Motor Repertoire Research Articles

Analysis of Palmar Grasp Strength in Term Newborns

Background: The normal motor development includes an increase of the motor repertoire throughout life. Aim: Analyze the palmar grasp strength in term newborns (TNB) during the first 72 hours after birth. Methods: Cohort prospective study, in healthy TNB. Palmar grasp strength was assessed by a simple, noninvasive and painless procedure, with the equipment M-Flex®. During the first 24-72 hours after birth, each newborn underwent a single assessment, consisting of hand width anthropometric measures and palmar grasp strength testing, where the equipment‘s rubber pad was placed at the base of fingers number 3, 4, and 5 for up to 30 seconds, performing three measurements for each hand. Assessed variables: age, time and maximum palmar grasp strength. ANOVA two-way parametric test was used considering p< 0.05 as a significant value. The study was approved by the Ethics Committee. Results: 216 newborns were included: 44 were 24 hours old, 97 were 48 hours old and 75 were 72 hours old; mean gestational age was 39 weeks (SD=1.47) and mean weight was 3167g (SD=462.9). The 72 hour-old newborns presented significantly higher palmar grasp strength when compared to 24 hour-old (F=0.2277, p=0.01) and the 48 hour-old ones (F=0.06330, p=0.01). Conclusions: There was a significant increase in the palmar grasp strength among the TNB between 24 and 72 hours after birth, indicating the integrity and maturation of brain cortex. Palmar grasp strength measurement may constitute an important resource for early neonatal neurologic assessment.

Motor repertoire and neurological outcome in preterm infants

Motor repertoire and neurological outcome in preterm infants

Robotic movement preferentially engages the action observation network

As humans, we gather a wide range of information about other people from watching them move. A network of parietal, premotor, and occipitotemporal regions within the human brain, termed the action observation network (AON), has been implicated in understanding others' actions by means of an automatic matching process that links observed and performed actions. Current views of the AON assume a matching process biased towards familiar actions; specifically, those performed by conspecifics and present in the observer's motor repertoire. In this study, we test how this network responds to form and motion cues when observing natural human motion compared to rigid robotic-like motion across two independent functional neuroimaging experiments. In Experiment 1, we report the surprising finding that premotor, parietal, occipitotemporal regions respond more robustly to rigid, robot-like motion than natural human motion. In Experiment 2, we replicate and extend this finding by demonstrating that the same pattern of results emerges whether the agent is a human or a robot, which suggests the preferential response to robot-like motion is independent of the agent's form. These data challenge previous ideas about AON function by demonstrating that the core nodes of this network can be flexibly engaged by novel, unfamiliar actions performed by both human and non-human agents. As such, these findings suggest that the AON is sensitive to a broader range of action features beyond those that are simply familiar.

The motor repertoire of extremely low-birthweight infants at term in relation to their neurological outcome

The aim of this study was to assess the motor repertoire of extremely low-birthweight infants at term-equivalent age (TEA), in relation to their neurological outcome. Using Prechtl's method, we assessed both the quality of general movements and a detailed motor optimality score in 13 extremely low-birthweight infants (four males; nine females; mean gestational age 27.9wks, SD 2.9wks; mean birthweight 798g, SD 129g) at TEA, and related them to general movements at the age of 3 months after term and neurological outcome at the age of 2 years 6 months. At TEA, 10 of the 13 infants had abnormal general movements. All infants showed abnormal leg lifting with extended legs; nine showed stiff movements, three showed cramped movements, and two showed cramped synchronized general movements. At 3 months, three infants still had abnormal general movements. Concurrent movements were abnormal in nine infants owing to monotony and jerkiness. Abnormal posture was seen in seven infants. None developed cerebral palsy; one infant showed cognitive and motor delay. Neurological outcome was not related to general movement quality and optimality score at TEA. Abnormal general movements at TEA are common in extremely low-birthweight infants. General movements often appear stiff and cramped with extended legs. At the age of 3 months after term, general movements are mostly normal, but concurrent movements are not. Nevertheless, these abnormalities do not imply an impaired neurological outcome such as cerebral palsy.

Imitation in Infancy: Rational or Motor Resonance?

The present study investigates the contribution of 2 mechanisms to imitation in infancy. The principle of rational action suggests that infants normatively evaluate the efficiency of observed actions. In contrast, it has been proposed that motor resonance (i.e., the mapping of others' actions onto one's own motor repertoire) plays a central role in imitation. This study tested 14-month-old infants (n = 95) in 5 conditions and manipulated the extent to which the observed actions could be matched onto the infants' own motor repertoire as well as whether the observed behavior appeared to be efficient. The results suggest that motor resonance plays a more central role in imitation in infancy than does a rational evaluation of the observed action.

Is There a Cartesian Renaissance of the Mind or Is It Time for a New Taxonomy for Low Responsive States?

The mass media have recently pointed out the likelihood of diagnostic errors in post-coma patients. Late recoveries of consciousness, even after 20 years, might indicate hidden misdiagnoses that are not corrected over a long period of time. The rate of misdiagnoses of patients in a vegetative state is very high when based on behavioral assessment strategies alone. An extremely restrictive motor repertoire, as occurs in locked-in patients, seems to be the major factor responsible for diagnostic confusion. Functional neuroimaging techniques are regarded as promising tools in unearthing covert awareness in behaviorally unresponsive patients who are unable to produce any motor output. However, unless we believe that these patients persistently live in an unconvincing Cartesian-like state, in which thinking and acting are mutually dissociated, we have to admit that a new taxonomy for low responsive states is called for. This taxonomy should take into account the possible syndromic overlap between disorders of consciousness and locked-in syndrome. We should suspect a "locked-in state" in behaviorally unresponsive patients unless we reach strong evidence that such is not the case; this is the only way to avoid dramatic misdiagnoses.

Neural correlates related to action observation in expert archers

A growing body of evidence suggests that activity of the mirror neuron system is dependent on the observer's motor experience of a given action. It remains unclear, however, whether activity of the mirror neuron system is also associated with the observer's motor experience in sports game. Therefore, the aim of the present study is to investigate differences in activation of the mirror neuron system during action observation between experts and non-archer control subjects. We used video of Western-style archery in which participants were asked to watch the archery movements. Hyperactivation of the premotor and inferior parietal cortex in expert archers relative to non-archer control subjects suggests that the human mirror neuron system could contain and expand representations of the motor repertoire. The fact that dorsomedial prefrontal cortex was more active in expert archers than in non-archer control subjects indicates a spontaneous engagement of theory of mind in experts when watching video of Western-style archery. Compared with the non-archer control subjects, expert archers showed greater activation in the neural system in regions associated with episodic recall from familiar and meaningful information, including the cingulate cortex, retrosplenial cortex, and parahippocampal gyrus. The results demonstrate that expertise effects stimulate brain activity not only in the mirror neuron system but also in the neural networks related to theory of mind and episodic memory.

Predicting and memorizing observed action: Differential premotor cortex involvement

Many studies have shown the involvement of the premotor cortex in action observation, recognizing this region as the neural marker of action simulation (i.e., internal modeling on the basis of the observer's own motor repertoire). So far, however, we have remained unaware of how action simulation differs from more general action representation in terms of premotor activation. The present fMRI experiment is the first to demonstrate how premotor structures contribute to action simulation as opposed to other action-related cognitive tasks, such as maintaining action representations. Using similar stimuli, a prediction condition requiring internal simulation of transiently occluded actions was compared to three different action-related control tasks differing solely in task instructions. Results showed right pre-SMA activation as a correlate of maintaining action representations in general. Moreover, the prediction condition was most efficient in activating the left pre-SMA and left PMd. These results suggest that the conjoint activation of the pre-SMA and PMd reflects a core neural driver of action simulation.

Bridging the gap between the other and me: the functional role of motor resonance and action effects in infants’ imitation

This paper investigates a two-stage model of infants' imitative learning from observed actions and their effects. According to this model, the observation of another person's action activates the corresponding motor code in the infants' motor repertoire (i.e. leads to motor resonance). The second process guiding imitative behavior results from the observed action effects. If the modeled action is followed by a salient action effect, the representation of this effect (i.e. perceptual code) will be associated with the activated motor code. If the infant later aims to obtain the same effect, the corresponding motor program will be activated and the model's action will therefore be imitated. Accordingly, the model assumes that for the imitation of novel actions the modeled action needs to elicit sufficient motor resonance and must be followed by a salient action effect. Using the head touch imitation paradigm, we tested these two assumptions derived from the model. To this end, we manipulated whether the actions demonstrated to the infants were or were not in the motor repertoire, i.e. elicited stronger or less strong motor resonance, and whether they were followed by salient action effects or not. The results were in line with the proposed two-stage model of infants' imitative learning and suggest that motor resonance is necessary, but not sufficient for infants' imitative learning from others' actions and their effects.

Secondary sensory area SII is crucially involved in the preparation of familiar movements compared to movements never made before

Secondary sensorimotor regions are involved in sensorimotor integration and movement preparation. These regions take part in parietal-premotor circuitry that is not only active during motor execution but also during movement observation and imagery. This activation particularly occurs when observed movements belong to one's own motor repertoire, consistent with the finding that motor imagery only improves performance when one can actually make such movement. We aimed to investigate whether imagery or observation of a movement that was never made before causes parietal-premotor activation or that the ability to perform this movement is indeed a precondition. Nine subjects [group Already Knowing It (AKI)] could abduct their hallux (moving big toe outward). Seven subjects initially failed to make such movement (Absolute Zero A0 group). They had to imagine, observe, or execute this movement, whereas fMRI data were obtained both before and after training. Contrasting abduction observation between the AKI-group and A0-group showed increased left SII and supplementary motor area activation. Comparing the observation of hallux flexion with abduction showed increased bilateral SII activation in the A0 and not in the AKI group. Prolonged training resulted in equal performance and similar cerebral activation patterns in the two groups. Thereby, conjunction analysis of the correlations on subject's range of abduction during execution, imagery, and observation of hallux abduction showed exclusive bilateral SII activation. The reduced SII involvement in A0 may imply that effective interplay between sensory predictions and feedback does not take place without actual movement experience. However, this can be acquired by training.

Neural correlates of dyadic interaction during infancy

This study examines the electrophysiological correlates of dyadic interaction in 14-month-old infants. Infants were presented with three conditions of live stimuli. A baseline condition involved the observation of moving geometric shapes. In a second condition the infant observed an adult performing movements that were not in reference to the infant and were not within the infant's proficient motor repertoire, such as dancing or hopping. A third condition involved face to face dyadic interactions in the context of an imitative game, where the infant and adult engaged in copying each other's hand and facial actions. Motor activity by the infant was controlled between conditions by synchronizing EEG with video frames of action. Infant EEG data was then edited offline to match in motor intensity across conditions. We expected mu rhythm (6-9 Hz) suppression during dyadic interactions relative to the amount of mu present in the baseline condition. This prediction was confirmed. We also observed suppressed mu in the interaction condition relative to the observation condition. The mu rhythm results suggest that infants at 14 months may well utilize a functioning mirroring system during dyadic interactions.

Timing and aging: Slowing of fastest regular tapping rate with preserved timing error detection and correction.

This study assessed motor limits of regular tapping, timing error detection, and correction in 60 participants aged from 19 to 98 years. Rate limitations on motor production were estimated from the average inter-tap interval when tapping as fast as possible for 30 s. Timing error detection required participants to judge whether a sound sequence presented at a slow, intermediate, or fast speed contained an irregularity because of phase shift. This was performed with or without synchronizing to the sounds. On the basis of the just-detectable positive phase shift (JND), participants synchronized with sequences containing phase shifts that were subliminal, just detectable or supraliminal. On average, JNDs were 9% of the inter-onset interval and by and large were not affected by synchronization tapping. Speed of error correction was estimated from the number of tones to return within 20% of the preshift synchronization error. Consistent with previous findings of motor slowing with aging, the fastest inter-tap interval increased with age. However, there was no age-related decline in JNDs or speed of error correction, both of which reflect predictive abilities for intervals within the motor repertoire of human adults. These results point towards intact timing error processing up to an advanced age. In assessing timing abilities in the brain of older adults, it is important to differentiate between motor slowing and its impact on rhythmic behavior (e.g., walking pace) from anticipatory mechanisms ('what to expect when') and how these are used to adjust the timing of actions ('what to do when').

561 The Relation Between Neurological Outcome at Toddler Age and Motor Repertoire During Infancy in Extremely Low Birth Weight (ELBW) Infants

Objective: To determine the relation between the quality of General Movements (GMs) of ELBW infants at term equivalent age (TEA), at 3 months after term, and neurological outcome.Methods: We assessed the quality of the motor repertoire (GMs and motor optimality scores, OS), using Prechtl's method, in 13 ELBW infants (GA 27.3 weeks, 25.1-31.9; BW 840 grams, 560-955) at TEA and again at 3 months after term. Normal GMs at 3 months are also known as fidgety movements (FMs). We analyzed the relation between quality of GMs, including OS, and neurological outcome at 2.5y.Results: At TEA 10/13 infants had abnormal GMs. All infants had abnormal leg lifting movements with extended legs. In 9/13 infants the movements appeared stiff. At 3 months, 3/13 infants had abnormal FMs. Concurrent movements were abnormal in 9/13 infants due to monotony and jerkiness. Abnormal posture was seen in 7/13 infants: mostly flat body and limb position (n=5) and/or the presence of an obligatory ATN posture (n=3). None of the children developed cerebral palsy. Cognitive and motor delay was seen in 1 infant. Neurological outcome was not related to GM-quality or OS.Conclusion: Abnormal GMs at TEA are common in ELBW infants. GMs appear stiff and extended legs are frequently seen. At 3 months FMs are mostly normal, but monotonous and jerky concurrent movements, as well as abnormal flat postures are frequent. These abnormalities do not implicate an abnormal neurological outcome.

Variability in the effector-specific pattern of motor facilitation during the observation of everyday actions: implications for the clinical use of action observation

Action observation is increasingly considered as a rehabilitation tool as it can increase the cortical excitability of muscles involved in the observed movements and therefore produce effector-specific motor facilitation. In order to investigate the action observation mechanisms, simple single joint intransitive movements have commonly been used. Still, how the observation of everyday movements which often are the prime target of rehabilitation affects the observer cortical excitability remains unclear. Using transcranial magnetic stimulations, we aimed at verifying if the observation of everyday movements made by the proximal or distal upper-limb produces effector-specific motor facilitation in proximal (arm) and distal (hand) muscles of healthy subjects. Results suggest that, similar to simple intransitive movements, observation of more complex everyday movements involving mainly the proximal or distal part of upper limb induces different patterns of motor facilitation across upper limb muscles (P=0.02). However, we observed large inter-individual variability in the strength of the effector-specific motor facilitation induced by action observation. Yet, subjects had similar types of response (strong or weak effector-specific effects) when watching proximal or distal movements indicating that the facilitation pattern was highly consistent within subjects (r=0.83–0.88, P<0.001). This suggests that some individuals are better than other at precisely mapping the observed movements on their motor repertoire and that this type of response holds for various types of everyday actions.

Implicit chord processing and motor representation in pianists

The aim of this paper is to assess the relevance of pitch dimension in auditory-motor interaction. Several behavioural and brain imaging studies have shown that auditory processing of sounds can activate motor representations, an effect which is however elicited only by action-related sounds, i.e., sounds linked to a specific motor repertoire. Music provides an appropriate framework for further exploration of this issue. Three groups of participants (pianists, non-pianist musicians and non-musicians) were tested with a shape decision task where left-hand and right-hand responses were required; each visual stimulus was paired with an auditory task-irrelevant stimulus (high-pitched or low-pitched piano-timbre chords). Of the three groups, only pianists had longer reaction times for left-hand/high-pitched chords and right-hand/low-pitched chords associations. These findings are consistent with an auditory-motor effect elicited by pitch dimension, as only pianists show an interaction between motor responses and implicit pitch processing. This interaction is consistent with the canonical mapping of hand gestures and pitch dimension on the piano keyboard. The results are discussed within the ideo-motor theoretical framework offered by the Theory of Event Coding (Hommel et al. in Behav Brain Sci 24:849-937, 2001).

When affordances climb into your mind: Advantages of motor simulation in a memory task performed by novice and expert rock climbers

Does the sight of multiple climbing holds laid along a path activate a motor simulation of climbing that path? One way of testing whether multiple affordances and their displacement influence the formation of a motor simulation is to study acquired motor skills. We used a behavioral task in which expert and novice rock climbers were shown three routes: an easy route, a route impossible to climb but perceptually salient, and a difficult route. After a distraction task, they were then given a recall test in which they had to write down the sequence of holds composing each route. We found no difference between experts and novices on the easy and impossible routes, whereas on the difficult route, the performance of experts was better than that of novices. This suggests that seeing a climbing wall activates a motor, embodied simulation, which relies not on perceptual salience, but on motor competence. More importantly, our results show that the capability to form this simulation is modulated by individuals’ motor repertoire and expertise, and that this strongly impacts recall.

Single-Neuron Responses in Humans during Execution and Observation of Actions

Direct recordings in monkeys have demonstrated that neurons in frontal and parietal areas discharge during execution and perception of actions [1-8]. Because these discharges "reflect" the perceptual aspects of actions of others onto the motor repertoire of the perceiver, these cells have been called mirror neurons. Their overlapping sensory-motor representations have been implicated in observational learning and imitation, two important forms of learning [9]. In humans, indirect measures of neural activity support the existence of sensory-motor mirroring mechanisms in homolog frontal and parietal areas [10, 11], other motor regions [12-15], and also the existence of multisensory mirroring mechanisms in nonmotor regions [16-19]. We recorded extracellular activity from 1177 cells in human medial frontal and temporal cortices while patients executed or observed hand grasping actions and facial emotional expressions. A significant proportion of neurons in supplementary motor area, and hippocampus and environs, responded to both observation and execution of these actions. A subset of these neurons demonstrated excitation during action-execution and inhibition during action-observation. These findings suggest that multiple systems in humans may be endowed with neural mechanisms of mirroring for both the integration and differentiation of perceptual and motor aspects of actions performed by self and others.

Observing or producing a motor action improves later perception of biological motion: Evidence for a gender effect

Two experiments are presented addressing the issue of whether observing (visual priming) or producing (motor priming) a running activity during a very short period (30 s) facilitates the perception of the direction of a point-light runner embedded in a dense dynamical mask. Experiment 1 showed that perceptual judgements improved and response time increased in the visual priming compared to the neutral priming condition (video of a moving car) in which judgements were at random. Because this effect was observed for male participants only, we performed a second experiment with the aim of evaluating the role of gender congruency in the visual priming condition. Results confirmed the facilitation effect and demonstrated that this effect was strictly dependent on the gender congruency between the perceiver and the priming information. Moreover, we found that actually producing a motor activity similar to the one presented in the video sequence improved to the same extent participants’ judgement of the direction of the point-light runner, without any gender effect. As a whole, these findings argue in favour of common representation for the perception and the production of human movement and showed that the perception of biological motion can be improved by prior motor activity either performed or observed. However, the gender-dependent effect of visual priming suggested that motor repertoire differed in males and females.

Monitoring Coordination during Bimanual Movements: Where Is the Mastermind?

One remarkable aspect of the human motor repertoire is the multitude of bimanual actions it contains. Still, the neural correlates of coordinated movements, in which the two hands share a common goal, remain debated. To address this issue, we designed two bimanual circling tasks that differed only in terms of goal conceptualization: a "coordination" task that required movements of both hands to adapt to each other to reach a common goal and an "independent" task that imposed a separate goal to each hand. fMRI allowed us to pinpoint three areas located in the right hemisphere that were more strongly activated in the coordination condition: the superior temporal gyrus (STG), the SMA, and the primary motor cortex (M1). We then used transcranial magnetic stimulation (TMS) to disrupt transiently the function of those three regions to determine their causal role in bimanual coordination. Right STG virtual lesions impaired bimanual coordination, whereas TMS to right M1 enhanced hand independence. TMS over SMA, left STG, or left M1 had no effect. The present study provides direct insight into the neural correlates of coordinated bimanual movements and highlights the role of right STG in such bimanual movements.

Development of adaptive motor behaviour in typically developing infants

During motor development, infants learn to select adaptive motor strategies out of their motor repertoire. The aim of this study is twofold: first, to investigate whether the presence of adaptive motor behaviour can be observed reliably, and second, to explore the ages at which clinically observable transition to adaptive motility emerges for four specific motor functions: abdominal progression, sitting motility, reaching and grasping. The reliability part of the study included 38 assessments of term and preterm infants in the age range of 4-18 months. The longitudinal prospective study included 30 term born typically developing infants with nine assessments between 3 and 18 months. On the basis of standardized video-recordings of spontaneous motor behaviour, the presence of adaptive motor strategies was scored. Intra- and interobserver reliability were good. Clinically observable transitions to adaptive selection started to emerge from 6 months onwards and peaked between 8 and 15 months. Transitions developed gradually and occurred at specific ages for different motor functions. Transition to adaptive motor behaviour can be observed reliably. Adaptive motor behaviour develops gradually from 6 months onwards at function-specific ages. Comparison of our results to literature showed that changes measured by neurophysiologic methods precede clinically observed transitions.