Action Interpretation Determines the Effects of Go/No-Go and Approach/Avoidance Actions on Stimulus Evaluation.

Executing go/no-go or approach/avoidance responses toward a stimulus can change its evaluation. To explain these effects, some theoretical accounts propose that executing these responses inherently triggers affective reactions (i.e., action execution), while others posit that the evaluative influences originate from interpreting these responses as valenced actions (i.e., action interpretation). To test the role of action execution and action interpretation in these evaluative effects, we developed a novel training task that combined both go/no-go and approach/avoidance actions orthogonally. Participants either responded or did not respond (i.e., go/no-go) to control a shopping cart on screen, and as a result, either collected or did not collect (i.e., approach/avoidance) certain food items. When the task instructions referred to the go/no-go actions (Experiment 1, N = 148), we observed an effect of these actions. Participants evaluated no-go items less positively than both go and untrained items. No effect of approach/avoidance actions was observed. Contrarily, when the task instructions referred to the approach/avoidance actions (Experiment 2, N = 158), we observed an approach/avoidance effect. Participants evaluated approached items more positively and avoided items less positively than untrained items. No effect of go/no-go actions was observed. This suggests that action interpretation determined whether go/no-go or approach/avoidance actions influenced stimulus evaluation, when the same motor responses were made. Further examination of the role of action interpretation can inform theories of how actions influence stimulus evaluation, and facilitate the use of these interventions in applied settings.

Movement-related increases in subthalamic activity optimize locomotion.

The subthalamic nucleus (STN) is traditionally thought to restrict movement. Lesion or prolonged STN inhibition increases movement vigor and propensity, while optogenetic excitation has opposing effects. However, STN neurons often exhibit movement-related increases in firing. To address this paradox, STN activity was recorded and manipulated in head-fixed mice at rest and during self-initiated and self-paced treadmill locomotion. We found that (1) most STN neurons (type 1) exhibit locomotion-dependent increases in activity, with half firing preferentially during the propulsive phase of the contralateral locomotor cycle; (2) a minority of STN neurons exhibit dips in activity or are uncorrelated with movement; (3) brief optogenetic inhibition of the lateral STN (where type 1 neurons are concentrated) slows and prematurely terminates locomotion; and (4) in Q175 Huntington's disease mice, abnormally brief, low-velocity locomotion is associated with type 1 hypoactivity. Together, these data argue that movement-related increases in STN activity contribute to optimal locomotor performance.

Immediate Effect of Physiotherapist-demonstrated Action Observation with Execution for Improving Upper Extremity Motor Function in Stroke: a Pre-post Pilot Study.

BACKGROUND: Video-demonstrated action-observation-execution is an effective intervention for motor re-learning in stroke rehabilitation. But customization of video for each task repeatedly questions its feasibility within limited resources, particularly for daily routine practice and in community settings. Physiotherapist-demonstrated action-observation-execution is a practical intervention based on the principle of observation and consecutive repetitions of observed real, live movements. The main objective of this study was to investigate the immediate effect of Physiotherapist-demonstrated action-observation-execution in upper extremity motor training in stroke. METHODS: Individuals with stroke were screened and 5 eligible participants were recruited. The research was a pre-post. A single session of Physiotherapist-demonstrated action-observation-execution was administered. A functional "Drinking" task was subdivided into simpler acts and trained. Pre and post intervention assessment of movement time using five hand-and-arm items of Nepali Wolf Motor Function Test were carried out. Global recovery was assessed in the form of Visual Analogue Scale. RESULTS: Paired t-test provided statistically significant difference in total movement time (mean difference=5.04 seconds, standard deviation=1.92, p=0.004) with larger effect size (0.95) indicating impressive improvement in movement time with the training. Substantial difference in global recovery score was noted (mean difference=17.40, standard deviation=3.65, p<0.0001, effect size=1.00) signifying the increased confidence and improved performance of upper extremity post treatment. CONCLUSIONS: The findings indicated that Physiotherapist-demonstrated action-observation-execution could be a feasible intervention to train motor functions in participants with stroke. Large-scale studies are recommended to establish the effectiveness of the intervention.

Lesion mapping and functional characterization of hemiplegic children with different patterns of hand manipulation.

Brain damage in children with unilateral cerebral palsy (UCP) affects motor function, with varying severity, making it difficult the performance of daily actions. Recently, qualitative and semi-quantitative methods have been developed for lesion classification, but studies on mild to moderate hand impairment are lacking. The present study aimed to characterize lesion topography and preserved brain areas in UCP children with specific patterns of hand manipulation. A homogeneous sample of 16 UCP children, aged 9 to 14 years, was enrolled in the study. Motor assessment included the characterization of the specific pattern of hand manipulation, by means of unimanual and bimanual measures (Kinematic Hand Classification, KHC; Manual Ability Classification System, MACS; House Functional Classification System, HFCS; Melbourne Unilateral Upper Limb Assessment, MUUL; Assisting Hand Assessment, AHA). The MRI morphological study included multiple methods: (a) qualitative lesion classification, (b) semi-quantitative classification (sq-MRI), (c) voxel-based morphometry comparing UCP and typically developed children (VBM-DARTEL), and (d) quantitative brain tissue segmentation (q-BTS). In addition, functional MRI was used to assess spared functional activations and cluster lateralization in the ipsilesional and contralesional hemispheres of UCP children during the execution of simple movements and grasping actions with the more affected hand. Lesions most frequently involved the periventricular white matter, corpus callosum, posterior limb of the internal capsule, thalamus, basal ganglia and brainstem. VMB-DARTEL analysis allowed to detect mainly white matter lesions. Both sq-MRI classification and q-BTS identified lesions of thalamus, brainstem, and basal ganglia. In particular, UCP patients with synergic hand pattern showed larger involvement of subcortical structures, as compared to those with semi-functional hand. Furthermore, sparing of gray matter in basal ganglia and thalamus was positively correlated with MUUL and AHA scores. Concerning white matter, q-BTS revealed a larger damage of fronto-striatal connections in patients with synergic hand, as compared to those with semi-functional hand. The volume of these connections was correlated to unimanual function (MUUL score). The fMRI results showed that all patients, but one, including those with cortical lesions, had activation in ipsilesional areas, regardless of lesion timing. Children with synergic hand showed more lateralized activation in the ipsilesional hemisphere both during grasping and simple movements, while children with semi-functional hand exhibited more bilateral activation during grasping. The study demonstrates that lesion localization, rather than lesion type based on the timing of their occurrence, is more associated with the functional level of hand manipulation. Overall, the preservation of subcortical structures and white matter can predict a better functional outcome. Future studies integrating different techniques (structural and functional imaging, TMS) could provide further evidence on the relation between brain reorganization and specific pattern of manipulation in UCP children.

The effect of motor imagery and action observation on autonomic functions in patients with chronic stroke.

OBJECTIVES: This study aimed to investigate the effects of motor imagery (MI), action observation (AO), and action execution (AE) interventions on the autonomic nervous system (ANS) in individuals with chronic stroke. METHODS: This was a single-center, randomized, case-control study. Thirty-six patients were randomly assigned to MI (n = 10), AO (n = 15), and the AE group (n = 11). Heart rate (HR)-based measurements (HR, heart rate variability (HRV)) and blood pressure were evaluated before the practice of each group. In the MI group, participants were instructed to imagine themselves walking at their own comfortable pace for 5 minutes. Meanwhile, in the AO group, participants were shown a video of a person walking for 5 minutes. Finally, in the AE group, participants were instructed to actually walk for 5 minutes. Then, all measurements were taken again. RESULTS: A statistically significant difference was found in HR and mean RR interval within the AE group (p < 0.05). There was a statistically significant difference in the Root Mean Square of Successive Differences Between Normal Heartbeats (RMSSD) (ms) within the AO group (p < 0.05). There was a significant difference in HR and mean RR intervals (ms) between groups (p < 0.05). According to post-hoc analyses, HR was statistically significantly higher in the AE group compared to the other groups, and the mean RR interval was statistically significantly lower (p < 0.05). CONCLUSIONS: In conclusion, in patients with chronic stroke, AE and AO may affect ANS by increasing sympathetic activation. It is recommended for future studies to evaluate whether patients actually engage in imagery during the MI task.

Possible disrupted biological movement processing in Developmental Coordination Disorder.

AIM: There is emerging evidence that the Mirror Neuron System (MNS) might contribute to the motor learning difficulties characteristic of Developmental Coordination Disorder (DCD). This study aimed to identify whether MNS activity differed between children with and without DCD during action observation, action execution and during a non-action baseline. METHODS: Electroencephalography (EEG) was used to measure mu rhythm (a proxy for MNS activation) in 8-12-year-old children either with (n = 20) or without (n = 19) a diagnosis of DCD. The mu rhythm was recorded at rest and during five experimental conditions: (1) observation of gross motor and (2) fine motor actions; (3) execution of gross motor and (4) fine motor actions; and (5) non-biological movement. To address whether potential co-occurring traits of other neurodevelopmental conditions were associated with differences in mu rhythm, parents reported their child's attention and social communication skills. Mixed and repeated measure ANOVAs were conducted to examine differences in mu desynchronization and mu power respectively. RESULTS: The non-DCD group showed greater mu rhythm desynchronization than children with DCD (i.e., more MNS activity), with both groups demonstrating increasing desynchronization from observation of fine actions to execution of gross actions. However, we also found that the children with DCD had less mu power during the non-biological movement condition than the non-DCD children, although mu power did not differ between groups during the resting condition. Correlations between mu desynchronization and children's attention and motor skills showed that poorer attention and motor abilities were associated with reduced MNS activity. CONCLUSION: Compared to children without DCD, the MNS in children with DCD did not distinguish between biological and non-biological movement. It is possible that the reduced specificity of the MNS in children with DCD is an underlying factor in the motor impairments observed in the disorder. The differential MNS activity could reflect broader atypical activity in perceptual networks that feed into the MNS in DCD.

Inhibition of the dorsomedial striatal direct pathway is essential for the execution of action sequences.

Contrary to the previous notion that the dorsomedial striatum (DMS) is crucial for acquiring new learning, accumulated evidence has suggested that the DMS also plays a role in the execution of already learned action sequences. Here, we examined how the direct and indirect pathways in the DMS regulate action sequences using a task that requires animals to press a lever consecutively. Cell-type-specific bulk Ca2+ recording revealed that the direct pathway was inhibited at the time of sequence execution. The sequence-related response was blunted in trials where the sequential behaviors were disrupted. Optogenetic activation at the sequence start caused distraction of action sequences without affecting motor function or memory of the task structure. By contrast with the direct pathway, the indirect pathway was slightly activated at the start of the sequence, but the optogenetic suppression of such sequence-related signaling did not impact the behaviors. These results suggest that the inhibition of the DMS direct pathway promotes sequence execution potentially by suppressing the formation of a new association.

Eye movements during motor imagery and execution reveal different visuomotor control strategies in manual interception.

Previous research has investigated the degree of congruency in gaze metrics between action execution (AE) and motor imagery (MI) for similar manual tasks. Although eye movement dynamics seem to be limited to relatively simple actions toward static objects, there is little evidence of how gaze parameters change during imagery as a function of more dynamic spatial and temporal task demands. This study examined the similarities and differences in eye movements during AE and MI for an interception task. Twenty-four students were asked to either mentally simulate or physically intercept a moving target on a computer display. Smooth pursuit, saccades, and response time were compared between the two conditions. The results show that MI was characterized by higher smooth pursuit gain and duration while no meaningful differences were found in the other parameters. The findings indicate that eye movements during imagery are not simply a duplicate of what happens during actual performance. Instead, eye movements appear to vary as a function of the interaction between visuomotor control strategies and task demands.

Evidence for a common mechanism supporting invigoration of action selection and action execution.

The speed, or vigor, of our movements can vary depending on circumstances. For instance, the promise of a reward leads to faster movements. Reward also leads us to move with a lower reaction time, suggesting that the process of action selection can also be invigorated by reward. It has been proposed that invigoration of action selection and of action execution might occur through a common mechanism, and thus these aspects of behavior might be coupled. To test this hypothesis, we asked participants to make reaching movements to "shoot" through a target at varying speeds to assess whether moving more quickly was also associated with more rapid action selection. We found that, when participants were required to move with a lower velocity, the speed of their action selection was also significantly slowed. This finding was recapitulated in a further dataset in which participants determined their own movement speed, but had to move slowly to stop their movement inside the target. By reanalyzing a previous dataset, we also found evidence for the converse relationship between action execution and action selection; when pressured to select actions more rapidly, people also executed movements with higher velocity. Our results establish that invigoration of action selection and action execution vary in tandem with one another, supporting the hypothesis of a common underlying mechanism.NEW & NOTEWORTHY We show that voluntary increases in the vigor of action execution lead action selection to also occur more rapidly. Conversely, hastening action selection by imposing a deadline to act also leads to increases in movement speed. These findings provide evidence that these two distinct aspects of behavior are modulated by a common underlying mechanism.

Motor engagement enhances incidental memory for task-irrelevant items.

Actions shape what we see and memorize. A previous study suggested the interaction between motor and memory systems by showing that memory encoding for task-irrelevant items was enhanced when presented with motor-response cues. However, in the studies on the attentional boost effect, it has been revealed that detection of the target stimulus can lead to memory enhancement without requiring overt action. Thus, the direct link between the action and memory remains unclear. To exclude the effect of the target detection process as a potential confounder, this study assessed the benefit of action for memory by separating items from the response cue in time. In our pre-registered online experiment (N = 142), participants responded to visual Go cues by pressing a key (i.e., motor task) or counting (i.e., motor-neutral cognitive task) while ignoring No-go cues. In each trial, two task-irrelevant images were sequentially presented after the cue disappearance. After encoding the Go/No-go tasks, participants performed a surprise recognition memory test for those images. Importantly, we quantified the impact of overt execution of the action by comparing memories with and without motor response and the impact of covert motor processes (e.g., preparation and planning of action) by comparing memory between the motor and cognitive tasks. The results showed no memory differences between Go and No-go trials in the motor task. This means that the execution itself was not critical for memory enhancement. However, the memory performance in the motor No-go trials was higher than that in the cognitive No-go trials, only for the items presented away from the cues in time. Therefore, engaging the motor task itself could increase incidental memory for the task-irrelevant items compared to a passive viewing situation. We added empirical evidence on the online interaction between action and memory encoding. These memory advantages could be especially brought in action preparation and planning. We believe this fact may expand our present understanding of everyday memory, such as active learning.

Peak frequency of the sensorimotor mu rhythm varies with autism-spectrum traits.

Autism spectrum disorder (ASD) is a neurodevelopmental syndrome characterized by impairments in social perception and communication. Growing evidence suggests that the relationship between deficits in social perception and ASD may extend into the neurotypical population. In electroencephalography (EEG), high autism-spectrum traits in both ASD and neurotypical samples are associated with changes to the mu rhythm, an alpha-band (8-12 Hz) oscillation measured over sensorimotor cortex which typically shows reductions in spectral power during both one's own movements and observation of others' actions. This mu suppression is thought to reflect integration of perceptual and motor representations for understanding of others' mental states, which may be disrupted in individuals with autism-spectrum traits. However, because spectral power is usually quantified at the group level, it has limited usefulness for characterizing individual variation in the mu rhythm, particularly with respect to autism-spectrum traits. Instead, individual peak frequency may provide a better measure of mu rhythm variability across participants. Previous developmental studies have linked ASD to slowing of individual peak frequency in the alpha band, or peak alpha frequency (PAF), predominantly associated with selective attention. Yet individual variability in the peak mu frequency (PMF) remains largely unexplored, particularly with respect to autism-spectrum traits. Here we quantified peak frequency of occipitoparietal alpha and sensorimotor mu rhythms across neurotypical individuals as a function of autism-spectrum traits. High-density 128-channel EEG data were collected from 60 participants while they completed two tasks previously reported to reliably index the sensorimotor mu rhythm: motor execution (bimanual finger tapping) and action observation (viewing of whole-body human movements). We found that individual measurement in the peak oscillatory frequency of the mu rhythm was highly reliable within participants, was not driven by resting vs. task states, and showed good correlation across action execution and observation tasks. Within our neurotypical sample, higher autism-spectrum traits were associated with slowing of the PMF, as predicted. This effect was not likely explained by volume conduction of the occipitoparietal PAF associated with attention. Together, these data support individual peak oscillatory alpha-band frequency as a correlate of autism-spectrum traits, warranting further research with larger samples and clinical populations.

Dissociable use-dependent processes for volitional goal-directed reaching.

Repetition of specific movement biases subsequent actions towards the practiced movement, a phenomenon known as use-dependent learning (UDL). Recent experiments that impose strict constraints on planning time have revealed two sources of use-dependent biases, one arising from dynamic changes occurring during motor planning and another reflecting a stable shift in motor execution. Here, we used a distributional analysis to examine the contribution of these biases in reaching. To create the conditions for UDL, the target appeared at a designated 'frequent' location on most trials, and at one of six 'rare' locations on other trials. Strikingly, the heading angles were bimodally distributed, with peaks at both frequent and rare target locations. Despite having no constraints on planning time, participants exhibited a robust bias towards the frequent target when movements were self-initiated quickly, the signature of a planning bias; notably, the peak near the rare target was shifted in the frequently practiced direction, the signature of an execution bias. Furthermore, these execution biases were not only replicated in a delayed-response task but were also insensitive to reward. Taken together, these results extend our understanding of how volitional movements are influenced by recent experience.

Shared population-level dynamics in monkey premotor cortex during solo action, joint action and action observation.

Studies of neural population dynamics of cell activity from monkey motor areas during reaching show that it mostly represents the generation and timing of motor behavior. We compared neural dynamics in dorsal premotor cortex (PMd) during the performance of a visuomotor task executed individually or cooperatively and during an observation task. In the visuomotor conditions, monkeys applied isometric forces on a joystick to guide a visual cursor in different directions, either alone or jointly with a conspecific. In the observation condition, they observed the cursor's motion guided by the partner. We found that in PMd neural dynamics were widely shared across action execution and observation, with cursor motion directions more accurately discriminated than task types. This suggests that PMd encodes spatial aspects irrespective of specific behavioral demands. Furthermore, our results suggest that largest components of premotor population dynamics, which have previously been suggested to reflect a transformation from planning to movement execution, may rather reflect higher cognitive-motor processes, such as the covert representation of actions and goals shared across tasks that require movement and those that do not.

20 Hz Transcranial Alternating Current Stimulation Inhibits Observation-Execution-Related Motor Cortex Excitability.

The present study aimed to investigate the effect of transcranial alternating current stimulation (tACS) on the primary motor cortex (M1) during action observation, and subsequent action execution, on motor cortex excitability. The participants received tACS at 10 Hz or 20 Hz, or a sham stimulation over the left M1 for 10 min while they observed a video displaying a repeated button-tapping task using the right hand, and then performed an identical task with their right hand. Motor-evoked potential (MEP) amplitudes were measured before (T0) and after the action observation paired with tACS or a sham stimulation (T1), and after the performance of the action (T2). The results showed that MEPs were significantly reduced at time point T1 (p = 0.042, Cohen's d = 0.611) and T2 (p = 0.0003, Cohen's d = 0.852) in the 20 Hz tACS condition, in contrast with the sham stimulation. There was a significantly smaller MEP amplitude at time point T2 in the 20 Hz tACS condition, as compared to the 10 Hz tACS condition (p = 0.01, Cohen's d = 0.622), but the MEP amplitude did not significantly change at time point T1 between the 20 Hz and 10 Hz tACS conditions (p = 0.136, Cohen's d = 0.536). There were no significant differences at time point T1 and T2 between the 10 Hz tACS condition and the sham stimulation. We conclude that 20 Hz tACS during action observation inhibited motor cortex excitability and subsequently inhibited execution-related motor cortex excitability. The effects of tACS on task-related motor cortex excitability are frequency-dependent.

Functional Imaging of the Cerebellum during Action Execution and Observation.

We employed the 14C-deoxyglucose autoradiographic method to map the activity in the cerebellar cortex of rhesus monkeys that performed forelimb movements either in the light or in the dark and of monkeys that observed forelimb movements executed by a human experimenter. The execution of forelimb movements, both in the light and in the dark, activated the forelimb representations in the cerebellar hemispheric extensions of 1) vermian lobules IV-VI and 2) vermian lobule VIIIB, ipsilaterally to the moving forelimb. Activations in the former forelimb representation involved both a paravermal and a lateral hemispheric region. Also, Crus II posterior in the ansiform lobule (the hemispheric expansion of lobule VIIB) was activated bilaterally by execution of movements in the light but not in the dark. Action observation activated the lateral-most region of the forelimb representation in the lateral hemispheric extension of vermian lobules IV-VI, as well as the crus II posterior, bilaterally. Our results demonstrate that the cerebellar cortex, in addition to its involvement in the generation of movement, is also recruited in the perception of observed movements. Moreover, our findings suggest a modularity gradient in the primate cerebellar cortex, which progresses from unimodal (medially) to multimodal (laterally) functional areas.

Using Functional Connectivity to Examine the Correlation between Mirror Neuron Network and Autistic Traits in a Typically Developing Sample: A fNIRS Study.

Mirror neuron network (MNN) is associated with one's ability to recognize and interpret others' actions and emotions and has a crucial role in cognition, perception, and social interaction. MNN connectivity and its relation to social attributes, such as autistic traits have not been thoroughly examined. This study aimed to investigate functional connectivity in the MNN and assess relationship between MNN connectivity and subclinical autistic traits in neurotypical adults. Hemodynamic responses, including oxy- and deoxy-hemoglobin were measured in the central and parietal cortex of 30 healthy participants using a 24-channel functional Near-Infrared spectroscopy (fNIRS) system during a live action-observation and action-execution task. Functional connectivity was derived from oxy-hemoglobin data. Connections with significantly greater connectivity in both tasks were assigned to MNN connectivity. Correlation between connectivity and autistic traits were performed using Pearson correlation. Connections within the right precentral, right supramarginal, left inferior parietal, left postcentral, and between left supramarginal-left angular regions were identified as MNN connections. In addition, individuals with higher subclinical autistic traits present higher connectivity in both action-execution and action-observation conditions. Positive correlation between MNN connectivity and subclinical autistic traits can be used in future studies to investigate MNN in a developing population with autism spectrum disorder.

Frequency-specific equivalence of brain activity on motor imagery during action observation and action execution.

BACKGROUND: Human motor imagery (MI), action execution, and action observation (AO) are functionally considered as equivalent. MI during AO can extensively induce activation of motor-related brain network in the absence of overt movement. The magnetoencephalography (MEG) provides an important technology to reveal and reflect human brain information processing in multi-frequency bands. Utilizing a MEG system, we aimed to quantitatively investigate the frequency-specific equivalent characteristics in brain processing patterns between MI during AO and action execution in multi-frequency bands, including delta, theta, alpha, beta, gamma, and high-frequency oscillations. METHODS: A total of 12 healthy subjects were studied with a whole-head MEG system during finger movement and MI during finger movement observation. We analyzed the brain activities in multi-frequency ranges of 1 Hz to 200 Hz. RESULTS: Both MI during AO and action execution evoked the distinctive brain activities in low frequency ranges (i.e. delta, theta, and alpha). Significant differences were found in global spectral power between finger movement and MI during AO in delta and alpha oscillations. Compared with finger movement, delta (1-4 Hz) oscillation power in MI during AO were obviously decreased in left and right frontals and occipitals, and theta (4-8 Hz) and alpha (8-13 Hz) oscillation power were obviously increased in frontal, parietal and occipital. CONCLUSION: MEG power evoked by finger movement and MI during AO is mainly concentrated in the energy distribution below 13 Hz. Furthermore, finger movement and MI during AO might share frequency-specific equivalence of brain neural activation dependent on different MEG frequency ranges.

Parallel fast and slow motor inhibition processes in Joint Action coordination.

Motor inhibition is essential to adapt to an ever-changing environment and to noise in state prediction. As a consequence, inhibitory motor control must also play a key role during Joint Action (JA) tasks, where the motor system has to further integrate inferences about others' action. Yet, very little research has been carried out on the contribution of motor inhibition in JA tasks. Here, we used an interactive task in which subjects were required to open a bottle with one hand. The bottle was held and stabilized by a co-actor (JA) or by a mechanical holder (vice clamp, no-JA). A first motion capture study characterized the reaching and grasping kinematics of the two conditions. In a second study, by means of Transcranial Magnetic Stimulation (TMS), we measured (i) corticospinal excitability (CSE), (ii) cortical silent period (cSP) and (iii) short-interval intracortical inhibition (sICI), during the reaching phase of the task. These latter two indexes respectively reflect slow corticospinal (GABAb-mediated) and fast intracortical (GABAa-mediated) inhibition. We found no modulation for CSE, while cSP was increased and intracortical inhibition was downregulated during JA. Interestingly, the cSP correlated with partners' predictability as a whole and with partners' behaviour in the previous trial. These results, beside showing clear dissociation between fast and slow inhibition during JA, also shed new light on the predictive role played by corticospinal inhibitory mechanisms in online mutual behavioural co-adaptation.

Comparison of Activation Patterns in Mirror Neurons and the Swallowing Network During Action Observation and Execution: A Task-Based fMRI Study.

BACKGROUND: Observation of a goal-directed motor action can excite the respective mirror neurons, and this is the theoretical basis for action observation (AO) as a novel tool for functional recovery during stroke rehabilitation. To explore the therapeutic potential of AO for dysphagia, we conducted a task-based functional magnetic resonance imaging (fMRI) study to identify the brain areas activated during observation and execution of swallowing in healthy participants. METHODS: Twenty-nine healthy volunteers viewed the following stimuli during fMRI scanning: an action-video of swallowing (condition 1, defined as AO), a neutral image with a Chinese word for "watching" (condition 2), and a neutral image with a Chinese word for "swallowing" (condition 3). Action execution (AE) was defined as condition 3 minus condition 2. One-sample t-tests were performed to define the brain regions activated during AO and AE. RESULTS: Many brain regions were activated during AO, including the middle temporal gyrus, inferior frontal gyrus, pre- and postcentral gyrus, supplementary motor area, hippocampus, brainstem, and pons. AE resulted in activation of motor areas as well as other brain areas, including the inferior parietal lobule, vermis, middle frontal gyrus, and middle temporal gyrus. Two brain areas, BA6 and BA21, were activated with both AO and AE. CONCLUSION: The left supplementary motor area (BA6) and left middle temporal gyrus (BA21), which contains mirror neurons, were activated in both AO and AE of swallowing. In this study, AO activated mirror neurons and the swallowing network in healthy participants, supporting its potential value in the treatment of dysphagia.