Transitive Versus Intransitive Complex Gesture Representation: A Comparison Between Execution, Observation and Imagination by fNIRS

Simultaneous multimodal fNIRS-EEG recordings reveal new insights in neural activity during motor execution, observation, and imagery

Motor execution, observation, and imagery are important skills used in motor learning and rehabilitation. The neural mechanisms underlying these cognitive-motor processes are still poorly understood. We used a simultaneous recording of functional near-infrared spectroscopy (fNIRS) and electroencephalogram (EEG) to elucidate the differences in neural activity across three conditions requiring these processes. Additionally, we used a new method called structured sparse multiset Canonical Correlation Analysis (ssmCCA) to fuse the fNIRS and EEG data and determine the brain regions of neural activity consistently detected by both modalities. Unimodal analyses revealed differentiated activation between conditions; however, the activated regions did not fully overlap across the two modalities (fNIRS: left angular gyrus, right supramarginal gyrus, as well as right superior and inferior parietal lobes; EEG: bilateral central, right frontal, and parietal). These discrepancies might be because fNIRS and EEG detect different signals. Using fused fNIRS-EEG data, we consistently found activation over the left inferior parietal lobe, superior marginal gyrus, and post-central gyrus during all three conditions, suggesting that our multimodal approach identifies a shared neural region associated with the Action Observation Network (AON). This study highlights the strengths of using the multimodal fNIRS-EEG fusion technique for studying AON. Neural researchers should consider using the multimodal approach to validate their findings.

Structured sparse multiset canonical correlation analysis of simultaneous fNIRS and EEG provides new insights into the human action-observation network

The action observation network (AON) is a network of brain regions involved in the execution and observation of a given action. The AON has been investigated in humans using mostly electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI), but shared neural correlates of action observation and action execution are still unclear due to lack of ecologically valid neuroimaging measures. In this study, we used concurrent EEG and functional Near Infrared Spectroscopy (fNIRS) to examine the AON during a live-action observation and execution paradigm. We developed structured sparse multiset canonical correlation analysis (ssmCCA) to perform EEG-fNIRS data fusion. MCCA is a generalization of CCA to more than two sets of variables and is commonly used in medical multimodal data fusion. However, mCCA suffers from multi-collinearity, high dimensionality, unimodal feature selection, and loss of spatial information in interpreting the results. A limited number of participants (small sample size) is another problem in mCCA, which leads to overfitted models. Here, we adopted graph-guided (structured) fused least absolute shrinkage and selection operator (LASSO) penalty to mCCA to conduct feature selection, incorporating structural information amongst the variables (i.e., brain regions). Benefitting from concurrent recordings of brain hemodynamic and electrophysiological responses, the proposed ssmCCA finds linear transforms of each modality such that the correlation between their projections is maximized. Our analysis of 21 right-handed participants indicated that the left inferior parietal region was active during both action execution and action observation. Our findings provide new insights into the neural correlates of AON which are more fine-tuned than the results from each individual EEG or fNIRS analysis and validate the use of ssmCCA to fuse EEG and fNIRS datasets.

A neural signature for combined action observation and motor imagery? An fNIRS study into prefrontal activation, automatic imitation, and self-other perceptions

INTRODUCTION

Research indicates that both observed and imagined actions can be represented in the brain as two parallel sensorimotor representations. One proposal is that higher order cognitive processes would align these two hypothetical action simulations.

METHODS

We investigated this hypothesis using an automatic imitation paradigm, with functional near-infrared spectroscopy recordings over the prefrontal cortex during different motor simulation states. On each trial, participants (n = 14) observed a picture of a rhythmical action (instructed action) followed by a distractor movie showing the same or different action. Participants then executed the instructed action. Distractor actions were manipulated to be fast or slow, and instructions were manipulated during distractor presentation: action observation (AO), combined action observation and motor imagery (AO+MI) and observe to imitate (intentional imitation). A pure motor imagery (MI) condition was also included.

RESULTS

Kinematic analyses showed that although distractor speed effects were significant under all instructions (shorter mean cycle times in execution for fast compared to slow trials), this imitation bias was significantly stronger for combined AO+MI than both AO and MI, and stronger for intentional imitation than the other three automatic imitation conditions. In the left prefrontal cortex, cerebral oxygenation was significantly greater for combined AO+MI than all other instructions. Participants reported that their representation of the self overlapped with the observed model significantly more during AO+MI than AO.

CONCLUSION

Left prefrontal activation may therefore be a neural signature of AO+MI, supporting attentional switching between concurrent representations of self (MI, top-down) and other (AO, bottom-up) to increase imitation and perceived closeness.

The Empowering Effect of Embodied Awareness Practice on Body Structural Map and Sensorimotor Activity: The Case of Feldenkrais Method

While outcomes of embodied awareness practices in terms of improved posture and flexibility, movement efficiency, and well-being are often reported, systematic investigations of such training effects and of the actual nature, extent, and neurofunctional correlates of learning mechanisms thought to lie at the core of such practices are very limited. The present study focused on the Feldenkrais method (FM), one of the most established embodied awareness practices, and aimed at investigating the neurofunctional outcomes of the somatic learning process at the core of the method by testing the modulations induced by a standardized FM protocol on the complexity of practicers’ body structural map and on the activity of their sensorimotor network during different movement-related tasks (i.e., gestures observation, execution, and imagery). Twenty-five participants were randomly divided into an experimental group—which completed a 28-session FM protocol based on guided group practice—and a control group, and underwent pre-/post-training psychometric and electrophysiological assessment. Data analysis highlighted, at the end of the FM protocol, a significant increase of EEG markers of cortical activation (task-related mu desynchronization) in precentral regions during action observation and in central regions during action execution and imagery. Also, posterior regions of the sensorimotor network showed systematic activation during all the action-related tasks.

Cerebral hemodynamic response during a live action-observation and action-execution task: A fNIRS study

Although many studies have examined the location of the action observation network (AON) in human adults, the shared neural correlates of action-observation and action-execution are still unclear partially due to lack of ecologically valid neuroimaging measures. In this study, we aim to demonstrate the feasibility of using functional near infrared spectroscopy (fNIRS) to measure the neural correlates of action-observation and action execution regions during a live task. Thirty adults reached for objects or observed an experimenter reaching for objects while their cerebral hemodynamic responses including oxy-hemoglobin (HbO) and deoxy-hemoglobin (HbR) were recorded in the sensorimotor and parietal regions. Our results indicated that the parietal regions, including bilateral superior parietal lobule (SPL), bilateral inferior parietal lobule (IPL), right supra-marginal region (SMG) and right angular gyrus (AG) share neural activity during action-observation and action-execution. Our findings confirm the applicability of fNIRS for the study of the AON and lay the foundation for future work with developmental and clinical populations.

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.

Characterizing the Action-Observation Network Through Functional Near-Infrared Spectroscopy: A Review

Functional near-infrared spectroscopy (fNIRS) is a neuroimaging technique that has undergone tremendous growth over the last decade due to methodological advantages over other measures of brain activation. The action-observation network (AON), a system of brain structures proposed to have “mirroring” abilities (e.g., active when an individual completes an action or when they observe another complete that action), has been studied in humans through neural measures such as fMRI and electroencephalogram (EEG); however, limitations of these methods are problematic for AON paradigms. For this reason, fNIRS is proposed as a solution to investigating the AON in humans. The present review article briefly summarizes previous neural findings in the AON and examines the state of AON research using fNIRS in adults. A total of 14 fNIRS articles are discussed, paying particular attention to methodological choices and considerations while summarizing the general findings to aid in developing better protocols to study the AON through fNIRS. Additionally, future directions of this work are discussed, specifically in relation to researching AON development and potential multimodal imaging applications.

The Effectiveness and Recommendation of Motor Imagery Techniques for Rehabilitation after Anterior Cruciate Ligament Reconstruction: A Systematic Review

Motor imagery (MI) reported positive effects in some musculoskeletal rehabilitation processes. The main objective of this study was to analyze the effectiveness of MI interventions after anterior cruciate ligament (ACL) reconstruction. A systematic review was conducted from November 2018 to December 2019 in PubMed, Scopus, Web of Science, The Cochrane Library, and Physiotherapy Evidence Database (PEDro). The methodological quality, degree of recommendation, and levels of evidence were analyzed. A total of six studies were included. Selected studies showed unequal results (positive and negative) regarding pain, anxiety, fear of re-injury, function, and activities of daily living. Regarding the range of motion, anthropometric measurements, and quality of life, the results were not conclusive. Muscle activation, strength, knee laxity, time to remove external support, and neurobiological factors showed some favorable results. Nevertheless, the results were based on a limited number of studies, small sample sizes, and a moderate-weak degree of recommendation. In conclusion, our review showed a broader view of the current evidence, including a qualitative assessment to implement MI after ACL surgery. There was no clear evidence that MI added to physiotherapy was an effective intervention after ACL surgery, although some studies showed positive results in clinical outcomes. More adequately-powered long-term randomized controlled trials are necessary.

Affective, Social, and Informative Gestures Reproduction in Human Interaction: Hyperscanning and Brain Connectivity

Gestural communication characterizes daily individuals' interactions in order to share information and to modify others' behavior. Social neuroscience has investigated the neural bases which support recognizing of different gestures. The present research, through the use of the hyperscanning approach, that allows the simultaneously recording of the activity of two or more individuals involved in a joint action, aims to investigate the neural bases of gestural communication. Moreover, by using hyperscanning paradigm we explore the inter-brain connectivity between two inter-agents, the one who performed the gesture (encoder) and the one who received it (decoder), with functional Near-infrared Spectroscopy (fNIRS) during the reproduction of affective, social and informative gestures with positive and negative valence. Result showed an increase in oxygenated hemoglobin concentration (O2Hb) and inter-brain connectivity in the dorsolateral prefrontal cortex (DLPFC) for affective gestures, in the superior frontal gyrus (SFG) for social gestures and the frontal eye fields (FEF) for informative gestures, for both encoder and decoder. Furthermore, it emerged that positive gestures activate more the left DLPFC, with an increase in inter-brain connectivity in DLPFC and SFG. The present study revealed the relevant function of the type and valence of gestures in affecting intra- and inter-brain connectivity.

Motor imagery in chronic neglect: An fMRI pilot study

AIM

Previous studies indicate the effectiveness of motor imagery training in stroke patients. To determine whether patients showing chronic visuospatial neglect symptoms may profit from motor imagery training, it is important to assess how the brain implements motor imagery when cortical systems involved in attentional control are impaired.

METHOD

Therefore, in this pilot study, nine chronic neglect patients with right-hemispheric stroke performed motor imagery of a finger opposition task during functional magnetic resonance imaging (fMRI).

RESULTS

Imagery of unaffected hand movements was related to activations in the left primary somatosensory and premotor cortices as well as in the left supplementary motor area. During the imagery of the affected hand, patients displayed activations in the left premotor cortex and supplementary motor area as well as left dorsolateral prefrontal cortex. Furthermore, time since onset and visual imagery capacity were negatively related to activation in the supplementary motor area during the imagery of the affected hand.

CONCLUSIONS

These initial results demonstrate motor imagery capacity in patients with chronic neglect via compensatory neural processing during motor imagery of the affected hand in ipsilateral brain regions, since we found that the supplementary motor area appears to be specifically related to neglect severity. Although our results must be treated with caution due to the small sample size and missing control group, they indicate that neglect is not necessarily an exclusion criterion for motor imagery training per se.

Linguistic and motor representations of everyday complex actions: an fNIRS investigation

The present work aimed at exploring functional correlates of motor and linguistic representations of everyday actions, with a specific interest in potential sensorimotor activation effects induced by the use of related action sentences. While it is indeed known that observing simple motor acts (e.g., precision grasping) and listening to the sound of specific actions (e.g., walking) activate sensorimotor structures, less is known when we move to more complex behaviors and more abstract linguistic representations (e.g., verbal descriptions). Again, the potential of linguistic representations to facilitate the activation of specific sensorimotor structures during action execution or observation is yet unexplored. We then aimed at investigating hemodynamic activation patterns (via functional near-infrared spectroscopy, fNIRS) within the sensorimotor network during different tasks based on everyday activities. Twenty volunteers were asked to execute (EXE), observe (OBS), or listen (LIS) to brief verbal descriptions of transitive actions, to observe them while listening to their description (OBS-LIS), or to execute them while listening to their description (EXE-LIS). Analyses highlighted that, in the left hemisphere, hemodynamic responses were the lowest during observation of complex actions and observation coupled with listening, greater during simple listening to verbal description of actions, and maximal when participants actually executed complex actions or executed them while listening to their verbal descriptions. The present results suggest that processing verbal descriptions of actions might keep the sensorimotor network more active than simply observing them. Such first pieces of evidence hint at potential implications for novel procedures for rehabilitation of movement and action deficits.