In Search of the Motor Engram: Motor Map Plasticity as a Mechanism for Encoding Motor Experience

Post-traumatic parkinsonism: The intricate twist between trauma, inflammation and neurodegeneration. A narrative review

Post-traumatic Parkinsonism (PTP) is a complex neurological disorder that is often associated with the occurrence of a traumatic brain injury (TBI). PTP can occur either in the acute or chronic phase of TBI. There is still uncertainty about the mechanisms provoking PTP, which can be the result of the acute blast itself or secondary neurodegenerative process occurring months to years post the acute trauma. Currently there is an underestimation of the clinical importance of PTP and lack of specific and proven therapeutic interventions, both in the pharmacological and the neurorehabilitation field. This narrative review aims to summarize the actual knowledge about PTP in terms of its pathophysiology, clinical aspects, treatments and perspective of care in the neurorehabilitative setting.

Advanced rehabilitation in ischaemic stroke research

At present, due to the rapid progress of treatment technology in the acute phase of ischaemic stroke, the mortality of patients has been greatly reduced but the number of disabled survivors is increasing, and most of them are elderly patients. Physicians and rehabilitation therapists pay attention to develop all kinds of therapist techniques including physical therapy techniques, robot-assisted technology and artificial intelligence technology, and study the molecular, cellular or synergistic mechanisms of rehabilitation therapies to promote the effect of rehabilitation therapy. Here, we discussed different animal and in vitro models of ischaemic stroke for rehabilitation studies; the compound concept and technology of neurological rehabilitation; all kinds of biological mechanisms of physical therapy; the significance, assessment and efficacy of neurological rehabilitation; the application of brain-computer interface, rehabilitation robotic and non-invasive brain stimulation technology in stroke rehabilitation.

Vagus nerve stimulation during training fails to improve learning in healthy rats

Learning new skills requires neuroplasticity. Vagus nerve stimulation (VNS) during sensory and motor events can increase neuroplasticity in networks related to these events and might therefore serve to facilitate learning on sensory and motor tasks. We tested if VNS could broadly improve learning on a wide variety of tasks across different skill domains in healthy, female adult rats. VNS was paired with presentation of stimuli or on successful trials during training, strategies known to facilitate plasticity and improve recovery in models of neurological disorders. VNS failed to improve either rate of learning or performance for any of the tested tasks, which included skilled forelimb motor control, speech sound discrimination, and paired-associates learning. These results contrast recent findings from multiple labs which found VNS pairing during training produced learning enhancements across motor, auditory, and cognitive domains. We speculate that these contrasting results may be explained by key differences in task designs, training timelines and animal handling approaches, and that while VNS may be able to facilitate rapid and early learning processes in healthy subjects, it does not broadly enhance learning for difficult tasks.

The pilot study of the effect of six-week robot-assisted ankle training on mobility and strength of lower extremity and life habits for children with cerebral palsy

Background

Children with cerebral palsy often have weak ankle muscles and reduced ankle dorsiflexion, which leads to activity limitations and eventually affects quality of life. Robotic ankle training was recently developed to facilitates muscle function through a high repetition of exercises. This study investigated the effect of six-week ankle training using the Anklebot device to improve lower limb structural and functional impairments and the resulting impact on quality of life.

Methods

Five children with spastic cerebral palsy aged between 4 and 11 years participated in six weeks of bilateral ankle assistive training using the Anklebot device. All lower limb muscle strength was measured with a hand-held dynameter, and range of motion was measured with a goniometer, at four different time points. Muscle architecture was assessed using a portable diagnostic ultrasound device, and quality of life was assessed using the Life Habits for Children scale, at two points in time only.

Results

Muscle strength and range of motion for all lower limb joints demonstrated significant improvement on both sides after training. The ankle muscle architecture showed non-significant improvement, while an overall significant improvement in the total score of the Life Habits for Children scale was detected after training.

Conclusion

Robot-assisted task-specific ankle training provides promising effects by allowing the required repetition to improve structural and functional muscle and joint impairments, which has a positive influence on the children's quality of life. However, due to a limited sample size, these results should be considered as preliminary; further study is needed.

Anodal M1 tDCS enhances online learning of rhythmic timing videogame skill

Transcranial direct current stimulation (tDCS) has been shown to modify excitability of the primary motor cortex (M1) and influence online motor learning. However, research on the effects of tDCS on motor learning has focused predominantly on simplified motor tasks. The purpose of the present study was to investigate whether anodal stimulation of M1 over a single session of practice influences online learning of a relatively complex rhythmic timing video game. Fifty-eight healthy young adults were randomized to either a-tDCS or SHAM conditions and performed 2 familiarization blocks, a 20-minute 5 block practice period while receiving their assigned stimulation, and a post-test block with their non-dominant hand. To assess performance, a performance index was calculated that incorporated timing accuracy elements and incorrect key inputs. The results showed that M1 a-tDCS enhanced the learning of the video game based skill more than SHAM stimulation during practice, as well as overall learning at the post-test. These results provide evidence that M1 a-tDCS can enhance acquisition of skills where quality or success of performance depends on optimized timing between component motions of the skill, which could have implications for the application of tDCS in many real-world contexts.

Gray matter volume of functionally relevant primary motor cortex is causally related to learning a hand motor task

Variability in brain structure is associated with the capacity for behavioral change. However, a causal link between specific brain areas and behavioral change (such as motor learning) has not been demonstrated. We hypothesized that greater gray matter volume of a primary motor cortex (M1) area active during a hand motor learning task is positively correlated with subsequent learning of the task, and that the disruption of this area blocks learning of the task. Healthy participants underwent structural MRI before learning a skilled hand motor task. Next, participants performed this learning task during fMRI to determine M1 areas functionally active during this task. This functional ROI was anatomically constrained with M1 boundaries to create a group-level "Active-M1" ROI used to measure gray matter volume in each participant. Greater gray matter volume in the left hemisphere Active-M1 ROI was related to greater motor learning in the corresponding right hand. When M1 hand area was disrupted with repetitive transcranial stimulation (rTMS), learning of the motor task was blocked, confirming its causal link to motor learning. Our combined imaging and rTMS approach revealed greater cortical volume in a task-relevant M1 area is causally related to learning of a hand motor task in healthy humans.

Selective plasticity of layer 2/3 inputs onto distal forelimb controlling layer 5 corticospinal neurons with skilled grasp motor training

Layer 5 neurons of the neocortex receive their principal inputs from layer 2/3 neurons. We seek to identify the nature and extent of the plasticity of these projections with motor learning. Using optogenetic and viral intersectional tools to selectively stimulate distinct neuronal subsets in rat primary motor cortex, we simultaneously record from pairs of corticospinal neurons associated with distinct features of motor output control: distal forelimb vs. proximal forelimb. Activation of Channelrhodopsin2-expressing layer 2/3 afferents onto layer 5 in untrained animals produces greater monosynaptic excitation of neurons controlling the proximal forelimb. Following skilled grasp training, layer 2/3 inputs onto corticospinal neurons controlling the distal forelimb associated with skilled grasping become significantly stronger. Moreover, peak excitatory response amplitude nearly doubles while latency shortens, and excitatory-to-inhibitory latencies become significantly prolonged. These findings demonstrate distinct, highly segregated, and cell-specific plasticity of layer 2/3 projections during skilled grasp motor learning.

Development of a Sensor Technology to Objectively Measure Dexterity for Cardiac Surgical Proficiency

BACKGROUND

Technical skill is essential for good outcomes in cardiac surgery. However, no objective methods exist to measure dexterity while performing surgery. The purpose of this study was to validate sensor-based hand motion analysis (HMA) of technical dexterity while performing a graft anastomosis within a validated simulator.

METHODS

Surgeons at various training levels performed an anastomosis while wearing flexible sensors (BioStamp nPoint, MC10 Inc) with integrated accelerometers and gyroscopes on each hand to quantify HMA kinematics. Groups were stratified as experts (n = 8) or novices (n = 18). The quality of the completed anastomosis was scored using the 10 Point Microsurgical Anastomosis Rating Scale (MARS10). HMA parameters were compared between groups and correlated with quality. Logistic regression was used to develop a predictive model from HMA parameters to distinguish experts from novices.

RESULTS

Experts were faster (11 ± 6 minutes vs 21 ± 9 minutes; P = .012) and used fewer movements in both dominant (340 ± 166 moves vs 699 ± 284 moves; P = .003) and nondominant (359 ± 188 moves vs 567 ± 201 moves; P = .02) hands compared with novices. Experts' anastomoses were of higher quality compared with novices (9.0 ± 1.2 MARS10 vs 4.9 ± 3.2 MARS10; P = .002). Higher anastomosis quality correlated with 9 of 10 HMA parameters, including fewer and shorter movements of both hands (dominant, r = -0.65, r = -0.46; nondominant, r = -0.58, r = -0.39, respectively).

CONCLUSIONS

Sensor-based HMA can distinguish technical dexterity differences between experts and novices, and correlates with quality. Objective quantification of hand dexterity may be a valuable adjunct to training and education in cardiac surgery training programs.

Frequency Specific Optogenetic Stimulation of the Locus Coeruleus Induces Task-Relevant Plasticity in the Motor Cortex

The locus ceruleus (LC) is the primary source of neocortical noradrenaline, which is known to be involved in diverse brain functions including sensory perception, attention, and learning. Previous studies have shown that LC stimulation paired with sensory experience can induce task-dependent plasticity in the sensory neocortex and in the hippocampus. However, it remains unknown whether LC activation similarly impacts neural representations in the agranular motor cortical regions that are responsible for movement planning and production. In this study, we test whether optogenetic stimulation of the LC paired with motor performance is sufficient to induce task-relevant plasticity in the somatotopic cortical motor map. Male and female TH-Cre + rats were trained on a skilled reaching lever-pressing task emphasizing the use of the proximal forelimb musculature, and a viral approach was used to selectively express ChR2 in noradrenergic LC neurons. Once animals reached criterial behavioral performance, they received five training sessions in which correct task performance was paired with optogenetic stimulation of the LC delivered at 3, 10, or 30 Hz. After the last stimulation session, motor cortical mapping was performed using intracortical microstimulation. Our results show that lever pressing paired with LC stimulation at 10 Hz, but not at 3 or 30 Hz, drove the expansion of the motor map representation of the task-relevant proximal FL musculature. These findings demonstrate that phasic, training-paired activation of the LC is sufficient to induce experience-dependent plasticity in the agranular motor cortex and that this LC-driven plasticity is highly dependent on the temporal dynamics of LC activation.

Hematopoietic Endothelial Progenitor cells enhance motor function and cortical motor map integrity following cerebral ischemia

Background

Hematopoietic stem cells (HSC) are recruited to ischemic areas in the brain and contribute to improved functional outcome in animals. However, little is known regarding the mechanisms of improvement following HSC administration post cerebral ischemia. To better understand how HSC effect post-stroke improvement, we examined the effect of HSC in ameliorating motor impairment and cortical dysfunction following cerebral ischemia.

Methods

Baseline motor performance of male adult rats was established on validated motor tests. Animals were assigned to one of three experimental cohorts: control, stroke, stroke + HSC. One, three and five weeks following a unilateral stroke all animals were tested on motor skills after which intracortical microstimulation was used to derive maps of forelimb movement representations within the motor cortex ipsilateral to the ischemic injury.

Results

Stroke + HSC animals significantly outperformed stroke animals on single pellet reaching at weeks 3 and 5 (28±3% and 33±3% versus 11±4% and 17±3%, respectively, p < 0.05 at both time points). Control animals scored 44±1% and 47±1%, respectively. Sunflower seed opening task was significantly improved in the stroke + HSC cohort versus the stroke cohort at week five-post stroke (79±4 and 48±5, respectively, p < 0.05). Furthermore, Stroke + HSC animals had significantly larger forelimb motor maps than animals in the stroke cohort. Overall infarct size did not significantly differ between the two stroked cohorts.

Conclusion

These data suggest that post stroke treatment of HSC enhances the functional integrity of residual cortical tissue, which in turn supports improved behavioral outcome, despite no observed reduction in infarct size.

The contribution of the basal ganglia and cerebellum to motor learning: A neuro-computational approach

Motor learning involves a widespread brain network including the basal ganglia, cerebellum, motor cortex, and brainstem. Despite its importance, little is known about how this network learns motor tasks and which role different parts of this network take. We designed a systems-level computational model of motor learning, including a cortex-basal ganglia motor loop and the cerebellum that both determine the response of central pattern generators in the brainstem. First, we demonstrate its ability to learn arm movements toward different motor goals. Second, we test the model in a motor adaptation task with cognitive control, where the model replicates human data. We conclude that the cortex-basal ganglia loop learns via a novelty-based motor prediction error to determine concrete actions given a desired outcome, and that the cerebellum minimizes the remaining aiming error.

Spared Premotor Areas Undergo Rapid Nonlinear Changes in Functional Organization Following a Focal Ischemic Infarct in Primary Motor Cortex of Squirrel Monkeys

Recovery of motor function after stroke is accompanied by reorganization of movement representations in spared cortical motor regions. It is widely assumed that map reorganization parallels recovery, suggesting a causal relationship. We examined this assumption by measuring changes in motor representations in eight male and six female squirrel monkeys in the first few weeks after injury, a time when motor recovery is most rapid. Maps of movement representations were derived using intracortical microstimulation techniques in primary motor cortex (M1), ventral premotor cortex (PMv), and dorsal premotor cortex (PMd) in 14 adult squirrel monkeys before and after a focal infarct in the M1 distal forelimb area. Maps were derived at baseline and at either 2 (n = 7) or 3 weeks (n = 7) postinfarct. In PMv the forelimb maps remained unchanged at 2 weeks but contracted significantly (-42.4%) at 3 weeks. In PMd the forelimb maps expanded significantly (+110.6%) at 2 weeks but contracted significantly (-57.4%) at 3 weeks. Motor deficits were equivalent at both time points. These results highlight two features of plasticity after M1 lesions. First, significant contraction of distal forelimb motor maps in both PMv and PMd is evident by 3 weeks. Second, an unpredictable nonlinear pattern of reorganization occurs in the distal forelimb representation in PMd, first expanding at 2 weeks, and then contracting at 3 weeks postinjury. Together with previous results demonstrating reliable map expansions in PMv several weeks to months after M1 injury, the subacute time period may represent a critical window for the timing of therapeutic interventions.SIGNIFICANCE STATEMENT The relationship between motor recovery and motor map reorganization after cortical injury has rarely been examined in acute/subacute periods. In nonhuman primates, premotor maps were examined at 2 and 3 weeks after injury to primary motor cortex. Although maps are known to expand late after injury, the present study demonstrates early map expansion at 2 weeks (dorsal premotor cortex) followed by contraction at 3 weeks (dorsal and ventral premotor cortex). This nonlinear map reorganization during a time of gradual behavioral recovery suggests that the relationship between map plasticity and motor recovery is much more complex than previously thought. It also suggests that rehabilitative motor training may have its most potent effects during this early dynamic phase of map reorganization.

The simultaneous changes in motor performance and EEG patterns in beta band during learning dart throwing skill in dominant and non-dominant hand

Background: Although changes in performance during the learning of various sports skills have been studied, however, how these changes at the brain level is still unknown. The aim of this study was to investigate simultaneous changes in motor performance and EEG patterns in beta band during learning dart throwing skill in dominant and non-dominant hand. Methodology: The samples consisted of 14 non-athlete students with an average age of 23 ± 2.5, which were divided into two group dominant hand (7) and non-dominant hand (7). Repeated measures ANOVA were used to measure data at the execution level and changes in EEG activity. Results: The results of this study at the performance level showed a significant reduction in the absolute error of dart throwing and at the same time at the brain level increased EEG activity in frontal and parietal-posterior regions along with decreased central area activity in acquisition and retention stages in both groups (P<.05). Also, there was a significant difference between the activity of EEG pattern in the dominant and non-dominant hand groups except for two channels AF3 and PO4 (P<.05). Conclusion: In general, the results of this study showed that along with relatively constant changes in performance during dart skill learning, relatively constant changes in EEG activity pattern occur, so that the concept of motor learning is also visible at the brain level. Also, the results of this study supported the existence of the different motor program for dominant and non-dominant hand control in the conditions of bilateral transfer control.

Practice makes plasticity: 10-Hz rTMS enhances LTP-like plasticity in musicians and athletes

Motor skill learning has been linked to functional and structural changes in the brain. Musicians and athletes undergo intensive motor training through the practice of an instrument or sport and have demonstrated use-dependent plasticity that may be subserved by long-term potentiation (LTP) processes. We know less, however, about whether the brains of musicians and athletes respond to plasticity-inducing interventions, such as repetitive transcranial magnetic stimulation (rTMS), differently than those without extensive motor training. In a pharmaco-rTMS study, we evaluated motor cortex excitability before and after an rTMS protocol in combination with oral administration of D-cycloserine (DCS) or placebo. In a secondary covariate analysis, we compared results between self-identified musicians and athletes (M&As) and non-musicians and athletes (non-M&As). Three TMS measures of cortical physiology were used to evaluate plasticity. We found that M&As did not have higher baseline corticomotor excitability. However, a plasticity-inducing protocol (10-Hz rTMS in combination with DCS) strongly facilitated motor-evoked potentials (MEPs) in M&As, but only weakly in non-M&As. Placebo and rTMS produced modest facilitation in both groups. Our findings suggest that motor practice and learning create a neuronal environment more responsive to plasticity-inducing events, including rTMS. These findings may explain one factor contributing to the high inter-individual variability found with MEP data. Greater capacity for plasticity holds implications for learning paradigms, such as psychotherapy and rehabilitation, by facilitating LTP-like activation of key networks, including recovery from neurological/mental disorders.

Functional properties of eyelid conditioned responses and involved brain centers

For almost a century the classical conditioning of nictitating membrane/eyelid responses has been used as an excellent and feasible experimental model to study how the brain organizes the acquisition, storage, and retrieval of new motor abilities in alert behaving mammals, including humans. Lesional, pharmacological, and electrophysiological approaches, and more recently, genetically manipulated animals have shown the involvement of numerous brain areas in this apparently simple example of associative learning. In this regard, the cerebellum (both cortex and nuclei) has received particular attention as a putative site for the acquisition and storage of eyelid conditioned responses, a proposal not fully accepted by all researchers. Indeed, the acquisition of this type of learning implies the activation of many neural processes dealing with the sensorimotor integration and the kinematics of the acquired ability, as well as with the attentional and cognitive aspects also involved in this process. Here, we address specifically the functional roles of three brain structures (red nucleus, cerebellar interpositus nucleus, and motor cortex) mainly involved in the acquisition and performance of eyelid conditioned responses and three other brain structures (hippocampus, medial prefrontal cortex, and claustrum) related to non-motor aspects of the acquisition process. The main conclusion is that the acquisition of this motor ability results from the contribution of many cortical and subcortical brain structures each one involved in specific (motor and cognitive) aspects of the learning process.

Corticospinal neurons from motor and somatosensory cortices exhibit different temporal activity dynamics during motor learning

The ability to learn motor skills implicates an improvement in accuracy, speed and consistency of movements. Motor control is related to movement execution and involves corticospinal neurons (CSp), which are broadly distributed in layer 5B of the motor and somatosensory cortices. CSp neurons innervate the spinal cord and are functionally diverse. However, whether CSp activity differs between different cortical areas throughout motor learning has been poorly explored. Given the importance and interaction between primary motor (M1) and somatosensory (S1) cortices related to movement, we examined the functional roles of CSp neurons in both areas. We induced the expression of GCaMP7s calcium indicator to perform photometric calcium recordings from layer 5B CSp neurons simultaneously in M1 and S1 cortices and track their activity while adult mice learned and performed a cued lever-press task. We found that during early learning sessions, the population calcium activity of CSp neurons in both cortices during movement did not change significantly. In late learning sessions the peak amplitude and duration of calcium activity CSp neurons increased in both, M1 and S1 cortices. However, S1 and M1 CSp neurons display a different temporal dynamic during movements that occurred when animals learned the task; both M1 and S1 CSp neurons activate before movement initiation, however, M1 CSp neurons continue active during movement performance, reinforcing the idea of the diversity of the CSp system and suggesting that CSp neuron activity in M1 and S1 cortices throughout motor learning have different functional roles for sensorimotor integration.

Expanding Rehabilitation Options for Dysphagia: Skill-Based Swallowing Training

Over the past four decades, our understanding of swallowing neural control has expanded dramatically. However, until recently, advances in rehabilitation approaches for dysphagia have not kept pace, with a persistent focussing on strengthening peripheral muscle. This approach is no doubt very appropriate for some if not many of our patients. But what if the dysphagia is not due to muscles weakness? The purpose of this clinical manuscript is to reflect on where we have been, where we are now and perhaps where we need to go in terms of our understanding of swallowing motor control and rehabilitation of motor control impairments. This compilation is presented to clinicians in the hope that suggesting approaches "outside the box" will inspire clinicians to focus their attention "inside the box" to ultimately improve rehabilitation and long-term outcomes for patients with dysphagia.

Transcranial Current Stimulation as a Tool of Neuromodulation of Cognitive Functions in Parkinson’s Disease

Decrease in cognitive function is one of the most common causes of poor life quality and early disability in patients with Parkinson’s disease (PD). Existing methods of treatment are aimed at both correction of motor and non-motor symptoms. Methods of adjuvant therapy (or complementary therapy) for maintaining cognitive functions in patients with PD are of interest. A promising subject of research in this regard is the method of transcranial electric current stimulation (tES). Here we reviewed the current understanding of the pathogenesis of cognitive impairment in PD and of the effects of transcranial direct current stimulation and transcranial alternating current stimulation on the cognitive function of patients with PD-MCI (Parkinson’s Disease–Mild Cognitive Impairment).

Rehabilitation in movement disorders: From basic mechanisms to clinical strategies

Movement disorders encompass a variety of conditions affecting the nervous system at multiple levels. The pathologic processes underlying movement disorders alter the normal neural functions and could lead to aberrant neuroplastic changes and to clinical phenomenology that is not expressed only through mere motor symptoms. Given this complexity, the responsiveness to pharmacologic and surgical therapies is often disappointing. Growing evidence supports the efficacy of neurorehabilitation for the treatment of movement disorders. Specific form of training involving both goal-based practice and aerobic training could drive and modulate neuroplasticity in order to restore the circuitries dysfunctions and to achieve behavioral gains. This chapter provides an overview of the alterations expressed in some movement disorders in terms of clinical signs and symptoms and plasticity, and suggests which ones and why tailored rehabilitation strategies should be adopted for the management of the different movement disorders.

Changes of neuroplasticity in cortical motor control of human masseter muscle related to orthodontic treatment

BACKGROUND

Orthodontic treatment is a common clinical method of malocclusion. Studies have found that neurons in the sensorimotor cortex of the brain undergo adaptive remodeling in response to changes in oral behavior or occlusion.

OBJECTIVE

To explore whether orthodontic treatment could be sufficient to cause neuroplastic changes in the corticomotor excitability of the masseter muscle.

METHODS

Fifteen Angle Class II malocclusion patients who were receiving orthodontic treatment participated in the study. Cortical excitability was assessed by electromyographic activity changes evoked by transcranial magnetic stimulation. Four orthodontic time points were recorded, including baseline, day 1, day 7, and day 30. Motor evoked potentials (MEPs) were recorded in the masseter muscle and the first dorsal interosseous muscle (FDI) serving as a control. The data were analysed by stimulus-response curves and corticomotor mapping. Statistical analyses involved repeated measures analysis of variance, two-way ANOVA, and Tukey's post hoc tests.

RESULTS

Motor evoked potentials (MEPs) of the masseter muscle were significantly decreased during orthodontic treatment compared with those of the baseline (p < .001). MEPs of the masseter muscle were dependent on session and stimulus intensity (p < .001), whereas MEPs of FDI were only dependent on stimulus intensity (p = .091). Finally, Tukey's post hoc tests demonstrated that MEPs of the masseter muscle on days 1 and 7, with 70%-90% stimulus intensities, were higher than those of baseline values (p < .001).

CONCLUSIONS

The present study suggested that orthodontic treatment can lead to neuroplastic changes in the corticomotor control of the masseter muscle, which may add to our understanding of the adaptive response of subjects to changes of oral environment during the orthodontic treatment.

Local activation of α2 adrenergic receptors is required for vagus nerve stimulation induced motor cortical plasticity

Vagus nerve stimulation (VNS) paired with rehabilitation training is emerging as a potential treatment for improving recovery of motor function following stroke. In rats, VNS paired with skilled forelimb training results in significant reorganization of the somatotopic cortical motor map; however, the mechanisms underlying this form of VNS-dependent plasticity remain unclear. Recent studies have shown that VNS-driven cortical plasticity is dependent on noradrenergic innervation of the neocortex. In the central nervous system, noradrenergic α2 receptors (α2-ARs) are widely expressed in the motor cortex and have been critically implicated in synaptic communication and plasticity. In current study, we examined whether activation of cortical α2-ARs is necessary for VNS-driven motor cortical reorganization to occur. Consistent with previous studies, we found that VNS paired with motor training enlarges the map representation of task-relevant musculature in the motor cortex. Infusion of α2-AR antagonists into M1 blocked VNS-driven motor map reorganization from occurring. Our results suggest that local α2-AR activation is required for VNS-induced cortical reorganization to occur, providing insight into the mechanisms that may underlie the neuroplastic effects of VNS therapy.

Enhancing memory using enactment: does meaning matter in action production?

ABSTRACTEnactment is an encoding strategy in which performing an action related to a target item enhances memory for that word, relative to verbal encoding. Precisely how this motor activity aids recall is unclear. We examined whether the action created during encoding needed to be semantically relevant to the to-be-remembered word, to enhance memory. In Experiment 1, participants were asked to either (a) enact, (b) perform unrelated motoric gestures, or (c) read forty-five action verbs. On a subsequent free-recall test, memory for enacted words was significantly higher relative to words read, or encoded with unrelated gestures. In Experiment 2, to reduce the ambiguity associated with initiating an unrelated gesture, participants were instructed to write target words in the air. Results were similar to Experiment 1. In Experiment 3, we replicated the results of Experiment 2 using video conferencing to record the onset time of action initiation for enacted, unrelated gesture, and read trials. Results showed that planning of meaningful actions may also contribute to the memory performance as evidenced by a longer onset time to initiate an action on enactment relative to gesturing and reading trials. These findings suggest that planning and executing meaningful actions drive the enactment benefit.

Neuroplasticity induced by the retention period of a complex motor skill learning in rats

Learning complex motor skills is an essential process in our daily lives. Moreover, it is an important aspect for the development of therapeutic strategies that refer to rehabilitation processes since motor skills previously acquired can be transferred to similar tasks (motor skill transfer) or recovered without further practice after longer delays (motor skill retention). Different acrobatic exercise training (AE) protocols induce plastic changes in areas involved in motor control and improvement in motor performance. However, the plastic mechanisms involved in the retention of a complex motor skill, essential for motor learning, are not well described. Thus, our objective was to analyze the brain plasticity mechanisms involved in motor skill retention in AE . Motor behavior tests, and the expression of synaptophysin (SYP), synapsin-I (SYS), and early growth response protein 1 (Egr-1) in brain areas involved in motor learning were evaluated. Young male Wistar rats were randomly divided into 3 groups: sedentary (SED), AE, and AE with retention period (AER). AE was performed three times a week for 8 weeks, with 5 rounds in the circuit. After a fifteen-day retention interval, the AER animals was again exposed to the acrobatic circuit. Our results revealed motor performance improvement in the AE and AER groups. In the elevated beam test, the AER group presented a lower time and greater distance, suggesting retention period is important for optimizing motor learning consolidation. Moreover, AE promoted significant plastic changes in the expression of proteins in important areas involved in control and motor learning, some of which were maintained in the AER group. In summary, these data contribute to the understanding of neural mechanisms involved in motor learning in an animal model, and can be useful to the construction of therapeutics strategies that optimize motor learning in a rehabilitative context.

Wearable Real-Time Haptic Biofeedback Foot Progression Angle Gait Modification to Assess Short-Term Retention and Cognitive Demand

Foot progression angle gait (FPA) modification is an important part of rehabilitation for a variety of neuromuscular and musculoskeletal diseases. While wearable haptic biofeedback could enable FPA gait modification for more widespread use than traditional tethered, laboratory-based approaches, retention, and cognitive demand in FPA gait modification via wearable haptic biofeedback are currently unknown and may be important to real-life implementation. Thus, the purpose of this study was to assess the feasibility of wearable haptic biofeedback to assess short-term retention and cognitive demand during FPA gait modification. Ten healthy participants performed toe-in (target 10 degrees change in internal rotation) and toe-out (target 10 degrees change in external rotation) haptic gait training trials followed by short-term retention trials, and cognitive multitasking trials. Results showed that participants were able to initially respond to the wearable haptic feedback to modify their FPA to adopt the new toe-in (9.7 ± 0.8 degree change in internal rotation) and toe-out (8.9 ± 1.0 degree change in external rotation) gait patterns. Participants retained the modified gait pattern on average within 3.9 ± 3.6 deg of the final haptic gait training FPA values. Furthermore, cognitive multitasking did not influence short-term retention in that there were no differences in gait performance during retention trials with or without cognitive multitasking. These results demonstrate that wearable haptic biofeedback can be used to assess short-term retention and cognitive demand during FPA gait modification without the need for traditional, tethered systems.

Hue discrimination in jewellery appraisers exceeds normal performance

PURPOSE

The FM-100 Hue test is used for vocational purposes where hue discrimination is of the upmost importance, such as in jewellery appraisals where small errors in hue discrimination can lead to significant differences in gemstone valuation. The purpose of this study was to determine if the cone contrast test (CCT) could predict performance on the FM-100 Hue, providing a potential alternative test for screening of jewellery appraisers.

METHODS

Members of the National Association of Jewelry Appraisers (NAJA; n = 18, ages 34 to 76 years) requiring colour vision certification with the FM-100 Hue were invited to participate in a study to assess performance on the Ishihara test, FM-100 Hue, Lanthony Desaturated D-15 and the CCT. The FM-100 Hue test was administered to award or renew NAJA certification, while the CCT was included as a possible alternative certification test.

RESULTS

Average CCT M and S cone scores were predictive of FM-100 Hue total error score (TES: F_1,16  = 7.77, p < 0.02; r²  = 0.33). The regression equation indicates that a CCT score of <60 is 3SD below the mean TES in our cohort of jewellery appraisers. Seventeen of 18 jewellery appraisers had FM-100 Hue TES scores significantly below the lower limit for age-matched normal values, indicating exceptional performance (p < 0.001).

CONCLUSIONS

Results indicate the CCT may be an effective substitute for the FM-100 Hue to provide certification of jewellery appraisers, but the small sample size warrants additional comparative validation to support sole utilisation of the CCT. It is of interest that this sample of jewellery appraisers showed lower (i.e., better) than normal TES scores despite mitigating senescence factors. It is conceivable that the enhanced jewellery appraisers' hue discrimination reflects perceptual learning, wherein reward-based repetition on specific tasks can improve performance, even in adulthood beyond critical periods.

Enhancement of Sensorimotor Cortical Adaptation after Dental Implantation in Comparison to the Conventional Denture - Demonstration by Functional MRI at 1-5T

Background and Purpose

Dental implantation is thought to be associated with enhancement of neuro-cortical sensorimotor activity which has been lost due to an edentulous state. Such changes are either feeble or absent after the placement of a conventional denture. In the present study, we test this hypothesis using blood oxygen level-dependent (BOLD) activity on functional MRI (fMRI) as a bio-surrogate.

Materials and Methods

fMRI was performed in 12 consecutive edentulous subjects (mean age = 59.2 years) after the placement of a conventional complete denture (CD) and subsequently after intraoral dental implantation (IOD). The semi-quantitative data of the BOLD activity was compiled to depict the activation seen in both scenarios in six anatomical regions. Statistical analysis was done to evaluate the significance of enhancement in BOLD activity in these regions in patients having an IOD as compared to those having a CD.

Results

The enhancement of BOLD activity on fMRI after placement of an IOD was much more significant as compared to that noted with CD. Using Wilcoxon's signed-rank test the nonparametric data showed a significant positive elevation in global and regional assigned mean ranks of BOLD activity.

Conclusion

Intraoral implantation leads to a significant elevation in the BOLD activity of the sensorimotor cortex as compared to the placement of a conventional CD.

Bypassing use-dependent plasticity in the primary motor cortex to preserve adaptive behavior

Behavioral adaptation, a central feature of voluntary movement, is known to rely on top-down cognitive control. For example, the conflict-adaptation effect on tasks such as the Stroop task leads to better performance (e.g. shorter reaction time) for incongruent trials following an already incongruent one. The role of higher-order cortices in such between-trial adjustments is well documented, however, a specific involvement of the primary motor cortex (M1) has seldom been questioned. Here we studied changes in corticospinal excitability associated with the conflict-adaptation process. For this, we used single-pulse transcranial-magnetic stimulation (TMS) applied between two consecutive trials in an interference flanker task, while measuring motor-evoked potentials (MEPs) after agonistic and antagonistic voluntary movements. In agonist movement, MEP amplitude was modulated by recent movement history with an increase favoring movement repetition, but no significant change in MEP size was observed whether a previous trial was incongruent or congruent. Critically, for an antagonist movement, the relative size of MEPs following incongruent trials correlated positively with the strength of behavioral adaptation measured as the degree of RT shortening across subjects. This post-conflict increase in corticospinal excitability related to antagonist muscle recruitment could compensate for a potential deleterious bias due to recent movement history that favors the last executed action. Namely, it prepares the motor system to rapidly adapt to a changing and unpredictable context by equalizing the preparation for all possible motor responses.

Current Methodological Pitfalls and Caveats in the Assessment of Exercise-Induced Changes in Peripheral Brain-Derived Neurotrophic Factor: How Result Reproducibility Can Be Improved

Neural mechanisms, such as enhanced neuroplasticity within the motor system, underpin exercise-induced motor improvements. Being a key mediator of motor plasticity, brain-derived neurotrophic factor (BDNF) is likely to play an important role in mediating exercise positive effects on motor function. Difficulties in assessing brain BDNF levels in humans have drawn attention to quantification of blood BDNF and raise the question of whether peripheral BDNF contributes to exercise-related motor improvements. Methodological and non-methodological factors influence measurements of blood BDNF introducing a substantial variability that complicates result interpretation and leads to inconsistencies among studies. Here, we discuss methodology-related issues and approaches emerging from current findings to reduce variability and increase result reproducibility.

White matter microstructural changes in short-term learning of a continuous visuomotor sequence

Efficient neural transmission is crucial for optimal brain function, yet the plastic potential of white matter (WM) has long been overlooked. Growing evidence now shows that modifications to axons and myelin occur not only as a result of long-term learning, but also after short training periods. Motor sequence learning (MSL), a common paradigm used to study neuroplasticity, occurs in overlapping learning stages and different neural circuits are involved in each stage. However, most studies investigating short-term WM plasticity have used a pre-post design, in which the temporal dynamics of changes across learning stages cannot be assessed. In this study, we used multiple magnetic resonance imaging (MRI) scans at 7 T to investigate changes in WM in a group learning a complex visuomotor sequence (LRN) and in a control group (SMP) performing a simple sequence, for five consecutive days. Consistent with behavioral results, where most improvements occurred between the two first days, structural changes in WM were observed only in the early phase of learning (d1-d2), and in overall learning (d1-d5). In LRNs, WM microstructure was altered in the tracts underlying the primary motor and sensorimotor cortices. Moreover, our structural findings in WM were related to changes in functional connectivity, assessed with resting-state functional MRI data in the same cohort, through analyses in regions of interest (ROIs). Significant changes in WM microstructure were found in a ROI underlying the right supplementary motor area. Together, our findings provide evidence for highly dynamic WM plasticity in the sensorimotor network during short-term MSL.

Corticospinal excitability and motor representation after long-term resistance training

It is poorly understood how the central nervous system adapts to resistance training, especially after years of exposure. We compared corticospinal excitability and motor representation assessed with transcranial magnetic stimulation (TMS) between long-term resistance trained (LRT, ≥3 years) versus untrained (UNT) males (n = 15/group). Motor-evoked potentials (MEPs) were obtained from the biceps brachii during isometric elbow flexion. Stimulus-response curves were created at the hotspot during 10% maximum voluntary torque (MVT) contractions. Maximum peak-to-peak MEP amplitude (MEPmax) was acquired with 100% stimulator output intensity, whilst 25%-100% MVT was produced. Maps were created during 10% MVT contractions, with an individualised TMS intensity eliciting 20% MEPmax at the hotspot. LRT had a 48% lower stimulus-response curve slope than UNT (p < .05). LRT also had a 66% larger absolute map size, although TMS intensity used for mapping was greater in LRT versus UNT (48% vs. 26% above active motor threshold) to achieve a target 20% MEPmax at the hotspot, due to the lower slope of LRT. Map size was strongly correlated with the TMS intensity used for mapping (r = 0.776, p < .001). Once map size was normalised to TMS intensity, there was no difference between the groups (p = .683). We conclude that LRT had a lower stimulus-response curve slope/excitability, suggesting higher neural efficiency. TMS map size was overwhelmingly determined by TMS intensity, even when the MEP response at the hotspot was matched among individuals, likely due to larger current spread with higher intensities. Motor representation appears similar between LRT and UNT given no difference in the normalised map size.

Differences in visio-spatial expertise between 1st division rugby players and non-athletes

The present study aimed to compare the visual expertise of non-athletes (n = 40; 19–35 years old; age: 22.13 ± 2.37 years) to amateur, non-professional South-African Rugby Union (SARU) first-division club rugby players (n = 40; 19–35 years old; age: 23.88 ± 4.36 years; training age mean: 9.0 ± 1.5 years). Research suggests that athletes have enhanced visio-spatial expertise in comparison to non-athletes. However, conflicting research suggests that this is not always the case as non-athletes possess similar visio-spatial expertise in certain visual skills. Participants underwent an optometric assessment after which the following 6 visio-spatial intelligence (VSI) components were measured; accommodation facility, saccadic eye movement, speed of recognition, peripheral awareness, visual memory and hand-eye coordination using the following tests; hart near far rock, saccadic eye movement, evasion, accumulator, flash memory and ball wall toss tests. Results indicated that first-division rugby players performed significantly better (p ≤ 0.05) in five of the six tests performed, except for visual memory (p = 0.893). While this study substantiates the notion that athletes, in this case first-division rugby players, performs significantly better in most VSI components, this is not the case for all, as with visual memory in this study. To more accurately distinguish between athletes and non-athletes, research should move away from tests that focus on basic visual function and develop sport specific testing methods that can be used by a variety of sports.

The Ties That Bind: Aberrant Plasticity and Networks Dysfunction in Movement Disorders-Implications for Rehabilitation

Background: Movement disorders encompass various conditions affecting the nervous system. The pathological processes underlying movement disorders lead to aberrant synaptic plastic changes, which in turn alter the functioning of large-scale brain networks. Therefore, clinical phenomenology does not only entail motor symptoms but also cognitive and motivational disturbances. The result is the disruption of motor learning and motor behavior. Due to this complexity, the responsiveness to standard therapies could be disappointing. Specific forms of rehabilitation entailing goal-based practice, aerobic training, and the use of noninvasive brain stimulation techniques could "restore" neuroplasticity at motor-cognitive circuitries, leading to clinical gains. This is probably associated with modulations occurring at both molecular (synaptic) and circuitry levels (networks). Several gaps remain in our understanding of the relationships among plasticity and neural networks and how neurorehabilitation could promote clinical gains is still unclear. Purposes: In this review, we outline first the networks involved in motor learning and behavior and analyze which mechanisms link the pathological synaptic plastic changes with these networks' disruption in movement disorders. Therefore, we provide theoretical and practical bases to be applied for treatment in rehabilitation.

Neurotrophin-3 upregulation associated with intravenous transplantation of bone marrow mononuclear cells induces axonal sprouting and motor functional recovery in the long term after neocortical ischaemia

Bone marrow mononuclear cells (BMMCs) have been identified as a relevant therapeutic strategy for the treatment of several chronic diseases of the central nervous system. The aim of this work was to evaluate whether intravenous treatment with BMMCs facilitates the reconnection of lesioned cortico-cortical and cortico-striatal pathways, together with motor recovery, in injured adult Wistar rats using an experimental model of unilateral focal neocortical ischaemia. Animals with cerebral cortex ischaemia underwent neural tract tracing for axonal fibre analysis, differential expression analysis of genes involved in apoptosis and neuroplasticity by RT-qPCR, and motor performance assessment by the cylinder test. Quantitative and qualitative analyses of axonal fibres labelled by an anterograde neural tract tracer were performed. Ischaemic animals treated with BMMCs showed a significant increase in axonal sprouting in the ipsilateral neocortex and in the striatum contralateral to the injured cortical areas compared to untreated rodents. In BMMC-treated animals, there was a trend towards upregulation of the Neurotrophin-3 gene compared to the other genes, as well as modulation of apoptosis by BMMCs. On the 56th day after ischaemia, BMMC-treated animals showed significant improvement in motor performance compared to untreated rats. These results suggest that in the acute phase of ischaemia, Neurotrophin-3 is upregulated in response to the lesion itself. In the long run, therapy with BMMCs causes axonal sprouting, reconnection of damaged neuronal circuitry and a significant increase in motor performance.

Development and plasticity of complex movement representations

The mammalian motor cortex is topographically organized into representations of discrete body parts (motor maps). Studies in adult rats using long-duration intracortical microstimulation (LD-ICMS) reveal that forelimb motor cortex is functionally organized into several spatially distinct areas encoding complex, multijoint movement sequences: elevate, advance, grasp, and retract. The topographical arrangement of complex movements during development and the influence of skilled learning are unknown. Here, we determined the emergence and topography of complex forelimb movement representations in rats between postnatal days (PND) 13 and 60. We further investigated the expression of the maps for complex movements under conditions of reduced cortical inhibition and whether skilled forelimb motor training could alter their developing topography. We report that simple forelimb movements are first evoked at PND 25 and are confined to the caudal forelimb area (CFA), whereas complex movements first reliably appear at PND 30 and are observed in both the caudal and rostral forelimb areas (RFA). During development, the topography of complex movement representations undergoes reorganization with "grasp" and "elevate" movements predominantly observed in the RFA and all four complex movements observed in CFA. Under reduced cortical inhibition, simple and complex movements were first observed in the CFA on PND 15 and 20, respectively, and the topography is altered relative to a saline control. Further, skilled motor learning was associated with increases in "grasp" and "retract" representations specific to the trained limb. Our results demonstrate that early-life motor experience during development can modify the topography of complex forelimb movement representations.NEW & NOTEWORTHY The motor cortex is topographically organized into maps of different body parts. We used to think that the function of motor cortex was to drive individual muscles, but more recently we have learned that it is also organized to make complex movements. However, the development and plasticity of those complex movements is completely unknown. In this paper, the emergence and topography of complex movement representation, as well as their plasticity during development, is detailed.

Corticospinal and spinal adaptations to motor skill and resistance training: Potential mechanisms and implications for motor rehabilitation and athletic development

Optimal strategies for enhancing strength and improving motor skills are vital in athletic performance and clinical rehabilitation. Initial increases in strength and the acquisition of new motor skills have long been attributed to neurological adaptations. However, early increases in strength may be predominantly due to improvements in inter-muscular coordination rather than the force-generating capacity of the muscle. Despite the plethora of research investigating neurological adaptations from motor skill or resistance training in isolation, little effort has been made in consolidating this research to compare motor skill and resistance training adaptations. The findings of this review demonstrated that motor skill and resistance training adaptations show similar short-term mechanisms of adaptations, particularly at a cortical level. Increases in corticospinal excitability and a release in short-interval cortical inhibition occur as a result of the commencement of both resistance and motor skill training. Spinal changes show evidence of task-specific adaptations from the acquired motor skill, with an increase or decrease in spinal reflex excitability, dependant on the motor task. An increase in synaptic efficacy of the reticulospinal projections is likely to be a prominent mechanism for driving strength adaptations at the subcortical level, though more research is needed. Transcranial electric stimulation has been shown to increase corticospinal excitability and augment motor skill adaptations, but limited evidence exists for further enhancing strength adaptations from resistance training. Despite the logistical challenges, future work should compare the longitudinal adaptations between motor skill and resistance training to further optimise exercise programming.

Understanding the Neurophysiological and Molecular Mechanisms of Exercise-Induced Neuroplasticity in Cortical and Descending Motor Pathways: Where Do We Stand?

Exercise is a promising, cost-effective intervention to augment successful aging and neurorehabilitation. Decline of gray and white matter accompanies physiological aging and contributes to motor deficits in older adults. Exercise is believed to reduce atrophy within the motor system and induce neuroplasticity which, in turn, helps preserve motor function during aging and promote re-learning of motor skills, for example after stroke. To fully exploit the benefits of exercise, it is crucial to gain a greater understanding of the neurophysiological and molecular mechanisms underlying exercise-induced brain changes that prime neuroplasticity and thus contribute to postponing, slowing, and ameliorating age- and disease-related impairments in motor function. This knowledge will allow us to develop more effective, personalized exercise protocols that meet individual needs, thereby increasing the utility of exercise strategies in clinical and non-clinical settings. Here, we review findings from studies that investigated neurophysiological and molecular changes associated with acute or long-term exercise in healthy, young adults and in healthy, postmenopausal women.

Corticospinal properties are associated with sensorimotor performance in action video game players

Notwithstanding the apparent demands regarding fine motor skills that are required to perform in action video games, the motor nervous system of players has not been studied systematically. In the present study, we hypothesized to find differences in sensorimotor performance and corticospinal characteristics between action video game players (Players) and Controls. We tested sensorimotor performance in video games tasks and used transcranial magnetic stimulation (TMS) to measure motor map, input-output (IO) and short intra-cortical inhibition (SICI) curves in the first dorsal interosseous (FDI) muscle of Players (n = 18) and Control (n = 18). Players scored higher in performance tests and had stronger SICI and higher motor evoked potential (MEP) amplitudes. Multiple linear regressions showed that Players and Control differed with respect to their relation between reaction time and corticospinal excitability. However, we did not find different motor map topography or different IO curves for Players when compared to Controls. Action video game players showed an increased efficiency of motor cortical inhibitory and excitatory neural networks. Players also showed a different relation of MEPs with reaction time. The present study demonstrates the potential of action video game players as an ideal population to study the mechanisms underlying visuomotor performance and sensorimotor learning.

Regional estimates of cortical thickness in brain areas involved in control of surgically restored limb movement in patients with tetraplegia

Context/Objective: Spinal cord injury (SCI) causes atrophy of brain regions linked to motor function. We aimed to estimate cortical thickness in brain regions that control surgically restored limb movement in individuals with tetraplegia. Design: Cross-sectional study. Setting: Sahlgrenska University hospital, Gothenburg, Sweden. Participants: Six individuals with tetraplegia who had undergone surgical restoration of grip function by surgical transfer of one elbow flexor (brachioradialis), to the paralyzed thumb flexor (flexor pollicis longus). All subjects were males, with a SCI at the C6 or C7 level, and a mean age of 40 years (range = 31-48). The average number of years elapsed since the SCI was 13 (range = 6-26). Outcome measures: We used structural magnetic resonance imaging (MRI) to estimate the thickness of selected motor cortices and compared these measurements to those of six matched control subjects. The pinch grip control area was defined in a previous functional MRI study. Results: Compared to controls, the cortical thickness in the functionally defined pinch grip control area was not significantly reduced (P = 0.591), and thickness showed a non-significant but positive correlation with years since surgery in the individuals with tetraplegia. In contrast, the anatomically defined primary motor cortex as a whole exhibited substantial atrophy (P = 0.013), with a weak negative correlation with years since surgery. Conclusion: Individuals with tetraplegia do not seem to have reduced cortical thickness in brain regions involved in control of surgically restored limb movement. However, the studied sample is very small and further studies with larger samples are required to establish these findings.

Effects of twelve weeks' aerobic training on motor cortex excitability

BACKGROUND

Regular physical activity or aerobic exercise is well known to increase brain plasticity. Recent studies have reported that aerobic exercise enhances neuroplasticity and motor learning. The aim of this study was to investigate if 12 weeks' aerobic training can modify cortical excitability and motor evoked potential (MEP) responses.

METHODS

Fifteen untrained males were recruited. Cortical excitability was investigated using TMS. VO2<inf>max</inf> was estimated using Cooper's test. Aerobic intervention lasted 12 weeks. The subjects performed a 6-week supervised aerobic workout, 3 times a week, at 60-75% of their maximum heart rate (HR<inf>max</inf>). Over the following 6 weeks, they performed a supervised aerobic workout 3 times a week at 70-75% of FC<inf>max</inf>.

RESULTS

After 8 weeks of aerobic training there was a significant increase of distance covered during Cooper's test (P<0.001) and a significant increase of VO2<inf>max</inf> (P<0.001); there was also an improvement in resting motor threshold (rMT decreased from 60.5±6.6% [T0] to 55.8±5.9% [T2]; P<0.001), motor evoked potential latency decreased (from 25.3±0.8 ms [T0] to 24.1±0.8 ms [T2]; P<0.001), and motor evoked potential amplitude increased (from 0.58±0.09 mV [T0] to 0.65±0.08 mV [T2]; P<0.001). Furthermore, after 12 weeks' aerobic training there were improvements in all parameters.

CONCLUSIONS

This study shows that aerobic activity seems to induce changes in cortical excitability if performed for a period longer than 4 weeks, in addition to typical cardiorespiratory benefits in previously untrained males.

Divergent Findings in Brain Reorganization After Spinal Cord Injury: A Review

Spinal cord injury (SCI) leads to a general lack of sensory and motor functions below the level of injury and may promote deafferentation-induced brain reorganization. Functional magnetic resonance imaging (fMRI) has been established as an essential tool in neuroscience research and can precisely map the spatiotemporal distribution of brain activity. Task-based fMRI experiments associated with the tongue, upper limbs, or lower limbs have been used as the primary paradigms to study brain reorganization following SCI. A review of the current literature on the subject shows one common trait: while most articles agree that brain networks are usually preserved after SCI, and that is not the case as some articles describe possible alterations in brain activation after the lesion. There is no consensus if those alterations indeed occur. In articles that show alterations, there is no agreement if they are transient or permanent. Besides, there is no consensus on which areas are most prone to activation changes, or on the intensity and direction (increase vs. decrease) of those possible changes. In this article, we present a critical review of the literature and trace possible reasons for those contradictory findings on brain reorganization following SCI. fMRI studies based on the ankle dorsiflexion, upper-limb, and tongue paradigms are used as case studies for the analyses.

Movement kinematics and speech accuracy in a nonword repetition task in school-age children who stutter

We investigated sensorimotor processes in school-age children who do (CWS) and do not stutter (CWNS) in a nonword repetition (NWR) task and evaluated changes in behavioral (percent speech accuracy) and speech kinematics measures (lip aperture variability, movement duration) with practice and retention. Thirteen CWS and 13 CWNS divided into two age groups (younger, 8-12 years; n = 6, older, 13-15 years, n = 7) repeated nonwords varying in phonological properties over two sessions separated by an hour. Participants in both groups also completed several baseline measures, including tests of digit span and nonword repetition (NRT). A marginal trend for lower speech accuracy was noted in the CWS compared to the CWNS in the NWR task. The younger CWS also performed poorly compared to the older CWS and age-matched CWNS in the NRT. Findings provided weak support for limitations in initial encoding and subsequent retrieval of phonemic information. The CWS demonstrated significantly reduced inter-articulatory coordination for the 3-syllable nonwords. While both groups demonstrated significantly slower movements with increase in nonword complexity at the 3-syllable level, such differences were enhanced in the CWS group and influenced further by participant age. Additionally, digit span influenced movement coordination in both groups with only the CWNS showing a significant negative correlation between the digit span scores and movement variability at the onset of practice in Session 1. The findings offer limited support for a sensorimotor integration deficit in CWS and the contributions of cognitive mechanisms to performance in NWR.

Is the Organization of the Primary Motor Cortex in Low Back Pain Related to Pain, Movement, and/or Sensation?

AIM/BACKGROUND

Primary motor cortex (M1) organization differs between individuals with and without chronic low back pain (CLBP), in parallel with motor and sensory impairments. This study investigated whether movement behaviour and tactile/pain sensation are related to M1 organisation in CLBP.

METHODS

Transcranial magnetic stimulation (TMS) was used to map the M1 representation of the erector spinae and multifidus muscles in 20 participants with and without CLBP. Cortical organisation was quantified by: map volume; center of gravity (CoG); number of peaks; and primary and secondary peak location. Movement behaviour was assessed as the ability to dissociate lumbar from thorax motion and sensory function as two-point discrimination, pressure pain thresholds, and pain intensity (visual analogue scale).

RESULTS

People with CLBP showed more anterior location of the CoG than controls. Map peaks were more numerous in CLBP participants who performed the movement task good than those with poor performance. In CLBP, smaller map volume correlated with greater pain during the movement task. Movement behaviour was not linearly correlated with M1 features.

CONCLUSIONS

This study confirms that M1 maps differ between people with and without CLBP, but these changes are variable within the CLBP group and are not related to motor and sensory features in a simple manner.

Neuroplasticity of Language Networks in Aphasia: Advances, Updates, and Future Challenges

Researchers have sought to understand how language is processed in the brain, how brain damage affects language abilities, and what can be expected during the recovery period since the early 19th century. In this review, we first discuss mechanisms of damage and plasticity in the post-stroke brain, both in the acute and the chronic phase of recovery. We then review factors that are associated with recovery. First, we review organism intrinsic variables such as age, lesion volume and location and structural integrity that influence language recovery. Next, we review organism extrinsic factors such as treatment that influence language recovery. Here, we discuss recent advances in our understanding of language recovery and highlight recent work that emphasizes a network perspective of language recovery. Finally, we propose our interpretation of the principles of neuroplasticity, originally proposed by Kleim and Jones (1) in the context of extant literature in aphasia recovery and rehabilitation. Ultimately, we encourage researchers to propose sophisticated intervention studies that bring us closer to the goal of providing precision treatment for patients with aphasia and a better understanding of the neural mechanisms that underlie successful neuroplasticity.

Compensatory Relearning Following Stroke: Cellular and Plasticity Mechanisms in Rodents

von Monakow’s theory of diaschisis states the functional ‘standstill’ of intact brain regions that are remote from a damaged area, often implied in recovery of function. Accordingly, neural plasticity and activity patterns related to recovery are also occurring at the same regions. Recovery relies on plasticity in the periinfarct and homotopic contralesional regions and involves relearning to perform movements. Seeking evidence for a relearning mechanism following stroke, we found that rodents display many features that resemble classical learning and memory mechanisms. Compensatory relearning is likely to be accompanied by gradual shaping of these regions and pathways, with participating neurons progressively adapting cortico-striato-thalamic activity and synaptic strengths at different cortico-thalamic loops – adapting function relayed by the striatum. Motor cortex functional maps are progressively reinforced and shaped by these loops as the striatum searches for different functional actions. Several cortical and striatal cellular mechanisms that influence motor learning may also influence post-stroke compensatory relearning. Future research should focus on how different neuromodulatory systems could act before, during or after rehabilitation to improve stroke recovery.