Differential effect of spinal cord injury and functional impairment on human brain activation

Brain region changes following a spinal cord injury

Brain-related complications are common in clinical practice after spinal cord injury (SCI); however, the molecular mechanisms of these complications are still unclear. Here, we reviewed the changes in the brain regions caused by SCI from three perspectives: imaging, molecular analysis, and electrophysiology. Imaging studies revealed abnormal functional connectivity, gray matter volume atrophy, and metabolic abnormalities in brain regions after SCI, leading to changes in the structure and function of brain regions. At the molecular level, chemokines, inflammatory factors, and damage-associated molecular patterns produced in the injured area were retrogradely transmitted through the corticospinal tract, cerebrospinal fluid, or blood circulation to the specific brain area to cause pathologic changes. Electrophysiologic recordings also suggested abnormal changes in brain electrical activity after SCI. Transcranial magnetic stimulation, transcranial direct current stimulation, and deep brain stimulation alleviated pain and improved motor function in patients with SCI; therefore, transcranial therapy may be a new strategy for the treatment of patients with SCI.

Effects of nasal inflammation on the olfactory bulb

Sinonasal diseases, such as rhinosinusitis, affect up to 12% of individuals each year which constitutes these diseases as some of the most common medical conditions in the world. Exposure to environmental pathogens and toxicants via the nasal cavity can result in a severe inflammatory state commonly observed in these conditions. It is well understood that the epithelial and neuronal cells lining the olfactory mucosa, including olfactory sensory neurons (OSNs), are significantly damaged in these diseases. Prolonged inflammation of the nasal cavity may also lead to hyposmia or anosmia. Although various environmental agents induce inflammation in different ways via distinct cellular and molecular interactions, nasal inflammation has similar consequences on the structure and homeostatic function of the olfactory bulb (OB) which is the first relay center for olfactory information in the brain. Atrophy of the OB occurs via thinning of the superficial OB layers including the olfactory nerve layer, glomerular layer, and superficial external plexiform layer. Intrabulbar circuits of the OB which include connectivity between OB projection neurons, OSNs, and interneurons become significantly dysregulated in which synaptic pruning and dendritic retraction take place. Furthermore, glial cells and other immune cells become hyperactivated and induce a state of inflammation in the OB which results in upregulated cytokine production. Moreover, many of these features of nasal inflammation are present in the case of SARS-CoV-2 infection. This review summarizes the impact of nasal inflammation on the morphological and physiological features of the rodent OB.

What the study of spinal cord injured patients can tell us about the significance of the body in cognition

Although in the last three decades philosophers, psychologists and neuroscientists have produced numerous studies on human cognition, the debate concerning its nature is still heated and current views on the subject are somewhat antithetical. On the one hand, there are those who adhere to a view implying 'disembodiment' which suggests that cognition is based entirely on symbolic processes. On the other hand, a family of theories referred to as the Embodied Cognition Theories (ECT) postulate that creating and maintaining cognition is linked with varying degrees of inherence to somatosensory and motor representations. Spinal cord injury induces a massive body-brain disconnection with the loss of sensory and motor bodily functions below the lesion level but without directly affecting the brain. Thus, SCI may represent an optimal model for testing the role of the body in cognition. In this review, we describe post-lesional cognitive modifications in relation to body, space and action representations and various instances of ECT. We discuss the interaction between body-grounded and symbolic processes in adulthood with relevant modifications after body-brain disconnection.

Pathological consequences of chronic olfactory inflammation on neurite morphology of olfactory bulb projection neurons

Chronic olfactory inflammation (COI) in conditions such as chronic rhinosinusitis significantly impairs the functional and anatomical components of the olfactory system. COI induced by intranasal administration of lipopolysaccharide (LPS) results in atrophy, gliosis, and pro-inflammatory cytokine production in the olfactory bulb (OB). Although chronic rhinosinusitis patients have smaller OBs, the consequences of olfactory inflammation on OB neurons are largely unknown. In this study, we investigated the neurological consequences of COI on OB projection neurons, mitral cells (MCs) and tufted cells (TCs). To induce COI, we performed unilateral intranasal administration of LPS to mice for 4 and 10 weeks. Effects of COI on the OB were examined using RNA-sequencing approaches and immunohistochemical analyses. We found that repeated LPS administration upregulated immune-related biological pathways in the OB after 4 weeks. We also determined that the length of TC lateral dendrites in the OB significantly decreased after 10 weeks of COI. The axon initial segment of TCs decreased in number and in length after 10 weeks of COI. The lateral dendrites and axon initial segments of MCs, however, were largely unaffected. In addition, dendritic arborization and AIS reconstruction both took place following a 10-week recovery period. Our findings suggest that olfactory inflammation specifically affects TCs and their integrated circuitry, whereas MCs are potentially protected from this condition. This data demonstrates unique characteristics of the OBs ability to undergo neuroplastic changes in response to stress.

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Early-stage chronic olfactory inflammation activates the ​interferon-γ-driven inflammatory pathways in the olfactory bulb.

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Tufted cells undergo neurite dysregulation in response to chronic olfactory inflammation.

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Mitral cells and interneurons in the external plexiform layer are largely unaffected by chronic olfactory inflammation.

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Tufted cells experience complete recovery from neurite dysregulation following a period of ceased inflammation

Does lack of brain injury mean lack of cognitive impairment in traumatic spinal cord injury?

OBJECTIVE

Traumatic spinal cord injury (tSCI) has implications in many areas, including cognitive functioning. Findings regarding cognitive problems in people with SCI are inconsistent, presumably due to multiple variables than can affect performance, among them emotional variables. The purpose of the current study was to elucidate cognitive sequalae in some individuals with tSCI with no medical record of brain injury, while taking emotional variables into consideration.

DESIGN

Cross-sectional, with two groups.

SETTING

A public rehabilitation center.

PARTICIPANTS

Twenty participants with tSCI at least ten months post injury and twenty non-SCI controls, matched for sex, age, and education.

INTERVENTION

None.

OUTCOME MEASURES

A battery of neuropsychological tests tapping executive functions, memory, attention, and naming abilities, in addition to questionnaires assessing depression and distress.

RESULTS

When emotional variables were statistically controlled, participants with tSCI showed higher levels of depression and distress and scored lower than non-SCI control participants on all cognitive tests except naming. Executive functions were found to have the highest effect size, though no specific ability was sensitive enough to differentiate between the groups in a binary logistic regression analysis.

CONCLUSION

In some individuals with chronic tSCI, lower cognitive ability that is unrelated to emotional distress might result from spinal cord damage and its implications in a population who's medical records show no indication of brain injury. This highlights the importance of conducting cognitive evaluation following SCI, so that deficits can be effectively addressed during rehabilitation.

Differences in sensorimotor and functional recovery between the dominant and non-dominant upper extremity following cervical spinal cord injury

STUDY DESIGN

Post hoc analysis of prospective multi-national, multi-centre cohort study.

OBJECTIVE

Determine whether cerebral dominance influences upper extremity recovery following cervical spinal cord injury (SCI).

SETTING

A multi-national subset of the longitudinal GRASSP dataset (n = 127).

METHODS

Secondary analysis of prospective, longitudinal multicenter study of individuals with cervical SCI (n = 73). Study participants were followed for up to 12 months after a cervical SCI, and the following outcome measures were serially assessed - the Graded Redefined Assessment of Strength, Sensibility, and Prehension (GRASSP) and the International Standards for the Neurological Classification of SCI (ISNCSCI), including upper extremity motor and sensory scores. Observed recovery and relative (percent) recovery were then determined for both the GRASSP and ISNCSCI, based on change from initial to last available assessment.

RESULTS

With the exception of prehension performance (quantitative grasping) following complete cervical SCI, there were no significant differences (p < 0.05) for observed and relative (percent) recovery, between the dominant and non-dominant upper extremities, as measured using GRASSP subtests, ISNCSCI motor scores and ISNCSCI sensory scores.

CONCLUSION

Despite well documented differences between the cerebral hemispheres, cerebral dominance appears to play a limited role in upper extremity recovery following acute cervical SCI.

18F-FDG positron emission tomography imaging of cortical reorganization in spinal trauma

Objective:

Spinal cord injury (SCI) extensively impacts the sensorimotor reorganization in the brain. The effects can be both anatomical and functional. To date, not many studies using 18F-Fluoro-2-Deoxyglucose positron emission tomography (18F-FDG PET) to evaluate metabolic changes in the brain are done. Understanding such changes is crucial for developing clinical management and evidence-based rehabilitation strategies for these patients.

Subjects and Methods:

In this study, we compared 18F-FDG PET imaging of 6 SCI patients with complete paraplegia and 19 controls. Statistical parametric mapping software was utilized to compare the images on a voxel to voxel basis (significance level P < 0.05 and clusters having >50 voxels).

Results:

The study showed raised metabolism in supplementary motor areas, comprehension centers, some areas in the parietal and temporal lobe, putamen and cerebellum while reduced metabolic uptake in areas like anterior cingulate gyrus, hippocampus and sensory cortical areas when SCI patients were compared against healthy controls. The frontal lobe showed varied results where certain regions showed higher metabolism while the others showed lower in patients compared with controls.

Conclusion:

Cerebral deafferentation or disuse atrophy can be linked with reduced metabolism while raised uptake can be associated with initiation and planning of movement and cognitive changes in the brain posttrauma.

Abnormal changes in motor cortical maps in humans with spinal cord injury

KEY POINTS

The functional role of motor cortical reorganization following spinal cord injury (SCI) remains largely unknown. Here, we tested motor maps in a hand muscle at rest and during voluntary contraction of the hand with and without voluntary contraction of a proximal arm muscle. Motor map area in participants with SCI decreased during hand voluntary contraction and further decreased during additional contraction of a proximal arm muscle compared with rest. In contrast, motor map area in controls increased during the same motor tasks. Participants with SCI with more severe sensory deficits in the hand showed larger decreases in motor map area. Ten minutes of hand muscle-tendon vibration increased the motor map area during voluntary contraction in SCI participants. These novel findings suggest that abnormal changes in motor cortical maps during voluntary contraction after SCI can be reshaped by sensory input, knowledge that can have implications for rehabilitation.

ABSTRACT

Motor cortical representations reorganize following cervical spinal cord injury (SCI). The functional role of this reorganization remains largely unknown. Using neuronavigated transcranial magnetic stimulation, we examined motor cortical maps during voluntary contraction in humans with chronic cervical SCI and age-matched controls. We constructed motor maps in the first dorsal interosseous (FDI) muscle at rest and during voluntary contraction of the FDI with and without voluntary contraction of the biceps brachi (BB). The role of sensory input into this reorganization was examined by muscle-tendon vibration. We found that, at rest, motor maps were larger in SCI (22.3 cm2 ) compared with control (12.6 cm2 , P < 0.001) participants. Motor map area increased during voluntary contraction of the FDI (120.7%) and further increased during contraction of the BB (143.9%) compared with rest in control subjects; however, motor map area decreased during voluntary contraction of the FDI (69.5%) and further decreased during contraction of the BB (55.5%) in individuals with SCI. SCI participants with larger decreases in map area during voluntary contraction of the FDI were those with larger sensory deficits in the hand and 10 min of hand muscle-tendon vibration increased motor map area. These results provide the first evidence of abnormal changes in motor cortical maps in humans with chronic SCI during voluntary contraction, suggesting that sensory input can help to reshape this reorganization.

Cortical layer-specific modulation of neuronal activity after sensory deprivation due to spinal cord injury

Abstract

Cortical areas have the capacity of large‐scale reorganization following sensory deafferentation. However, it remains unclear whether this phenomenon is a unique process that homogeneously affects the entire deprived cortical region or whether it is susceptible to changes depending on neuronal networks across distinct cortical layers. Here, we studied how the local circuitry within each layer of the deafferented cortex forms the basis for neuroplastic changes after immediate thoracic spinal cord injury (SCI) in anaesthetized rats. In vivo electrophysiological recordings from deafferented hindlimb somatosensory cortex showed that SCI induces layer‐specific changes mediating evoked and spontaneous activity. In supragranular layer 2/3, SCI increased gamma oscillations and the ability of these neurons to initiate up‐states during spontaneous activity, suggesting an altered corticocortical network and/or intrinsic properties that may serve to maintain the excitability of the cortical column after deafferentation. On the other hand, SCI enhanced the infragranular layers’ ability to integrate evoked sensory inputs leading to increased and faster neuronal responses. Delayed evoked response onsets were also observed in layer 5/6, suggesting alterations in thalamocortical connectivity. Altogether, our data indicate that SCI immediately modifies the local circuitry within the deafferented cortex allowing supragranular layers to better integrate spontaneous corticocortical information, thus modifying column excitability, and infragranular layers to better integrate evoked sensory inputs to preserve subcortical outputs. These layer‐specific neuronal changes may guide the long‐term alterations in neuronal excitability and plasticity associated with the rearrangements of somatosensory networks and the appearance of central sensory pathologies usually associated with spinal cord injury.

Key points

Sensory stimulation of forelimb produces cortical evoked responses in the somatosensory hindlimb cortex in a layer‐dependent manner.

Spinal cord injury favours the input statistics of corticocortical connections between intact and deafferented cortices.

After spinal cord injury supragranular layers exhibit better integration of spontaneous corticocortical information while infragranular layers exhibit better integration of evoked sensory stimulation.

Cortical reorganization is a layer‐specific phenomenon.

Cortical morphometric changes associated with completeness, level, and duration of spinal cord injury in humans: A case-control study

OBJECTIVE

This study investigated how the injury completeness, level, and duration of spinal cord injury (SCI) affect cortical morphometric changes in humans.

METHODS

T1-weighted images were acquired from 59 SCI patients and 37 healthy controls. Voxel-based morphometry analyses of the gray matter volume (GMV) were performed between SCI patients and healthy controls, complete SCI and incomplete SCI, and tetraplegia and paraplegia. Correlation analyses were performed to explore the associations between GMV and clinical variables in SCI patients.

RESULTS

Compared to healthy controls, SCI patients showed decreased GMV in bilateral middle frontal gyrus, left superior frontal gyrus (SFG), left medial frontal gyrus in the whole-brain analysis, while increased GMV in right supplementary motor area and right pallidum in ROI analysis. The complete SCI had lower GMV in left primary somatosensory cortex (S1) and higher GMV in left primary motor cortex compared with incomplete SCI. Lower GMV was identified in left thalamus and SFG in tetraplegia than that in paraplegia. Moreover, time since injury was positive with the GMV in right pallidum, positive correlations were observed between the GMV in bilateral S1 and total motor and sensory scores, whereas the GMV in left cuneus was negatively correlated with total motor and sensory scores in SCI patients.

CONCLUSIONS

The study provided imaging evidence for identifying cerebral structural abnormalities in SCI patients and significant differences in complete/incomplete and paraplegia/tetraplegia subgroups. These results suggested brain structural changes occur after SCI and these changes may depend on the injury completeness, level, and duration.

Detection of cerebral reorganization associated with degenerative cervical myelopathy using diffusion spectral imaging (DSI)

Degenerative Cervical Myelopathy (DCM) is a spinal cord disorder that causes significant physical disabilities in older patients. While most DCM research focuses on the spinal cord, widespread reorganization of the brain may occur to compensate for functional impairment. This observational study used diffusion spectrum imaging (DSI) to examine reorganization of cerebral white matter associated with neurological impairment as measured by the modified Japanese Orthopedic Association (mJOA), and severity of neck disability as measured by the Neck Disability Index (NDI) score. A total of 47 patients were included in the cervical spondylosis (CS) cohort: 38 patients with DCM (mean mJOA = 14.6, and mean NDI = 12.0), and 9 neurologically asymptomatic patients with spinal cord compression (mJOA = 18, and mean NDI = 7.0). 28 healthy volunteers (HCs) served as the control group. Lower generalized fractional anisotropy (GFA) was observed throughout much of the brain in patients compared to HCs (p < 0.05). Fiber pathways associated with somatosensory functions, such as the corpus callosum and corona radiata, showed increased quantitative anisotropy (QA) in patients compared to HCs. Correlation analyses further suggested that structural connectivity was enhanced to compensate for neurological dysfunction within sensorimotor regions, where fibers such as the posterior corona radiata had NQA values that were negatively associated with mJOA (p = 0.0020, R² = 0.2935) and positively associated with NDI score (p = 0.0164, R² = 0.1889). Altogether, these results suggest that DCM and neurologically asymptomatic spinal cord compression patients tend to have long-term reorganization within the brain, particularly in those regions responsible for the perception and integration of sensory information, motor regulation, and pain modulation.

Lower-Limb Sensorimotor Deprivation-Related Brain Activation in Patients With Chronic Complete Spinal Cord Injury

This study aims to investigate functional brain reorganization brought about by the loss of physical movement and sensory feedback in lower limbs in chronic spinal cord injury (SCI). Eleven paraplegia patients with SCI and 13 healthy controls (HCs) were recruited. The experimental task used was a visuomotor imagery task requiring subjects to engage in visualization of repetitive tapping movements of the upper or lower limbs. Blood oxygen level-dependent (BOLD) responses were captured during the experimental task, along with the accuracy rate and the response time. The SCI patients performed worse in the Rey Auditory Verbal Learning Test (RAVLT) and the Trail Making Test. SCI patients had a larger BOLD signal in the left lingual gyrus and right external globus pallidus (GPe) when imagining lower-limb movements. For the upper-limb task, SCI patients showed stronger BOLD responses than the HCs in extensive areas over the brain, including the bilateral precentral gyrus (preCG), bilateral inferior parietal gyrus, right GPe, right thalamus, left postcentral gyrus, and right superior temporal gyrus. In contrast, the HCs displayed stronger BOLD responses in the medial frontal gyrus and anterior cingulate gyrus for both upper- and lower-limb tasks than the SCI patients. In the SCI group, for the upper-limb condition, the amplitudes of BOLD responses in the left preCG were negatively correlated with the time since injury (r = -0.72, p = 0.012). For the lower-limb condition, the amplitudes of BOLD responses in the left lingual gyrus were negatively correlated with the scores on the Short Delay task of the RAVLT (r = -0.73, p = 0.011). Our study provided imaging evidence for abnormal changes in brain function and worsened cognitive test performance in SCI patients. These findings suggested possible compensatory strategies adopted by the SCI patients for the loss of sensorimotor function from the lower limbs when performing a limb imagery task.

The impact of level of injury on patterns of cognitive dysfunction in individuals with spinal cord injury

Context: While it is well recognized that physical and physiological changes are more prominent in individuals with higher neurologic levels of spinal cord injury (SCI), the impact of level of lesion on cognition is less clear. Design: Cross-sectional, 3-group. Setting: Non-profit rehabilitation research foundation. Participants: 59 individuals with SCI (30 with tetraplegia, 29 with paraplegia) and 30 age-matched healthy controls (HC). Interventions: None. Outcome Measures: Neuropsychological tests in the domains of attention, working memory, processing speed, executive control, and learning and memory. Results: Results indicated significantly lower test performance in individuals with paraplegia on new learning and memory testing compared to HC. In contrast, compared to HC the group with tetraplegia, showed a significantly impaired performance on a processing speed task, and both the tetraplegia and the paraplegia groups were similarly impaired on a verbal fluency measure. SCI groups did not differ on any cognitive measure. Conclusion: Individuals with SCI may display different patterns of cognitive performance based on their level of injury.

Visuo-motor and interoceptive influences on peripersonal space representation following spinal cord injury

Peripersonal space (PPS) representation is modulated by information coming from the body. In paraplegic individuals, whose lower limb sensory-motor functions are impaired or completely lost, the representation of PPS around the feet is reduced. However, passive motion can have short-term restorative effects. What remains unclear is the mechanisms underlying this recovery, in particular with regard to the contribution of visual and motor feedback and of interoception. Using virtual reality technology, we dissociated the motor and visual feedback during passive motion in paraplegics with complete and incomplete lesions and in healthy controls. The results show that in the case of paraplegics, the presence of motor feedback was necessary for the recovery of PPS representation, both when the motor feedback was congruent and when it was incongruent with the visual feedback. In contrast, visuo-motor incongruence led to an inhibition of PPS representation in the control group. There were no differences in sympathetic responses between the three groups. Nevertheless, in individuals with incomplete lesions, greater interoceptive sensitivity was associated with a better representation of PPS around the feet in the visuo-motor incongruent conditions. These results shed new light on the modulation of PPS representation, and demonstrate the importance of residual motor feedback and its integration with other bodily information in maintaining space representation.

Spinal cord lesions

A spinal cord injury (SCI) may result in impairments of motor, sensory, and autonomous functions below the injury level. Worldwide, the prevalence of SCI is 1:1000 and the incidence is between 4 and 9 new cases per 100,000 people per year. Most common causes for traumatic SCI are traffic accidents, falls, and violence. Nowadays, the proportion of patients with tetraplegia and paraplegia is equal. In industrialized countries, the percentage of nontraumatic injuries increases together with age. Most patients with initially preserved motor functions below the injury level show a substantial functional recovery, while three quarters of patients with initially complete SCI remain that way. In SCI, brain-computer interfaces (BCIs) may be used in the subacute phase as part of a restorative therapy program and, later, for control of assistive devices most needed by individuals with high cervical lesions. Research on structural and functional reorganization of the deefferented and deafferented brain after SCI is inconclusive mainly because of varying methods of analysis and the heterogeneity of the investigated populations. A better characterization of study participants with SCI together with documentation of confounding factors such as antispasticity medication or neuropathic pain is indicated.

Disconnected Body Representation: Neuroplasticity Following Spinal Cord Injury

Neuroplastic changes in somatotopic organization within the motor and somatosensory systems have long been observed. The interruption of afferent and efferent brain–body pathways promotes extensive cortical reorganization. Changes are majorly related to the typical homuncular organization of sensorimotor areas and specific “somatotopic interferences”. Recent findings revealed a relevant peripheral contribution to the plasticity of body representation in addition to the role of sensorimotor cortices. Here, we review the ways in which structures and brain mechanisms react to missing or critically altered sensory and motor peripheral signals. We suggest that these plastic events are: (i) variably affected across multiple timescales, (ii) age-dependent, (iii) strongly related to altered perceptual sensations during and after remapping of the deafferented peripheral area, and (iv) may contribute to the appearance of secondary pathological conditions, such as allodynia, hyperalgesia, and neuropathic pain. Understanding the considerable complexity of plastic reorganization processes will be a fundamental step in the formulation of theoretical and clinical models useful for maximizing rehabilitation programs and resulting recovery.

Anticipation of wheelchair and rollerblade actions in spinal cord injured people, rollerbladers, and physiotherapists

Embodied Cognition Theories (ECT) postulate that higher-order cognition is heavily influenced by sensorimotor signals. We explored the active role of somatosensory afferents and motor efferents in modulating the perception of actions in people who have suffered a massive body-brain disconnection because of spinal cord injury (SCI), which leads to sensory-motor loss below the lesion. We assessed whether the habitual use of a wheelchair enhances the capacity to anticipate the endings of tool-related actions, with respect to actions that have become impossible. In a Temporal Occlusion task, three groups of participants (paraplegics, rollerbladers and physiotherapists) observed two sets of videos depicting an actor who attempted to climb onto a platform using a wheelchair or rollerblades. Three different outcomes were possible, namely: a) success (the actor went up the step); b) fail (the actor stopped before the step without going up) and c) fall (the actor fell without going up). Each video set comprised 5 different durations increasing in complexity: in the shortest (600ms) only preparatory body movements were shown and in the longest (3000ms) the complete action was shown. The participants were requested to anticipate the outcome (success, fail, fall). The main result showed that the SCI group performed better with the wheelchair videos and poorer with rollerblade videos than both groups, even if the physiotherapists group never used rollerblades. In line with the ECT, this suggests that the action anticipation skills are not only influenced by motor expertise, but also by motor connection.

Reorganization of the somatosensory pathway after subacute incomplete cervical cord injury

Objective

The main purpose of the present study was to investigate the possible somatosensory-related brain functional reorganization after traumatic spinal cord injury (SCI).

Methods

Thirteen patients with subacute incomplete cervical cord injury (ICCI) and thirteen age- and sex-matched healthy controls (HCs) were recruited. Eleven patients and all the HCs underwent both sensory task-related brain functional scanning and whole brain structural scanning on a 3.0 Tesla MRI system, and two patients underwent only structural scanning; the process of structural scanning was completed on thirteen patients, while functional scanning was only applied to eleven patients. We performed sensory task-related functional MRI (fMRI) to investigate the functional changes in the brain. In addition, voxel-based morphometry (VBM) was applied to explore whether any sensory-related brain structural changes occur in the whole brain after SCI.

Results

Compared with HCs, ICCI patients exhibited decreased activation in the left postcentral gyrus (postCG), the brainstem (midbrain and right pons) and the right cerebellar lobules IV-VI. Moreover, a significant positive association was found between the activation in the left PostCG and the activation in both the brainstem and the right cerebellar lobules IV-VI. Additionally, the decrease in gray matter volume (GMV) was detected in the left superior parietal lobule (SPL). The decrease of white matter volume (WMV) was observed in the right temporal lobe, the right occipital lobe, and the right calcarine gyrus. No structural change in the primary sensory cortex (S1), the secondary somatosensory cortex (S2) or the thalamus was detected.

Conclusion

These functional and structural findings may demonstrate the existence of an alternative pathway in the impairment of somatosensory function after SCI, which consists of the ipsilateral cerebellum, the brainstem and the contralateral postCG. It provides a new theoretical basis for the mechanism of sensory-related brain alteration in SCI patients and the rehabilitation therapy based on this pathway in the future.

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We found that sensory-related brain reorganization may not occur in the thalamus in patients with ICCI.

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We found that brain structural reorganization did not occur in the S1 or the S2 in patients with ICCI.

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We observed that SCI can cause brain structural reorganization in non-sensory-related areas.

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We observed that an alternative pathway may exist in the impairment of somatosensory function after SCI.

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.

Reactivating the Dormant Motor Cortex After Spinal Cord Injury With EEG Neurofeedback: A Case Study With a Chronic, Complete C4 Patient

Chronic spinal cord injury (SCI) patients present poor motor cortex activation during movement attempts. The reactivation of this brain region can be beneficial for them, for instance, allowing them to use brain-machine interfaces for motor rehabilitation or restoration. These brain-machine interfacess generally use electroencephalography (EEG) to measure the cortical activation during the attempts of movement, quantifying it as the event-related desynchronization (ERD) of the alpha/mu rhythm. Based on previous evidence showing that higher tonic EEG alpha power is associated with higher ERD, we hypothesized that artificially increasing the alpha power over the motor cortex of these patients could enhance their ERD (ie, motor cortical activation) during movement attempts. We used EEG neurofeedback (NF) to enhance the tonic EEG alpha power, providing real-time visual feedback of the alpha oscillations measured over the motor cortex. This approach was evaluated in a C4, ASIA A, SCI patient (9 months after the injury) who did not present ERD during the movement attempts of his paralyzed hands. The patient performed 4 NF sessions (in 4 consecutive days) and screenings of his EEG activity before and after each session. After the intervention, the patient presented a significant increase in the alpha power over the motor cortex, and a significant enhancement of the mu ERD in the contralateral motor cortex when he attempted to close the assessed right hand. As a proof of concept investigation, this article shows how a short NF intervention might be used to enhance the motor cortical activation in patients with chronic tetraplegia.

Dynamic Reorganization of Motor Networks During Recovery from Partial Spinal Cord Injury in Monkeys

After spinal cord injury (SCI), the motor-related cortical areas can be a potential substrate for functional recovery in addition to the spinal cord. However, a dynamic description of how motor cortical circuits reorganize after SCI is lacking. Here, we captured the comprehensive dynamics of motor networks across SCI in a nonhuman primate model. Using electrocorticography over the sensorimotor areas in monkeys, we collected broadband neuronal signals during a reaching-and-grasping task at different stages of recovery of dexterous finger movements after a partial SCI at the cervical levels. We identified two distinct network dynamics: grasping-related intrahemispheric interactions from the contralesional premotor cortex (PM) to the contralesional primary motor cortex (M1) in the high-γ band (>70 Hz), and motor-preparation-related interhemispheric interactions from the contralesional to ipsilesional PM in the α and low-β bands (10–15 Hz). The strengths of these networks correlated to the time course of behavioral recovery. The grasping-related network showed enhanced activation immediately after the injury, but gradually returned to normal while the strength of the motor-preparation-related network gradually increased. Our findings suggest a cortical compensatory mechanism after SCI, where two interdependent motor networks redirect activity from the contralesional hemisphere to the other hemisphere to facilitate functional recovery.

Cortical Reorganization of Sensorimotor Systems and the Role of Intracortical Circuits After Spinal Cord Injury

The plasticity of sensorimotor systems in mammals underlies the capacity for motor learning as well as the ability to relearn following injury. Spinal cord injury, which both deprives afferent input and interrupts efferent output, results in a disruption of cortical somatotopy. While changes in corticospinal axons proximal to the lesion are proposed to support the reorganization of cortical motor maps after spinal cord injury, intracortical horizontal connections are also likely to be critical substrates for rehabilitation-mediated recovery. Intrinsic connections have been shown to dictate the reorganization of cortical maps that occurs in response to skilled motor learning as well as after peripheral injury. Cortical networks incorporate changes in motor and sensory circuits at subcortical or spinal levels to induce map remodeling in the neocortex. This review focuses on the reorganization of cortical networks observed after injury and posits a role of intracortical circuits in recovery.

Delayed pain decrease following M1 tDCS in spinal cord injury: A randomized controlled clinical trial

Despite some encouraging findings for the treatment of neuropathic pain in patients with spinal cord injury (SCI), transcranial direct current stimulation (tDCS) directed to the primary motor cortex (M1) has faced some mixed results. Prior to translating this technology to clinical care, consistent results and durable effects need to be found. We, therefore, aimed to assess the direct and long-term effects of tDCS on pain following SCI. We performed a two-phase randomized sham-controlled clinical trial where patients received 5days of tDCS followed by a 3-month follow-up period (Phase I); then, Phase II consisted of 10days of tDCS with an 8-week follow-up period. We assessed the level of pain with the Visual Analogue Scale (VAS). Patients' quality of life and life satisfaction were also evaluated. 33 patients were enrolled in Phase I and 9 in Phase II. We observed a treatment effect at 1-week follow-up for Phase I and at 4-week follow-up for Phase II. The overall level of pain was significantly lower for the active group, as compared to sham, in Phase II. Our exploratory study shows that tDCS does seem to be a promising tool to manage pain in patients with SCI and repeated stimulation sessions are needed to induce long-lasting effects. Based on our protocol, it appears that adding a second treatment period could induce long-lasting effects. Clinicaltrials.gov identification number: NCT01599767.

Functional cortical reorganization in cases of cervical spondylotic myelopathy and changes associated with surgery

OBJECTIVE The physiological mechanisms underlying the recovery of motor function after cervical spondylotic myelopathy (CSM) surgery are poorly understood. Neuronal plasticity allows neurons to compensate for injury and disease and to adjust their activities in response to new situations or changes in their environment. Cortical reorganization as well as improvement in corticospinal conduction happens during motor recovery after stroke and spinal cord injury. In this study the authors aimed to understand the cortical changes that occur due to CSM and following CSM surgery and to correlate these changes with functional recovery by using blood oxygen level-dependent (BOLD) functional MRI (fMRI). METHODS Twenty-two patients having symptoms related to cervical cord compression due to spondylotic changes along with 12 age- and sex-matched healthy controls were included in this study. Patients underwent cervical spine MRI and BOLD fMRI at 1 month before surgery (baseline) and 6 months after surgery. RESULTS Five patients were excluded from analysis because of technical problems; thus, 17 patients made up the study cohort. The mean overall modified Japanese Orthopaedic Association score improved in patients following surgery. Mean upper-extremity, lower-extremity, and sensory scores improved significantly. In the preoperative patient group the volume of activation (VOA) was significantly higher than that in controls. The VOA after surgery was reduced as compared with that before surgery, although it remained higher than that in the control group. In the preoperative patient group, activations were noted only in the left precentral gyrus (PrCG). In the postoperative group, activations were seen in the left postcentral gyrus (PoCG), as well as the PrCG and premotor and supplementary motor cortices. In postoperative group, the VOA was higher in both the PrCG and PoCG as compared with those in the control group. CONCLUSIONS There is over-recruitment of sensorimotor cortices during nondexterous relative to dexterous movements before surgery. After surgery, there was recruitment of other cortical areas such as the PoCG and premotor and supplementary motor cortices, which correlated with improvement in dexterity, but activation in these areas was greater than that found in controls. The results show that improvement in dexterity and finer movements of the upper limbs is associated with recruitment areas other than the premotor cortex to compensate for the damage in the cervical spinal cord.

Exercise Training Promotes Functional Recovery after Spinal Cord Injury

The exercise training is an effective therapy for spinal cord injury which has been applied to clinic. Traditionally, the exercise training has been considered to improve spinal cord function only through enhancement, compensation, and replacement of the remaining function of nerve and muscle. Recently, accumulating evidences indicated that exercise training can improve the function in different levels from end-effector organ such as skeletal muscle to cerebral cortex through reshaping skeletal muscle structure and muscle fiber type, regulating physiological and metabolic function of motor neurons in the spinal cord and remodeling function of the cerebral cortex. We compiled published data collected in different animal models and clinical studies into a succinct review of the current state of knowledge.

Recruitment of Polysynaptic Connections Underlies Functional Recovery of a Neural Circuit after Lesion

The recruitment of additional neurons to neural circuits often occurs in accordance with changing functional demands. Here we found that synaptic recruitment plays a key role in functional recovery after neural injury. Disconnection of a brain commissure in the nudibranch mollusc, Tritonia diomedea, impairs swimming behavior by eliminating particular synapses in the central pattern generator (CPG) underlying the rhythmic swim motor pattern. However, the CPG functionally recovers within a day after the lesion. The strength of a spared inhibitory synapse within the CPG from Cerebral Neuron 2 (C2) to Ventral Swim Interneuron B (VSI) determines the level of impairment caused by the lesion, which varies among individuals. In addition to this direct synaptic connection, there are polysynaptic connections from C2 and Dorsal Swim Interneurons to VSI that provide indirect excitatory drive but play only minor roles under normal conditions. After disconnecting the pedal commissure (Pedal Nerve 6), the recruitment of polysynaptic excitation became a major source of the excitatory drive to VSI. Moreover, the amount of polysynaptic recruitment, which changed over time, differed among individuals and correlated with the degree of recovery of the swim motor pattern. Thus, functional recovery was mediated by an increase in the magnitude of polysynaptic excitatory drive, compensating for the loss of direct excitation. Since the degree of susceptibility to injury corresponds to existing individual variation in the C2 to VSI synapse, the recovery relied upon the extent to which the network reorganized to incorporate additional synapses.

The Modulation of Neurotrophin and Epigenetic Regulators: Implication for Astrocyte Proliferation and Neuronal Cell Apoptosis After Spinal Cord Injury

Objective

To investigate alterations in the expression of the main regulators of neuronal survival and death related to astrocytes and neuronal cells in the brain in a mouse model of spinal cord injury (SCI).

Methods

Eight-week-old male imprinting control region mice (n=36; 30–35 g) were used in this study and randomly assigned to two groups: the naïve control group (n=18) and SCI group (n=18). The mice in both groups were randomly allocated to the following three time points: 3 days, 1 week, and 2 weeks (n=6 each). The expression levels of regulators such as brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), nerve growth factor (NGF), histone deacetylase 1 (HDAC1), and methyl-CpG-binding protein 2 (MeCP 2) in the brain were evaluated following thoracic contusive SCI. In addition, the number of neuronal cells in the motor cortex (M1 and M2 areas) and the number of astrocytes in the hippocampus were determined by immunohistochemistry.

Results

BDNF expression was significantly elevated at 2 weeks after injury (p=0.024). The GDNF level was significantly elevated at 3 days (p=0.042). The expression of HDAC1 was significantly elevated at 1 week (p=0.026). Following SCI, compared with the control the number of NeuN-positive cells in the M1 and M2 areas gradually and consistently decreased at 2 weeks after injury. In contrast, the number of astrocytes was significantly increased at 1 week (p=0.029).

Conclusion

These results demonstrate that the upregulation of BDNF, GDNF and HDAC1 might play on important role in brain reorganization after SCI.

Improvement of grasping after motor imagery in C6-C7 tetraplegia: A kinematic and MEG pilot study

PURPOSE

Grasp recovery after C6-C7-spinal cord injury (SCI) requires learning "tenodesis grasp" whereby active wrist extension elicits passive thumb-to-forefinger and finger-to-palm flexion. Evidence that motor imagery (MI) promotes upper limb function after tetraplegia is growing, but whether MI potentiates grasp recovery in C6-C7-SCI individuals who have successfully learned the "tenodesis grasp" remains unknown.

METHODS

Six chronic stable C6-C7-SCI inpatients and six healthy control participants were included. C6-C7-SCI participants imagined grasping movements and controls visualized geometric forms for 45 minutes, three times a week for five weeks. Three separate measures taken over a five week period before the intervention formed the baseline. Intervention effects were assessed immediately after the intervention and eight weeks later. Each testing session consisted of kinematic recordings during reach-to-grasp and magnetoencephalographic (MEG) recordings during wrist extension.

RESULTS

During baseline, kinematic wrist extension angle during "tenodesis grasp" and MEG contralateral sensorimotor cortex (cSMC) activity during wrist extension were stable. Moreover, SCI participants exhibited a greater number of voxels within cSMC than controls. After MI sessions, wrist extension angle increased during "tenodesis grasp" and the number of voxels within cSMC during wrist extension decreased and became similar to controls.

CONCLUSION

These findings provide further support for the use of MI to reinforce a compensatory grasping movement (tenodesis) and induce brain plasticity.

Therapy induces widespread reorganization of motor cortex after complete spinal transection that supports motor recovery

Reorganization of the somatosensory system and its relationship to functional recovery after spinal cord injury (SCI) has been well studied. However, little is known about the impact of SCI on organization of the motor system. Recent studies suggest that step-training paradigms in combination with spinal stimulation, either electrically or through pharmacology, are more effective than step training alone at inducing recovery and that reorganization of descending corticospinal circuits is necessary. However, simpler, passive exercise combined with pharmacotherapy has also shown functional improvement after SCI and reorganization of, at least, the sensory cortex. In this study we assessed the effect of passive exercise and serotonergic (5-HT) pharmacological therapies on behavioral recovery and organization of the motor cortex. We compared the effects of passive hindlimb bike exercise to bike exercise combined with daily injections of 5-HT agonists in a rat model of complete mid-thoracic transection. 5-HT pharmacotherapy combined with bike exercise allowed the animals to achieve unassisted weight support in the open field. This combination of therapies also produced extensive expansion of the axial trunk motor cortex into the deafferented hindlimb motor cortex and, surprisingly, reorganization within the caudal and even the rostral forelimb motor cortex areas. The extent of the axial trunk expansion was correlated to improvement in behavioral recovery of hindlimbs during open field locomotion, including weight support. From a translational perspective, these data suggest a rationale for developing and optimizing cost-effective, non-invasive, pharmacological and passive exercise regimes to promote plasticity that supports restoration of movement after spinal cord injury.

Short- and Long-Intracortical Inhibition in Incomplete Spinal Cord Injury

BACKGROUND

Short- (SICI) and long-interval intracortical inhibition (LICI) are involved in the control of movement and movement initiation. Alterations to the two circuits can result in direct alterations to the physiology of the muscles and can be used to explain the physiological changes to individuals with spinal cord injury (SCI).

OBJECTIVE

To probe changes in GABAergic function by characterizing the recruitment curves of SICI and LICI interval intracortical inhibition in an upper limb muscle in chronic SCI participants with injury between C3 and C7.

METHODS

Recruitment curves were elicited with conditioning stimulus intensities determined as a percentage of active motor threshold (AMT) (SICI, 60% to 110% AMT; LICI, 90% to 130% AMT) and recorded from the flexor carpi radialis muscle during an isometric contraction equal to 15% to 20% of maximum voluntary contraction.

RESULTS

AMT was greater and motor-evoked potential sizes were lower in SCI compared with uninjured controls. SICI magnitude was not different between groups, although the range of conditioning stimulus intensities to evoke SICI was unique to each group. LICI was reduced in the control group during active contraction and remained present in SCI.

DISCUSSION

LICI was increased in the actively contracted flexor carpi radialis muscle in individuals with SCI compared with age-matched controls. These findings indicate that GABAB function mediating LICI is different in SCI versus controls.

CONCLUSIONS

Increased LICI in SCI may be attributed to the medication baclofen or to changes in the neural mechanisms controlling contraction-related modulation of the LICI circuit.

Motor imagery reinforces brain compensation of reach-to-grasp movement after cervical spinal cord injury

Individuals with cervical spinal cord injury (SCI) that causes tetraplegia are challenged with dramatic sensorimotor deficits. However, certain rehabilitation techniques may significantly enhance their autonomy by restoring reach-to-grasp movements. Among others, evidence of motor imagery (MI) benefits for neurological rehabilitation of upper limb movements is growing. This literature review addresses MI effectiveness during reach-to-grasp rehabilitation after tetraplegia. Among articles from MEDLINE published between 1966 and 2015, we selected ten studies including 34 participants with C4 to C7 tetraplegia and 22 healthy controls published during the last 15 years. We found that MI of possible non-paralyzed movements improved reach-to-grasp performance by: (i) increasing both tenodesis grasp capabilities and muscle strength; (ii) decreasing movement time (MT), and trajectory variability; and (iii) reducing the abnormally increased brain activity. MI can also strengthen motor commands by potentiating recruitment and synchronization of motoneurons, which leads to improved recovery. These improvements reflect brain adaptations induced by MI. Furthermore, MI can be used to control brain-computer interfaces (BCI) that successfully restore grasp capabilities. These results highlight the growing interest for MI and its potential to recover functional grasping in individuals with tetraplegia, and motivate the need for further studies to substantiate it.

Interactive Effects Between Exercise and Serotonergic Pharmacotherapy on Cortical Reorganization After Spinal Cord Injury

BACKGROUND

In rat models of spinal cord injury, at least 3 different strategies can be used to promote long-term cortical reorganization: (1) active exercise above the level of the lesion; (2) passive exercise below the level of the lesion; and (3) serotonergic pharmacotherapy. Whether and how these potential therapeutic strategies-and their underlying mechanisms of action-interact remains unknown. Methods In spinally transected adult rats, we compared the effects of active exercise above the level of the lesion (treadmill), passive exercise below the level of the lesion (bike), serotonergic pharmacotherapy (quipazine), and combinations of the above therapies (bike+quipazine, treadmill+quipazine, bike+treadmill+quipazine) on long-term cortical reorganization (9 weeks after the spinal transection). Cortical reorganization was measured as the percentage of cells recorded in the deafferented hindlimb cortex that responded to tactile stimulation of the contralateral forelimb. Results Bike and quipazine are "competing" therapies for cortical reorganization, in the sense that quipazine limits the cortical reorganization induced by bike, whereas treadmill and quipazine are "collaborative" therapies, in the sense that the reorganization induced by quipazine combined with treadmill is greater than the reorganization induced by either quipazine or treadmill.

CONCLUSIONS

These results uncover the interactive effects between active/passive exercise and serotonergic pharmacotherapy on cortical reorganization after spinal cord injury, emphasizing the importance of understanding the effects of therapeutic strategies in spinal cord injury (and in other forms of deafferentation) from an integrated system-level approach.

A cerebral blood flow evaluation during cognitive tasks following a cervical spinal cord injury: a case study using transcranial Doppler recordings

A spinal cord injury (SCI) is one of the most common neurological disorders. In this paper, we examined the consequences of upper SCI in a male participant on the cerebral blood flow velocity. In particular, transcranial Doppler was used to study these effects through middle cerebral arteries (MCA) during resting-state periods and during cognitive challenges (non-verbal word-generation tasks and geometric-rotation tasks). Signal characteristics were analyzed from raw signals and envelope signals (maximum velocity) in the time domain, the frequency domain and the time-frequency domain. The frequency features highlighted an increase of the peak frequency in L-MCA and R-MCA raw signals, which revealed stronger cerebral blood flow during geometric/verbal processes respectively. This underlined a slight dominance of the right hemisphere during word-generation periods and a slight dominance of the left hemisphere during geometric processes. This finding was confirmed by cross-correlation in the time domain and by the entropy rate in information-theoretic domain. A comparison of our results to other neurological disorders (Alzheimer's disease, Parkinson's disease, autism, epilepsy, traumatic brain injury) showed that the SCI had similar effects such as general decreased cerebral blood flow and similar regular hemispheric dominance in a few cases.

Brain Activation Evoked by Sensory Stimulation in Patients with Spinal Cord Injury : Functional Magnetic Resonance Imaging Correlations with Clinical Features

OBJECTIVE

The purpose of this study is to determine whether the changes of contralateral sensorimotor cortical activation on functional magnetic resonance imaging (fMRI) can predict the neurological outcome among spinal cord injury (SCI) patients when the great toes are stimulated without notice.

METHODS

This study enrolled a total of 49 patients with SCI and investigated each patient's preoperative fMRI, postoperative fMRI, American Spinal Injury Association (ASIA) score, and neuropathic pain occurrence. Patients were classified into 3 groups according to the change of blood oxygenation level dependent (BOLD) response on perioperative fMRI during proprioceptive stimulation with repetitive passive toe movements : 1) patients with a response of contralateral sensorimotor cortical activation in fMRI were categorized; 2) patients with a response in other regions; and 3) patients with no response. Correlation between the result of fMRI and each parameter was analyzed.

RESULTS

In fMRI data, ASIA score was likely to show greater improvement in patients in group A compared to those belonging to group B or C (p<0.001). No statistical significance was observed between the result of fMRI and neuropathic pain (p=0.709). However, increase in neuropathic pain in response to the signal change of the ipsilateral frontal lobe on fMRI was statistically significant (p=0.030).

CONCLUSION

When there was change of BOLD response at the contralateral sensorimotor cortex on perioperative fMRI after surgery, relief of neurological symptoms was highly likely for traumatic SCI patients. In addition, development of neuropathic pain was likely to occur when there was change of BOLD response at ipsilateral frontal lobe.

Evolution of EEG Motor Rhythms after Spinal Cord Injury: A Longitudinal Study

Spinal cord injury (SCI) does not only produce a lack of sensory and motor function caudal to the level of injury, but it also leads to a progressive brain reorganization. Chronic SCI patients attempting to move their affected limbs present a significant reduction of brain activation in the motor cortex, which has been linked to the deafferentation. The aim of this work is to study the evolution of the motor-related brain activity during the first months after SCI. Eighteen subacute SCI patients were recruited to participate in bi-weekly experimental sessions during at least two months. Their EEG was recorded to analyze the temporal evolution of the event-related desynchronization (ERD) over the motor cortex, both during motor attempt and motor imagery of their paralyzed hands. The results show that the α and β ERD evolution after SCI is negatively correlated with the clinical progression of the patients during the first months after the injury. This work provides the first longitudinal study of the event-related desynchronization during the subacute phase of spinal cord injury. Furthermore, our findings reveal a strong association between the ERD changes and the clinical evolution of the patients. These results help to better understand the brain transformation after SCI, which is important to characterize the neuroplasticity mechanisms involved after this lesion and may lead to new strategies for rehabilitation and motor restoration of these patients.

Change of Brain Functional Connectivity in Patients With Spinal Cord Injury: Graph Theory Based Approach

Objective

To investigate the global functional reorganization of the brain following spinal cord injury with graph theory based approach by creating whole brain functional connectivity networks from resting state-functional magnetic resonance imaging (rs-fMRI), characterizing the reorganization of these networks using graph theoretical metrics and to compare these metrics between patients with spinal cord injury (SCI) and age-matched controls.

Methods

Twenty patients with incomplete cervical SCI (14 males, 6 females; age, 55±14.1 years) and 20 healthy subjects (10 males, 10 females; age, 52.9±13.6 years) participated in this study. To analyze the characteristics of the whole brain network constructed with functional connectivity using rs-fMRI, graph theoretical measures were calculated including clustering coefficient, characteristic path length, global efficiency and small-worldness.

Results

Clustering coefficient, global efficiency and small-worldness did not show any difference between controls and SCIs in all density ranges. The normalized characteristic path length to random network was higher in SCI patients than in controls and reached statistical significance at 12%-13% of density (p<0.05, uncorrected).

Conclusion

The graph theoretical approach in brain functional connectivity might be helpful to reveal the information processing after SCI. These findings imply that patients with SCI can build on preserved competent brain control. Further analyses, such as topological rearrangement and hub region identification, will be needed for better understanding of neuroplasticity in patients with SCI.

Re-establishing the disrupted sensorimotor loop in deafferented and deefferented people: The case of spinal cord injuries

Acting efficiently in the world depends on the activity of motor and somatosensory systems, the integration of which is necessary for the proper functioning of the sensorimotor loop (SL). Profound alterations of SL functioning follow spinal cord injury (SCI), a condition that brings about a disconnection of the body from the brain. Such disconnection creates a substantial deprivation of somatosensorial inputs and motor outputs. Consequent somatic deficits and motor paralysis affect the body below the lesion level. A complete restoration of normal functions of the SL cannot be expected until basic neuroscience has found a way to re-establish the interrupted neural connectivity. Meanwhile, studies should focus on the development of technical solutions for dealing with the disruption of the sensorimotor loop. This review discusses the structural and functional adaptive reorganization of the brain after SCI, and the maladaptive mechanisms that impact on the processing of body related information, which alter motor imagery strategies and EEG signals. Studies that show how residual functions (e.g. face tactile sensitivity) may help people to restore a normal body image are also reviewed. Finally, data on how brain and residual body signals may be used to improve brain computer interface systems is discussed in relation to the issue of how such systems may help SCI people to re-enter the world and interact with objects and other individuals.

Altered spontaneous brain activity in patients with acute spinal cord injury revealed by resting-state functional MRI

Background

Previous neuroimaging studies have provided evidence of structural and functional reorganization of brain in patients with chronic spinal cord injury (SCI). However, it remains unknown whether the spontaneous brain activity changes in acute SCI. In this study, we investigated intrinsic brain activity in acute SCI patients using a regional homogeneity (ReHo) analysis based on resting-state functional magnetic resonance imaging.

Methods

A total of 15 patients with acute SCI and 16 healthy controls participated in the study. The ReHo value was used to evaluate spontaneous brain activity, and voxel-wise comparisons of ReHo were performed to identify brain regions with altered spontaneous brain activity between groups. We also assessed the associations between ReHo and the clinical scores in brain regions showing changed spontaneous brain activity.

Results

Compared with the controls, the acute SCI patients showed decreased ReHo in the bilateral primary motor cortex/primary somatosensory cortex, bilateral supplementary motor area/dorsal lateral prefrontal cortex, right inferior frontal gyrus, bilateral dorsal anterior cingulate cortex and bilateral caudate; and increased ReHo in bilateral precuneus, the left inferior parietal lobe, the left brainstem/hippocampus, the left cingulate motor area, bilateral insula, bilateral thalamus and bilateral cerebellum. The average ReHo values of the left thalamus and right insula were negatively correlated with the international standards for the neurological classification of spinal cord injury motor scores.

Conclusion

Our findings indicate that acute distant neuronal damage has an immediate impact on spontaneous brain activity. In acute SCI patients, the ReHo was prominently altered in brain regions involved in motor execution and cognitive control, default mode network, and which are associated with sensorimotor compensatory reorganization. Abnormal ReHo values in the left thalamus and right insula could serve as potential biomarkers for assessment of neuronal damage and the prediction of clinical outcomes in acute SCI.

Cortical reorganization after spinal cord injury: always for good?

Plasticity constitutes the basis of behavioral changes as a result of experience. It refers to neural network shaping and re-shaping at the global level and to synaptic contacts remodeling at the local level, either during learning or memory encoding, or as a result of acute or chronic pathological conditions. 'Plastic' brain reorganization after central nervous system lesions has a pivotal role in the recovery and rehabilitation of sensory and motor dysfunction, but can also be "maladaptive". Moreover, it is clear that brain reorganization is not a "static" phenomenon but rather a very dynamic process. Spinal cord injury immediately initiates a change in brain state and starts cortical reorganization. In the long term, the impact of injury - with or without accompanying therapy - on the brain is a complex balance between supraspinal reorganization and spinal recovery. The degree of cortical reorganization after spinal cord injury is highly variable, and can range from no reorganization (i.e. "silencing") to massive cortical remapping. This variability critically depends on the species, the age of the animal when the injury occurs, the time after the injury has occurred, and the behavioral activity and possible therapy regimes after the injury. We will briefly discuss these dependencies, trying to highlight their translational value. Overall, it is not only necessary to better understand how the brain can reorganize after injury with or without therapy, it is also necessary to clarify when and why brain reorganization can be either "good" or "bad" in terms of its clinical consequences. This information is critical in order to develop and optimize cost-effective therapies to maximize functional recovery while minimizing maladaptive states after spinal cord injury.

Effect of overground training augmented by mental practice on gait velocity in chronic, incomplete spinal cord injury

OBJECTIVE

To compare the efficacy of a regimen combining mental practice (MP) with overground training (OT) with the efficacy of a regimen consisting of OT only on gait velocity and lower extremity motor outcomes in individuals with chronic (>12mo postinjury), incomplete spinal cord injury (SCI).

DESIGN

Randomized, controlled, single-blinded study.

SETTING

Outpatient rehabilitation laboratories.

PARTICIPANTS

Subjects with chronic, incomplete SCI (N=18).

INTERVENTIONS

Subjects were randomly assigned to receive (1) OT only, occurring 3d/wk for 8 weeks; or (2) OT augmented by MP (MP + OT), during which randomly assigned subjects listened to an MP audio recording directly after OT sessions.

MAIN OUTCOME MEASURES

Subjects were administered a test of gait velocity as well as the Tinetti Performance Oriented Mobility Assessment, Spinal Cord Injury Independence Measure, and Satisfaction With Life Scale on 2 occasions before intervention, 1 week after intervention, and 12 weeks after intervention.

RESULTS

A significant increase in gait velocity was exhibited across subjects at both 1 week posttherapy (P=.005) and at 12 weeks posttherapy (P=.006). However, no differences were seen in intervention response at either 1 or 12 weeks postintervention among subjects in the MP + OT group versus the OT-only group.

CONCLUSIONS

OT was associated with significant gains in gait velocity, and these gains were not augmented by further addition of MP.

Central correlates of impaired information processing in people with spinal cord injury

This investigation examined the impact of spinal cord injury (SCI) on task-relevant processing using event-related potentials. Thirty-seven participants with chronic SCI and 37 healthy able-bodied controls were tested in this study. An auditory two-tone button press oddball discrimination paradigm was used to evoke the N100, P200, N200, and P300 components of the event-related potential. During the early sensory/perceptual stages of target stimulus processing, the SCI group showed an earlier right posterior P200 latency relative to the controls. In the later more cognitive stages, a pattern of diminished left and right posterior P300 amplitude was also evident. This was further coupled with increased false-positive errors and greater variability of response time in the SCI group. The results of this study indicate that people with SCI show disturbances in inhibitory function and alterations in both early perceptual encoding processes and in later executive functioning that engages contextual/memory-updating operations.

Epigenetic regulation in the brain after spinal cord injury : a comparative study

OBJECTIVE

After spinal cord injury (SCI), functional and structural reorganization occurs at multiple levels of brain including motor cortex. However, the underlying mechanism still remains unclear. The current study was performed to investigate the alterations in the expression of the main regulators of neuronal development, survival and death, in the brain following thoracic contusive SCI in a mouse model.

METHODS

Eight-week-old female imprinting control region mice (n=60; 30-35 g) were used in this study. We analyzed the expression levels of regulators such as brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), nerve growth factor (NGF) and histone deacetylase (HDAC) 1 in the brain following thoracic contusive SCI.

RESULTS

The expression of BDNF levels were elevated significantly compared with control group at 2 weeks after injury (p<0.05). The expression of NGF levels were elevated at 2, 4 weeks compared with control group, but these difference were not significant (p>0.05). The GDNF levels were elevated at 2 week compared with control group, but these differences were not significant (p>0.05). The difference of HDAC1 levels were not significant at 2, 4 and 8 weeks compared with control group (p>0.05).

CONCLUSION

These results demonstrate that the upregulation of BDNF may play on important role in brain reorganization after SCI.