The touch in action: exploring sensorimotor interactions with motor imagery.

The current research investigates the role of tactile information and its associated neural substrates in controlling the action. We employ a combination of motor and sensory components by asking participants to imagine exerting force with the index finger while either touching or not touching a surface. Assuming action imagination and action performance present similar patterns of activation along the motor system, we applied single-pulse transcranial magnetic stimulation over the primary motor cortex (M1) during action imagination. We observed increased amplitude of motor-evoked potentials (MEPs) of the relevant muscle when imagined actions were performed concurrently with tactile stimulation, suggesting a facilitatory effect of touch on the motor system. The motor system activity was scaled-based on the different amounts of force required, and crucially, this effect was specific to the body part involved in the action imagined. An intriguing positive correlation was observed between participants' ratings of their imagery level of vividness and the activation of the motor system, indicating that those participants exhibiting MEPs scaled correctly also had strong visualization abilities, as reflected by their capacity to accurately distinguish between varying levels of force.

Postural adjustments to self-triggered perturbations under conditions of changes in body orientation.

We studied anticipatory and compensatory postural adjustments (APAs and CPAs) associated with self-triggered postural perturbations in conditions with changes in the initial body orientation. In particular, we were testing hypotheses on adjustments in the reciprocal and coactivation commands, role of proximal vs. distal muscles, and correlations between changes in indices of APAs and CPAs. Healthy young participants stood on a board with full support or reduced support area and held a standard load in the extended arms. They released the load in a self-paced manned with a standard small-amplitude arm movement. Electromyograms of 12 muscles were recorded and used to compute reciprocal and coactivation indices between three muscle pairs on both sides of the body. The subject's body was oriented toward one of three targets: straight ahead, 60° to the left, and 60° to the right. Body orientation has stronger effects on proximal muscle pairs compared to distal muscles. It led to more consistent changes in the reciprocal command compared to the coactivation command. Indices of APAs and CPAs showed positive correlations across conditions. We conclude that the earlier suggested hierarchical relations between the reciprocal and coactivation command could be task-specific. Predominance of negative or positive correlations between APA and CPA indices could also be task-specific.

Olfaction and gustation in blindness: a state of the art of the literature.

To date, there are quite a few studies assessing olfaction and gustation in blindness, with great variability in sample size, participants' age, blindness onset and smell and taste evaluation methods. Indeed, the evaluation of olfactory and gustatory performance can differ depending on several factors, including cultural differences. Therefore, here we analysed through a narrative review, all the works reporting a smell and taste assessment in blind individuals during the last 130 years, trying to summarize and address the knowledge in this field.

Transcranial direct current stimulation (tDCS) modulates motor execution in a limb reaching task.

The majority of human activities show a trade-off between movement speed and accuracy. Here we tested 16 participants in a quick pointing action after 20 minutes (2 mA) of transcranial direct current stimulation (tDCS) delivered at the supplementary motor area in a single-blind crossover design study for testing the feedforward components in the control of action. tDCS stimuli were delivered in three randomized sessions of stimulations as anodal, cathodal and sham as a control. The task performed pre- and post-tDCS stimulation, was to point as fast and as precise as possible with the big toe to targets having different sizes (2 and 8 cm; Width) and positioned at different distances (20 and 60 cm; Distance). An optoelectronic motion capture system was used to collect the kinematics of movement. The result indicates that individuals after receiving anodal stimulation decreased their movement time and increased their movement speed, while the opposite happened after receiving a cathodal stimulation. The scarcity of studies in this area invites us to plan a research that aims at the trade-off especially in the clinical settings.

The effect of motor and cognitive placebos on the serial reaction time task.

Motor learning is a key component of human motor functions. Repeated practice is essential to gain proficiency over time but may induce fatigue. The aim of this study was to determine whether motor performance and motor learning (as assessed with the serial reaction time task, SRTT) and perceived fatigability (as assessed with subjective scales) are improved after two types of placebo interventions (motor and cognitive). A total of 90 healthy volunteers performed the SRTT with the right hand in three sessions (baseline, training and final). Before the training and the final session, one group underwent a motor-related placebo intervention in which inert electrical stimulation (TENS) was applied over the hand and accompanied by verbal suggestion that it improves movement execution (placebo-TENS). The other group underwent a cognitive-related placebo intervention in which sham transcranial direct current stimulation (tDCS) was delivered to the supraorbital area and accompanied by verbal suggestion that it increases attention (placebo-tDCS). A control group performed the same task without receiving treatment. Overall better performance on the SRTT (not ascribed to sequence-specific learning) was noted for the placebo-TENS group, which also reported less perceived fatigability at the physical level. The same was observed in a subgroup tested 24 hr later. The placebo-tDCS group reported less perceived fatigability, both at the mental and physical level. These findings indicate that motor- and cognitive-related placebo effects differently shape motor performance and perceived fatigability on a repeated motor task.

Spinal reflexive movement follows general tau theory.

BACKGROUND: Tau theory explains how both intrinsically and perceptually guided movements are controlled by the brain. According to general tau theory, voluntary, self-paced human movements are controlled by coupling the tau of the movement (i.e., the rate of closure of the movement gap at its current closure rate) onto an intrinsically generated tau-guide (Lee in Ecol Psychol 10:221-250, 1998). To date there are no studies that have looked at involuntary movements, which are directly guided by innate patterns of neural energy generated at the level of the spinal cord or brain, and that can be explained by general tau theory. This study examines the guidance of an involuntary movement generated by the Patellar reflex in presence of a minimized gravitational field. RESULTS: The results showed that the Patellar reflexive movement is strongly coupled to an intrinsic tau-guide particularly when the limb is not moving in the direction of gravity. CONCLUSION: These results suggest that the same principles of control underpin both voluntary and involuntary movements irrespective of whether they are generated in the brain or the spinal cord. Secondly, given that movements like the patellar reflex are visible from infancy, one might conclude that tau-guidance is an innate form of motor control, or neural blueprint, that has evolved over time.

Representational momentum in adolescent dancers.

An observer's memory for the final position of a previously viewed moving target is often displaced slightly forward in the direction of the target motion. This forward displacement, named representational momentum (RM), reflects the implied momentum of the target and is influenced by the level of familiarity that the observer has with the target observed. In this study, we investigated whether RM would be present in adolescents when they viewed actions from their domain of expertise, which would allow them to anticipate the sequence of familiar movements. We thus recruited adolescent ballet dancers and asked them to view a typical ballet jump (grand jeté) in photos as in a classical RM paradigm. The ascending, descending, and flying (between ascending and descending) phases of the jump were used to test the effects of the momentum of the jump combined with the effects of gravity, and adolescent dancers' performance was compared with age-matched non-dancers. Results revealed that all adolescents exhibited RM in the ascending and descending phases of the jump with a greater RM effect in the descending than in the ascending phases. Crucially, only dancers exhibited RM in the flying phase of the jump. Our findings provided evidence of the presence of RM phenomenon in adolescents along with the tendency of an amplified effect due to the level of expertise.

The Effects of Nicotine on Cortical Excitability After Exercise: A Double-Blind Randomized, Placebo-controlled, Crossover Study.

PURPOSE: The use of smokeless tobacco/nicotine products is common among athletes, but clear evidence for their positive or negative effect on sports performance is lacking. Nicotine is a psychoactive substance involved in numerous neuronal processes including cortical excitability. The aim of this study was to evaluate its effect on cortical excitability associated with aerobic exercise in nicotine-naive healthy volunteers. METHODS: Ten nicotine-naive healthy volunteers were recruited for this double-blind, randomized, crossover study to compare the effect of snus (8 mg nicotine), an oral, smokeless tobacco product, to placebo on cortical excitability before and after aerobic exercise. Transcranial magnetic stimulation (TMS) was used to measure changes in corticomotor excitability (motor-evoked potentials, MEPs) and electromyography of leg muscles during maximal voluntary contractions (MVC) to assess changes in muscle contractions. Before and after aerobic exercise and with or without nicotine treatment, MEPs and MVCs were measured. RESULTS: Analysis of TMS data showed lower motor cortex activation (lower MEP amplitude) after snus administration compared with placebo, whereas electromyography data showed no difference in muscle contraction between snus and placebo treatment. CONCLUSIONS: These findings suggest a general reduction in cortical excitability, without no relevant effect on physical performance.

Cervical Spine Motion During Vehicle Extrication of Healthy Volunteers.

Objective: Prehospital spinal motion restriction as a prevention technique for secondary neurological injury is a key principle in emergency medicine. Our aim was to evaluate the effectiveness of different cervical spinal cord motion restriction techniques of awake and cooperative healthy volunteers during extrication.Methods: Twenty-three healthy volunteers were asked to exit a car (unassisted) with a rigid cervical collar (CC condition) or without it (autonomous exit: AE; instructed exit: IE); they were also extricated by two rescuers after setting a rigid cervical collar and by using an extrication device (CC + XT condition). Eight 3 D infrared cameras were calibrated around the vehicle to measure cervical spine angle, angular speed and acceleration in the sagittal plane. Surface wireless EMG electrodes were used to record superior trapezius, erector spinae and rectus abdominis muscle activity. All measures were recorded during two phases: device positioning (maneuver) and vehicle exiting.Results: The lowest range of motion was observed in CC during maneuver and exit (about 17°), the greatest in AE and IE (about 45°); when the extrication device was utilized along with the cervical collar (CC + XT) an increase, rather than a further decrease, in the range of motion was observed (about 25° during maneuver and exit). Larger values of angular speed and acceleration were observed in CC + XT when compared to CC, both during maneuver and exit (p < 0.001). The lowest EMG activity was observed during maneuver in CC and CC + XT; during exit a lower EMG activity was observed in CC + XT compared to CC (p < 0.001). Thus, when an extrication device is utilized (CC + XT), a lower active control of the cervical spine region is associated with faster and more brisk movements of the cervical spine compared to CC alone.Conclusions: Our findings support the idea that spinal motion restriction via rigid cervical collar of awake and cooperative trauma patients is effective in reducing cervical spine motion in the sagittal plane during vehicle extrication.

Interactive footstep sounds modulate the perceptual-motor aftereffect of treadmill walking.

In this study, we investigated the role of interactive auditory feedback in modulating the inadvertent forward drift experienced while attempting to walk in place with closed eyes following a few minutes of treadmill walking. Simulations of footstep sounds upon surface materials such as concrete and snow were provided by means of a system composed of headphones and shoes augmented with sensors. In a control condition, participants could hear their actual footstep sounds. Results showed an overall enhancement of the forward drift after treadmill walking independent of the sound perceived, while the strength of the aftereffect, measured as the proportional increase (posttest/pretest) in forward drift, was higher under the influence of snow compared to both concrete and actual sound. In addition, a higher knee angle flexion was found during the snow sound condition both before and after treadmill walking. Behavioral results confirmed those of a perceptual questionnaire, which showed that the snow sound was effective in producing strong pseudo-haptic illusions. Our results provide evidence that the walking in place aftereffect results from a recalibration of haptic, visuo-motor but also sound-motor control systems. Self-motion perception is multimodal.

(Dis-)Harmony in movement: effects of musical dissonance on movement timing and form.

While the origins of consonance and dissonance in terms of acoustics, psychoacoustics and physiology have been debated for centuries, their plausible effects on movement synchronization have largely been ignored. The present study aimed to address this by investigating whether, and if so how, consonant/dissonant pitch intervals affect the spatiotemporal properties of regular reciprocal aiming movements. We compared movements synchronized either to consonant or to dissonant sounds and showed that they were differentially influenced by the degree of consonance of the sound presented. Interestingly, the difference was present after the sound stimulus was removed. In this case, the performance measured after consonant sound exposure was found to be more stable and accurate, with a higher percentage of information/movement coupling (tau coupling) and a higher degree of movement circularity when compared to performance measured after the exposure to dissonant sounds. We infer that the neural resonance representing consonant tones leads to finer perception/action coupling which in turn may help explain the prevailing preference for these types of tones.

Enhanced corticobulbar excitability in chronic smokers during visual exposure to cigarette smoking cues.

BACKGROUND: Neuroimaging studies of chronic smokers report altered activity of several neural regions involved in the processing of rewarding outcomes. Neuroanatomical evidence suggests that these regions are directly connected to the tongue muscle through the corticobulbar pathways. Accordingly, we examined whether corticobulbar excitability might be considered a somatic marker for nicotine craving. METHODS: We compared motor-evoked potential (MEP) amplitudes recorded from the tongue and the extensor carpi radialis (control muscle) of chronic smokers under drug withdrawal and intake conditions as well as a nonsmoker group. All participants were tested during passive exposure to pictures showing a smoking cue or a meaningless stimulus. In the intake condition, chronic smokers were asked to smoke a real cigarette (CSn: group 1) or a placebo (CSp: group 2). RESULTS: Results show that MEP amplitudes recorded from the tongues of participants in the CSn and CSp groups under the withdrawal condition were selectively enhanced during exposure to a smoking cue. However, this effect on tongue MEP amplitudes disappeared in the intake condition for both the CSn and CSp groups. LIMITATIONS: Limitations include the fact that the study was conducted in 2 different laboratories, the small sample size, the absence of data on chronic smoker craving strength and the different tastes of the real and placebo cigarettes. CONCLUSION: These results suggest that, in chronic smokers, tongue muscle MEP amplitudes are sensitive to neural processes active under the physiological status of nicotine craving. This finding implicates a possible functional link between neural excitability of the corticobulbar pathway and the reward system in chronic smokers.

Time flies when we view a sport action.

Humans' time evaluation within the range of hundreds of milliseconds is often distorted, and time is judged as much longer than actually is. This consistent overestimation has been interpreted as an indicator of the threshold level for the sensitivity of the perceptuomotor system. The purpose of this study was to investigate how the perception of time, both in sub- and supra-second timescales, changes for elite athletes that are considered as individuals with highly developed motor perceptual capabilities and with great sense of time particularly for the extremely short timescales. For this purpose, we asked elite pole-vaulters to reproduce the exposure times of a familiar image showing a pole-vault jump and non-familiar images as a fencing lunge and scrambled pixels and compared their estimates with controls. While the time distortion in the supra-second range was similar for athletes and controls independently from the image presented, in the sub-second range of time, athletes were more accurate and less variable than controls, while for all the participants, the images were perceived differently. Time was perceived as shorter when viewing the pole-vault jump image followed by the fencing lunge and last the scrambled pixels, providing the evidence that action observation distorts individuals' time perception by compressing the perceived passage of time. Remarkably though pole-vaulters' higher precision and lower variability than controls indicate their ability to compensate for this distortion due to a well-refined internal clock developed through sport training.

Fooling the kickers but not the goalkeepers: behavioral and neurophysiological correlates of fake action detection in soccer.

Studies demonstrate that elite athletes are able to extract kinematic information of observed domain-specific actions to predict their future course. Little is known, however, on the perceptuo-motor processes and neural correlates of the athletes' ability to predict fooling actions. Combining psychophysics and transcranial magnetic stimulation, we explored the impact of motor and perceptual expertise on the ability to predict the fate of observed actual or fake soccer penalty kicks. We manipulated the congruence between the model's body kinematics and the subsequent ball trajectory and investigated the prediction performance and cortico-spinal reactivity of expert kickers, goalkeepers, and novices. Kickers and goalkeepers outperformed novices by anticipating the actual kick direction from the model's initial body movements. However, kickers were more often fooled than goalkeepers and novices in cases of incongruent actions. Congruent and incongruent actions engendered a comparable facilitation of kickers' lower limb motor representation, but their neurophysiological response was correlated with their greater susceptibility to be fooled. Moreover, when compared with actual actions, motor facilitation for incongruent actions was lower among goalkeepers and higher among novices. Thus, responding to fooling actions requires updation of simulative motor representations of others' actions and is facilitated by visual rather than by motor expertise.

Neural underpinnings of the interplay between actual touch and action imagination in social contexts.

While there is established evidence supporting the involvement of the sense of touch in various actions, the neural underpinnings of touch and action interplay in a social context remain poorly understood. To prospectively investigate this phenomenon and offer further insights, we employed a combination of motor and sensory components by asking participants to imagine exerting force with the index finger while experiencing their own touch, the touch of one another individual, the touch of a surface, and no touch. Based on the assumption that the patterns of activation in the motor system are similar when action is imagined or actually performed, we proceeded to apply a single-pulse transcranial magnetic stimulation over the primary motor cortex (M1) while participants engaged in the act of imagination. Touch experience was associated with higher M1 excitability in the presence and in the absence of force production imagination, but only during force production imagination M1 excitability differed among the types of touch: both biological sources, the self-touch and the touch of one other individual, elicited a significant increase in motor system activity when compared to touching a non-living surface or in the absence of touch. A strong correlation between individual touch avoidance questionnaire values and facilitation in the motor system was present while touching another person, indicating a social aspect for touch in action. The present study unveils the motor system correlates when the sensory/motor components of touch are considered in social contexts.

General tau theory as a model to evaluate audiovisual interplay in interceptive actions.

When interacting with the environment, sensory information is essential to guide movements. Picking up the appropriate sensory information (both visual and auditory) about the progression of an event is required to reach the right place at the right time. In this study, we aimed to see if general tau theory could explain the audiovisual guidance of movement in interceptive action (an interception task). The specific contributions of auditory and visual sensory information were tested by timing synchronous and asynchronous audiovisual interplays in successful interceptive trials. The performance was computed by using the tau-coupling model for information-movement guidance. Our findings revealed that while the auditory contribution to movement guidance did change across conditions, the visual contribution remained constant. In addition, when comparing the auditory and visual contributions, the results revealed a significant decrease in the auditory compared to the visual contribution in just one of the asynchronous conditions where the visual target was presented after the sound. This may be because more attention was drawn to the visual information, resulting in a decrease in the auditory guidance of movement. To summarize, our findings reveal how tau-coupling can be used to disentangle the relative contributions of the visual and auditory sensory modalities in movement planning.

Postural Threat Influences the Coupling Between Anticipatory and Compensatory Postural Adjustments in Response to an External Perturbation.

Fear of falling increases conscious control of balance and postural threat warrants accurate anticipatory motor commands for keeping a safe body posture. This study examines the anticipatory (APAs) and compensatory (CPAs) postural adjustments generated in response to an external perturbation while individuals are positioned at two different altitudes (2 cm and 80 cm) from the floor level. The main result indicates that due to the perceived emotional threat, different agonist and antagonist muscles synergies (R and C-Indexes) are manifested, particularly during the anticipatory phase. The results suggest that the CNS sends central commands for anticipating postural adjustments by adopting primarily a muscle reciprocal activation instead of a muscle co-activation strategy. Interestingly, the APAs strategies were modified under different postural threats by controlling the agonist-antagonist muscles at different joints of lower extremity. For CPAs the reciprocal activation was less applied compared to muscles co-activation to unsure larger margin for compensatory adjustments as needed and re-establish the postural stability. The results indicate that when facing to a postural threat, the CNS modulates the anticipatory and compensatory phases of postural adjustments to minimize the risk of falling.

Synergies Stabilizing Vertical Posture in Spaces of Control Variables.

In this study, we address the question: Can the central nervous system stabilize vertical posture in the abundant space of neural commands? We assume that the control of vertical posture is associated with setting spatial referent coordinates (RC) for the involved muscle groups, which translates into two basic commands, reciprocal and co-activation. We explored whether the two commands co-varied across trials to stabilize the initial postural state. Young, healthy participants stood quietly against an external horizontal load and were exposed to smooth unloading episodes. Linear regression between horizontal force and center of mass coordinate during the unloading phase was computed to define the intercept (RC) and slope (apparent stiffness, k). Hyperbolic regression between the intercept and slope across unloading episodes and randomization analysis both demonstrated high indexes of co-variation stabilizing horizontal force in the initial state. Higher co-variation indexes were associated with lower average k values across the participants suggesting destabilizing effects of muscle coactivation. Analysis of deviations in the {RC; k} space keeping the posture unchanged (motor equivalent) between two states separated by a voluntary quick body sway showed significantly larger motor equivalent deviations compared to non-motor equivalent ones. This is the first study demonstrating posture-stabilizing synergies in the space of neural control variables using various computational methods. It promises direct applications to studies of postural disorders and rehabilitation.

A Practical Framework for Academics to Implement Public Engagement Interventions and Measure Their Impact.

Academic institutions have shown an increased interest in the so-called third mission to offer an impactful contribution to society. Indeed, public engagement programs ensure knowledge transfer and help to inspire positive public discourse. We aimed to propose a comprehensive framework for academic institutions planning to implement a public engagement intervention and to suggest potential indicators to measure its impact. To inform the framework development, we searched the literature on public engagement, the third mission, and design theory in electronic databases and additional sources (e.g., academic recommendations) and partnered with a communication agency offering non-academic advice. In line with this framework, we designed a public engagement intervention to foster scientific literacy in Italian youth, actively involving them in the development of the intervention. Our framework is composed of four phases (planning/design, implementation, immediate impact assessment, and medium- and long-term assessment). Impact indicators were subdivided into outcome variables that were immediately describable (e.g., changed understanding and awareness of the target population) and measurable only in the medium or long run (e.g., adoption of the intervention by other institutions). The framework is expected to maximize the impact of public engagement interventions and ultimately lead to better reciprocal listening and mutual understanding between academia and the public.

Affective sounds entering the peripersonal space influence the whole-body action preparation.

The peripersonal space (PPS), the space surrounding us, is found to have enhanced multisensory-motor representation in the brain. In this study, we investigate how approaching sounds stopping at different distances within the peripersonal space, and carrying emotional content (positive, negative, and neutral), modulate the preparation of action as performing a Step. Premotor reaction times were measured by means of anticipatory forces and muscular activations to capture action preparation, the kinematics of stepping was considered for defining action performance, and for each stimulus, the individual perceived level of arousal and valence was evaluated. In general, we found a prompter premotor reaction for closer sounds compared to the farther ones and the fastest reactions detected for the neutral sound at each distance. We interpreted this time facilitation for neutral sound due to the large frequency spectrum of the stimuli and the absence of affective component and semantical content to decode. Interestingly, while at the close distance, none difference was found between positive and negative emotional stimuli, at the far distance faster reactions were present for negative compared to the positive sounds indicating that when arousal is less enhanced individuals are able to differentiate the emotional content of a sound. The kinematics observed after action initiation sustained the anticipatory results by showing that larger steps were performed when reacting to close compared to far sounds, being perceived as more arousing, and this happened particularly for neutral and negative sounds. Altogether, the results showed that action preparation is influenced by the vicinity and by the valence carried by looming auditory stimuli. For discriminating the stimuli valence, a certain distance, still within the PPS, is necessary; when instead stimuli are too close to the body valence discrimination is not performed.