The Human Mirror Neuron System and Embodied Representations

Differences between Monolinguals and Bilinguals in Phonetic and Phonological Learning and the Connection with Auditory Sensory Memory

Bilingualism has been linked with improved function regarding certain aspects of linguistic processing, e.g., novel word acquisition and learning unfamiliar sound patterns. Two non mutually-exclusive approaches might explain these results. One is related to executive function, speculating that more effective learning is achieved through actively choosing relevant information while inhibiting potentially interfering information. While still controversial, executive function enhancements attributed to bilingual experience have been reported for decades. The other approach, understudied to date, emphasizes the role of sensory mechanisms, specifically auditory sensory memory. Bilinguals outperformed monolinguals in tasks involving auditory processing and episodic memory recall, but the questions whether (1) bilinguals' auditory sensory memory skills are also enhanced, and (2) phonetic skill and auditory sensory memory are correlated, remain open, however. Our study is innovative in investigating phonetic learning skills and auditory sensory memory in the same speakers from two groups: monolinguals and early bilinguals. The participants were trained and tested on an artificial accent of English and their auditory sensory memory was assessed based on a digit span task. The results demonstrated that, compared to monolinguals, bilinguals exhibit enhanced auditory sensory memory and phonetic and phonological learning skill, and a correlation exists between them.

Physiological Response of Imagery Running with or without an Avatar in 3D Virtual Reality: A Preliminary Study

OBJECTIVES The present study is aimed at observing the physiological response imagery running with an avatar in 3D virtual reality (VR) and to explore the differences in physiological responses between imagery running with and without an avatar in 3D VR.METHODS We randomly assigned 32 healthy adults to either a group with Avatar (n = 19) or a group without (n = 13). The group with avatar performed imagery exercise with an avatar in 3D VR and the group without Avatar performed it without an avatar in 3D VR. Both groups were instructed to mentally imagine performing running in VR without executing actual physical movements. We recorded electro-physiological data before, during, and after the 20-min intervention. We also measured the participants’ level of presence and intensity of experienced cybersickness.RESULTS In the group with Avatar, all physiological responses increased from the resting to the intervention period. The group with Avatar also showed a higher level of presence and fewer cybersickness symptoms than the group without Avatar.CONCLUSIONS The results suggest imagery running with an avatar in 3D VR might be effective as an alternative exercise.

Prosody production networks are modulated by sensory cues and social context

The neurobiology of emotional prosody production is not well investigated. In particular, the effects of cues and social context are not known. The present study sought to differentiate cued from free emotion generation and the effect of social feedback from a human listener. Online speech filtering enabled functional magnetic resonance imaging during prosodic communication in 30 participants. Emotional vocalizations were (i) free, (ii) auditorily cued, (iii) visually cued or (iv) with interactive feedback. In addition to distributed language networks, cued emotions increased activity in auditory and—in case of visual stimuli—visual cortex. Responses were larger in posterior superior temporal gyrus at the right hemisphere and the ventral striatum when participants were listened to and received feedback from the experimenter. Sensory, language and reward networks contributed to prosody production and were modulated by cues and social context. The right posterior superior temporal gyrus is a central hub for communication in social interactions—in particular for interpersonal evaluation of vocal emotions.

Vibrato changes following imagery

OBJECTIVES

This study investigated acoustic change in singers' vibrato following imagery and non-imagery tasks.

STUDY DESIGN

The study used a fully randomized cross-over (six conditions × two times) block design, in which each singer received each intervention in random order. Data were analyzed using the general linear model (GLM). Main effects for time and condition and interaction effects (time × condition) were calculated for each dependent measure.

METHODS

Six classically trained female singers recorded an 8-bar solo before and after three nonvocal, 25 minute tasks. Each singer performed the tasks in a different randomized order in a single sitting. Task 1 involved imagery of the breath directed up and down as far from the larynx as possible; Task 2 used Braille music code, enabling the singer to engage in tactile, kinesthetic and visual imagery related to music but unrelated to breath function; Task 3 was a nonimagery activity requiring the completion of a cloze passage about breath function. From the 11 longest notes in each solo, spectrograms of the partials were produced and assessed for pre- to post-test changes in vibrato rate, vibrato extent, and sound pressure level (SPL).

RESULTS

Only the breathing imagery task produced significantly more moderate and regular vibrato rates. Vibrato extent was not responsive to any intervention.

CONCLUSIONS

Findings indicate that breathing imagery regulates singers' vibrato in a manner consistent with that of a more proficient, warmed-up voice.

Early semantic and phonological effects on temporal- and muscle-specific motor resonance

Previous studies using functional magnetic resonance imaging and transcranial magnetic stimulation (TMS) explored the relationships between linguistic processing and motor resonance, i.e. the activation of the motor system while perceiving others performing an action. These studies have mainly investigated a specific linguistic domain, i.e. semantics, whereas phonology has been largely neglected. Here we used single-pulse TMS to compare the effects of semantic and phonological processing with motor resonance effects. We applied TMS to the primary motor hand area while subjects observed object-oriented actions and performed semantic and phonological tasks related to the observed action. Motor evoked potentials were recorded in two hand muscles, one of them more involved in the execution of the observed actions than the other one, at three different timepoints (0, 200 and 400 ms after stimulus onset). The results demonstrated increased corticospinal excitability that was muscle-specific (i.e. restricted to the hand muscle involved in the observed action), hemisphere-specific (left), and time-specific (400 ms after stimulus onset). The results suggest an additive effect of independent semantic and phonological processing on motor resonance. The novel phonological effect reported here expands the links between language and the motor system and is consistent with a theory of shared control for hand and mouth. Furthermore, the timing of the semantic effect suggests that motor activation during semantic processing is not an 'epiphenomenon' but rather is essential to the construction of meaning.

Neural representations of unfamiliar objects are modulated by sensorimotor experience

Sensory/functional accounts of semantic memory organization emphasize that object representations in the brain reflect the modalities involved in object knowledge acquisition. The present study aimed to elucidate the impact of different types of object-related sensorimotor experience on the neural representations of novel objects. Sixteen subjects engaged in an object matching task while their brain activity was assessed with functional magnetic resonance imaging (fMRI), before and after they acquired knowledge about previously unfamiliar objects. In three training sessions subjects learned about object function, actively manipulating only one set of objects (manipulation training objects, MTO), and visually exploring a second set (visual training objects, VTO). A third object set served as control condition and was not part of the training (no training objects, NTO). While training-related activation increases were observed in the fronto-parietal cortex for both VTO and MTO, post training activity in the left inferior/middle frontal gyrus and the left posterior inferior parietal lobule was higher for MTO than VTO and NTO. As revealed by Dynamic Causal Modeling of effective connectivity between the regions with enhanced post training activity, these effects were likely caused, respectively, by a down-regulation of a fronto-parietal tool use network in response to VTO, and by an increased connectivity for MTO. This pattern of findings indicates that the modalities involved in sensorimotor experience influence the formation of neural representations of objects in semantic memory, with manipulation experience specifically yielding higher activity in regions of the fronto-parietal cortex.

Observed effector-independent motor learning by observing

A compelling idea in cognitive neuroscience links motor control and action observation. Recent work supports the idea that a link exists not just between action observation and action planning, but between observation and motor learning. Several studies support the idea that cortical regions that underlie active motor learning also play a role in motor learning by observing. The goal of the present study was to test whether motor learning by observing is effector dependent (as in active motor learning) or effector independent (as in studies of action observation and mirror neurons). Right-handed human subjects observed a video depicting another individual learning to reach to visual targets in a force field (FF). The video showed reaching in a clockwise FF (CWFF) or a counter-clockwise FF (CCWFF), and depicted an individual reaching with the right or left arm. After observation, all subjects were asked to reach in a CWFF, using their right arm. As in our prior studies, subjects who observed a CWFF prior to the CWFF test performed better than subjects who observed a CCWFF. We show here that this effect was seen both when observers watched others reach using their right arm, and when observers watched others learning to reach using the left arm. These results suggest that information about novel forces learned through observation is represented in an effector-independent coordinate frame, and are consistent with the idea that the brain links not only observation and movement, but motor learning as well, through abstract representations of actions.

Individual differences in audio-vocal speech imitation aptitude in late bilinguals: functional neuro-imaging and brain morphology

An unanswered question in adult language learning or late bi and multilingualism is why individuals show marked differences in their ability to imitate foreign accents. While recent research acknowledges that more adults than previously assumed can still acquire a "native" foreign accent, very little is known about the neuro-cognitive correlates of this special ability. We investigated 140 German-speaking individuals displaying varying degrees of "mimicking" capacity, based on natural language text, sentence, and word imitations either in their second language English or in Hindi and Tamil, languages they had never been exposed to. The large subject pool was strictly controlled for previous language experience prior to magnetic resonance imaging. The late-onset (around 10 years) bilinguals showed significant individual differences as to how they employed their left-hemisphere speech areas: higher hemodynamic activation in a distinct fronto-parietal network accompanied low ability, while high ability paralleled enhanced gray matter volume in these areas concomitant with decreased hemodynamic responses. Finally and unexpectedly, males were found to be more talented foreign speech mimics.

Reading action word affects the visual perception of biological motion

In the present study, we investigate whether reading an action-word can influence subsequent visual perception of biological motion. The participant's task was to perceptually judge whether a human action identifiable in the biological motion of a point-light display embedded in a high density mask was present or not in the visual sequence, which lasted for 633 ms on average. Prior to the judgement task, participants were exposed to an abstract verb or an action verb for 500 ms, which was related to the human action according to a congruent or incongruent semantic relation. Data analysis showed that correct judgements were not affected by action verbs, whereas a facilitation effect on response time (49 ms on average) was observed when a congruent action verb primed the judgement of biological movements. In relation with the existing literature, this finding suggests that the perception, the planning and the linguistic coding of motor action are subtended by common motor representations.

How can surgical training benefit from theories of skilled motor development, musical skill acquisition and performance psychology?

Trainee surgeons must acquire expert status in the context of reduced hours, reduced operating room time and the need to learn complex skills involving screen-mediated techniques, computers and robotics. Ever more sophisticated surgical simulation strategies have been helpful in providing surgeons with the opportunity to practise, but not all of these strategies are widely available. Similarities in the motor skills required in skilled musical performance and surgery suggest that models of music learning, and particularly skilled motor development, may be applicable in training surgeons. More attention should be paid to factors associated with optimal arousal and optimal performance in surgical training - lessons learned from helping anxious musicians optimise performance and manage anxiety may also be transferable to trainee surgeons. The ways in which the trainee surgeon moves from novice to expert need to be better understood so that this process can be expedited using current knowledge in other disciplines requiring the performance of complex fine motor tasks with high cognitive load under pressure.

Functional connectivity of the superior human temporal sulcus in the brain resting state at 3T

INTRODUCTION

The superior temporal sulcus (STS) constitutes a polymodal associative area providing higher-order visual representation of other's action and emotion, necessary for imitation, empathizing, and mentalizing. In monkeys, STS is connected with the cerebellum, which is also involved in motor, emotional, and cognitive functions. However, in humans, very few data are available concerning the functional connectivity of polymodal STS in general and its functional links with the cerebellum, in particular. This study was therefore designed to investigate the intrinsically connected network of STS during the brain resting state with possible involvement of the cerebellum.

METHODS

Data from 14 right-handed healthy volunteers were acquired at rest and analyzed by region of interest (ROI)-based functional connectivity. Blood-oxygen-level-dependent (BOLD) signal fluctuations of separate six ROIs located in the right and left posterior, medial, and anterior STS were successively used to identify significant temporal correlations with BOLD signal fluctuations of other brain regions.

RESULTS

Low-frequency BOLD signals of the right and left posterior, medial, and lateral STS share a common bilateral circuit encompassing the ventrolateral prefrontal, premotor/motor, insular, parietal temporal, occipital, and cerebellar cortices (lobules VI/VIIA), thalamus, and striatum.

CONCLUSION

The STS-centered network (1) is intrinsically connected during the brain resting, (2) encompasses the whole caudalmost two thirds of STS, (3) may partly represent the whole STS structural connectivity, and includes the motor and cognitive neocerebellum (lobules VI/VIIA).

Modulation of cortical motor outputs by the symbolic meaning of visual stimuli

The observation of an action modulates motor cortical outputs in specific ways, in part through mediation of the mirror neuron system. Sometimes we infer a meaning to an observed action based on integration of the actual percept with memories. Here, we conducted a series of experiments in healthy adults to investigate whether such inferred meanings can also modulate motor cortical outputs in specific ways. We show that brief observation of a neutral stimulus mimicking a hand does not significantly modulate motor cortical excitability (Study 1) although, after prolonged exposure, it can lead to a relatively nonspecific modulation (Study 2). However, when such a neutral stimulus is preceded by exposure to a hand stimulus, the latter appears to serve as a prime, perhaps enabling meaning to the neutral stimulus, which then modulates motor cortical excitability in accordance with mirror neuron-driving properties (Studies 2 and 3). Overall results suggest that a symbolic value ascribed to an otherwise neutral stimulus can modulate motor cortical outputs, revealing the influence of top-down inputs on the mirror neuron system. These findings indicate a novel aspect of the human mirror neuron system: an otherwise neutral stimulus can acquire specific mirror neuron-driving properties in the absence of a direct association between motor practice and perception. This significant malleability in the way that the mirror neuron system can code otherwise meaningless (i.e. arbitrarily associated) stimuli may contribute to coding communicative signals such as language. This may represent a mirror neuron system feature that is unique to humans.

Component Neural Systems for the Creation of Emotional Memories during Free Viewing of a Complex, Real-World Event

To investigate the neural systems that contribute to the formation of complex, self-relevant emotional memories, dedicated fans of rival college basketball teams watched a competitive game while undergoing functional magnetic resonance imaging (fMRI). During a subsequent recognition memory task, participants were shown video clips depicting plays of the game, stemming either from previously-viewed game segments (targets) or from non-viewed portions of the same game (foils). After an old–new judgment, participants provided emotional valence and intensity ratings of the clips. A data driven approach was first used to decompose the fMRI signal acquired during free viewing of the game into spatially independent components. Correlations were then calculated between the identified components and post-scanning emotion ratings for successfully encoded targets. Two components were correlated with intensity ratings, including temporal lobe regions implicated in memory and emotional functions, such as the hippocampus and amygdala, as well as a midline fronto-cingulo-parietal network implicated in social cognition and self-relevant processing. These data were supported by a general linear model analysis, which revealed additional valence effects in fronto-striatal-insular regions when plays were divided into positive and negative events according to the fan's perspective. Overall, these findings contribute to our understanding of how emotional factors impact distributed neural systems to successfully encode dynamic, personally-relevant event sequences.

The mirror neuron system: a neural substrate for methods in stroke rehabilitation

Mirror neurons found in the premotor and parietal cortex respond not only during action execution, but also during observation of actions being performed by others. Thus, the motor system may be activated without overt movement. Rehabilitation of motor function after stroke is often challenging due to severity of impairment and poor to absent voluntary movement ability. Methods in stroke rehabilitation based on the mirror neuron system--action observation, motor imagery, and imitation--take advantage of this opportunity to rebuild motor function despite impairments, as an alternative or complement to physical therapy. Here the authors review research into each condition of practice, and discuss the relevance of the mirror neuron system to stroke recovery.