Synergistic influences of sensory and central stimuli on non-voluntary rhythmic arm movements

In recent years, neuromodulation of the cervical spinal circuitry has become an area of interest for investigating rhythmogenesis of the human spinal cord and interaction between cervical and lumbosacral circuitries, given the involvement of rhythmic arm muscle activity in many locomotor tasks. We have previously shown that arm muscle vibrostimulation can elicit non-voluntary upper limb oscillations in unloading body conditions. Here we investigated the excitability of the cervical spinal circuitry by applying different peripheral and central stimuli in healthy humans. The rationale for applying combined stimuli is that the efficiency of only one stimulus is generally limited. We found that low-intensity electrical stimulation of the superficial arm median nerve can evoke rhythmic arm movements. Furthermore, the movements were enhanced by additional peripheral stimuli (e.g., arm muscle vibration, head turns or passive rhythmic leg movements). Finally, low-frequency transcranial magnetic stimulation of the motor cortex significantly facilitated rhythmogenesis. The findings are discussed in the general framework of a brain-spinal interface for developing adaptive central pattern generator-modulating therapies.     

DNA methylation and behavioral changes induced by neonatal spinal transection

Although the importance of epigenetic mechanisms in behavioral development has been gaining attention in recent years, research has largely focused on the brain. To our knowledge, no studies to date have investigated epigenetic changes in the developing spinal cord to determine the dynamic manner in which the spinal epigenome may respond to environmental input during behavioral development. Animal studies demonstrate that spinal cord plasticity is heightened during early development, is somewhat preserved following neonatal transection, and that spinal injured animals are responsive to sensory feedback. Because epigenetic alterations have been implicated in brain plasticity and are highly responsive to experience, these alterations are promising candidates for molecular substrates of spinal plasticity as well. Thus, the current study investigated behavioral changes in the development of weight-bearing locomotion and epigenetic modifications in the spinal cord of infant rats following a neonatal low-thoracic spinal transection or sham surgery on postnatal day (P)1. Specifically, global levels of methylation and methylation status of the brain-derived neurotrophic factor (Bdnf) gene, a neurotrophin heavily involved in both CNS and behavioral plasticity, particularly in development, were examined in lumbar tissue harvested on P10 from sham and spinal-transected subjects. Behavioral results demonstrate that compared to shams, spinal-transected subjects exhibit significantly reduced partial-weight bearing hindlimb activity. Molecular data demonstrate group differences in global lumbar methylation levels as well as exon-specific group differences in Bdnf methylation. This study represents an initial step toward understanding the relationship between epigenetic mechanisms and plasticity associated with spinal cord and locomotor development.     

Limb-specific emotional modulation of cervical spinal cord neurons

Emotional stimuli receive prioritized attentional and motoric processing in the brain. Recent data have indicated that emotional stimuli enhance activity in the cervical spinal cord as well. In the present study, we used fMRI to investigate the specificity of this emotion-dependent spinal cord activity. We examined whether the limb depicted in a passively viewed image (upper vs. lower) differentially influenced activity in the cervical segments that innervate the upper limbs, and whether this effect was enhanced by emotion. Participants completed four fMRI runs: neutral–upper limb, neutral–lower limb, negative–upper limb, and negative–lower limb. The results indicated main effects of limb and emotion, with upper limbs and negative stimuli eliciting greater activity than lower limbs and neutral stimuli, respectively. For upper-limb runs, negative stimuli evoked more activity than did neutral stimuli. Additionally, negative stimuli depicting upper limbs produced stronger responses than did negative stimuli depicting lower limbs. These results suggest that emotional stimuli augment limb-specific responses in the spinal cord.     

The role of the human thalamus in language and memory: evidence from electrophysiological studies

The data reviewed here indicate that electrical stimulation of the dominant ventrolateral thalamus can produce deficits in language processing that are not seen after similar stimulation of the nondominant ventrolateral thalamus. The nature of the language deficit produced varies, depending upon the rostrocaudal location of the stimulation site. Stimulation of the anterior left ventrolateral thalamus in right-handed patients resulted in production of a repeated erroneous word, stimulation of the medial ventrolateral thalamus evoked perseveration, and stimulation of the posterior ventrolateral thalamus and anterior pulvinar resulted in misnaming and omissions. Additional studies have examined the effect of electrical thalamic stimulation on verbal and nonverbal short-term memory. Left (but not right) ventrolateral thalamic stimulation during verbal memory input greatly decreased subsequent recall errors, while stimulation during verbal memory retrieval increased recall errors. This finding contrasted with those obtained from studies on nonverbal memory, in which right ventrolateral stimulation during memory input decreased recall errors, while left thalamic stimulation at the same stage increased recall errors. Left pulvinar stimulation disrupted verbal memory processing, while right pulvinar stimulation disrupted nonverbal memory processing. Limited evidence suggests that the effects of thalamic electrical stimulation on verbal memory may persist for several days after the stimulation has ended. The lateralization of thalamic functions also affects the motoric aspects of speech production. Left (but not right) ventrolateral thalamic stimulation disrupted speech articulation and increased the expiratory phase of respiration. The fact that these motor effects were evoked from the same general area of the thalamus that produced the language deficits discussed above raises the possibility that the thalamus is involved in coordinating the cognitive and motoric aspects of language production. A model of thalamic function is discussed in which defined regions of the thalamus operate as a "specific alerting response," increasing the input to memory of category-specific material while simultaneously inhibiting retrieval from memory.     

Electromyographic activity,H-reflex modulation and corticospinal input to forearm motoneurones during active and passive rhythmic movements

Four subjects produced coordinated movements, consisting of flexion and extension of the wrist in ipsilateral (right wrist only), contralateral (left wrist only), inphase (both wrists in flexion or both in extension) and antiphase (one wrist in flexion, the other in extension) conditions. Electromyographic (EMG) activity was recorded from right wrist flexor and extensor muscles. In one session, transcranial magnetic stimuli (TMS) of the left motor cortex, around threshold intensity, evoked short-latency responses in the right wrist extensors and flexors. In another session, the median nerve at the cubital fossa was stimulated to elicit an H-reflex in the right flexor carpi radialis (rFCR). A movement cycle was divided into 8 segments. In total, 10 identical stimuli were delivered during each segment in each condition, at two movement frequencies. The magnitude of the EMG reponses to TMS was modulated markedly during movements made in the ipsilateral condition, and in both bimanual conditions. EMG activity was greater, and motor-evoked potentials (MEPs) were larger in the antiphase condition than in the inphase condition. When the amplitudes of the MEPs were normalised with respect to background EMG, no significant differences between the bimanual conditions were obtained. For H-reflexes, significant differences between the two bimanual conditions were observed, suggesting differences in levels of excitability of the Ia afferent pathway. These differences were attributed to segmental input associated with changes in muscle length arising from limb movement, and upon descending input to the spinal cord, possibly mediated by Renshaw cell inhibition. During rhythmic passive movement of the right limb, H-reflexes were inhibited and MEPs potentiated in a cyclic fashion. Passive movement of the contralateral left limb resulted in inhibition of both responses.PsycINFO classification: 2330; 2530; 2540     

Reflex conditioning in a spinal man.

A man with a completely transected spinal cord and a spastic neurogenic bladder was conditioned to void upon the presentation of an external stimulus. A classical conditioning paradigm was employed in which strong abdominal shock (unconditioned stimulus) was paired with an initially neutral mild electrical stimulation of the thigh (conditioned stimulus; CS). After the pairing trials, a reliable conditioned response of urination was elicited by the CS alone. The conditioned response did not extinguish over time, and the procedure left the bladder with clinically safe residual amounts of urine. Practical implications of the conditioning technique for the treatment of spastic neurogenic bladder conditions in spinally injured patients are discussed, as is the theoretical significance of conditioning at the reflex level in the absence of cortical involvement.     

Method for studying spinal evoked potentials]

The authors describe a new method of examing evoked spinal potentials. Derivation is by means of unipolar needle electrodes which are ventrolaterally introduced into the cervical disk space as far as the posterior longitudinal ligament. Detection of a spinal potential following the stimulation of brachial and crural nerves allows to exclude the possibility of complete transverse lesion of the spinal cord or severing of the peripheral nerve or plexus.     

Human locomotor adjustments during perturbed walking

The locomotor adjustment induced by step perturbation of human subjects walking on a treadmill was described by a quantitative analysis of the EMG activities of selected trunk and leg muscles and by rotations of leg joints. The role of the proprioceptive input in the EMG reaction was also evaluated. The perturbation was obtained by a rapid and unexpected increase of belt speed. The motor response showed the stereotyped characteristics of a motor automatism and was accomplished without affecting the basic motor pattern of the gait. The EMG adjustment showed short-latency reflex responses (40–60 msec) of muscles acting at the joints more directly affected by the perturbing stimulus. This result supports the hypothesis of a spinal neuronal mechanism involved in the rapid adjustment of gait. The activity of primary spindle afferents seems to play an important role in the production of the faster EMG responses.     

Effects of monotonous stimulation on cortical alertness in fast and slow habituation groups

The present study investigated cortical alertness in Ss displaying fast and slow habituation of the evoked skin conductance response (SCR). From Sokolov's statement (Perception and the conditioned reflex, 1963, Pergamon) that the final stage of habituation is sleep, it was predicted that during monotonous stimulation, Ss displaying rapid habituation of the evoked SCR would show a more rapid decline in cortical alertness than Ss displaying slow habituation. Quantified EEG and electrodermal measures of cortical alertness were obtained from fast and slow habituation groups tested under conditions of either repetitive auditory stimulation or reduced sensory input. The results indicated that 8–13 Hz EEG abundance declined more rapidly in fast than in the slow habituation groups under both conditions of monotonous stimulation. No differences were obtained for the lower EEG frequencies (4–8 and 2–4 Hz) or for tonic electrodermal measures.     

Organization of short-term verbal memory in language areas of human cortex: Evidence from electrical stimulation

Short-term verbal memory (STVM) performance was measured during electrical stimulation of human left frontal-parietal-temporal cortex, at craniotomy under local anesthesia for the treatment of medically intractable epilepsy. The areas of cortex where stimulation alters language, as measured by object naming, are separate but adjacent to the areas where stimulation alters STVM. There are differential effects of stimulation during input, storage, and output phases of STVM at different cortical sites. These suggest that cortex adjacent to the posterior language area is a site of storage of STVM, while cortex adjacent to anterior language area is involved in retrieval from STVM.     

On the refractoriness of somesthetic temporal acuity

Preconditioning, with a burst of electrical pulse stimuli elevates the threshold for temporal acuity as measured with a technique requiring the S to detect a short gap in an otherwise regular burst of similar stimuli. Only a small amount of backward inhibition can be observed. The temporal duration of the inhibitory effect (up to 700 msec.) suggests that repetitive after-discharges of second-order afferents in Ike spinal cord may underlie this behavioral measure by actually filling in the intervals which are used by the S to make the judgment. The phenomenon is thus thought to be a disruption of a true temporal judgment rather than one indirectly mediated by an amplitude judgment, and as such it represents a significant datum on the temporal resolving power of time dimensions of neural coding.     

A double-blind,sham-controlled,trial of home-administered rhythmic 10-Hz median nerve stimulation for the reduction of tics,and suppression of the urge-to-tic,in individuals with Tourette syndrome and chronic tic disorder

Tourette syndrome (TS) and chronic tic disorder (CTD) are neurological disorders of childhood onset characterized by the occurrence of tics; repetitive, purposeless, movements or vocalizations of short duration which can occur many times throughout a day. Currently, effective treatment for tic disorders is an area of considerable unmet clinical need. We aimed to evaluate the efficacy of a home-administered neuromodulation treatment for tics involving the delivery of rhythmic pulse trains of median nerve stimulation (MNS) delivered via a wearable ‘watch-like’ device worn at the wrist. We conducted a UK-wide parallel double-blind sham-controlled trial for the reduction of tics in individuals with tic disorder. The device was programmed to deliver rhythmic (10 Hz) trains of low-intensity (1–19 mA) electrical stimulation to the median nerve for a pre-determined duration each day, and was intended to be used by each participant in their home once each day, 5 days each week, for a period of 4 weeks. Between 18th March 2022 and 26th September 2022, 135 participants (45 per group) were initially allocated, using stratified randomization, to one of the following groups; active stimulation; sham stimulation or to a waitlist (i.e. treatment as usual) control group. Recruited participants were individuals with confirmed or suspected TS/CTD aged 12 years of age or upward with moderate to severe tics. Researchers involved in the collection or processing of measurement outcomes and assessing the outcomes, as well as participants in the active and sham groups and their legal guardians were all blind to the group allocation. The primary outcome measure used to assess the ‘offline’ or treatment effect of stimulation was the Yale Global Tic Severity Scale–Total Tic Severity Score (YGTSS–TTSS) assessed at the conclusion of 4 weeks of stimulation. The primary outcome measure used to assess the ‘online’ effects of stimulation was tic frequency, measured as the number of tics per minute (TPM) observed, based upon blind analysis of daily video recordings obtained while stimulation was delivered. The results demonstrated that after 4-week stimulation, tic severity (YGTSS-TTSS) had reduced by 7.1 points (35 percentile reduction) for the active stimulation group compared to 2.13/2.11 points for the sham stimulation and waitlist control groups. The reduction in YGTSS–TTSS for the active stimulation group was substantially larger, clinically meaningful (effect size = .5) and statistically significant (p = .02) compared to both the sham stimulation and waitlist control groups, which did not differ from one another (effect size = −.03). Furthermore, blind analyses of video recordings demonstrated that tic frequency (tics per minute) reduced substantially (−15.6 TPM) during active stimulation compared to sham stimulation (−7.7 TPM). This difference represents a statistically significant (p < .03) and clinically meaningful reduction in tic frequency (>25 percentile reduction: effect size = .3). These findings indicate that home-administered rhythmic MNS delivered through a wearable wrist-worn device has the potential to be an effective community-based treatment for tic disorders.     

The coordinated movement of the spine and pelvis during running

Previous research into running has demonstrated consistent patterns in pelvic, lumbar and thoracic motions between different human runners. However, to date, there has been limited attempt to explain why observed coordination patterns emerge and how they may relate to centre of mass (CoM) motion. In this study, kinematic data were collected from the thorax, lumbar spine, pelvis and lower limbs during over ground running in n = 28 participants. These data was subsequently used to develop a theoretical understanding of the coordination of the spine and pelvis in all three body planes during the stance phase of running. In the sagittal plane, there appeared to be an antiphase coordinate pattern which may function to increase femoral inclination at toe off whilst minimising anterior–posterior accelerations of the CoM. In the medio-lateral direction, CoM motion appears to facilitate transition to the contralateral foot. However, an antiphase coordination pattern was also observed, most likely to minimise unnecessary accelerations of the CoM. In the transverse plane, motion of the pelvis was observed to lag slightly behind that of the thorax. However, it is possible that the close coupling between these two segments facilitates the thoracic rotation required to passively drive arm motion. This is the first study to provide a full biomechanical rationale for the coordination of the spine and pelvis during human running. This insight should help clinicians develop an improved understanding of how spinal and pelvic motions may contribute to, or result from, common running injuries.     

Emergence of rhythm during motor learning

Complex motor skill often consists of a fixed sequence of movements. Recent studies show that a stereotyped temporal pattern or rhythm emerges as we learn to perform a motor sequence. This is because the sequence is reorganized during learning as serial chunks of movements in both a sequence-specific and subject-specific manner. On the basis of human imaging studies we propose that the formation of chunk patterns is controlled by the cerebellum, its posterior and anterior lobes contributing, respectively, to the temporal patterns before and after chunk formation. The motor rhythm can assist the motor networks in the cerebral cortex to control automatic movements within chunks and the cognitive networks to control non-automatic movements between chunks, respectively. In this way, organized motor skill can be performed automatically and flexibly.     

The effects of viscous loading of the human forearm flexors on the stability of coordination

This experiment investigated whether the stability of rhythmic unimanual movements is primarily a function of perceptual/spatial orientation or neuro-mechanical in nature. Eight participants performed rhythmic flexion and extension movements of the left wrist for 30s at a frequency of 2.25 Hz paced by an auditory metronome. Each participant performed 8 flex-on-the-beat trials and 8 extend-on-the-beat trials in one of two load conditions, loaded and unload. In the loaded condition, a servo-controlled torque motor was used to apply a small viscous load that resisted the flexion phase of the movement only. Both the amplitude and frequency of the movement generated in the loaded and unloaded conditions were statistically equivalent. However, in the loaded condition movements in which participants were required to flex-on-the-beat became less stable (more variable) while extend-on-the-beat movements remained unchanged compared with the unload condition. The small alteration in required muscle force was sufficient to result in reliable changes in movement stability even a situation where the movement kinematics were identical. These findings support the notion that muscular constraints, independent of spatial dependencies, can be sufficiently strong to reliably influence coordination in a simple unimanual task.     

特殊类型的无骨折脱位型颈髓损伤治疗分析

为了探讨多节段后纵韧带骨化伴颈椎间盘突出的无骨折脱位型颈髓损伤的治疗,回顾了本院收治的4例多节段后纵韧带骨化伴颈椎间盘突出的无骨折脱位型颈髓损伤患者的临床资料,并结合相关文献报道进行分析。结果显示,4例患者均早期行前后路联合手术椎管减压,3例患者行预防性气管切开,4例患者术后随访时间6个月～48个月,平均随访24个月。固定节段均获骨性融合,内固定物无松动、断裂;后路手术无再关门现象。术后神经功能评价按Frankel分级,均有1个～2个级别恢复,术前A级2例,B级2例;术后B级2例,C级1例,D级1例。提示对于多节段后纵韧带骨化伴颈椎间盘突出的无骨折脱位型颈髓损伤早期行前后路联合手术减压;预防性气管切开可获得良好的治疗结果。     

A study of EEG coherence in DCD children during motor synchronization task

This paper investigates the hypothesis that the coordination difficulties of DCD children are associated with an increased coherence in the cortical motor regions, which persists with age. Forty-eight children participated in the study (24 DCD and 24 Controls). Their ages ranged from 8 to 13 years, divided into three groups (8-9, 10-11, and 12-13 years old). Children were required to perform finger flexion or extension either in synchrony or in syncopation with a rhythmic metronome, while a 32-channel EEG was recorded. Along with stability measures of motor performance, we analyzed the spectral EEG coherence between intrahemispheric (left frontal/left central; left central/left parietal) and interhemispheric (left central/right central) sites. Spectral coherence assesses functional coupling between distant areas of the brain. Two frequency bands related to sensorimotor activation were chosen: alpha (8-12 Hz) and beta (12-30 Hz). The synchrony task was chosen as a rest condition against which the two syncopation conditions at 0.5 Hz and 1.3 Hz were contrasted. For intrahemispheric comparison, 8-9-year-old DCD children showed that coherence between fronto-central regions increased for both rhythms and conditions, as compared to controls. No difference was found for interhemispheric comparisons. As frontal sites are related to motor planning, our results suggest that youngest DCD children were forced to maintain a high level of pre-programming to compensate for the difficulties caused by the perceptual-motor requirements of the task in light of their coordination disorder.     

Electrical stimulation of the pedunculopontine tegmental nucleus in freely moving awake rats: time- and site-specific effects on two-way active avoidance conditioning

The pedunculopontine tegmental nucleus (PPTg) is involved in the regulation of thalamocortical transmission and of several functions related to ventral and dorsal striatal circuits. Stimulation of the PPTg in anesthetized animals increases cortical arousal, cortical acetylcholine release, bursting activity of mesopontine dopaminergic cells, and striatal dopamine release. It was hypothetized that PPTg stimulation could improve learning by enhancing cortical arousal and optimizing the activity of striatal circuits. We tested whether electrical stimulation (ES) of the PPTg, applied to freely-moving awake rats previously implanted with a chronic electrode, would improve the acquisition and/or the retention of two-way active avoidance conditioning, and whether this effect would depend on the specific PPTg region stimulated (anterior vs posterior) and on the time of ES: just before (pre-training) or after (post-training) each of three training sessions. The treatment consisted of 20 min of ES (0.2 ms pulses at 100 Hz; current intensity: 40-80 microA). The results showed that (1) this stimulation did not induce either any signs of distress nor abnormal behaviors, apart from some motor stereotyped behaviors that disappeared when current intensity was lowered; (2) pre-training ES applied to the anterior PPTg improved the acquisition of two-way active avoidance, (3) no learning improvement was found after either post-training ES of the anterior PPTg, or pre- and post-training ES of the posterior PPTg. The results give support to a role of PPTg in learning-related processes, and point to the existence of functional PPTg regions.     

A preliminary study of a traumatic injury prevention program

Abstract

This study examined the long-term impact of a five component spinal cord injury prevention program presented to adolescents. A sample of 445 teenagers who attended a junior high school in which an educational intervention was presented three years earlier and a control group of 379 students who had not been exposed to the intervention completed a questionnaire assessing their safety knowledge, attitudes, and self-reported behaviors. Total scores on the questionnaire between treatment and control groups differed significantly. Students in the treatment group reported significantly more frequent seat belt use, stronger belief that seat belts were important to their safety, lower likelihood of riding with friends who had been drinking, higher rates of friends' use of seat belts, greater awareness of the age group most likely to be injured, and increased knowledge that they could prevent spinal cord injury.     

一期前后联合入路治疗上颈椎畸形

回顾9例因颅底凹陷症合并其它畸形在我科接受一期经口咽齿状突切除、后路枕骨大孔减压、寰枢椎或枕颈融合术治疗的,临床资料,观察该术式对脊髓功能、枕颈部稳定性的影响及其临床疗效。本组术前诊断均为颅底凹陷症合并邻近结构畸形。所有患者均接受前后联合入路手术。末次随访JOA评分15±1分。影像学检查示齿状突残留基底部均位于钱氏线以下,脊髓减压充分,寰枢间、枕颈间植骨均获坚强融合,融合时间平均3．9±1.1个月。因此一期前后路联合手术治疗颅底凹陷症,脊髓减压充分,重建稳定性后骨融合好,治疗效果满意。