurons responding not only to the observation of mouth actions, but also to sounds characteristic to actions have been found. In humans, through an fMRI study, it has been shown that the observation of actions performed with the hand, the mouth and the foot leads to the activation of different sectors of Broca's area and premotor cortex, according to the effector involved in the observed action, following a somatotopic pattern which resembles the classical motor cortex homunculus. On the other hand the evidence is growing that human ventral premotor cortex, especially Brodmann's area 44, is involved in polymodal action processing. These results strongly support the existence of an execution-observation matching system (mirror neuron system). It has been proposed that this system is involved in polymodal action recognition and might represent a precursor of language processing. Experimental evidence in favour of this hypothesis both in the monkey and humans is shortly reviewed.

Embodied spatial transformations: "Body analogy" for the mental rotation of objects

The cognitive advantage of imagined spatial transformations of the human body over that of more unfamiliar objects (e.g., Shepard-Metzler [S-M] cubes) is an issue for validating motor theories of visual perception. In 6 experiments, the authors show that providing S-M cubes with body characteristics (e.g., by adding a head to S-M cubes to evoke a posture) facilitates the mapping of the cognitive coordinate system of one's body onto the abstract shape. In turn, this spatial embodiment improves object shape matching. Thanks to the increased cohesiveness of human posture in people's body schema, imagined transformations of the body operate in a less piecemeal fashion as compared with objects (S-M cubes or swing-arm desk lamps) under a similar spatial configuration, provided that the pose can be embodied. If the pose cannot be emulated (covert imitation) by the sensorimotor system, the facilitation due to motoric embodiment will also be disrupted.

Brain mechanisms linking language and action

For a long time the cortical systems for language and actions were believed to be independent modules. However, as these systems are reciprocally connected with each other, information about language and actions might interact in distributed neuronal assemblies. A critical case is that of action words that are semantically related to different parts of the body (for example, 'lick', 'pick' and 'kick'): does the comprehension of these words specifically, rapidly and automatically activate the motor system in a somatotopic manner, and does their comprehension rely on activity in the action system?