Sensorimotor System Research Articles

Grip force control under sudden change of friction.

A task as simple as holding a cup between your fingers generates complex motor commands to finely regulate the forces applied by muscles. These fine force adjustments ensure the stability and integrity of the object by preventing it from slipping out of grip during manipulation and by reacting to perturbations. To do so, our sensorimotor system constantly monitors tactile and proprioceptive information about the force object exerts on fingertips and the friction of the surfaces to determine the optimal gripforce. While the literature describes the transient responses, humans can generate to react to perturbations in load force, it is yet to be determined if humans can also react to abrupt changes in friction while already holding an object. Only recently technology using imperceivable ultrasonic vibrations became available to modulate friction in real time to investigate thisquestion. In this study, we used an object with an integrated friction modulation device suspended in a pulley system controlling the load. With this device, we explored the rapid adaptation of the sensorimotor system to changes in friction alone and in combination with changes in load. When load force and friction changed simultaneously, the grip force response was regulated based on the grip safety requirements. Participants increased their grip force in response to decrease in friction. However, they did not adjust their grip force when the friction increased, which is expected based on our biomechanical model of friction sensingmechanisms. KEY POINTS: Simple tasks like pouring water into a glass mobilize intricate interactions between fingertip sensory inputs and motor commands to account for the weight change and friction. It has been investigated how humans react to force perturbations when holding an object, but very little is known about how frictional changes are sensed and acted upon while holding an object, for example, due to sweating or condensation. We engineered a unique experimental object that utilizes imperceivable ultrasonic vibrations to change the frictional properties of the surface in a few milliseconds. This apparatus enabled us to study how human subjects react to change of friction when gripping or holding an object. We showed that humans adjust the strength of their grasp when forces in the direction of gravity either increase or decrease; however, frictional change evokes adjustments only when friction decreases.

The multisensory control of sequential actions

Many motor tasks are comprised of sequentially linked action phases, as when reaching for, lifting, transporting, and replacing a cup of coffee. During such tasks, discrete visual, auditory and/or haptic feedback are typically associated with mechanical events at the completion of each action phase, as when breaking and subsequently making contact between the cup and the table. An emerging concept is that important sensorimotor control operations, that affect subsequent action phases, are centred on these discrete multisensory events. By predicting sensory feedback at the completion of action phases, and comparing with the actual feedback that arises, task performance can be continuously monitored. If errors are detected, the sensorimotor system can quickly respond with task-protective corrective actions. The aim of this study was to investigate how discrete multisensory feedback at the completion of action phases are used in these control operations. To investigate this question, 42 healthy human participants (both male and female) performed a visually guided sequential reaching task where auxiliary discrete visual, auditory and/or haptic feedback was associated with the completion of action phases. Occasionally however, this feedback was removed in one or two modalities. The results show that although the task was visually guided, its control was critically influenced by discrete auditory and haptic feedback. Multisensory integration effects occurred, that enhanced the corrective actions, when auditory feedback was unexpectedly removed along with haptic or visual feedback. This multisensory enhancement may facilitate the ability to detect errors during sequential actions and amplify task-protective corrective actions.

Aberrant network topological structure of sensorimotor superficial white-matter system in major depressive disorder.

White-matter tracts play a pivotal role in transmitting sensory and motor information, facilitating interhemispheric communication and integrating different brain regions. Meanwhile, sensorimotor disturbance is a common symptom in patients with major depressive disorder (MDD). However, the role of aberrant sensorimotor white-matter system in MDD remains largely unknown. Herein, we investigated the topological structure alterations of white-matter morphological brain networks in 233 MDD patients versus 257 matched healthy controls (HCs) from the DIRECT consortium. White-matter networks were derived from magnetic resonance imaging (MRI) data by combining voxel-based morphometry (VBM) and three-dimensional discrete wavelet transform (3D-DWT) approaches. Support vector machine (SVM) analysis was performed to discriminate MDD patients from HCs. The results indicated that the network topological changes in node degree, node efficiency, and node betweenness were mainly located in the sensorimotor superficial white-matter system in MDD. Using network nodal topological properties as classification features, the SVM model could effectively distinguish MDD patients from HCs. These findings provide new evidence to highlight the importance of the sensorimotor system in brain mechanisms underlying MDD from a new perspective of white-matter morphological network.

The brain’s sensitivity to sensory error can be modulated by altering perceived variability

When individuals make a movement that produces an unexpected outcome, they learn from the resulting error. This process, essential in both acquiring new motor skills and adapting to changing environments, critically relies on error sensitivity, which governs how much behavioral change results from a given error. Although behavioral and computational evidence suggests error sensitivity can change in response to task demands, neural evidence regarding the flexibility of error sensitivity in the human brain is lacking. Here, we tested whether the nervous system’s sensitivity to errors, as measured by prediction-driven suppression of auditory cortical activity, can be modulated by altering participants’ (both males and females) perceived variability during speech. Our results showed that error sensitivity, as measured by this suppression, was increased after exposure to an auditory perturbation that increased speakers’ perceived variability. The current study establishes the validity of behaviorally modulating the nervous system’s sensitivity to errors, which has significant potential to enhance motor learning and rehabilitation.Significance StatementError sensitivity, how responsive the sensorimotor system is to perceived errors, is typically considered a stable, intrinsic characteristic. Here, however, we demonstrate that a temporary manipulation of motor output variability induces a persistent change in a neural index of error sensitivity, highlighting a potential avenue to enhance motor learning and rehabilitation.

Two service evaluations of LEAPlets – An early years programme for children in foster care and adoption, based on the BUSS® (Building Underdeveloped Sensorimotor Systems) Model

BUSS® is a relationally based intervention, bringing an appreciation of the role nurture, touch and movement play in the development of bodily regulation in early childhood. Following a neurosequential understanding of development ( Perry and Hambrick, 2008 ), BUSS® works to support foster carers and adoptive parents in understanding both the disruptive impact of trauma on the development of their child’s foundation sensorimotor systems and the critical role they can play in ameliorating this disruption. Good bodily regulation offers children a platform upon which relationships, emotional regulation and learning can grow ( Lloyd, 2023 ). LEAPlets is a group for children and their parents and carers, based on the BUSS® Model. It aims to build attachment relationships, supporting parents and carers in understanding and rebuilding their child’s foundation sensorimotor systems. This paper brings together two service evaluation projects of LEAPlets carried out by clinical psychologists in training. The first evaluation is of LEAPlets as a school readiness programme for children in foster care in Leeds. The second evaluation is the LEAPlets group in One Adoption West Yorkshire (OAWY) for new adoptive parents and their newly adopted children. While more research is needed, both studies showed improvements for the children in bodily and emotional regulation, communication and relationships, as well as positive changes in skill development, understanding of their child, and relationships for foster carers and adoptive parents. Models like LEAPlets, which address both the relational and sensorimotor consequences of early trauma, may usefully form part of early intervention programmes for care-experienced children. Training to run LEAPlets groups has been developed, and groups are now running in England, Wales and the Republic of Ireland. This will be explored and discussed, with reference to school readiness, impact on foster carers and supporting adoptive families early in their life together.

Evolutionary robotics as a modelling tool in evolutionary biology.

The use of evolutionary robotic systems to model aspects of evolutionary biology is well-established. Yet, few studies have asked the question, "What kind of model is an evolutionary robotic system?" This paper seeks to address that question in several ways. First, it is addressed by applying a structured model description developed for physical robot models of animal sensorimotor systems, then by outlining the strengths and limitations of evolutionary robotics for modelling evolutionary biology, and, finally, by considering the deepest questions in evolution and which of them might feasibly be modelled by evolutionary robotics. The paper concludes that although evolutionary robotics faces serious limitations in exploring deeper questions in evolutionary biology, its bottom-up approach to modelling populations of evolving phenotypes and their embodied interactions holds significant value for both testing and generating hypotheses.

Positron emission tomography neuroimaging of [18F]fluorodeoxyglucose uptake and related behavior in the Pink1-/- rat model of Parkinson disease.

Parkinson disease (PD) is a neurodegenerative condition affecting multiple sensorimotor and cognitive systems. The Pink1-/- rat model exhibits vocal, cognitive, and limb use deficits seen in idiopathic PD. We sought to measure glucose metabolism in brain regions in Pink1-/- and wild type (WT) rats, and to associate these to measures of ultrasonic vocalization, cognition, and limb use behavior. Pink1-/- (n = 12) and WT (n = 14) rats were imaged by [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET) in a repeated measures design at approximately 10 months of age and 6 weeks later. Relative regional glucose metabolism was indexed by whole brain normalized FDG uptake, which was calculated for 18 regions identified a priori for comparison. Behavioral measures included tests of communication via ultrasonic vocalization, cognition with 5-Choice Serial Reaction Time Test (5-CSRTT), and limb use with Cylinder Test and Challenge Beam. Relative glucose metabolism was significantly different in Pink1-/- rats in prelimbic area, striatum, nucleus ambiguus, globus pallidus, and posterior parietal association cortex compared to WT controls. For behavioral measures, Pink1-/- rats demonstrated quieter vocalizations with a restricted frequency range, and they showed increased number of foot-faults and hindlimb steps (shuffling) in limb motor tests. Significant behavior vs. brain correlations included associations of ultrasonic vocalization parameters with glucose metabolism indices in locus coeruleus and substantia nigra. FDG PET reveals abnormalities in relative regional brain glucose metabolism in Pink1-/- rats in brain regions that are important to cognition, vocalization, and limb motor control that are also impacted by Parkinson disease. This method may be useful for mechanistic studies of behavioral deficits and therapeutic interventions in translational studies in the Pink1-/- PD model.

Alterations in Endogenous Stem Cell Populations in the Acute Phase of Blast-Induced Spinal Cord Injury.

Blast-induced spinal cord injury (bSCI) is prevalent among military populations and frequently leads to irreversible spinal cord tissue damage that manifests as sensorimotor and autonomic nervous system dysfunction. Clinical recovery from bSCI has been proven to be multifactorial, as it is heavily dependent on the function of numerous cell populations in the tissue environment, as well as extensive ongoing inflammatory processes. This varied recovery process is thought to be due to irreversible spinal cord damage after 72 hours post-injury. Stem cell therapy for spinal cord injuries has long been investigated due to these cells' proliferative nature, ability to enhance neuro-regeneration, neuroprotection, remyelination of axons, and modulation of the immune and inflammatory responses. Therefore, this study hypothesizes that the impaired function after injury is due to a lack of specific ectoderm and neural stem cell population activity at the injury site. This study aimed to elucidate changes in endogenous stem cell patterns by evaluating immunohistochemical staining densities of various stem cell markers using a preclinical thoracolumbar bSCI model. Analysis was performed 24-, 48-, and 72 hours following blast exposure. Behavior tests to assess sensory and mechanical functions were also performed. The following Cluster of differentiation (CD) markers CD105, CD45, CD133, and Vimentin, Nanog homebox (NANOG), and sex determining region Y HMG-box 2 (SOX2) positive cell populations were significantly elevated with trending increases in Octamer-binding transcription factor 4 (OCT4) in the thoracolumbar region of spinal cord tissue at 72 hours following bSCI (p < 0.05). Behavior analyses showed significant decreases in paw withdrawal thresholds in the hind limbs and changes in locomotion at 48- and 72 hours post-injury (p < 0.05). The significant increase in mesenchymal, pluripotent, and neural stem cell populations within the thoracolumbar region post-injury suggests that migratory patterns of stem cell populations are likely altered in response to bSCI. Behavioral deficits were consistent with those experienced by military personnel, such as increased pain-like behavior, reduced proprioception and coordination, and increased anxiety-like behavior post-bSCI, which underlines the translational capabilities of this model. While further research is vital to understand better the intrinsic and synergistic chemical and mechanical factors driving the migration of stem cells after traumatic injury, increased endogenous stem cell populations at the injury site indicate that stem cell-based treatments in patients suffering from bSCI could prove beneficial.

Physical therapy in a patient with viral -encephalitis hemi-paresis: A Case report

The purpose of the rehabilitation program is to improve motor skills, coordination, sensory system, mobilization and other existing disorders to achieve activity of daily living (ADL). Physical therapy as part of the multidisciplinary approach can provide core stability exercises, muscular facilitation and stimulation of motion of the upper and lower extremities, balance exercises and mobility exercises, as well as strengthening exercises with PNF facilitation and active stimulation techniques and using the patient's body weight as a training burden. Bobath approach and facilitation exercise can reduce spasticity by strengthening the antagonist muscles. MMT right upper extremity 3/5, left upper extremity 4/5, right lower extremity 2/5, and left lower extremity 3/5. Ashworth scale right upper extremity 1/4, right lower extremity 2/4, and left lower extremity 1/4. Clonus is reduced, the patient can stand with maximum support without clonus for 10 minutes. Trunk impairment scale 12/23 and Barthel index 65/100. Anthropometric examination showed differences in the circumference of the lower extremities, namely the right patella circumference 34-32 cm left, right upper leg 39 cm-left 37 cm, and left lower leg 29-24 cm. Mobilize the patient to a laying position with minimal assistance. Mobilization of the patient is being able to sit with minimal assistance, namely stabilization in the pelvis, sitting to standing with moderate support, which is supported at the knee bilaterally, and standing with support at the knee and pelvic for 10 minutes. This case report concludes that although physiotherapy is done late with strengthening exercise and core stability strengthening techniques, lying down strengthening exercise, it can improve motor skills, coordination, which in turn will increase the patient's independence in carrying out functional activities and ADLs.

A "Conscious" Loss of Balance: Directing Attention to Movement Can Impair the Cortical Response to Postural Perturbations.

"Trying too hard" can interfere with skilled movement, such as sports and music playing. Postural control can similarly suffer when conscious attention is directed toward it ("conscious movement processing"; CMP). However, the neural mechanisms through which CMP influences balance remain poorly understood. We explored the effects of CMP on electroencephalographic (EEG) perturbation-evoked cortical responses and subsequent balance performance. Twenty healthy young adults (age = 25.1 ± 5 years; 10 males and 10 females) stood on a force plate-embedded moveable platform while mobile EEG was recorded. Participants completed two blocks of 50 discrete perturbations, containing an even mix of slower (186 mm/s peak velocity) and faster (225 mm/s peak velocity) perturbations. One block was performed under conditions of CMP (i.e., instructions to consciously control balance), while the other was performed under "Control" conditions with no additional instructions. For both slow and fast perturbations, CMP resulted in significantly smaller cortical N1 signals (a perturbation-evoked potential localized to the supplementary motor area) and lower sensorimotor beta EEG activity 200-400 ms postperturbation. Significantly greater peak velocities of the center of pressure (i.e., greater postural instability) were also observed during the CMP condition. Our findings provide the first evidence that disruptions to postural control during CMP may be a consequence of insufficient cortical activation relevant for balance (i.e., insufficient cortical N1 responses followed by enhanced beta suppression). We propose that conscious attempts to minimize postural instability through CMP acts as a cognitive dual-task that dampens the sensitivity of the sensorimotor system for future losses of balance.

Sensorimotor brain–computer interface performance depends on signal-to-noise ratio but not connectivity of the mu rhythm in a multiverse analysis of longitudinal data

Objective.Serving as a channel for communication with locked-in patients or control of prostheses, sensorimotor brain-computer interfaces (BCIs) decode imaginary movements from the recorded activity of the user's brain. However, many individuals remain unable to control the BCI, and the underlying mechanisms are unclear. The user's BCI performance was previously shown to correlate with the resting-state signal-to-noise ratio (SNR) of the mu rhythm and the phase synchronization (PS) of the mu rhythm between sensorimotor areas. Yet, these predictors of performance were primarily evaluated in a single BCI session, while the longitudinal aspect remains rather uninvestigated. In addition, different analysis pipelines were used to estimate PS in source space, potentially hindering the reproducibility of the results.Approach.To systematically address these issues, we performed an extensive validation of the relationship between pre-stimulus SNR, PS, and session-wise BCI performance using a publicly available dataset of 62 human participants performing up to 11 sessions of BCI training. We performed the analysis in sensor space using the surface Laplacian and in source space by combining 24 processing pipelines in a multiverse analysis. This way, we could investigate how robust the observed effects were to the selection of the pipeline.Main results.Our results show that SNR had both between- and within-subject effects on BCI performance for the majority of the pipelines. In contrast, the effect of PS on BCI performance was less robust to the selection of the pipeline and became non-significant after controlling for SNR.Significance.Taken together, our results demonstrate that changes in neuronal connectivity within the sensorimotor system are not critical for learning to control a BCI, and interventions that increase the SNR of the mu rhythm might lead to improvements in the user's BCI performance.

Exploring the Behavioral Traits of Male Mutant Crup Mice as an Experimental Neurodegenerative Disease Model

The congenic BALB/c-crup (‘crup’ meaning ‘cruza-pernas’ in Portuguese or cross legs in English), a homozygous recessive mutant mouse derived from N-ethyl-N-nitrosourea mutagenesis, exhibits a unique phenotype characterized by hindlimb crossing when the mouse is suspended by its tail, along with age-related neuromotor issues. The study aimed to identify the genetic mutation causing the BALB/c-crup phenotype and evaluate the behavioral responses of the mice. Open field test, elevated plus maze, and elevated beam experiments were conducted to evaluate general activity, motor function, as well as sensorimotor and autonomic nervous systems. Genetic mapping and exome analysis identified a nonsynonymous (missense mutation), a single nucleotide variant, in the Taf15 gene. This mutation results in the p.G55S substitution, where glycine is replaced by serine at position 55 in the gene product. Longitudinal assessment by the open field test revealed altered locomotion, decreased mobility, and reduced rearing and grooming frequency in mutant mice. Sensorimotor function declines were observed through reduced surface righting reflex scores, grip strength, and increased hindquarter angle. In the elevated beam test, mutants exhibited tail hypotonia and aversion to traversing the beam. The elevated plus maze revealed altered behavior in closed arms, suggesting increased anxiety-like behavior or sensorimotor impairment. Our findings provide insights into neurologic and behavioral anomalies associated with a Taf15 gene mutation. The altered locomotion, sensory impairments, and disorientation observed in the crup phenotype indicate a progressive neuromotor condition, potentially serving as a novel mouse model for neurodegenerative diseases.

Brain Functional Alterations in Patients With Benign Paroxysmal Positional Vertigo Demonstrate the Visual-Vestibular Interaction and Integration.

This study aimed to analyze the features of resting-state functional magnetic resonance imaging (rs-fMRI) and clinical relevance in patients with benign paroxysmal positional vertigo (BPPV) that have undergone repositioning maneuvers. A total of 38 patients with BPPV who have received repositioning maneuvers and 38 matched healthy controls (HCs) were enrolled in the present study from March 2018 to August 2021. Imaging analysis software was employed for functional image preprocessing and indicator calculation, mainly including the amplitude of low-frequency fluctuation (ALFF), fractional ALFF (fALFF), percent amplitude of fluctuation (PerAF), and seed-based functional connectivity (FC). Statistical analysis of the various functional indicators in patients with BPPV and HCs was also conducted, and correlation analysis with clinical data was performed. Patients with BPPV displayed decrease in ALFF, fALFF, and PerAF values, mainly in the bilateral occipital lobes in comparison with HCs. Additionally, their ALFF and fALFF values in the proximal vermis region of the cerebellum increased relative to HCs. The PerAF values in the bilateral paracentral lobules, the right supplementary motor area (SMA), and the left precuneus decreased in patients with BPPV and were negatively correlated with dizziness visual analog scale (VAS) scores 1 week after repositioning (W1). In addition, in the left fusiform gyrus and lingual gyrus, the PerAF values show a negative correlation with dizziness handicap inventory (DHI) scores at initial visit (W0). Seed-based FC analysis using the seeds from differential clusters of fALFF, ALFF, and PerAF showed reductions between the left precuneus and bilateral occipital lobe, the left precuneus and left paracentral lobule, and within the occipital lobes among patients with BPPV. The spontaneous activity of certain brain regions in the bilateral occipital and frontoparietal lobes of patients with BPPV was reduced, whereas the activity in the cerebellar vermis was increased. Additionally, there were reductions in FC between the precuneus and occipital cortex or paracentral lobule, as well as within the occipital cortex. The functional alterations in these brain regions may be associated with the inhibitory interaction and functional integration of visual, vestibular, and sensorimotor systems. The functional alterations observed in the visual cortex and precuneus may represent adaptive responses associated with residual dizziness.

Enhancement of perceptual and cognitive functions in near-death experience: A perspective from embodiment theories

The phenomenon of near-death experience (NDE) is attracting a growing attention among researchers of various fields. In this study, we looked at NDE from a cognitive perspective to find out how NDE events are embodied when people recall and describe them. We examined the descriptions of a group of people talking about what they had experienced in the state of NDE. Based on the gesture-as-simulated-action theory, we assumed that co-speech gestures occurring when people were talking about their experiences were physical realizations of mentally-simulated events. The results showed that the number of iconic and metaphoric gestures occurring with expressions referring to NDE events was significantly larger than those occurred with expressions referring to ordinary events. Based on these results, we suggest that embodied memory for NDE events is stronger than embodied memory for ordinary non-NDE events. NDE events are perceived, recalled, and embodied by strong activation of sensorimotor systems in a state of perceptual and cognitive enhancement, although sensorimotor systems seem to be unresponsive to sensory stimuli during NDE. Finally, based on theories of embodied cognition, we conclude that the enhancement of cognitive functions that takes place in the state of NDE is the result of enhancement in perceptual functions.

Disrupted white matter structural networks in patients with acute ischemic stroke in the right basal ganglia

Widespread structural changes have been observed in patients with stroke in previous diffusion tensor imaging studies. However, the topological organization of white matter structural networks after acute ischemic stroke (AIS) in the right basal ganglia (BG) remains unknown. The aim of our study is to investigate whether the topological structure of the white matter structural network is altered in patients with AIS in the right BG, and its relationship with cognition. Graph theoretical analysis was employed to investigate the topological architecture of whole-brain white matter structural networks in 40 AIS patients in the right BG and 40 healthy controls (HC), and network-based statistics (NBS) were applied to examine structural connectivity alterations. Compared to HC, AIS patients exhibited altered global network properties characterized by increased small-worldness, normalized clustering coefficient, and shortest path length, as well as decreased clustering coefficient, local efficiency, and global efficiency. The nodes with significantly decreased nodal properties in AIS patients were primarily located in the default mode network, limbic system, sensorimotor system, salience network, and central executive network. Reduced structural connectivity detected by NBS in AIS patients were primarily located in the lesional hemisphere. Furthermore, altered nodal properties were correlated with cognitive scores. Documenting the alterations in the topological patterns of white matter structural networks will help to promote the understanding of the neural mechanisms of cognitive impairment after AIS in the right BG.

Neurophysiological evidence of sensory prediction errors driving speech sensorimotor adaptation.

The human sensorimotor system has a remarkable ability to quickly and efficiently learn movements from sensory experience. A prominent example is sensorimotor adaptation, learning that characterizes the sensorimotor system's response to persistent sensory errors by adjusting future movements to compensate for those errors. Despite being essential for maintaining and fine-tuning motor control, mechanisms underlying sensorimotor adaptation remain unclear. A component of sensorimotor adaptation is implicit (i.e., the learner is unaware of the learning process) which has been suggested to result from sensory prediction errors-the discrepancies between predicted sensory consequences of motor commands and actual sensory feedback. However, to date no direct neurophysiological evidence that sensory prediction errors drive adaptation has been demonstrated. Here, we examined prediction errors via magnetoencephalography (MEG) imaging of the auditory cortex (n = 34) during sensorimotor adaptation of speech to altered auditory feedback, an entirely implicit adaptation task. Specifically, we measured how speaking-induced suppression (SIS)--a neural representation of auditory prediction errors--changed over the trials of the adaptation experiment. SIS refers to the suppression of auditory cortical response to speech onset (in particular, the M100 response) to self-produced speech when compared to the response to passive listening to identical playback of that speech. SIS was reduced (reflecting larger prediction errors) during the early learning phase compared to the initial unaltered feedback phase. Furthermore, reduction in SIS positively correlated with behavioral adaptation extents, suggesting that larger prediction errors were associated with more learning. In contrast, such a reduction in SIS was not found in a control experiment in which participants heard unaltered feedback and thus did not adapt. In addition, in some participants who reached a plateau in the late learning phase, SIS increased (reflecting smaller prediction errors), demonstrating that prediction errors were minimal when there was no further adaptation. Together, these findings provide the first neurophysiological evidence for the hypothesis that prediction errors drive human sensorimotor adaptation.

Serotonergic modulation of swallowing in a complete fly vagus nerve connectome

How the body interacts with the brain to perform vital life functions, such as feeding, is a fundamental issue in physiology and neuroscience. Here, we use a whole-animal scanning transmission electron microscopy volume of Drosophila to map the neuronal circuits that connect the entire enteric nervous system to the brain via the insect vagus nerve at synaptic resolution. We identify a gut-brain feedback loop in which Piezo-expressing mechanosensory neurons in the esophagus convey food passage information to a cluster of six serotonergic neurons in the brain. Together with information on food value, these central serotonergic neurons enhance the activity of serotonin receptor 7-expressing motor neurons that drive swallowing. This elemental circuit architecture includes an axo-axonic synaptic connection from the glutamatergic motor neurons innervating the esophageal muscles onto the mechanosensory neurons that signal to the serotonergic neurons. Our analysis elucidates a neuromodulatory sensory-motor system in which ongoing motor activity is strengthened through serotonin upon completion of a biologically meaningful action, and it may represent an ancient form of motor learning.

Development of Symptom Specific Dysphagia Quality of Life Questionnairein Tamil.

Swallowing intricately involves sensorimotor systems, pivotal for integrating upper digestive and respiratory functions. Dysphagia, challenging swallowing, often precipitates anxiety and depression, deeply affecting the quality of life (QOL). Understanding patient-centric symptoms is vital for assessing dysphagia's QOL impact. This study aimed at developing and validating the Symptom Specific Dysphagia Quality of Life Questionnaire in Tamil (SSDQOL-T). SSDQOL-T was developed in Tamil and underwent rigorous content validation. This questionnaire was administered to 120 normal individuals and 32 dysphagia patients, assessing various swallowing difficulties and their QOL impact. Results indicate SSDQOL-T's good internal consistency (Cronbach's α = 0.78). Significant differences in swallowing ability and QOL were noted across age groups, with older adults experiencing heightened symptoms. A high significance in mean score was obtained between healthy adults and dysphagia across all sub-domains with a 'p-value' of 0.0005. Symptoms that were found to have high significance were cough/gag reflex, regurgitation, odynophagia, globus sensation, heartburn and tiredness when compared between mechanical and degenerative dysphagia group. Strong correlations were found between SSDQOL-T scores and the Dysphagia Handicap Index in Tamil (r = 0.89). The SSDQOL-T questionnaire provides a robust tool for evaluating dysphagia-related QOL in the Tamil-speaking population. Its validation underscores its clinical relevance and utility for understanding the multidimensional impact of dysphagia. This study emphasizes the importance of culturally sensitive assessment tools in comprehensively evaluating dysphagia's QOL implications.

Amelioration of Focal Hand Dystonia via Low-Frequency Repetitive Somatosensory Stimulation.

Dystonia presents a growing concern based on evolving prevalence insights. Previous research found that, in cervical dystonia, high-frequency repetitive somatosensory stimulation (RSS; HF-RSS) applied on digital nerves paradoxically diminishes sensorimotor inhibitory mechanisms, whereas low-frequency RSS (LF-RSS) increases them. However, direct testing on affected body parts was not conducted. This study aims to investigate whether RSS applied directly to forearm muscles involved in focal hand dystonia can modulate cortical inhibitory mechanisms and clinical symptoms. We applied HF-RSS and LF-RSS, the latter either synchronously or asynchronously, on forearm muscles involved in dystonia. Outcome measures included paired-pulse somatosensory evoked potentials, spatial lateral inhibition measured by double-pulse somatosensory evoked potentials, short intracortical inhibition tested with transcranial magnetic stimulation, electromyographic activity from dystonic muscles, and behavioral measures of hand function. Both synchronous and asynchronous low-frequency somatosensory stimulation improved cortical inhibitory interactions, indicated by increased short intracortical inhibition and lateral spatial inhibition, as well as decreased amplitude of paired-pulse somatosensory evoked potentials. Opposite effects were observed with high-frequency stimulation. Changes in electrophysiological markers were paralleled by behavioral outcomes: although low-frequency stimulations improved hand function tests and reduced activation of dystonic muscles, high-frequency stimulation operated in an opposite direction. Our findings confirm the presence of abnormal homeostatic plasticity in response to RSS in the sensorimotor system of patients with dystonia, specifically in inhibitory circuits. Importantly, this aberrant response can be harnessed for therapeutic purposes through the application of low-frequency electrical stimulation directly over dystonic muscles. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Spinal Cord Transcutaneous Stimulation in Cervical Spinal Cord Injury: A Review Examining Upper Extremity Neuromotor Control, Recovery Mechanisms, and Future Directions.

Cervical spinal cord injury (SCI) results in significant sensorimotor impairments below the injury level, notably in the upper extremities (UEs), impacting daily activities and quality of life. Regaining UE function remains the top priority for individuals post-cervical SCI. Recent advances in understanding adaptive plasticity within the sensorimotor system have led to the development of novel non-invasive neurostimulation strategies, such as spinal cord transcutaneous stimulation (scTS), to facilitate UE motor recovery after SCI. This comprehensive review investigates the neuromotor control of UE, the typical recovery trajectories following SCI, and the therapeutic potential of scTS to enhance UE motor function in individuals with cervical SCI. Although limited in number with smaller sample sizes, the included research articles consistently suggest that scTS, when combined with task-specific training, improves voluntary control of arm and hand function and sensation. Further, the reported improvements translate to the recovery of various UE functional tasks and positively impact the quality of life in individuals with cervical SCI. Several methodological limitations, including stimulation site selection and parameters, training strategies, and sensitive outcome measures, require further advancements to allow successful translation of scTS from research to clinical settings. This review also summarizes the current literature and proposes future directions to support establishing approaches for scTS as a viable neuro-rehabilitative tool.