Abstract Processing of lexical verbs involves automatic access to argument structure entries entailed within the verb's representation. Recent neuroimaging studies with young normal listeners suggest that this involves bilateral posterior peri-sylvian tissue, with graded activation in these regions based on argument structure complexity. The aim of the present study was to examine the neural mechanisms of verb processing using fMRI in older normal volunteers and patients with stroke-induced agrammatic aphasia, a syndrome in which verb, as compared with noun, production often is selectively impaired, but verb comprehension in both on-line and off-line tasks is spared. Fourteen healthy listeners and five age-matched aphasic patients performed a lexical decision task, which examined verb processing by argument structure complexity, that is, one-argument (i.e., intransitive; v1); two-argument (i.e., transitive; v2), and three-argument (v3) verbs. Results for the age-matched listeners largely replicated those for younger participants studied by Thompson et al.[Thompson, C. K., Bonakdarpour, B., Fix, S. C., Blumenfeld, H. K., Parrish, T. B., Gitelman, D. R., et al. Neural correlates of verb argument structure processing. Journal of Cognitive Neuroscience, 19, 1753-1767, 2007]: v3-v1 comparisons showed activation of the angular gyrus in both hemispheres, and this same heteromodal region was activated in the left hemisphere in the (v2 + v3)- v1 contrast. Similar results were derived for the agrammatic aphasic patients; however, activation was unilateral (in the right hemisphere for three participants) rather than bilateral likely because these patients' lesions extended to the left temporo-parietal region. All performed the task with high accuracy, and despite differences in lesion site and extent, they recruited spared tissue in the same regions as healthy normals. Consistent with psycholinguistic models of sentence processing, these findings indicate that the posterior language network is engaged for processing verb argument structure and is crucial for semantic integration of argument structure information.

How do we understand the actions of others as they are described to us through language? Embodied theories of conceptual knowledge suggest that sensory-motor representations of actions similar to those involved in the performance of the action described are recruited during language comprehension. The extent of this recruitment, however, and the brain mechanisms supporting this process remain unknown. Using fMRI, we investigate these issues by examining how people understand sentences that convey three different degrees of physical effort and by comparing this process to action execution. To understand the effort implied by the stimulus sentence, object and action properties associated with nouns and verbs respectively must be integrated: pushing the piano implies more physical effort than pushing the chair. Results indicated that a pre-motor region, which was also active in action execution, was sensitive to the degree of effort implied by the language. Interestingly, the anterior inferior frontal gyrus, a region typically associated with semantic processing, was not active in action execution but was nevertheless modulated by the effort implied. Inter-region correlations also suggested that this region was strongly correlated with pre-motor and posterior temporal regions. Overall, results suggest that (a) language understanding elicits action representations retaining a degree of specificity that was previously unsuspected, including unique properties of interactions with objects, and (b) these representations, which result from integrating the words' semantic information, may be computed within a collaborative neural network that includes the anterior inferior frontal gyrus.

Moving a set dinner table often takes two people, and doing so without spilling the glasses requires the close coordination of the two agents' actions. It has been argued that the mirror neuron system may be the key neural locus of such coordination. Instead, here we show that such coordination recruits two separable sets of areas: one that could translate between motor and visual codes and one that could integrate these information to achieve common goals. The former includes regions of the putative mirror neuron system, the latter, regions of the prefrontal, posterior parietal and temporal lobe adjacent to the putative mirror neuron system. Both networks were more active while participants cooperated with a human agent, responding to their actions, compared to a computer that did not, evidencing their social dimension. This finding shows that although the putative mirror neuron system can play a critical role in joint actions by translating both agents' actions into a common code, the flexible remapping of our own actions with those of others required during joint actions seems to be performed outside of the putative mirror neuron system.

Everyday communication is accompanied by visual information from several sources, including co-speech gestures, which provide semantic information listeners use to help disambiguate the speaker's message. Using fMRI, we examined how gestures influence neural activity in brain regions associated with processing semantic information. The BOLD response was recorded while participants listened to stories under three audiovisual conditions and one auditory-only (speech alone) condition. In the first audiovisual condition, the storyteller produced gestures that naturally accompany speech. In the second, the storyteller made semantically unrelated hand movements. In the third, the storyteller kept her hands still. In addition to inferior parietal and posterior superior and middle temporal regions, bilateral posterior superior temporal sulcus and left anterior inferior frontal gyrus responded more strongly to speech when it was further accompanied by gesture, regardless of the semantic relation to speech. However, the right inferior frontal gyrus was sensitive to the semantic import of the hand movements, demonstrating more activity when hand movements were semantically unrelated to the accompanying speech. These findings show that perceiving hand movements during speech modulates the distributed pattern of neural activation involved in both biological motion perception and discourse comprehension, suggesting listeners attempt to find meaning, not only in the words speakers produce, but also in the hand movements that accompany speech. Hum Brain Mapp, 2009.(c) 2009 Wiley-Liss, Inc.

Modern neuroimaging provides a common platform for neuroscience and related disciplines to explore the human brain, mind, and behavior. We base our review on the social shaping of the human mind and discuss various aspects of brain function related to social interaction. Despite private mental contents, people can share their understanding of the world using, beyond verbal communication, nonverbal cues such as gestures, facial expressions, and postures. The understanding of nonverbal messages is supported by the brain's mirroring systems that are shaped by individual experience. Within the organism-environment system, tight links exist between action and perception, both within an individual and between several individuals. Therefore, any comprehensive brain imaging study of the neuronal basis of social cognition requires appreciation of the situated and embodied nature of human cognition, motivating simultaneous monitoring of brain and bodily functions within a socially relevant environment. Because single-person studies alone cannot unravel the dynamic aspects of interpersonal interactions, it seems both necessary and beneficial to move towards "two-person neuroscience"; technological shortcomings and a limited conceptual framework have so far hampered such a leap. We conclude by discussing some major disorders of social interaction.

We propose an integrative cognitive neuroscience framework for understanding the cognitive and neural foundations of religious belief. Our analysis reveals 3 principle psychological dimensions of religious belief (God's perceived level of involvement, God's perceived emotion, and doctrinal/experiential religious knowledge), which functional MRI localizes within networks processing Theory of Mind regarding intent and emotion, abstract semantics, and imagery. Our results are unique in demonstrating that specific components of religious belief are mediated by well-known brain networks, and support contemporary psychological theories that ground religious belief within evolutionary adaptive cognitive functions.

This study measured event-related potentials (ERPs) during multiple goal and trait inferences, under spontaneous or intentional instructions. Participants read sentences describing several goal-implying behaviors of a target person from which also a strong trait could be inferred or not. The last word of each sentence determined the consistency with the inference induced during preceding sentences. In comparison with behaviors that implied only a goal, stronger waveforms beginning at approximately 150 ms were obtained when the behaviors additionally implied a trait. These ERPs showed considerable parallels between spontaneous and intentional inferences. This suggests that traits embedded in a stream of goal-directed behaviors were detected more rapidly and automatically than mere goals, irrespective of the participants' spontaneous or intentional instructions. In line with this, source localization (LORETA) of the ERPs show predominantly activation in the temporo-parietal junction (TPJ) during 150-200 ms, suggesting that goals were detected at that time interval. During 200-300 ms, activation was stronger at the medial prefrontal cortex (mPFC) for multiple goals and traits as opposed to goals only, suggesting that traits were inferred during this time window. A cued recall measure taken after the presentation of the stimulus material support the occurrence of goal and trait inferences and shows significant correlations with the neural components, indicating that these components are valid neural indices of spontaneous and intentional social inferences. The early detection of multiple goal and trait inferences is explained in terms of their greater social relevance, leading to privileged attention allocation and processing in the brain.

Mirror neurons are defined as neurons in the monkey cortex which respond to goal oriented actions, whether the behavior is self-generated or produced by another. Here we briefly review this literature and consider evidence from behavioral, neuropsychological, and brain imaging studies for a similar mirror neuron system in humans. Furthermore, we review functions of this system related to action comprehension and motor imagery, as well as evidence for speculations on the system's ties with conceptual knowledge and language.

The ability to perceive facial motion is important to successfully interact in social environments. Previously, imaging studies have investigated neural correlates of facial motion primarily using abstract motion stimuli. Here, we studied how the brain processes natural non-rigid facial motion in direct comparison to static stimuli and matched phase-scrambled controls. As predicted from previous studies, dynamic faces elicit higher responses than static faces in lateral temporal areas corresponding to hMT+/V5 and STS. Interestingly, individually defined, static-face-sensitive regions in bilateral fusiform gyrus and left inferior occipital gyrus also respond more to dynamic than static faces. These results suggest integration of form and motion information during the processing of dynamic faces even in ventral temporal and inferior lateral occipital areas. In addition, our results show that dynamic stimuli are a robust tool to localize areas related to the processing of static and dynamic face information.

Many neuroimaging studies of the mirror neuron system (MNS) examine if certain voxels in the brain are shared between action observation and execution (shared voxels, sVx). Unfortunately, finding sVx in standard group analyses is not a guarantee that sVx exist in individual subjects. Using unsmoothed, single-subject analyses we show sVx can be reliably found in all 16 investigated participants. Beside the ventral premotor (BA6/44) and inferior parietal cortex (area PF) where mirror neurons (MNs) have been found in monkeys, sVx were reliably observed in dorsal premotor, supplementary motor, middle cingulate, somatosensory (BA3, BA2, and OP1), superior parietal, middle temporal cortex and cerebellum. For the premotor, somatosensory and parietal areas, sVx were more numerous in the left hemisphere. The hand representation of the primary motor cortex showed a reduced BOLD during hand action observation, possibly preventing undesired overt imitation. This study provides a more detailed description of the location and reliability of sVx and proposes a model that extends the original idea of the MNS to include forward and inverse internal models and motor and sensory simulation, distinguishing the MNS from a more general concept of sVx.

Understanding the intentions of others while watching their actions is a fundamental building block of social behavior. The neural and functional mechanisms underlying this ability are still poorly understood. To investigate these mechanisms we used functional magnetic resonance imaging. Twenty-three subjects watched three kinds of stimuli: grasping hand actions without a context, context only (scenes containing objects), and grasping hand actions performed in two different contexts. In the latter condition the context suggested the intention associated with the grasping action (either drinking or cleaning). Actions embedded in contexts, compared with the other two conditions, yielded a significant signal increase in the posterior part of the inferior frontal gyrus and the adjacent sector of the ventral premotor cortex where hand actions are represented. Thus, premotor mirror neuron areas-areas active during the execution and the observation of an action-previously thought to be involved only in action recognition are actually also involved in understanding the intentions of others. To ascribe an intention is to infer a forthcoming new goal, and this is an operation that the motor system does automatically.

Functional brain imaging studies have demonstrated increased activity in dorsal premotor and posterior parietal cortex when performing spatial stimulus-response compatibility tasks (SRC). We tested the specific role of these regions in stimulus-response mapping using single-pulse transcranial magnetic stimulation (TMS). Subjects were scanned using functional magnetic resonance imaging (fMRI) prior to the TMS session during performance of a task in which spatial compatibility was manipulated. For each subject, the area of increased signal within the regions of interest was registered onto their own high-resolution T1-weighted anatomic scan. TMS was applied to these areas for each subject using a frameless stereotaxic system. Task accuracy and reaction time (RT) were measured during blocks of compatible or incompatible trials and during blocks of real TMS or sham stimulation. On each trial, a single TMS pulse was delivered at 50, 100, 150, or 200 ms after the onset of the stimulus in the left or right visual field. TMS over the left premotor cortex produced various facilitatory effects, depending on the timing of the stimulation. At short intervals, TMS appeared to prime the left dorsal premotor cortex to select a right-hand response more quickly, regardless of stimulus-response compatibility. The strongest effect of stimulation, however, occurred at the 200-ms interval, when TMS facilitated left-hand responses during the incompatible condition. Facilitation of attention to the contralateral visual hemifield was observed during stimulation over the parietal locations. We conclude that the left premotor cortex is one of the cortical regions responsible for overriding automatic stimulus-response associations.

Imitation is a basic form of motor learning during development. We have a preference to imitate the actions of others as if looking in a mirror (specular imitation: i.e., when the actor moves the left hand, the imitator moves the right hand) rather than with the anatomically congruent hand (anatomic imitation: i.e., actor and imitator both moving the right hand). We hypothesized that this preference reflects changes in activity in previously described frontoparietal cortical areas involved in directly matching observed and executed actions (mirror neuron areas). We used functional magnetic resonance imaging to study brain activity in normal volunteers imitating left and right hand movements with their right hand. Bilateral inferior frontal and right posterior parietal cortex were more active during specular imitation compared with anatomic imitation and control motor tasks. Furthermore this same pattern of activity was also observed in the rostral part of the supplementary motor area (SMA-proper) of the right hemisphere. These findings suggest that the degree of involvement of frontoparietal mirror areas in imitation depends on the nature of the imitative behavior, ruling out a linguistic mediation of these areas in imitation. Moreover, activity in the SMA appears to be tightly coupled to frontoparietal mirror areas when subjects copy the actions of others.

Behavioral studies reveal that imitation performance and the motor system are strongly influenced by the goal of the action to be performed. We used functional magnetic resonance imaging (fMRI) to assess the effect of explicit action goals on neural activity during imitation. Subjects imitated index finger movements in the absence and presence of visible goals (red dots that were reached for by the finger movement). Finger movements were either ipsilateral or contralateral. The pars opercularis of the inferior frontal gyrus showed increased blood oxygen level-dependent fMRI signal bilaterally for imitation of goal-oriented actions, compared with imitation of actions with no explicit goal. In addition, bilateral dorsal premotor areas demonstrated greater activity for goal-oriented actions, for contralateral movements and an interaction effect such that goal-oriented contralateral movements yielded the greatest activity. These results support the hypothesis that areas relevant to motor preparation and motor execution are tuned to coding goal-oriented actions and are in keeping with single-cell recordings revealing that neurons in area F5 of the monkey brain represent goal-directed aspects of actions.

Impairments in praxic functioning are common after stroke, most frequently when the left hemisphere is affected. Several recent studies of apraxia after stroke have made advances in understanding the right hemisphere contribution to praxis, particularly for the performance of novel actions. Moreover, quantitative lesion analysis in stroke patients indicates the importance of cortical regions such as the intraparietal sulcus and the middle frontal gyrus for subserving praxic function. Complex neuropsychological models have been developed to account for the many dissociations observed in the types of errors observed in stroke patients. Relatively lacking, however, are models that attempt to relate the neurological data to what is known about praxis from functional neuroimaging in normal subjects and from physiological studies in the monkey. Moreover, a coherent interpretation of the results of apraxia studies remains hampered by the lack of a standard testing instrument to assess the nature and severity of apraxic impairments in the groups tested.

In the course of developing an atlas and reference system for the normal human brain throughout the human age span from structural and functional brain imaging data, the International Consortium for Brain Mapping (ICBM) developed a set of "normal" criteria for subject inclusion and the associated exclusion criteria. The approach was to minimize inclusion of subjects with any medical disorders that could affect brain structure or function. In the past two years, a group of 1685 potential subjects responded to solicitation advertisements at one of the consortium sites (UCLA). Subjects were screened by a detailed telephone interview and then had an in-person history and physical examination. Of those who responded to the advertisement and considered themselves to be normal, only 31.6%(532 subjects) passed the telephone screening process. Of the 348 individuals who submitted to in-person history and physical examinations, only 51.7% passed these screening procedures. Thus, only 10.7% of those individuals who responded to the original advertisement qualified for imaging. The most frequent cause for exclusion in the second phase of subject screening was high blood pressure followed by abnormal signs on neurological examination. It is concluded that the majority of individuals who consider themselves normal by self-report are found not to be so by detailed historical interviews about underlying medical conditions and by thorough medical and neurological examinations. Recommendations are made with regard to the inclusion of subjects in brain imaging studies and the criteria used to select them.

The mirror neuron system (MNS) has been proposed to play an important role in social cognition by providing a neural mechanism by which others' actions, intentions, and emotions can be understood. Here functional magnetic resonance imaging was used to directly examine the relationship between MNS activity and two distinct indicators of social functioning in typically-developing children (aged 10.1 years+/-7 months): empathy and interpersonal competence. Reliable activity in pars opercularis, the frontal component of the MNS, was elicited by observation and imitation of emotional expressions. Importantly, activity in this region (as well as in the anterior insula and amygdala) was significantly and positively correlated with established behavioral measures indexing children's empathic behavior (during both imitation and observation) and interpersonal skills (during imitation only). These findings suggest that simulation mechanisms and the MNS may indeed be relevant to social functioning in everyday life during typical human development.

In primates, ventral premotor and rostral inferior parietal neurons fire during the execution of hand and mouth actions. Some cells (called mirror neurons) also fire when hand and mouth actions are just observed. Mirror neurons provide a simple neural mechanism for understanding the actions of others. In humans, posterior inferior frontal and rostral inferior parietal areas have mirror properties. These human areas are relevant to imitative learning and social behavior. Indeed, the socially isolating condition of autism is associated with a deficit in mirror neuron areas. Strategies inspired by mirror neuron research recently have been used in the treatment of autism and in motor rehabilitation after stroke. Ann Neurol 2007.

People all over the world use their hands to communicate expressively. Autonomous gestures, also known as emblems, are highly social in nature, and convey conventionalized meaning without accompanying speech. To study the neural bases of cross-cultural social communication, we used single pulse transcranial magnetic stimulation (TMS) to measure corticospinal excitability (CSE) during observation of culture-specific emblems. Foreign Nicaraguan and familiar American emblems as well as meaningless control gestures were performed by both a Euro-American and a Nicaraguan actor. Euro-American participants demonstrated higher CSE during observation of the American compared to the Nicaraguan actor. This motor resonance phenomenon may reflect ethnic and cultural ingroup familiarity effects. However, participants also demonstrated a nearly significant (p = 0.053) actor by emblem interaction whereby both Nicaraguan and American emblems performed by the American actor elicited similar CSE, whereas Nicaraguan emblems performed by the Nicaraguan actor yielded higher CSE than American emblems. The latter result cannot be interpreted simply as an effect of ethnic ingroup familiarity. Thus, a likely explanation of these findings is that motor resonance is modulated by interacting biological and cultural factors.

The role of superior temporal cortex in speech comprehension is well established, but the complete network of regions involved in understanding language in ecologically valid contexts is less clearly understood. In a functional magnetic resonance imaging (fMRI) study, we presented 24 subjects with auditory or audiovisual narratives, and used model-free intersubject correlational analyses to reveal brain areas that were modulated in a consistent way across subjects during the narratives. Conventional comparisons to a resting state were also performed. Both analyses showed the expected recruitment of superior temporal areas, however, the intersubject correlational analyses also revealed an extended network of areas involved in narrative speech comprehension. Two findings stand out in particular. Firstly, many areas in the "default mode" network (typically deactivated relative to rest) were systematically modulated by the time-varying properties of the auditory or audiovisual input. These areas included the anterior cingulate and adjacent medial frontal cortex, and the posterior cingulate and adjacent precuneus. Secondly, extensive bilateral inferior frontal and premotor regions were implicated in auditory as well as audiovisual language comprehension. This extended network of regions may be important for higher-level linguistic processes, and interfaces with extralinguistic cognitive, affective, and interpersonal systems.

Over the last decade, many neuroimaging studies have assessed the human brain networks underlying action observation and imitation using a variety of tasks and paradigms. Nevertheless, questions concerning which areas consistently contribute to these networks irrespective of the particular experimental design, and how such processing may be lateralized remain unresolved. The current study aimed at identifying cortical areas consistently involved in action observation and imitation by combining activation likelihood estimation (ALE) meta-analysis with probabilistic cytoarchitectonic maps. Meta-analysis of 139 functional magnetic resonance and positron emission tomography experiments revealed a bilateral network for both action observation and imitation. Additional subanalyses for different effectors within each network revealed highly comparable activation patterns to the overall analyses on observation and imitation, respectively, indicating an indepedence of these findings from potential confounds. Conjunction analysis of action observation and imitation meta-analyses revealed a bilateral network within frontal premotor, parietal and temporo-occipital cortex. The most consistently rostral inferior parietal area was PFt providing evidence for possible a homology of this region to macaque area PF. The observation and imitation networks differed particularly with respect to the involvement of Broca's area: whereas both networks involved a caudo-dorsal part of BA 44, activation during observation was most consistent in a more rostro-dorsal location, i.e. dorsal BA 45, while activation during imitation was most consistent in a more ventro-caudal aspect, i.e. caudal BA 44. The present meta-analysis thus summarizes and amends previous descriptions of the human brain networks related to action observation and imitation.

There is much current debate about the existence of mirror neurons in humans. To identify mirror neurons in the inferior frontal gyrus (IFG) of humans, we used a repetition suppression paradigm while measuring neural activity with functional magnetic resonance imaging. Subjects either executed or observed a series of actions. Here we show that in the IFG, responses were suppressed both when an executed action was followed by the same rather than a different observed action and when an observed action was followed by the same rather than a different executed action. This pattern of responses is consistent with that predicted by mirror neurons and is evidence of mirror neurons in the human IFG.

OBJECTIVE: The mirror neuron system (MNS) is an observation-execution matching system activated, in humans, during action observation, motor learning, and imitation of action. We used functional MRI (fMRI) to investigate the properties of the MNS in patients with multiple sclerosis (MS). METHODS: Using a 3 tesla scanner, we acquired fMRI in 16 right-handed patients with relapsing-remitting MS and 14 controls. Two motor tasks were studied. The first consisted of repetitive flexion-extension of the last four fingers of the right hand (simple task) alternated to epochs of rest; the second (MNS task) consisted of observation of a movie showing the hand of another subject while performing the same task. RESULTS: During the simple task, compared to controls, patients with MS had more significant activations of the contralateral primary sensorimotor cortex and supplementary motor area. During the MNS task, both groups showed the activation of several visual areas, the infraparietal sulcus, and the inferior frontal gyrus (IFG), bilaterally. The IFG and the visual areas were significantly more active in patients than controls. The between-group interaction analysis showed that in patients with MS, part of the regions of the MNS were more active also during the simple task. CONCLUSIONS: This study suggests increased activation of the mirror neuron system in patients with multiple sclerosis (MS) with a normal level of function and widespread CNS damage. The potentialities of this system in facilitating clinical recovery in patients with MS and other neurologic conditions should be investigated.

Complex human behavior is organized around temporally distal outcomes. Behavioral studies based on tasks such as normal prehension, multi-step object use and imitation establish the existence of relative hierarchies of motor control. The retrieval errors in apraxia also support the notion of a hierarchical model for representing action in the brain. In this review, three functional brain imaging studies of action observation using the method of repetition suppression are used to identify a putative neural architecture that supports action understanding at the level of kinematics, object centered goals and ultimately, motor outcomes. These results, based on observation, may match a similar functional-anatomic hierarchy for action planning and execution. If this is true, then the findings support a functional-anatomic model that is distributed across a set of interconnected brain areas that are differentially recruited for different aspects of goal-oriented behavior, rather than a homogeneous mirror neuron system for organizing and understanding all behavior.

Recent research in cognitive neuroscience has found that observation of human actions activates the 'mirror system' and provokes automatic imitation to a greater extent than observation of non-biological movements. The present study investigated whether this human bias depends primarily on phylogenetic or ontogenetic factors by examining the effects of sensorimotor experience on automatic imitation of non-biological robotic, stimuli. Automatic imitation of human and robotic action stimuli was assessed before and after training. During these test sessions, participants were required to execute a pre-specified response (e.g. to open their hand) while observing a human or robotic hand making a compatible (opening) or incompatible (closing) movement. During training, participants executed opening and closing hand actions while observing compatible (group CT) or incompatible movements (group IT) of a robotic hand. Compatible, but not incompatible, training increased automatic imitation of robotic stimuli (speed of responding on compatible trials, compared with incompatible trials) and abolished the human bias observed at pre-test. These findings suggest that the development of the mirror system depends on sensorimotor experience, and that, in our species, it is biased in favour of human action stimuli because these are more abundant than non-biological action stimuli in typical developmental environments.

The highly convoluted and cytoarchitectonically diverse inferior frontal gyrus (IFG) of humans is known to be critically involved in a wide range of complex operations including speech and language processing. The neural circuitry that underlies these operations is not fully understood. We hypothesized that this neural circuitry includes functional connections within and between the three major IFG subgyri: the pars orbitalis, pars triangularis, and pars opercularis. To test this hypothesis we employed electrical stimulation tract-tracing techniques in 10 human patients undergoing surgical treatment for intractable epilepsy. The approach involved delivering repeated bipolar electrical stimuli to one site on the IFG while recording the electrical response evoked by that stimulus from a 64-contact grid overlying more distant IFG sites. In all subjects, stimulation of a site on one subgyrus evoked polyphasic potentials at distant sites, either on the same subgyrus or on an adjacent subgyrus. This provided prima facie evidence for a functional connection between the site of stimulation and the sites of the evoked response. The averaged evoked potentials tended to aggregate as response fields. The spatial spread of a response field indicated a divergent projection from the site of stimulation. When two or more sites were stimulated, the resulting evoked potentials exhibited different waveforms while the respective response fields could overlap substantially, suggesting that input from multiple sites converged but by engaging different neural circuits. The earliest deflection in the evoked potential ranged from 2 to 10 msec. No differences were noted between language-dominant and language-nondominant hemispheres. J. Comp. Neurol. 503:550-559, 2007.(c) 2007 Wiley-Liss, Inc.

We assessed the role of the human mirror neuron system (MNS) in complementary actions using functional magnetic resonance imaging while participants prepared to execute imitative or complementary actions. The BOLD signal in the right inferior frontal gyrus and bilateral inferior parietal lobes was greater during preparation of complementary than during imitative actions, suggesting that the MNS may be essential in dynamically coupling action observation to action execution.

The posterior inferior frontal gyrus (pIFG) and anterior inferior parietal lobule (aIPL) form the core regions of the human "mirror neuron system" that matches an observed movement onto its internal motor representation. We used event-related functional MRI to examine whether simple intransitive finger movements evoke "mirror activity" in the pIFG and aIPL. In separate sessions, participants either merely observed visuospatial stimuli or responded to them as quickly as possible with a spatially compatible finger movement. A picture of a relaxed hand with static dots on the tip of the index and little finger was continuously presented as high-level baseline. Four types of stimuli were presented in a pseudorandom order: a color change of a dot, a moving finger, a moving dot, or a simultaneous finger-dot movement. Dot movements were spatially and kinematically matched to finger movements. Participants were faster at imitating a finger movement than performing the same movement in response to a moving dot or a color change of a dot. Though imitative responses were facilitated, fMRI revealed no additional "mirror activity" in the pIFG and aIPL during the observation or imitation of finger movements as opposed to observing or responding to a moving dot. Mere observation of a finger movement alone failed to induce significant activation of the pIFG and aIPL. The lack of a signature of "mirror neuron activity" in the inferior frontoparietal cortex is presumably due to specific features of the task which may have favored stimulus-response mapping based on common spatial coding. We propose that the responsiveness of human frontoparietal mirror neuron areas to simple intransitive movements critically depends on the experimental context.

This paper addresses the problem of body mapping in robotic imitation where the demonstrator and imitator may not share the same embodiment [degrees of freedom (DOFs), body morphology, constraints, affordances, and so on]. Body mappings are formalized using a unified (linear) approach via correspondence matrices, which allow one to capture partial, mirror symmetric, one-to-one, one-to-many, many-to-one, and many-to-many associations between various DOFs across dissimilar embodiments. We show how metrics for matching state and action aspects of behavior can be mathematically determined by such correspondence mappings, which may serve to guide a robotic imitator. The approach is illustrated and validated in a number of simulated 3-D robotic examples, using agents described by simple kinematic models and different types of correspondence mappings.