Internal Motor Representation Research Articles

Mental imagery for addressing mechanisms underlying motor impairments in children with attention deficit hyperactivity disorder (ADHD).

Children with attention deficit hyperactivity disorder (ADHD) exhibit various degrees of motor and cognitive impairments in fine and gross motor skills. These impairments impact social functioning, while also hindering academic achievement, self-esteem, and participation. Specifically, motor impairments are not fully addressed by current therapies. For example, approximately 50% of children with ADHD exhibit significant motor impairments, as per clinical measures, while the other 50% experience more impairments in motor planning, execution and control than do typically developed (TD) children. Such findings indicate that ADHD-specific mechanisms may be underpinning motor impairments. In this paper, we outline ADHD impairments in motor planning, execution, and control, and the potential role of two such mechanisms: internal motor representation and timing perception. Next, we suggest mental imagery as an approach for treating ADHD motor impairments, potentially through addressing internal motor representation and timing perception.

Mu-desynchronization, N400 and corticospinal excitability during observation of natural and anatomically unnatural finger movements.

The action observation networks (AON) (or the mirror neuron system) are the neural underpinnings of visuomotor integration and play an important role in motor control. Besides, one of the main functions of the human mirror neuron system is recognition of observed actions and the prediction of its outcome through the comparison with the internal mental motor representation. Previous studies focused on the human mirror neurons (MNs) activation during object-oriented movements observation, therefore intransitive movements observation effects on MNs activity remains relatively little-studied. Moreover, the dependence of MNs activation on the biomechanical characteristics of observed movement and their biological plausibility remained highly underexplored. In this study we proposed that naturalness of observed intransitive movement can modulate the MNs activity. Event-related desynchronization (ERD) of sensorimotor electroencephalography (EEG) rhythms, N400 event-related potentials (ERPs) component and corticospinal excitability were investigated in twenty healthy volunteers during observation of simple non-transitive finger flexion that might be either biomechanically natural or unnatural when finger wriggled out toward the dorsal side of palm. We showed that both natural and unnatural movements caused mu/beta-desynchronization, which gradually increased during the flexion phase and returned to baseline while observation of extension. Desynchronization of the mu-rhythm was significantly higher during observation of the natural movements. At the same time, beta-rhythm was not found to be sensitive to the action naturalness. Also, observation of unnatural movements caused an increased amplitude of the N400 component registered in the centro-parietal regions. We suggest that the sensitivity of N400 to intransitive action observation with no explicit semantic context might imply the broader role of N400 sources within AON. Surprisingly, no changes in corticospinal excitability were found. This lack of excitability modulation by action observation could be related with dependence of the M1 activity on the observed movement phase.

Learning Actions From Natural Language Instructions Using an ON-World Embodied Cognitive Architecture.

Endowing robots with the ability to view the world the way humans do, to understand natural language and to learn novel semantic meanings when they are deployed in the physical world, is a compelling problem. Another significant aspect is linking language to action, in particular, utterances involving abstract words, in artificial agents. In this work, we propose a novel methodology, using a brain-inspired architecture, to model an appropriate mapping of language with the percept and internal motor representation in humanoid robots. This research presents the first robotic instantiation of a complex architecture based on the Baddeley's Working Memory (WM) model. Our proposed method grants a scalable knowledge representation of verbal and non-verbal signals in the cognitive architecture, which supports incremental open-ended learning. Human spoken utterances about the workspace and the task are combined with the internal knowledge map of the robot to achieve task accomplishment goals. We train the robot to understand instructions involving higher-order (abstract) linguistic concepts of developmental complexity, which cannot be directly hooked in the physical world and are not pre-defined in the robot's static self-representation. Our proposed interactive learning method grants flexible run-time acquisition of novel linguistic forms and real-world information, without training the cognitive model anew. Hence, the robot can adapt to new workspaces that include novel objects and task outcomes. We assess the potential of the proposed methodology in verification experiments with a humanoid robot. The obtained results suggest robust capabilities of the model to link language bi-directionally with the physical environment and solve a variety of manipulation tasks, starting with limited knowledge and gradually learning from the run-time interaction with the tutor, past the pre-trained stage.

Cortical Localization of the Sensory-Motor Transformation in a Whisker Detection Task in Mice

Responding to a stimulus requires transforming an internal sensory representation into an internal motor representation. Where and how this sensory-motor transformation occurs is a matter of vigorous debate. Here, we trained male and female mice in a whisker detection go/no-go task in which they learned to respond (lick) following a transient whisker deflection. Using single unit recordings, we quantified sensory-related, motor-related, and choice-related activities in whisker primary somatosensory cortex (S1), whisker region of primary motor cortex (wMC), and anterior lateral motor cortex (ALM), three regions that have been proposed to be critical for the sensory-motor transformation in whisker detection. We observed strong sensory encoding in S1 and wMC, with enhanced encoding in wMC, and a lack of sensory encoding in ALM. We observed strong motor encoding in all three regions, yet largest in wMC and ALM. We observed the earliest choice probability in wMC, despite earliest sensory responses in S1. Based on the criteria of having both strong sensory and motor representations and early choice probability, we identify whisker motor cortex as the cortical region most directly related to the sensory-motor transformation. Our data support a model of sensory encoding originating in S1, sensory amplification and sensory-motor transformation occurring within wMC, and motor signals emerging in ALM after the sensory-motor transformation.

Neurons Modulated by Action Execution and Observation in the Macaque Medial Parietal Cortex

The observation of an action evokes discharges in a rich network of cortical areas [1-14]. In the present study, we have evaluated the effect of grasp execution and of the observation of others' grasping on the activity of neurons in the medial parietal area V6A, an area of the reach-to-grasp network never explored to date in this regard. Although V6A neurons are typically active during one's own grasping execution but not while one observes another's grasping, a minority of neurons showed mirror properties, active both when monkeys performed the taskand when they observed it being performed by the experimenter. Recent studies have shown that the discharge of mirror neurons may vary from congruent to noncongruent [7, 10, 15-17], but most mirror neurons show a clear relation between the visual action they respond to and the motor response they code [10], thus matching the sensory description of an observed action with its corresponding internal motor representation. In all V6A putative mirrorneurons, instead, neural representations during execution and observation were highly dissimilar, discounting the possibility that V6A specifically encodes the grip type performed by another agent. Notably, we have found that in these neurons, the neural representation of an object changed according to whether grasping was allowed or performed and whether the object was the target of another agent's grasping. In other words, rather than code another agent's observed action, V6A neurons appear to primarily encode the relevance, in the grasping context, of the target object.

Reflections on the differential organization of mirror neuron systems for hand and mouth and their role in the evolution of communication in primates

It is now generally accepted that the motor system is not purely dedicated to the control of behavior, but also has cognitive functions. Mirror neurons have provided a new perspective on how sensory information regarding others' actions and gestures is coupled with the internal cortical motor representation of them. This coupling allows an individual to enrich his interpretation of the social world through the activation of his own motor representations. Such mechanisms have been highly preserved in evolution as they are present in humans, apes and monkeys. Recent neuroanatomical data showed that there are two different connectivity patterns in mirror neuron networks in the macaque: one is concerned with sensorimotor transformation in relation to reaching and hand grasping within the traditional parietal-premotor circuits; the second one is linked to the mouth/face motor control and the new data show that it is connected with limbic structures. The mouth mirror sector seems to be wired not only for ingestive behaviors but also for orofacial communicative gestures and vocalizations. Notably, the hand and mouth mirror networks partially overlap, suggesting the importance of hand-mouth synergies not only for sensorimotor transformation, but also for communicative purposes in order to better convey and control social signals.

EFFECT OF OBSERVING DIFFERENT MODEL DEMONSTRATIONS ON THE DEVELOPMENT OF INTERNAL MOTOR REPRESENTATION

This study was designed to investigate the relative effects of observing video, point-light, and stick-figure model demonstrations on the development of internal motor representation of a highly complex sport skill. Forty one novice female and male students were randomly assigned to video, point-light, stick-figure and no-demonstration control groups. Internal motor representation was evaluated by a computer - based test using the error detection paradigm. Participants had to view ten digital photos representing different phases of a Baseball pitching and were instructed to identify by mouse-clicking various movement errors. The test was respectively performed after 5 familiarization trials (pre-test), 3 acquisition blocks of 10 trials (post-test) and one week without practice (retention test). Participants observed related model demonstrations prior to each acquisition block. Results showed that demonstration groups improved their scores in either post-test or retention test; however these improvements were not statistically significant. Moreover, there was no significant difference between groups either in post-test or retention test. The findings are discussed in terms of difficulty of errors, insufficient amount of physical or observational practice, and small sample size.

Dynamical entrainment of corticospinal excitability during rhythmic movement observation: a Transcranial Magnetic Stimulation study.

Spontaneous modulations of corticospinal excitability during action observation have been interpreted as evidence for the activation of internal motor representations equivalent to the observed action. Alternatively or complementary to this perspective, growing evidence shows that motor activity during observation of rhythmic movements can be modulated by direct visuomotor couplings and dynamical entrainment. In-phase and anti-phase entrainment spontaneously occur, characterized by cyclic movements proceeding simultaneously in the same (in-phase) or opposite (anti-phase) direction. Here we investigate corticospinal excitability during the observation of vertical oscillations of an index finger using Transcranial Magnetic Stimulation (TMS). Motor-evoked potentials (MEPs) were recorded from participants' flexor and extensor muscles of the right index finger, placed in either a maximal steady flexion or extension position, with stimulations delivered at maximal flexion, maximal extension or mid-trajectory of the observed finger oscillations. Consistent with the occurrence of dynamical motor entrainment, increased and decreased MEP responses - suggesting the facilitation of stable in-phase and anti-phase relations but not an unstable 90° phase relation - were found in participants' flexors. Anti-phase motor facilitation contrasts with the activation of internal motor representation as it involves activity in the motor system opposite from activity required for the execution of the observed movement. These findings demonstrate the relevance of dynamical entrainment theories and methods for understanding spontaneous motor activity in the brain during action observation and the mechanisms underpinning coordinated movements during social interaction.

Parietal Cortices and Body Information

Proprioceptive signals originating from skeletal muscles and joints contribute to the formation of both the human body schema and the body image. In this chapter, we introduce various types of bodily illusions that are elicited by proprioceptive inputs, and we discuss distinct functions implemented by different parietal cortices. First, we illustrate the primary importance of the motor network in the processing of proprioceptive (kinesthetic) signals originating from muscle spindles. Next, we argue that the right inferior parietal cortex, in concert with the inferior frontal cortex (both regions connected by the inferior branch of the superior longitudinal fasciculus-SLF III), may be involved in the conscious experience of body image. Further, we hypothesize other functions of distinct parietal regions: the association between internal hand motor representation with external object representation in the left inferior parietal cortex, visuo-kinesthetic processing in the bilateral posterior parietal cortices, and the integration of somatic signals from different body parts in the higher-order somatosensory parietal cortices. Our results indicate that a distinct parietal region, in concert with its anatomically and functionally connected frontal regions, probably plays specialized roles in the processing of body-related information.

Perceptual decisions regarding object manipulation are selectively impaired in apraxia or when tDCS is applied over the left IPL

This study evaluated whether apraxia can be understood as due to impaired motor representations or motor imagery necessary for appropriate object-use, imitation, and pantomime. The causal role of the left inferior parietal lobe (IPL), which is heavily implicated in apraxia, is also evaluated. These processes are appraised in light of the proposed ventro-dorsal sub-stream of the classic two visual pathway model, where perceptual information from the ventral stream and the dorsal action stream are integrated and essential for object manipulation. Using a task assessing object-use perception, stroke patients with apraxia demonstrated a selective deficit during perceptual decisions reliant on the integration of visible and known object properties to select the appropriate grasp for object-use. This deficit increased with apraxia severity. A dissociation was evident in these patients showing intact non-motoric perceptual decisions regarding the functional semantic relationship between two objects in the absence of the actor (e.g. how a hammer hits a nail). Converging evidence was found using a modified version of the same task in a neuromodulation study that directly targeted the left IPL in healthy participants using transcranial direct current stimulation (tDCS). Application of inhibitory stimulation over the left IPL reduced performance during perceptual decisions regarding object manipulation whilst performance was unaffected during functional semantic decisions. Excitatory stimulation of the left IPL did not affect performance in either task. Combined, these results suggest that the left inferior parietal lobe is critical for motor imagery, and that apraxia may be caused by an inability to use internal motor representations of object manipulation. These results are discussed in terms of motoric and non-motoric perceptual processes and the proposal of an additional ventro-dorsal sub-stream within the dorsal and ventral visual pathways model.

Evidence of motor-control difficulties in children with attention deficit hyperactivity disorder, explored through a hierarchical motor-systems perspective

ABSTRACTIntroduction: Attention deficit hyperactivity disorder (ADHD) may reflect a disorder of neural systems that regulate motor control. The current study investigates motor dysfunction in children with ADHD using a hierarchical motor-systems perspective where frontal–striatal/“medial” brain systems are viewed as regulating parietal/“lateral” brain systems in a top down manner, to inhibit automatic environmentally driven responses in favor of goal-directed behavior. It was hypothesized that due to frontal–striatal hypoactivation, children with ADHD would have difficulty with higher order motor control tasks felt to be dependent on these systems, yet have preserved general motor function. Method: A total of 63 children—ADHD and matched controls—completed experimental motor tasks that required maintenance of internal motor representations and the ability to inhibit visually driven responses. Children also completed a measure of motor inhibition, and a portion of the sample completed general motor function tasks. Results: On motor tasks that required them to maintain internal motor representations and to inhibit automatic motor responses, children with ADHD had significantly greater difficulty than controls, yet on measures of general motor dexterity, their performance was comparable. Children with ADHD displayed significantly greater intraindividual (subject) variability than controls. Intraindividual variability (IIV) contributed to variations in performance across the motor tasks, but did not account for all of the variance on all tasks. Conclusions: These findings suggest that children with ADHD may be more controlled by external stimuli than by internally represented information, possibly due to dysfunction of the medial motor system. However, it is likely that children with ADHD also display general motor-execution problems (as evidenced by IIV findings), suggesting that atypicalities may extend to both medial and lateral motor systems. Findings are interpreted within the context of contemporary theories regarding motor dysfunction in ADHD, and implications for understanding externalizing behaviors in ADHD are discussed.

Neural basis of learning from television in young children

Abstract It has been shown that preschool children can learn as well from video presentations as from live presentations in word acquisition, action imitation, and object searching. Several cognitive theories have been proposed to explain the developmental changes accompanying the onset of learning from TV, but the underlying neural mechanism is unclear. One possible mechanism is the mirror-matching system, in which observation of action recruits an observer׳s internal motor representation of the same action. Using near-infrared spectroscopy, we examined whether sensorimotor regions are activated when children learn rule-based actions from a live model versus a televised model. The results revealed that children learned the actions equally well from both live and televised models, but activations in the left sensorimotor regions were marginally stronger when learning from the live model than from the televised model. These results may contribute to our understanding of how to support children׳s learning from television.

Efficient foot motor control by Neymar’s brain

How very long-term (over many years) motor skill training shapes internal motor representation remains poorly understood. We provide valuable evidence that the football brain of Neymar da Silva Santos Júnior (the Brasilian footballer) recruits very limited neural resources in the motor-cortical foot regions during foot movements. We scanned his brain activity with a 3-tesla functional magnetic resonance imaging (fMRI) while he rotated his right ankle at 1 Hz. We also scanned brain activity when three other age-controlled professional footballers, two top-athlete swimmers and one amateur footballer performed the identical task. A comparison was made between Neymar’s brain activity with that obtained from the others. We found activations in the left medial-wall foot motor regions during the foot movements consistently across all participants. However, the size and intensity of medial-wall activity was smaller in the four professional footballers than in the three other participants, despite no difference in amount of foot movement. Surprisingly, the reduced recruitment of medial-wall foot motor regions became apparent in Neymar. His medial-wall activity was smallest among all participants with absolutely no difference in amount of foot movement. Neymar may efficiently control given foot movements probably by largely conserving motor-cortical neural resources. We discuss this possibility in terms of over-years motor skill training effect, use-dependent plasticity, and efficient motor control.

Bimanual coupling paradigm as an effective tool to investigate productive behaviors in motor and body awareness impairments

When humans move simultaneously both hands strong coupling effects arise and neither of the two hands is able to perform independent actions. It has been suggested that such motor constraints are tightly linked to action representation rather than to movement execution. Hence, bimanual tasks can represent an ideal experimental tool to investigate internal motor representations in those neurological conditions in which the movement of one hand is impaired. Indeed, any effect on the “moving” (healthy) hand would be caused by the constraints imposed by the ongoing motor program of the ‘impaired’ hand. Here, we review recent studies that successfully utilized the above-mentioned paradigms to investigate some types of productive motor behaviors in stroke patients. Specifically, bimanual tasks have been employed in left hemiplegic patients who report illusory movements of their contralesional limbs (anosognosia for hemiplegia). They have also been administered to patients affected by a specific monothematic delusion of body ownership, namely the belief that another person’s arm and his/her voluntary action belong to them. In summary, the reviewed studies show that bimanual tasks are a simple and valuable experimental method apt to reveal information about the motor programs of a paralyzed limb. Therefore, it can be used to objectively examine the cognitive processes underpinning motor programming in patients with different delusions of motor behavior. Additionally, it also sheds light on the mechanisms subserving bimanual coordination in the intact brain suggesting that action representation might be sufficient to produce these effects.

Motor resonance mechanisms are preserved in Alzheimer’s disease patients

This study aimed to better characterize the sensorimotor mechanisms underlying motor resonance, namely the relationship between motion perception and movement production in patients suffering from Alzheimer’s disease (AD). This work first gives a kinematic description of AD patients’ upper limb movements, then it presents a simple paradigm in which a dot with different velocities is moved in front of the participant who is instructed to point to its final position when it stopped. AD patients’ actions, as well as healthy elderly participants, were similarly influenced by the dot velocity, suggesting that motor resonance mechanisms are not prevented by pathology. In contrast, only patients had anticipatory motor response: i.e. they started moving before the end of the stimulus motion, unlike what was requested by the experimenter. While the automatic imitation of the stimulus suggests an intact ability to match the internal motor representations with that of the visual model, the uncontrolled motion initiation would indicate AD patients’ deficiency to voluntarily inhibit response production. These findings might open new clinical perspectives suggesting innovative techniques in training programs for people with dementia. In particular, the preservation of the motor resonance mechanisms, not dependent on conscious awareness, constitutes an intact basis upon which clinicians could model both physical and cognitive interventions for healthy elderly and AD patients. Furthermore, the evaluation of the inhibitory functions, less sensitive to the level of education than other methods, might be useful for screening test combined with the traditional AD techniques. However, further investigations to understand if this feature is specific to AD or is present also in other neurodegenerative diseases are needed.

Delayed monitoring of accuracy errors compared to commission errors in ACC

Error detection is essential for monitoring performance and preparing subsequent behavioral adjustments, and is associated with specific neural responses in the anterior cingulate cortex (ACC). To investigate whether different brain mechanisms subserve the processing of commission vs. accuracy errors, we recorded EEG in adult participants while they performed a novel speeded GO-NOGO aiming task (“the Shoot-NoShoot paradigm”). Our ERP results show that commission errors (responding during NOGO trials) elicited a classical error-related negativity (ERN) component, followed by an error-related positivity (Pe), as well as a negativity peaking before response onset (pre-ERN). By contrast, spatial accuracy errors elicited a feedback-related negativity (FRN), which correlated with the spatial discrepancy between response and target position across subjects. Fast hits also elicited a pre-ERN but no ERN, suggesting that this pre-response monitoring component might be related to the detection of error likelihood. Although source analysis revealed similar generators in ACC for these different error-related negativities, the respective timing differed, suggesting that commission errors are detected rapidly based on internal motor representations, whereas the detection of accuracy errors in ACC relies on the additional and swift processing of external visual information.

How Frontoparietal Brain Regions Mediate Imitative and Complementary Actions: An fMRI Study

The ‘mirror neuron system’ (MNS), located within inferior parietal lobe (IPL) and inferior frontal gyrus (IFG), creates an internal motor representation of the actions we see and has been implicated in imitation. Recently, the MNS has been implicated in non-identical responses: when the actions we must execute do not match those that we observe. However, in such conflicting situations non action-specific cognitive control networks also located in frontoparietal regions may be involved. In the present functional magnetic resonance imaging (fMRI) study participants made both similar and dissimilar actions within two action contexts: imitative and complementary. We aimed to determine whether activity within IPL/IFG depends on (i) responding under an imitative versus complementary context (ii) responding with similar versus dissimilar responses, and (iii) observing hand actions versus symbolic arrow cue stimuli. Activity within rIPL/rIFG regions was largest during observation of hand actions compared with arrow cues. Specifically, rIPL/rIFG were recruited only during the imitative context, when participants responded with similar actions. When responding to symbolic arrow cues, rIPL/rIFG activity increased during dissimilar responses, reflecting increased demands placed on general cognitive control mechanisms. These results suggest a specific role of rIPL/rIFG during imitation of hand actions, and also a general role of frontoparietal areas in mediating dissimilar responses to both hand actions and symbolic stimuli. We discuss our findings in relation to recent work that has examined the role of frontoparietal brain structures in joint-actions and inter-actor cooperation. We conclude that the specific brain regions identified here to show increased activation during action observation conditions are likely to form part of a mechanism specifically involved in matching observed actions directly with internal motor plans. Conversely, observation of arrow cues recruited part of a wider cognitive control network involved in the rapid remapping of stimulus-response associations.

Mirror systems.

Mirror neurons are a class of visuomotor neurons, discovered in the monkey premotor cortex and in an anatomically connected area of the inferior parietal lobule, that activate both during action execution and action observation. They constitute a circuit dedicated to match actions made by others with the internal motor representations of the observer. It has been proposed that this matching system enables individuals to understand others' behavior and motor intentions. Here we will describe the main features of mirror neurons in monkeys. Then we will present evidence of the presence of a mirror system in humans and of its involvement in several social-cognitive functions, such as imitation, intention, and emotion understanding. This system may have several implications at a cognitive level and could be linked to specific social deficits in humans such as autism. Recent investigations addressed the issue of the plasticity of the mirror neuron system in both monkeys and humans, suggesting also their possible use in rehabilitation. WIREs Cogn Sci 2011 2 22-38 DOI: 10.1002/wcs.89 For further resources related to this article, please visit the WIREs website.

Modulation of the motor area activity during observation of a competitive game

Watching competitive games is a pervasive entertainment in humans and likely to be facilitated by our social cognitive abilities. We investigated the brain activity during observation of a competitive game by using near-infrared spectroscopy. The result showed that activity in the motor area was significantly greater when the individual's favored player won, compared with when the same player lost. The motor area was also activated when the individuals themselves performed the same action, showing the mirror neuron system property. Our results first showed that the motor area activity during observation of competitive games was modulated by the outcome of the game. We suggest that the observer's brain is more likely to share the winner's internal motor representation than that of the loser.

How moving objects become animated: The human mirror neuron system assimilates non-biological movement patterns

The so-called mirror neuron system (MNS) responds when humans observe actions performed by a member of their own species. This activity is understood as an internal motor representation of the observed movement pattern. By contrasting meaningless human hand movements with meaningless artificial movements of objects in space, we tested the claim that exclusively movements belonging to the human motor repertoire have direct access to the MNS. Eighteen participants observed video clips of moving hands and objects while the hemodynamic response was recorded with functional magnetic resonance imaging. Second-level analysis of the hemodynamic response revealed substantially overlapping activation patterns for both types of movements including relevant structures of the MNS (bilateral premotor and parietal areas, occipito-temporal junction, postcentral gyrus and the right superior temporal sulcus). This suggests that perceptual processing of moving hands and objects recruits similar and overlapping cortical networks. Direct comparison of the two movement types revealed stronger activations for hand movements mainly in structures of the MNS suggesting an “expertise effect”. Overall, our results provide evidence that observing movements not explicitly belonging to the human motor repertoire can activate the human MNS, most likely because an association with a biological movement is evoked.