Human brain plasticity: an emerging view of the multiple substrates and mechanisms that cause cortical changes and related sensory dysfunctions after injuries of sensory inputs from the body

Delta waves as a sign of cortical plasticity after full-face transplantation

This study focused on detecting the reflections of healing and change in cortex activation in full-face transplantation and lesions patients on EEG activity. Face transplant patients have facial lesions before transplantation and, to identify pre-face transplant patients' brain activity in the absence of pre-transplant recordings, we used data obtained from pre-transplant facial lesion patients. Ten healthy, four facial lesion and three full-face transplant patients participated in this study. EEG data recorded for four different sensory stimuli (brush from the right face, right hand, left face, and left-hand regions) were analyzed using wavelet packet transform method. EEG waves were analyzed for standard bands. Our findings indicate significant change in the 2-4 Hz frequency range which may be a result of ongoing or previous cortical reorganization for face lesion and transplant patients. Alterations of the delta wave seen in patients with facial lesion and face transplant can also be explained by the intense central plasticity. Our findings show that the delta band differences might be used as a marker in the evaluation of post-transplant cortical plasticity in the future.

Virtual and Augmented Reality in Management of Phantom Limb Pain: A Systematic Review

Upper and lower limb amputations are frequently associated with phantom limb pain (PLP). Recently, virtual reality (VR) and augmented reality (AR) have been reported as a potential therapy of PLP. We have conducted a systematic review of literature to evaluate the efficacy of VR and AR in managing PLP. Four databases were searched: PubMed, EMBASE, Cumulative Index to Nursing and Allied Health Literature, and Web of Science. We utilized the Preferred Reporting Items for Systematic Reviews and Meta-Analysis for our organization. The initial search resulted in 164 results. After title, abstract, and full-text screening, 9 studies were included. One study was of good quality and 8 studies were of fair to poor quality. Seven studies utilized VR and 2 studies utilized AR. The number of treatment sessions ranged from 1 to 28 and the duration ranged from 10 minutes to 2 hours. Several pain scales were used to evaluate PLP pre- and postintervention including Numeric Rating Scale, Pain Rating Index, McGill Pain Questionnaire, and Visual Analog Scale. All the studies reported improvement of PLP on one or more of pain scales after one or more sessions of VR or AR. Despite the promising results reported by literature, we cannot recommend using VR or AR for PLP. Most of the studies are of poor design and have limited sample size with high bias levels. Therefore, no substantial evidence can be derived from them. However, we do believe further research with high-quality randomized controlled trials should take place to increase the knowledge of the potential advantages.

Asymmetry of thalamic hypometabolism on FDG-PET/CT in neurofibromatosis type 1: Association with peripheral tumor burden

BACKGROUND AND PURPOSE

Thalamic hypometabolism is a consistent finding in brain PET with F-18 fluorodeoxyglucose (FDG) in patients with neurofibromatosis type 1 (NF1). However, the pathophysiology of this metabolic alteration is unknown. We hypothesized that it might be secondary to disturbance of peripheral input to the thalamus by NF1-characteristic peripheral nerve sheath tumors (PNSTs). To test this hypothesis, we investigated the relationship between thalamic FDG uptake and the number, volume, and localization of PNSTs.

METHODS

This retrospective study included 22 adult NF1 patients (41% women, 36.2 ± 13.0 years) referred to whole-body FDG-PET/contrast-enhanced CT for suspected malignant transformation of PNSTs and 22 sex- and age-matched controls. Brain FDG uptake was scaled voxelwise to the individual median uptake in cerebellar gray matter. Bilateral mean and left-right asymmetry of thalamic FDG uptake were determined using a left-right symmetric anatomical thalamus mask. PNSTs were manually segmented in contrast-enhanced CT.

RESULTS

Thalamic FDG uptake was reduced in NF1 patients by 2.0 standard deviations (p < .0005) compared to controls. Left-right asymmetry was increased by 1.3 standard deviations (p = .013). Thalamic hypometabolism was higher in NF1 patients with ≥3 PNSTs than in patients with ≤2 PNSTs (2.6 vs. 1.6 standard deviations, p = .032). The impact of the occurrence of paraspinal/paravertebral PNSTs and of the mean PNST volume on thalamic FDG uptake did not reach statistical significance (p = .098 and p = .189). Left-right asymmetry of thalamic FDG uptake was not associated with left-right asymmetry of PNST burden (p = .658).

CONCLUSIONS

This study provides first evidence of left-right asymmetry of thalamic hypometabolism in NF1 and that it might be mediated by NF1-associated peripheral tumors.

Efficacy of balance exercises intervention on postural control-related impairment in children with sensorineural hearing loss

BACKGROUND

Sensorineural hearing loss is the most common type of permanent hearing impairment and results in postural control and motor deficits in children that may affect or delay all developmental indicators.

OBJECTIVE

The purpose of the study was to investigate the efficacy of balance exercises intervention on postural control-related impairment in children with sensorineural hearing loss.

METHODS

Forty students of both genders, ages ranging from 10 to 16 years, diagnosed with severe to profound sensorineural hearing loss, were selected from the Public School for the Deaf and Hard of Hearing in El-Minia district, Minia governorate, Egypt. They divided randomly into two groups, 20 (study group), received balance exercises in addition to their ordinary daily living activities. Meanwhile, the control group of 20 children practiced only the ordinary daily living activities. The outcome was assessed pre-treatment and post-treatment by Humac Balance System and Bruininks-Oseretsky Test (BOT-2) subtest (5) for balance.

RESULTS

Regarding the Humac balance system and subtest (5) of BOT-2, there was a statistically significant difference between pre-treatment data and post-treatment data of the study group with a p value equal to 0.036 or less. However, no statistically significant difference was observed in the control group with a p value equal to 0.096 or more. Finally, there was a statistically significant difference between the groups with respect to the post-treatment data, where the p value was 0.014 or less.

CONCLUSION

Postural control of children with sensorineural hearing loss has been improved by balance exercises.

The effect of dorsal column lesions in the primary somatosensory cortex and medulla of adult rats

Spinal cord injury is a devastating condition that haunts human lives. Typically, patients experience referred phantom sensations on the hand when they are touched on the face. In adult monkeys, massive deafferentations such as chronic dorsal column lesions at higher cervical levels result in the large-scale expansion of face inputs into the deafferented hand cortex of area 3b. However, adult rats with thoracic dorsal column lesions do not demonstrate such large-scale reorganization. The large-scale face expansion in area 3b of monkeys is driven by the reorganization of the cuneate nucleus in the medulla. The sprouting of afferents from the trigeminal nucleus to the adjacent deafferented cuneate nucleus is facilitated by close proximity and compactness of the medulla in primates. Previously, in adult rats with thoracic lesions, the cuneate nucleus was not deafferented and its functional organization was not explored. The extent of the deafferentation and the duration of the recovery period are two major factors that determine the extent of reorganization. Hence, higher cervical (C3-C4) dorsal column lesions were performed, which cause massive deafferentations, and physiological maps were obtained after prolonged recovery periods (3 weeks -18 months). In spite of the above, the expansion of the intact face inputs was not observed in the deafferented zones of the primary somatosensory cortex (SI) and medulla of adult rats. The deafferented forelimb and hindlimb representations in SI were unresponsive to cutaneous stimulation of any part of the body. The cuneate and gracile nuclei in rats with complete dorsal column lesions remained mostly inactive except for a few sites which responded to stimulation of the spared upper arm. Hence, dorsal column lesions have different effects on the adult primate and rodent somatosensory systems. Appreciating this inter-species difference can aid in identifying the underlying neural substrates and restrict maladaptive reorganizations to cure phantom sensations.

Dynamic changes of resting state functional network following acute ischemic stroke

Stroke, the second common cause of death in the world, is commonly considered to the well-known phenomenon of diaschisis. After stroke, regions far from the lesion can show altered neural activity. However, the comprehensive treatment recovery mechanism of acute ischemic stroke remains unclear. This study aims to investigate the impact of comprehensive treatment on resting state brain functional connectivity to reveal the therapeutic mechanism through a three time points study design. Twenty-one acute ischemic stroke patients and twenty matched healthy controls (HC) were included. Resting state functional magnetic resonance imaging (fMRI) and clinical evaluations were assessed in three stages: baseline (less than 72hours after stroke onset), post-first month and post-third month. Amplitude of low-frequency fluctuations (ALFF) and Independent component analysis (ICA) were conducted. We found: 1) stroke patients had decreased ALFF in the right cuneus (one of the important parts of the visual network). After three months, ALFF increased to the normal level; 2) the decreased functional connectivity in the right cuneus within the visual network and restored three months after onset. However, the decreased functional connectivity in the right precuneus within the default mode network restored one month after onset; 3) a significant association was found between the clinical scale score change over time and improvement in the cuneus and precuneus functional connectivity. Our results demonstrate the importance of the cuneus and precuneus within the visual network and default mode network in stroke recovery. These findings suggest that the different restored patterns of neural functional networks may contribute to the neurological function recovery. It has potential applications from stroke onset through rehabilitation because different rehabilitation phase corresponds to specific strategies.

Hopeless Neuroma-The Neurotized Free Flap Tissue Augmentation as Salvage Therapy-A Concept and Clinical Demonstration

Therapy-resistant neuroma pain is a devastating condition for patients and surgeons. Although various methods are described to surgically deal with neuromas, some discontinuity and stump neuroma therapies have anatomical limitations. It is widely known that a neurotizable target for axon ingrowth is beneficial for dealing with neuromas. The nerve needs "something to do". Furthermore, sufficient soft tissue coverage plays a major role in sufficient neuroma therapy. We aimed, therefore, to demonstrate our approach for therapy of resistant neuromas with insufficient tissue coverage using free flaps, which are sensory neurotized via anatomical constant branches. The central idea is to provide a new target, a new "to do" for the painful mislead axons, as well as an augmentation of deficient soft tissues. As indication is key, we furthermore demonstrate clinical cases and common neurotizable workhorse flaps.

Grip force as a functional window to somatosensory cognition

Analysis of grip force signals tailored to hand and finger movement evolution and changes in grip force control during task execution provide unprecedented functional insight into somatosensory cognition. Somatosensory cognition is the basis of our ability to act upon and to transform the physical world around us, to recognize objects on the basis of touch alone, and to grasp them with the right amount of force for lifting and manipulating them. Recent technology has permitted the wireless monitoring of grip force signals recorded from biosensors in the palm of the human hand to track and trace human grip forces deployed in cognitive tasks executed under conditions of variable sensory (visual, auditory) input. Non-invasive multi-finger grip force sensor technology can be exploited to explore functional interactions between somatosensory brain mechanisms and motor control, in particular during learning a cognitive task where the planning and strategic execution of hand movements is essential. Sensorial and cognitive processes underlying manual skills and/or hand-specific (dominant versus non-dominant hand) behaviors can be studied in a variety of contexts by probing selected measurement loci in the fingers and palm of the human hand. Thousands of sensor data recorded from multiple spatial locations can be approached statistically to breathe functional sense into the forces measured under specific task constraints. Grip force patterns in individual performance profiling may reveal the evolution of grip force control as a direct result of cognitive changes during task learning. Grip forces can be functionally mapped to from-global-to-local coding principles in brain networks governing somatosensory processes for motor control in cognitive tasks leading to a specific task expertise or skill. Under the light of a comprehensive overview of recent discoveries into the functional significance of human grip force variations, perspectives for future studies in cognition, in particular the cognitive control of strategic and task relevant hand movements in complex real-world precision task, are pointed out.

The effects of robot-assisted gait training combined with non-invasive brain stimulation on lower limb function in patients with stroke and spinal cord injury: A systematic review and meta-analysis

Objective:

This study aimed to investigate the effect of robot-assisted gait training (RAGT) therapy combined with non-invasive brain stimulation (NIBS) on lower limb function in patients with stroke and spinal cord injury (SCI).

Data sources

PubMed, Cochrane Central Register of Controlled Trials, Ovid MEDLINE, and Web of Science were searched.

Study selection

Randomized controlled trials (RCTs) published as of 3 March 2021. RCTs evaluating RAGT combined with NIBS, such as transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS), for lower limb function (e.g., Fugl-Meyer assessment for patients with stroke) and activities (i.e., gait velocity) in patients with stroke and SCI were included.

Data extraction

Two reviewers independently screened the records, extracted the data, and assessed the risk of bias.

Data synthesis

A meta-analysis of five studies (104 participants) and risk of bias were conducted. Pooled estimates demonstrated that RAGT combined with NIBS significantly improved lower limb function [standardized mean difference (SMD) = 0.52; 95% confidence interval (CI) = 0.06–0.99] but not lower limb activities (SMD = −0.13; 95% CI = −0.63–0.38). Subgroup analyses also failed to find a greater improvement in lower limb function of RAGT with tDCS compared to sham stimulation. No significant differences between participant characteristics or types of NIBS were observed.

Conclusion

This meta-analysis demonstrated that RAGT therapy in combination with NIBS was effective in patients with stroke and SCI. However, a greater improvement in lower limb function and activities were not observed using RAGT with tDCS compared to sham stimulation.

Influence of Neck Pain, Cervical Extensor Muscle Fatigue, and Manual Therapy on Wrist Proprioception

OBJECTIVE

The purpose of this study was to examine the effects of submaximal isometric neck muscle fatigue and manual therapy on wrist joint position sense (JPS) within healthy individuals and individuals with subclinical neck pain (SCNP).

METHODS

Twelve healthy participants and 12 participants with SCNP were recruited. Each group completed 2 sessions, with 48 hours between sessions. On day 1, both groups performed 2 wrist JPS tests using a robotic device. The tests were separated by a submaximal isometric fatigue protocol for the cervical extensor muscles (CEM). On day 2, both groups performed a wrist JPS test, followed by a cervical treatment consisting of manual therapy (SCNP) or neck rest (20 minutes, control group) and another wrist JPS test. Joint position sense was measured as the participant's ability to recreate a previously presented wrist angle. Each wrist JPS test included 12 targets, 6 into wrist flexion and 6 into wrist extension. Kinematic data from the robot established absolute, variability, and constant error.

RESULTS

Absolute error significantly decreased (P = .01) from baseline to post-fatigue in the SCNP group (baseline = 4.48 ± 1.58°; post-fatigue = 3.90 ± 1.45°) and increased in the control group (baseline = 3.12 ± 0.98°; post-fatigue = 3.81 ± 0.90°). The single session of manual cervical treatment significantly decreased absolute error in participants with SCNP (P = .004).

CONCLUSION

This study demonstrated that neck pain or fatigue can lead to altered afferent input to the central nervous system and can affect wrist JPS. Our findings demonstrate that acute wrist proprioception may be improved in individuals with SCNP by a single cervical manual therapy session.

Electromyographic Responses of Neck, Back, and Limb Outlet Muscles Associated With High-Velocity, Low-Amplitude Manual Cervical and Upper Thoracic Spinal Manipulation of Individuals With Mild Neck Disability: A Descriptive Observational Investigation

OBJECTIVES

The purpose of this study was to investigate the extent of electromyographic responses associated with manual high-velocity, low-amplitude (HVLA) spinal manipulation systematically applied to the upper and lower cervical and upper thoracic spines in a cohort with mild neck disability.

METHODS

The study was a descriptive observational investigation, with all participants receiving the same interventions. Nineteen participants with mild neck disability received 6 manual HVLA manipulations to the cervical and upper thoracic spine. Bipolar surface electromyography electrode pairs were used to measure responses of 16 neck, back, and limb outlet muscles bilaterally. The number of electromyographic responses was then calculated.

RESULTS

Electromyographic responses associated with cervical and thoracic manipulation occurred in a median of 4 of the 16 (range: 1-14) recorded muscles. Cervical spinal manipulation was associated with the highest rates of electromyographic responses in neck muscles, whereas responses in back muscles were highest after upper thoracic manipulation.

CONCLUSION

Cervical spinal manipulation was associated with the highest rate of electromyographic responses in muscles of the cervical spine (sternocleidomastoid and splenius cervicis), whereas responses in back muscles (upper and middle trapezius, latissimus dorsi, and longissimus thoracis) were highest after upper thoracic manipulations. This result suggests that electromyographic muscular responses associated with spinal manipulation primarily occur locally (close to the target segment) rather than distally.

Tactile Sensation Improves Following Motor Rehabilitation for Chronic Stroke: The VIGoROUS Randomized Controlled Trial

Background. Up to 85% of people with chronic stroke experience somatosensory impairment, which contributes to poor sensorimotor control and non-use of the affected limb. Neurophysiological mechanisms suggest motor rehabilitation may improve tactile sense post-stroke, however, somatosensory recovery has rarely been reported in controlled trials. Objective. To compare the effect of four upper limb motor rehabilitation programs on the recovery of tactile sensation in adults with chronic stroke. Methods. Adults with chronic stroke and mild or moderate upper extremity hemiparesis (n = 167) were enrolled in a multi-site randomized controlled trial. Participants completed three weeks of gaming therapy, gaming therapy with additional telerehabilition, Constraint-Induced Movement therapy, or traditional rehabilitation. Here, we report the results of a secondary outcome, tactile sensation, measured with monofilaments, before and after treatment, and 6 months later. Results. A mixed-effects general linear model revealed similar positive change in tactile sensitivity regardless of the type of training. On average, participants were able to detect a stimulus that was 32% and 33% less after training and at 6-month follow-up, respectively. One-third of participants experienced recategorization of their level of somatosensory impairment (e.g., regained protective sensation) following training. Poorer tactile sensation at baseline was associated with greater change. Conclusions. About one-third of individuals with mild/moderate chronic hemiparesis experience sustained improvements in tactile sensation following motor rehabilitation, regardless of the extent of tactile input in the rehabilitation program. Potential for sensory improvement is an additional motivator for those post-stroke. Characteristics of those who improve and mechanisms of improvement are important future questions. Clinicaltrials.gov NCT02631850.

Evaluating the Effectiveness of a New Auditory Training Program on the Speech Recognition Skills and Auditory Event-Related Potentials in Elderly Hearing Aid Users

<b><i>Introduction:</i></b> The objective of this study was to evaluate the effectiveness of a new auditory training (AT) program on the speech recognition in the noise and on the auditory event-related potentials in elderly hearing aid users. <b><i>Methods:</i></b> Thirty-three elderly individuals using hearing aids aged from 60 to 80 years participated. A new AT program was developed for the study. AT program lasts for 8 weeks and includes sound discrimination exercises and cognitive exercises. Seventeen individuals (mean age 72.17 ± 6.94) received AT and 16 individuals (mean age 71.75 ± 6.81) did not receive AT. The mismatch negativity (MMN) test and matrix test were used to evaluate the effectiveness of AT. Tests were conducted for the study group before and after the AT. The tests were carried out for the control group at the same times with the study group and the results were compared. <b><i>Results:</i></b> In comparison with the first evaluation, the last evaluation of the study group demonstrated a significant difference regarding the decrease of mean latency in the MMN wave (<i>p</i> = 0.038), and regarding the improving score of matrix test (<i>p</i> = 0.004), there was no difference in the control group. <b><i>Conclusion:</i></b> The AT program prepared for the study was effective in improving speech recognition in noise in the elderly, and the efficiency of AT could be demonstrated with MMN and matrix test.

Consciousness Beyond Neural Fields: Expanding the Possibilities of What Has Not Yet Happened

In the field theories in physics, any particular region of the presumed space-time continuum and all interactions between elementary objects therein can be objectively measured and/or accounted for mathematically. Since this does not apply to any of the field theories, or any other neural theory, of consciousness, their explanatory power is limited. As discussed in detail herein, the matter is complicated further by the facts than any scientifically operational definition of consciousness is inevitably partial, and that the phenomenon has no spatial dimensionality. Under the light of insights from research on meditation and expanded consciousness, chronic pain syndrome, healthy aging, and eudaimonic well-being, we may conceive consciousness as a source of potential energy that has no clearly defined spatial dimensionality, but can produce significant changes in others and in the world, observable in terms of changes in time. It is argued that consciousness may have evolved to enable the human species to generate such changes in order to cope with unprecedented and/or unpredictable adversity. Such coping could, ultimately, include the conscious planning of our own extinction when survival on the planet is no longer an acceptable option.

OUP accepted manuscript

Myasthenia gravis is an autoimmune disease affecting neuromuscular transmission and causing skeletal muscle weakness. Additionally, systemic inflammation, cognitive deficits and autonomic dysfunction have been described. However, little is known about myasthenia gravis-related reorganization of the brain. In this study, we thus investigated the structural and functional brain changes in myasthenia gravis patients. Eleven myasthenia gravis patients (age: 70.64 ± 9.27; 11 males) were compared to age-, sex- and education-matched healthy controls (age: 70.18 ± 8.98; 11 males). Most of the patients (n = 10, 0.91%) received cholinesterase inhibitors. Structural brain changes were determined by applying voxel-based morphometry using high-resolution T₁-weighted sequences. Functional brain changes were assessed with a neuropsychological test battery (including attention, memory and executive functions), a spatial orientation task and brain-derived neurotrophic factor blood levels. Myasthenia gravis patients showed significant grey matter volume reductions in the cingulate gyrus, in the inferior parietal lobe and in the fusiform gyrus. Furthermore, myasthenia gravis patients showed significantly lower performance in executive functions, working memory (Spatial Span, P = 0.034, d = 1.466), verbal episodic memory (P = 0.003, d = 1.468) and somatosensory-related spatial orientation (Triangle Completion Test, P = 0.003, d = 1.200). Additionally, serum brain-derived neurotrophic factor levels were significantly higher in myasthenia gravis patients (P = 0.001, d = 2.040). Our results indicate that myasthenia gravis is associated with structural and functional brain alterations. Especially the grey matter volume changes in the cingulate gyrus and the inferior parietal lobe could be associated with cognitive deficits in memory and executive functions. Furthermore, deficits in somatosensory-related spatial orientation could be associated with the lower volumes in the inferior parietal lobe. Future research is needed to replicate these findings independently in a larger sample and to investigate the underlying mechanisms in more detail.

Efficacy of fine motor and balance exercises on fine motor skills in children with sensorineural hearing loss

BACKGROUND

Childhood hearing impairment is a major disability associated with delayed motor development. The affected Fine motor performance in children with sensorineural hearing loss (SNHL) could be due to dynamic balance deficits and visual-motor incoordination.

OBJECTIVE

This study was designed to investigate the effects of fine motor exercises with or without balancing exercises on fine motor skills in children with SNHL.

METHODS

One hundred and eighty (180) children their age ranged from 8 to 18 years old diagnosed with SNHL were selected. They were divided into three groups, 60 children (control group) practiced only their ordinary activities of daily living, 60 children (fine motor exercises group) practiced fine motor exercises, and 60 children (fine motor and balance exercise) group practiced fine motor and balance exercises. The outcomes were assessed by the Bruininks Oseretsky Test of the motor proficiency second edition scale (BOT-2).

RESULTS

Generally, there was a statistically significant difference between control group and fine motor exercises group where (p <  0.05), besides, there was a statistically significant difference between control group and fine motor and balance exercises group where (p <  0.05). But, there was no statistically significant difference between fine motor exercises group and fine motor and balance exercises group where (p >  0.05).

CONCLUSIONS

The Fine Motor performance of children with SNHL has been improved by Fine motor with or without balancing exercises according to (BOT-2).

Central functional reorganization and recovery following facial-hypoglossal neurorrhaphy for facial paralysis

OBJECTIVE

Functional deficits induced by nerve injuries can be restored by achieving effective reinnervation of the denervated targets and functional reorganization of the central nervous system after nerve reconstruction. In this study, we investigated the effect and extent of cortical functional reorganization related to the ability of transferred hypoglossal neurons to restore facial function in facial paralysis patients after a surgical bridge of neurorrhaphy ectopically between the ipsilateral hypoglossal nerve and injured facial nerve.

METHODS

We treated 23 patients (35.4 ± 10.3 years, 10 males) and followed them up for 2.9 ± 0.61 years. We used motor-task-related functional magnetic resonance imaging to map activation change at multiple time points before and after neurorrhaphy; 20 normal subjects were included as control.

RESULTS

All patients regained facial function to some extent after neurorrhaphy. Enhanced activation in motor-related cortices gradually returned to normal levels and was positively correlated with regained facial function. The related cortical functional areas included the left middle temporal gyrus, left inferior frontal gyrus, insula, bilateral motor cortex and the supplementary motor area extending to the paracingulate involved in intensive eye closing, as well as the left superior temporal gyrus, right putamen and the bilateral motor cortex involved in lip pursing. Intriguingly, significant correlations were found between the pre-surgery activation while intensive eye closing in bilateral motor cortex and recovery of facial nerve function induced by the neurorrhaphy treatment.

CONCLUSION

This is the first study mapping activation change in motor cortices at multiple time points before and after repair of the facial nerve. The cortex functional reorganization found may suggest potential treatment targets in the central nervous system for adjuvant therapies such as repetitive transcranial magnetic stimulation to further improve functional recovery.

Metabolic Brain Network Analysis With 18F-FDG PET in a Rat Model of Neuropathic Pain

Neuropathic pain has been found to be related to profound reorganization in the function and structure of the brain. We previously demonstrated changes in local brain activity and functional/metabolic connectivity among selected brain regions by using neuroimaging methods. The present study further investigated large-scale metabolic brain network changes in 32 Sprague–Dawley rats with right brachial plexus avulsion injury (BPAI). Graph theory was applied in the analysis of 2-deoxy-2-[18F] fluoro-D-glucose (¹⁸F-FDG) PET images. Inter-subject metabolic networks were constructed by calculating correlation coefficients. Global and nodal network properties were calculated and comparisons between pre- and post-BPAI (7 days) status were conducted. The global network properties (including global efficiency, local efficiency and small-world index) and nodal betweenness centrality did not significantly change for all selected sparsity thresholds following BPAI (p > 0.05). As for nodal network properties, both nodal degree and nodal efficiency measures significantly increased in the left caudate putamen, left medial prefrontal cortex, and right caudate putamen (p < 0.001). The right entorhinal cortex showed a different nodal degree (p < 0.05) but not nodal efficiency. These four regions were selected for seed-based metabolic connectivity analysis. Strengthened connectivity was found among these seeds and distributed brain regions including sensorimotor area, cognitive area, and limbic system, etc. (p < 0.05). Our results indicated that the brain had the resilience to compensate for BPAI-induced neuropathic pain. However, the importance of bilateral caudate putamen, left medial prefrontal cortex, and right entorhinal cortex in the network was strengthened, as well as most of their connections with distributed brain regions.

Neurofeedback Training of Auditory Selective Attention Enhances Speech-In-Noise Perception

Selective attention enhances cortical responses to attended sensory inputs while suppressing others, which can be an effective strategy for speech-in-noise (SiN) understanding. Emerging evidence exhibits a large variance in attentional control during SiN tasks, even among normal-hearing listeners. Yet whether training can enhance the efficacy of attentional control and, if so, whether the training effects can be transferred to performance on a SiN task has not been explicitly studied. Here, we introduce a neurofeedback training paradigm designed to reinforce the attentional modulation of auditory evoked responses. Young normal-hearing adults attended one of two competing speech streams consisting of five repeating words (“up”) in a straight rhythm spoken by a female speaker and four straight words (“down”) spoken by a male speaker. Our electroencephalography-based attention decoder classified every single trial using a template-matching method based on pre-defined patterns of cortical auditory responses elicited by either an “up” or “down” stream. The result of decoding was provided on the screen as online feedback. After four sessions of this neurofeedback training over 4 weeks, the subjects exhibited improved attentional modulation of evoked responses to the training stimuli as well as enhanced cortical responses to target speech and better performance during a post-training SiN task. Such training effects were not found in the Placebo Group that underwent similar attention training except that feedback was given only based on behavioral accuracy. These results indicate that the neurofeedback training may reinforce the strength of attentional modulation, which likely improves SiN understanding. Our finding suggests a potential rehabilitation strategy for SiN deficits.

3D bioprinted human iPSC-derived somatosensory constructs with functional and highly purified sensory neuron networks

Engineering three-dimensional (3D) sensible tissue constructs, along with the complex microarchitecture wiring of the sensory nervous system, has been an ongoing challenge in the tissue engineering field. By combining 3D bioprinting and human pluripotent stem cell (hPSC) technologies, sensible tissue constructs could be engineered in a rapid, precise, and controllable manner to replicate 3D microarchitectures and mechanosensory functionalities of the native sensory tissue (e.g. response to external stimuli). Here, we introduce a biofabrication approach to create complex 3D microarchitecture wirings. We develop an hPSC-sensory neuron (SN) laden bioink using highly purified and functional SN populations to 3D bioprint microarchitecture wirings that demonstrate responsiveness to warm/cold sense-inducing chemicals and mechanical stress. Specifically, we tailor a conventional differentiation strategy to our purification method by utilizing p75 cell surface marker and DAPT treatment along with neuronal growth factors in order to selectively differentiate neural crest cells into SNs. To create spatial resolution in 3D architectures and grow SNs in custom patterns and directions, an induced pluripotent stem cell (iPSC)-SN-laden gelatin bioink was printed on laminin-coated substrates using extrusion-based bioprinting technique. Then the printed constructs were covered with a collagen matrix that guided SNs growing in the printed micropattern. Using a sacrificial bioprinting technique, the iPSC-SNs were seeded into the hollow microchannels created by sacrificial gelatin ink printed in the gelatin methacryloyl supporting bath, thereby demonstrating controllability over axon guidance in curved lines up to several tens of centimeters in length on 2D substrates and in straight microchannels in 3D matrices. Therefore, this biofabrication approach could be amenable to incorporate sensible SN networks into the engineered skin equivalents, regenerative skin implants, and augmented somatosensory neuro-prosthetics that have the potential to regenerate sensible functions by connecting host neuron systems in injured areas.

When having a limb means feeling overcomplete. Xenomelia, the chronic sense of disownership and the right parietal lobe hypothesis

ABSTRACTXenomelia is a rare condition characterized by a persistent and intense desire for amputation of one or more healthy limbs. Some frequent clinical manifestations suggest the involvement of distinct neural substrates. Specifically, recent aetiopathological hypotheses about xenomelia propose a neurodevelopmental origin, highlighting the putative contribution of the right parietal lobe and right insula, known to subserve the construction of a coherent representation of the body as a whole. This literature review is aimed at analysing relevant findings about structural and functional brain correlates of xenomelia, focusing on the identification of key regions and their hemispheric distribution. Finally, implications about the potential link between xenomelia and phylogenetic development of the right parietal lobe are discussed. Despite a certain degree of heterogeneity and the spatial extension of networks involved, signs of partial right-sided lateralization of cortical nodes and left-sided lateralization of subcortical nodes emerged. Indeed, some areas-rsPL, riPL, PMC and rInsula-have been consistently found altered in xenomelia. In conclusion, the presence of both structural and functional multi-layered brain abnormalities in xenomelia suggests a multifactorial aetiology; however, as the prevalence of correlational studies, causal relationships remain to be investigated.

Toward a Theory of the Mechanism of High-Velocity, Low-Amplitude Technique: A Literature Review

This review seeks to integrate the current literature to create a more unified and inclusive theory regarding the therapeutic mechanism of high-velocity, low-amplitude (HVLA) technique. The authors review the literature currently available regarding the physiologic effects of HVLA. The progression from an articulatory model to a neuromuscular one is discussed, and the body of work demonstrating that HVLA has a centralized mechanism of action, rather than just a local one, is described.

Altered cerebrovascular response to acute exercise in patients with Huntington's disease

The objective of this study was to determine whether a single session of exercise was sufficient to induce cerebral adaptations in individuals with Huntington’s disease and to explore the time dynamics of any acute cerebrovascular response. In this case–control study, we employed arterial-spin labelling MRI in 19 Huntington’s disease gene-positive participants (32–65 years, 13 males) and 19 controls (29–63 years, 10 males) matched for age, gender, body mass index and self-reported activity levels, to measure global and regional perfusion in response to 20 min of moderate-intensity cycling. Cerebral perfusion was measured at baseline and 15, 40 and 60 min after exercise cessation. Relative to baseline, we found that cerebral perfusion increased in patients with Huntington’s disease yet was unchanged in control participants in the precentral gyrus (P = 0.016), middle frontal gyrus (P = 0.046) and hippocampus (P = 0.048) 40 min after exercise cessation (+15 to +32.5% change in Huntington’s disease participants, −7.7 to 0.8% change in controls). The length of the disease‐causing trinucleotide repeat expansion in the huntingtin gene predicted the change in the precentral gyrus (P = 0.03) and the intensity of the exercise intervention predicted hippocampal perfusion change in Huntington’s disease participants (P < 0.001). In both groups, exercise increased hippocampal blood flow 60 min after exercise cessation (P = 0.039). These findings demonstrate the utility of acute exercise as a clinically sensitive experimental paradigm to modulate the cerebrovasculature. Twenty minutes of aerobic exercise induced transient cerebrovascular adaptations in the hippocampus and cortex selectively in Huntington’s disease participants and likely represents latent neuropathology not evident at rest.

Seven Properties of Self-Organization in the Human Brain

The principle of self-organization has acquired a fundamental significance in the newly emerging field of computational philosophy. Self-organizing systems have been described in various domains in science and philosophy including physics, neuroscience, biology and medicine, ecology, and sociology. While system architecture and their general purpose may depend on domain-specific concepts and definitions, there are (at least) seven key properties of self-organization clearly identified in brain systems: (1) modular connectivity, (2) unsupervised learning, (3) adaptive ability, (4) functional resiliency, (5) functional plasticity, (6) from-local-to-global functional organization, and (7) dynamic system growth. These are defined here in the light of insight from neurobiology, cognitive neuroscience and Adaptive Resonance Theory (ART), and physics to show that self-organization achieves stability and functional plasticity while minimizing structural system complexity. A specific example informed by empirical research is discussed to illustrate how modularity, adaptive learning, and dynamic network growth enable stable yet plastic somatosensory representation for human grip force control. Implications for the design of “strong” artificial intelligence in robotics are brought forward.

Similar 2-point discrimination and stereognosia but better locognosia at long term with an independent home-based sensory reeducation program vs no reeducation after low-median nerve transection and repair

STUDY DESIGN

Prospective controlled study.

INTRODUCTION

Previous studies evaluated the effectiveness of sensory reeducation (SR) after peripheral nerve injury and repair. However, evidence for long-term clinical usefulness of SR is inconclusive.

PURPOSE OF THE STUDY

The purpose of this study is to compare the sensory results of patients with low-median nerve complete transection and microsurgical repair, with and without SR at long term.

METHODS

We prospectively studied 52 consecutive patients (mean age, 36 years; range, 20-47 years) with low-median nerve complete transection and microsurgical repair. When reinnervation was considered complete with perception of vibration with a 256-cycles per second tuning fork (mean, 3.5 months after nerve injury and repair), the patients were sequentially allocated (into 2 groups [group SR, 26 patients, SR; group R, 26 patients, reassured on recovery without SR). SR was conducted in a standardized fashion, in 2 stages, as an independent home-based program: the first stage was initiated when reinnervation was considered complete, and included instruction in home exercises to identify familiar objects and papers of different roughness, and localization of light touch (eyes open and closed); the second stage was initiated when the patients experienced normal static and moving 2-point discrimination (2PD) at the index fingertip of injured hand, and included instruction in home exercises for stereognosia, supplementary exercises for localization of light touch, and identification of small objects (eyes open and closed). Exercises were prescribed for 5-10 minutes, 4 times per day. At 1.5, 3, and 6 years after nerve injury and repair, we evaluated the static and moving 2PD, stereognosia with the Moberg's pick-up test, and locognosia with the modified Marsh test. Comparison between groups and time points was done with the nonparametric analysis of variance (Kruskal-Wallis analysis of variance).

RESULTS

Static and moving 2PD and stereognosia were not significantly different between groups at any study period. Locognosia was significantly better at 1.5 and 3 years in group SR; locognosia was excellent in 17 patients of group SR vs 5 patients of group R at 1.5-year follow-up and in 14 patients of group SR vs 5 patients of group R at 3-year follow-up. Locognosia was not different between the study groups at 6-year follow-up.

CONCLUSION

A 2-stage home program of SR improved locognosia at 1.5 and 3 years after low-median nerve complete transection and repair without significant differences in other modalities or the 6-year follow-up of a small subsample.

Unilateral Brachial Plexus Lesion Impairs Bilateral Touch Threshold

Unilateral brachial plexus injury (BPI) impairs sensory and motor functions of the upper limb. This study aimed to map in detail brachial plexus sensory impairment both in the injured and the uninjured upper limb. Touch sensation was measured through Semmes-Weinstein monofilaments at the autonomous regions of the brachial plexus nerves, hereafter called points of exclusive innervation (PEIs). Seventeen BPI patients (31.35 years±6.9 SD) and 14 age-matched healthy controls (27.57 years±5.8 SD) were tested bilaterally at six selected PEIs (axillary, musculocutaneous, median, radial, ulnar, and medial antebrachial cutaneous [MABC]). As expected, the comparison between the control group and the brachial plexus patients' injured limb showed a robust difference for all PEIs (p ≤ 0.001). Moreover, the comparison between the control group and the brachial plexus uninjured limb revealed a difference for the median (p = 0.0074), radial (p = 0.0185), ulnar (p = 0.0404), and MABC (p = 0.0328) PEIs. After splitting the sample into two groups with respect to the dominance of the injured limb, higher threshold values were found for the uninjured side when it occurred in the right dominant limb compared to the control group at the median (p = 0.0456), radial (p = 0.0096), and MABC (p = 0.0078) PEIs. This effect was absent for the left, non-dominant arm. To assess the effect of the severity of sensory deficits observed in the injured limb upon the alterations of the uninjured limb, a K-means clustering algorithm (k = 2) was applied resulting in two groups with less or more severe sensory impairment. The less severely affected patients presented higher thresholds at the median (p = 0.0189), radial (p = 0.0081), ulnar (p = 0.0253), and MABC (p = 0.0187) PEIs in the uninjured limb in comparison with the control group, whereas higher thresholds at the uninjured limb were found only for the median PEI (p = 0.0457) in the more severely affected group. In conclusion, an expressive reduction in touch threshold was found for the injured limb allowing a precise mapping of the impairment caused by the BPI. Crucially, BPI also led to reduced tactile threshold in specific PEIs in the uninjured upper limb. These new findings suggest a superordinate model of representational plasticity occurring bilaterally in the brain after a unilateral peripheral injury.

A Touch-Observation and Task-Based Mirror Therapy Protocol to Improve Sensorimotor Control and Functional Capability of Hands for Patients With Peripheral Nerve Injury

IMPORTANCE

To develop a practical program in the early phase after nerve repair for more rapid return of function.

OBJECTIVE

To investigate the effects of touch-observation and task-based mirror therapy on the sensorimotor outcomes of patients with nerve repair.

DESIGN

An assessor-blinded study with a randomized controlled design.

SETTING

University hospital.

PARTICIPANTS

We recruited 12 patients with median or ulnar nerve repair between the level of midpalm and elbow referred by the plastic surgeons.

INTERVENTION

The patients were randomized into touch-observation and task-based mirror therapy or control groups, and both groups received training for 12 wk.

OUTCOMES AND MEASURES

The Semmes-Weinstein monofilament (SWM) test, two-point discrimination test, Purdue Pegboard Test (PPT), Minnesota Manual Dexterity Test (MMDT), and pinch-holding-up activity test were assessed at pretreatment, immediately after treatment, and 12 wk after the last treatment.

RESULTS

The experimental group showed greater improvements in the results of the pinch-holding-up activity test and the PPT Unilateral Pin Insertion, Bilateral Pin Insertion, and Assembly subtests. However, change on the SWM test revealed no significant difference between the two groups.

CONCLUSIONS AND RELEVANCE

Touch-observation and task-based mirror therapy is an effective but low-cost treatment protocol to optimize sensorimotor control and functional capability of the upper limb in patients with peripheral nerve injury.

Increased Voluntary Activation of the Elbow Flexors Following a Single Session of Spinal Manipulation in a Subclinical Neck Pain Population

To investigate the effects of a single session of spinal manipulation (SM) on voluntary activation of the elbow flexors in participants with subclinical neck pain using an interpolated twitch technique with transcranial magnetic stimulation (TMS), eighteen volunteers with subclinical neck pain participated in this randomized crossover trial. TMS was delivered during elbow flexion contractions at 50%, 75% and 100% of maximum voluntary contraction (MVC) before and after SM or control intervention. The amplitude of the superimposed twitches evoked during voluntary contractions was recorded and voluntary activation was calculated using a regression analysis. Dependent variables were analyzed with two-way (intervention × time) repeated measures ANOVAs. Significant intervention effects for SM compared to passive movement control were observed for elbow flexion MVC (p = 0.04), the amplitude of superimposed twitch (p = 0.04), and voluntary activation of elbow flexors (p =0.03). Significant within-group post-intervention changes were observed for the superimposed twitch (mean group decrease of 20.9%, p < 0.01) and voluntary activation (mean group increase of 3.0%, p < 0.01) following SM. No other significant within-group changes were observed. Voluntary activation of the elbow flexors increased immediately after one session of spinal manipulation in participants with subclinical neck pain. A decrease in the amplitude of superimposed twitch during elbow flexion MVC following spinal manipulation suggests a facilitation of motor cortical output.

Spiking Neural Network Modelling Approach Reveals How Mindfulness Training Rewires the Brain

There has been substantial interest in Mindfulness Training (MT) to understand how it can benefit healthy individuals as well as people with a broad range of health conditions. Research has begun to delineate associated changes in brain function. However, whether measures of brain function can be used to identify individuals who are more likely to respond to MT remains unclear. The present study applies a recently developed brain-inspired Spiking Neural Network (SNN) model to electroencephalography (EEG) data to provide novel insight into: i) brain function in depression; ii) the effect of MT on depressed and non-depressed individuals; and iii) neurobiological characteristics of depressed individuals who respond to mindfulness. Resting state EEG was recorded from before and after a 6 week MT programme in 18 participants. Based on self-report, 3 groups were formed: non-depressed (ND), depressed before but not after MT (responsive, D⁺) and depressed both before and after MT (unresponsive, D^-). The proposed SNN, which utilises a standard brain-template, was used to model EEG data and assess connectivity, as indicated by activation levels across scalp regions (frontal, frontocentral, temporal, centroparietal and occipitoparietal), at baseline and follow-up. Results suggest an increase in activation following MT that was site-specific as a function of the group. Greater initial activation levels were seen in ND compared to depressed groups, and this difference was maintained at frontal and occipitoparietal regions following MT. At baseline, D⁺ had great activation than D^-. Following MT, frontocentral and temporal activation reached ND levels in D⁺ but remained low in D^-. Findings support the SNN approach in distinguishing brain states associated with depression and responsiveness to MT. The results also demonstrated that the SNN approach can be used to predict the effect of mindfulness on an individual basis before it is even applied.

Auditory and Cognitive Training for Cognition in Adults With Hearing Loss: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis examined the efficacy of auditory training and cognitive training to improve cognitive function in adults with hearing loss. A literature search of academic databases (e.g., MEDLINE, Scopus) and gray literature (e.g., OpenGrey) identified relevant articles published up to January 25, 2018. Randomized controlled trials (RCTs) or repeated measures designs were included. Outcome effects were computed as Hedge’s g and pooled using random-effects meta-analysis (PROSPERO: CRD42017076680). Nine studies, five auditory training, and four cognitive training met the inclusion criteria. Following auditory training, the pooled effect was small and statistically significant for both working memory (g = 0.21; 95% CI [0.05, 0.36]) and overall cognition (g = 0.19; 95% CI [0.07, 0.31]). Following cognitive training, the pooled effect for working memory was small and statistically significant (g = 0.34; 95% CI [0.16, 0.53]), and the pooled effect for overall cognition was large and significant (g = 1.03; 95% CI [0.41, 1.66]). However, this was dependent on the classification of training approach. Sensitivity analyses revealed no statistical difference between the effectiveness of auditory and cognitive training for improving cognition upon removal of a study that used a combined auditory–cognitive approach, which showed a very large effect. Overall certainty in the estimation of effect was “low” for auditory training and “very low” for cognitive training. High-quality RCTs are needed to determine which training stimuli will provide optimal conditions to improve cognition in adults with hearing loss.

Differences in neuroplasticity after spinal cord injury in varying animal models and humans

Rats have been the primary model to study the process and underlying mechanisms of recovery after spinal cord injury. Two weeks after a severe spinal cord contusion, rats can regain weight-bearing abilities without therapeutic interventions, as assessed by the Basso, Beattie and Bresnahan locomotor scale. However, many human patients suffer from permanent loss of motor function following spinal cord injury. While rats are the most understood animal model, major differences in sensorimotor pathways between quadrupeds and bipeds need to be considered. Understanding the major differences between the sensorimotor pathways of rats, non-human primates, and humans is a start to improving targets for treatments of human spinal cord injury. This review will discuss the neuroplasticity of the brain and spinal cord after spinal cord injury in rats, non-human primates, and humans. A brief overview of emerging interventions to induce plasticity in humans with spinal cord injury will also be discussed.

A review of current theories and treatments for phantom limb pain

Following amputation, most amputees still report feeling the missing limb and often describe these feelings as excruciatingly painful. Phantom limb sensations (PLS) are useful while controlling a prosthesis; however, phantom limb pain (PLP) is a debilitating condition that drastically hinders quality of life. Although such experiences have been reported since the early 16th century, the etiology remains unknown. Debate continues regarding the roles of the central and peripheral nervous systems. Currently, the most posited mechanistic theories rely on neuronal network reorganization; however, greater consideration should be given to the role of the dorsal root ganglion within the peripheral nervous system. This Review provides an overview of the proposed mechanistic theories as well as an overview of various treatments for PLP.

Non-invasive brain stimulation for fine motor improvement after stroke: a meta-analysis

The aim of this study was to determine whether non-invasive brain stimulation (NIBS) techniques improve fine motor performance in stroke. We searched PubMed, EMBASE, Web of Science, SciELO and OpenGrey for randomized clinical trials on NIBS for fine motor performance in stroke patients and healthy participants. We computed Hedges' g for active and sham groups, pooled data as random-effects models and performed sensitivity analysis on chronicity, montage, frequency of stimulation and risk of bias. Twenty-nine studies (351 patients and 152 healthy subjects) were reviewed. Effect sizes in stroke populations for transcranial direct current stimulation and repeated transcranial magnetic stimulation were 0.31 [95% confidence interval (CI), 0.08-0.55; P = 0.010; Tau² , 0.09; I² , 34%; Q, 18.23; P = 0.110] and 0.46 (95% CI, 0.00-0.92; P = 0.05; Tau² , 0.38; I² , 67%; Q, 30.45; P = 0.007). The effect size of non-dominant healthy hemisphere transcranial direct current stimulation on non-dominant hand function was 1.25 (95% CI, 0.09-2.41; P = 0.04; Tau² , 1.26; I² , 93%; Q, 40.27; P < 0.001). Our results show that NIBS is associated with gains in fine motor performance in chronic stroke patients and healthy subjects. This supports the effects of NIBS on motor learning and encourages investigation to optimize their effects in clinical and research settings.

Motor and sensory effects of ipsilesional upper extremity hypothermia and contralesional sensory training for chronic stroke patients

As hypothermia by immersion can reduce the sensory nerve conduction velocity, this study hypothesized that the reduction of sensory input to the ipsilesional upper extremity (UE) using cryotherapy would reduce the inhibitory activity of the contralesional hemisphere in chronic stroke subjects.

OBJECTIVE

In this study, hypothermia was applied by immersing the ipsilesional UE in association with sensory training of the contralesional UE of stroke patients to assess the immediate (e.g. sensorimotor function, hemodynamics, and levels of comfort) and long-term (sensory and motor performances of the UEs) effects.

METHODS

The sample included 27 stroke patients allocated into group 1 (n = 14), which received conventional physiotherapy for the affected UE, and group 2 (n = 13), which underwent 10 sessions of immersion hypothermia of the ipsilesional wrist and hand. Assessments were performed pre- and post-treatment and at follow-up using esthesiometry, the Fugl-Meyer Assessment (FMA), the Nottingham Sensory Assessment, functional tests, tactile and weight discrimination, motor sequence, level of comfort, and hemodynamic parameters.

RESULTS

The immediate effects of hypothermia using immersion of the ipsilesional UE in association with sensory training of the contralesional UE were hemodynamic stability during and after hypothermia, the absence of sensory abnormalities in the contralesional UE, hypoesthesia in the ipsilesional extremity (dermatomes C6 and C8) (P < 0.05), the maintenance of acceptable levels of comfort, and good patient compliance to the technique. The long-term effects included significant increases in scores on tests performed without functional vision, in scores on blindfolded functional tests, and in tactile localization and joint position sense for the contralesional hand in group 2 as well as the maintenance of these gains at long-term follow-up (5 weeks). Improvement was also found in the tactile function of the C6 and C7 dermatomes of the contralesional hand (P < 0.05).

CONCLUSIONS

The use of immersion hypothermia on the ipsilesional UE in association with sensory training of the contralesional UE improved motor function and sensitivity in the contralesional UE of individuals with chronic stroke. Immersion hypothermia of the ipsilesional UE in chronic stroke patients is a safe, practical, inexpensive, and easily applied technique.

Somatosensory maps

Somatosensory areas containing topographic maps of the body surface are a major feature of parietal cortex. In primates, parietal cortex contains four somatosensory areas, each with its own map, with the primary cutaneous map in area 3b. Rodents have at least three parietal somatosensory areas. Maps are not isomorphic to the body surface, but magnify behaviorally important skin regions, which include the hands and face in primates, and the whiskers in rodents. Within each map, intracortical circuits process tactile information, mediate spatial integration, and support active sensation. Maps may also contain fine-scale representations of touch submodalities, or direction of tactile motion. Functional representations are more overlapping than suggested by textbook depictions of map topography. The whisker map in rodent somatosensory cortex is a canonic system for studying cortical microcircuits, sensory coding, and map plasticity. Somatosensory maps are plastic throughout life in response to altered use or injury. This chapter reviews basic principles and recent findings in primate, human, and rodent somatosensory maps.

Preservation of hand movement representation in the sensorimotor areas of amputees

Denervation due to amputation is known to induce cortical reorganization in the sensorimotor cortex. Although there is evidence that reorganization does not lead to a complete loss of the representation of the phantom limb, it is unclear to what extent detailed, finger-specific activation patterns are preserved in motor cortex, an issue that is also relevant for development of brain-computer interface solutions for paralysed people. We applied machine learning to obtain a quantitative measure for the functional organization within the motor and adjacent cortices in amputees, using high resolution functional MRI and attempted hand gestures. Subjects with above-elbow arm amputation (n = 8) and non-amputated controls (n = 9) made several gestures with either their right or left hand. Amputees attempted to make gestures with their amputated hand. Images were acquired using 7 T functional MRI. The sensorimotor cortex was divided into four regions, and activity patterns were classified in individual subjects using a support vector machine. Classification scores were significantly above chance for all subjects and all hands, and were highly similar between amputees and controls in most regions. Decodability of phantom movements from primary motor cortex reached the levels of right hand movements in controls. Attempted movements were successfully decoded from primary sensory cortex in amputees, albeit lower than in controls but well above chance level despite absence of somatosensory feedback. There was no significant correlation between decodability and years since amputation, or age. The ability to decode attempted gestures demonstrates that the detailed hand representation is preserved in motor cortex and adjacent regions after denervation. This encourages targeting sensorimotor activity patterns for development of brain-computer interfaces.

Factors Affecting Volume Changes of the Somatosensory Cortex in Patients with Spinal Cord Injury: To Be Considered for Future Neuroprosthetic Design

Spinal cord injury (SCI) leads to severe chronic disability, but also to secondary adaptive changes upstream to the injury in the brain which are most likely induced due to the lack of afferent information. These neuroplastic changes are a potential target for innovative therapies such as neuroprostheses, e.g., by stimulation in order to evoke sensation or in order to suppress phantom limb pain. Diverging results on gray matter atrophy have been reported in patients with SCI. Detectability of atrophy seems to depend on the selection of the regions of interest, while whole-brain approaches are not sensitive enough. In this study, we discussed previous research approaches and analyzed differential atrophic changes in incomplete SCI using manual segmentation of the somatosensory cortex. Patients with incomplete SCI (ASIA C-D), with cervical (N = 5) and thoracic (N = 6) injury were included. Time since injury was ≤12 months in 7 patients, and 144, 152, 216, and 312 months in the other patients. Age at the injury was ≤26 years in 4 patients and ≥50 years in 7 patients. A sample of 12 healthy controls was included in the study. In contrast to all previous studies that used voxel-based morphometry, we performed manual segmentation of the somatosensory cortex in the postcentral gyrus from structural magnetic resonance images and normalized the calculated volumes against the sum of volumes of an automated whole-head segmentation. Volumes were smaller in patients than in controls (p = 0.011), and as a tendency, female patients had smaller volumes than male patients (p = 0.017, uncorrected). No effects of duration (subacute vs. chronic), level of lesion (cervical vs. thoracic), region (left vs. right S1), and age at onset (≤26 vs. ≥50 years) was found. Our results demonstrate volume loss of S1 in incomplete SCI and encourage further research with larger sample sizes on volumetric changes in the acute and chronic stage of SCI, in order to document the moderating effect of type and location of injury on neuroplastic changes. A better understanding of neuroplastic changes in the sensorimotor cortex after SCI and its interaction with sex is needed in order to develop efficient rehabilitative interventions and neuroprosthetic technologies.

Irreversible changes occurring in long-term denervated Schwann cells affect delayed nerve repair

OBJECTIVE

Multiple factors may affect functional recovery after peripheral nerve injury, among them the lesion site and the interval between the injury and the surgical repair. When the nerve segment distal to the lesion site undergoes chronic degeneration, the ensuing regeneration (when allowed) is often poor. The aims of the current study were as follows: 1) to examine the expression changes of the neuregulin 1/ErbB system during long-term nerve degeneration; and 2) to investigate whether a chronically denervated distal nerve stump can sustain nerve regeneration of freshly axotomized axons.

METHODS

This study used a rat surgical model of delayed nerve repair consisting of a cross suture between the chronically degenerated median nerve distal stump and the freshly axotomized ulnar proximal stump. Before the suture, a segment of long-term degenerated median nerve stump was harvested for analysis. Functional, morphological, morphometric, and biomolecular analyses were performed.

RESULTS

The results showed that neuregulin 1 is highly downregulated after chronic degeneration, as well as some Schwann cell markers, demonstrating that these cells undergo atrophy, which was also confirmed by ultrastructural analysis. After delayed nerve repair, it was observed that chronic degeneration of the distal nerve stump compromises nerve regeneration in terms of functional recovery, as well as the number and size of regenerated myelinated fibers. Moreover, neuregulin 1 is still downregulated after delayed regeneration.

CONCLUSIONS

The poor outcome after delayed nerve regeneration might be explained by Schwann cell impairment and the consequent ineffective support for nerve regeneration. Understanding the molecular and biological changes occurring both in the chronically degenerating nerve and in the delayed nerve repair may be useful to the development of new strategies to promote nerve regeneration. The results suggest that neuregulin 1 has an important role in Schwann cell activity after denervation, indicating that its manipulation might be a good strategy for improving outcome after delayed nerve repair.

Unilateral nasal obstruction affects motor representation development within the face primary motor cortex in growing rats

Postnatal growth is influenced by genetic and environmental factors. Nasal obstruction during growth alters the electromyographic activity of orofacial muscles. The facial primary motor area represents muscles of the tongue and jaw, which are essential in regulating orofacial motor functions, including chewing and jaw opening. This study aimed to evaluate the effect of chronic unilateral nasal obstruction during growth on the motor representations within the face primary motor cortex (M1). Seventy-two 6-day-old male Wistar rats were randomly divided into control (n = 36) and experimental (n = 36) groups. Rats in the experimental group underwent unilateral nasal obstruction after cauterization of the external nostril at 8 days of age. Intracortical microstimulation (ICMS) mapping was performed when the rats were 5, 7, 9, and 11 wk old in control and experimental groups (n = 9 per group per time point). Repeated-measures multivariate ANOVA was used for intergroup and intragroup statistical comparisons. In the control and experimental groups, the total number of positive ICMS sites for the genioglossus and anterior digastric muscles was significantly higher at 5, 7, and 9 wk, but there was no significant difference between 9 and 11 wk of age. Moreover, the total number of positive ICMS sites was significantly smaller in the experimental group than in the control at each age. It is possible that nasal obstruction induced the initial changes in orofacial motor behavior in response to the altered respiratory pattern, which eventually contributed to face-M1 neuroplasticity.NEW & NOTEWORTHY Unilateral nasal obstruction in rats during growth periods induced changes in arterial oxygen saturation (SpO₂) and altered development of the motor representation within the face primary cortex. Unilateral nasal obstruction occurring during growth periods may greatly affect not only respiratory function but also craniofacial function in rats. Nasal obstruction should be treated as soon as possible to avoid adverse effects on normal growth, development, and physiological functions.

A longitudinal study of pain, personality, and brain plasticity following peripheral nerve injury

We do not know precisely why pain develops and becomes chronic after peripheral nerve injury (PNI), but it is likely due to biological and psychological factors. Here, we tested the hypotheses that (1) high Pain Catastrophizing Scale (PCS) scores at the time of injury and repair are associated with pain and cold sensitivity after 1-year recovery and (2) insula gray matter changes reflect the course of injury and improvements over time. Ten patients with complete median and/or ulnar nerve transections and surgical repair were tested ∼3 weeks after surgical nerve repair (time 1) and ∼1 year later for 6 of the 10 patients (time 2). Patients and 10 age-/sex-matched healthy controls completed questionnaires that assessed pain (patients) and personality and underwent quantitative sensory testing and 3T MRI to assess cortical thickness. In patients, pain intensity and neuropathic pain correlated with pain catastrophizing. Time 1 pain catastrophizing trended toward predicting cold pain thresholds at time 2, and at time 1 cortical thickness of the right insula was reduced. At time 2, chronic pain was related to the time 1 pain-PCS relationship and cold sensitivity, pain catastrophizing correlated with cold pain threshold, and insula thickness reversed to control levels. This study highlights the interplay between personality, sensory function, and pain in patients following PNI and repair. The PCS-pain association suggests that a focus on affective or negative components of pain could render patients vulnerable to chronic pain. Cold sensitivity and structural insula changes may reflect altered thermosensory or sensorimotor awareness representations.

Occupation-based intervention versus rote exercise in modified constraint-induced movement therapy for patients with median and ulnar nerve injuries: a randomized controlled trial

Objective:

To investigate effect of practice type during modified constraint-induced movement therapy on hand function in patients with chronic median and ulnar nerve injuries.

Design:

A prospective, single-blinded, randomized controlled clinical trial.

Setting:

Participants’ private home.

Subjects:

A convenience sample of 36 outpatient participants allocated randomly to three equal groups.

Interventions:

Intervention groups underwent 3-hour intensive training of affected hand each day, 3-day a week, 4-week in association with immobilisation of healthy hand: occupation-based group practiced meaningful occupations while rote exercise-based group performed rote exercises during constraint-induced movement therapy. Control group performed different activities with affected hand for 1.5-hour each day during 4-week without restriction of healthy hand.

Main measures:

A blinded assessor tested Canadian occupational performance measure, box and block, Static two-point discrimination, disabilities of arm, shoulder, hand questionnaire, and self-assessment manikin in a random order across sessions 3-time as baseline (pre-test), after 4-week intervention (post-test), and 1-month after intervention period (follow up).

Results:

Scores significantly changed in intervention groups compared to control. Despite significantly more improvement in occupation-based than rote exercise-based group in subjective measures at post-test and follow up (Canadian occupational performance measure: mean change 4.7 vs. 2.1 for performance, P< 0.001 and mean change 5.3 vs. 2.6 for satisfaction, P< 0.001), it was significant just at follow up for box and block and static two-point discrimination.

Conclusions:

Practice content of constraint-induced movement therapy is a critical part of its effectiveness on improving outcomes following peripheral nerve repair in favour of occupation-based intervention in present study.

Sensory re-education after nerve injury of the upper limb: a systematic review

Objective : To systematically review the available evidence for the effectiveness of sensory re-education to improve the sensibility of the hand in patients with a peripheral nerve injury of the upper limb.

Data sources : Studies were identified by an electronic search in the databases MEDLINE, Cumulative Index to Nursing & Allied Health Literature (CINAHL), EMBASE, the Cochrane Library, the Physiotherapy Evidence Database (PEDro), and the database of the Dutch National Institute of Allied Health Professions (Doconline) and by screening the reference lists of relevant articles.

Review methods : Two reviewers selected studies that met the following inclusion criteria: all designs except case reports, adults with impaired sensibility of the hand due to a peripheral nerve injury of the upper limb, and sensibility and functional sensibility as outcome measures. The methodological quality of the included studies was independently assessed by two reviewers. A best-evidence synthesis was performed, based on design, methodological quality and significant findings on outcome measures.

Results : Seven studies, with sample sizes ranging from 11 to 49, were included in the systematic review and appraised for content. Five of these studies were of poor methodological quality. One uncontrolled study (N = 1 3 ) was considered to be of sufficient methodological quality, and one randomized controlled trial ( N = 49) was of high methodological quality. Best-evidence synthesis showed that there is limited evidence for the effectiveness of sensory re-education, provided by a statistically significant improvement in sensibility found in one high-quality randomized controlled trial.

Conclusion : There is a need for further well-defined clinical trials to assess the effectiveness of sensory re-education of patients with impaired sensibility of the hand due to a peripheral nerve injury.

Test-retest agreement and reliability of quantitative sensory testing 1 year after breast cancer surgery

OBJECTIVES

Quantitative sensory testing (QST) is used to assess sensory dysfunction and nerve damage by examining psychophysical responses to controlled, graded stimuli such as mechanical and thermal detection and pain thresholds. In the breast cancer population, 4 studies have used QST to examine persistent pain after breast cancer treatment, suggesting neuropathic pain being a prominent pain mechanism. However, the agreement and reliability of QST has not been described in the postsurgical breast cancer population, hindering exact interpretation of QST studies in this population. The aim of the present study was to assess test-retest properties of QST after breast cancer surgery.

METHODS

A total of 32 patients recruited from a larger ongoing prospective trial were examined with QST 12 months after breast cancer surgery and reexamined a week later. A standardized QST protocol was used, including sensory mapping for mechanical, warmth and cold areas of sensory dysfunction, mechanical thresholds using monofilaments and pin-prick, thermal thresholds including warmth and cold detection thresholds and heat pain threshold, with bilateral examination. Agreement and reliability were assessed by Bland-Altman plots, descriptive statistics, coefficients of variance, and intraclass correlation.

RESULTS

Bland-Altman plots showed high variation on the surgical side. Intraclass coefficients ranged from 0.356 to 0.847 (moderate to substantial reliability). Between-patient variation was generally higher (0.9 to 14.5 SD) than within-patient variation (0.23 to 3.55 SD). There were no significant differences between pain and pain-free patients. The individual test-retest variability was higher on the operated side compared with the nonoperated side.

DISCUSSION

The QST protocol reliability allows for group-to-group comparison of sensory function, but less so for individual follow-up after breast cancer surgery.