Potential Amplitude Research Articles

Investigation of Metaplasticity Associated with Transcranial Focused Ultrasound Neuromodulation in Humans.

Low-intensity transcranial focused ultrasound stimulation (TUS) is a novel technique for noninvasive brain stimulation (NIBS). TUS delivered in a theta (5 Hz) burst pattern (tbTUS) induces plasticity in the human primary motor cortex (M1) for 30-60 min, showing promise for therapeutic development. Metaplasticity refers to activity-dependent changes in neural functions governing synaptic plasticity; depotentiation is the reversal of long-term potentiation (LTP) by a subsequent protocol with no effect alone. Metaplasticity can enhance plasticity induction and clinical efficacy of NIBS protocols. In our study, we compared four NIBS protocol combinations to investigate metaplasticity on tbTUS in humans of either sex. We delivered four interventions: (1) sham continuous theta burst stimulation with 150 pulses (cTBS150) followed by real tbTUS (tbTUS only), (2) real cTBS150 followed by sham tbTUS (cTBS only), (3) real cTBS150 followed by real tbTUS (metaplasticity), and (4) real tbTUS followed by real cTBS150 (depotentiation). We measured motor-evoked potential amplitude, short-interval intracortical inhibition, long-interval intracortical inhibition, intracortical facilitation (ICF), and short-interval intracortical facilitation before and up to 90 min after plasticity intervention. Plasticity effects lasted at least 60 min longer when tbTUS was primed with cTBS150 compared with tbTUS alone. Plasticity was abolished when cTBS150 was delivered after tbTUS. cTBS150 alone had no significant effect. No changes in M1 intracortical circuits were observed. Plasticity induction by tbTUS can be modified in manners consistent with homeostatic metaplasticity and depotentiation. This substantiates evidence that tbTUS induces LTP-like processes and suggests that metaplasticity can be harnessed in the therapeutic development of TUS.

Electrophysiological properties of neurons in the visual sensory layers of the superior colliculus in early postnatal mice

Objective: To investigate the action potential firing patterns of neurons in the visual sensory layers of the superior colliculus in early postnatal mice and the electrophysiological characteristics of neurons with different firing patterns. Methods: This experimental study utilized whole-cell patch-clamp recordings performed on neurons in the visual sensory layers of the superior colliculus using brain slices from 57 healthy male C57BL/6J mice aged 14 to 20 days (weighing 5.0 to 8.9 g) using brain slices. In current-clamp mode, action potential characteristics were analyzed based on the first action potential generated by depolarizing current, and the firing patterns of neurons were recorded using step depolarizing currents. Neuronal firing patterns were analyzed using hierarchical clustering, and the active electrical properties of neurons with different firing patterns were compared. Results: A total of 135 neurons from the visual sensory layers of the superior colliculus were successfully recorded. Cluster analysis of the neuronal firing patterns identified three types of firing patterns: tonic firing (97, 72%), phasic firing (26, 19%), and single firing (12, 9%). The number of action potentials for each firing pattern was 13.30±7.38, 3.73±3.61, and 0.83±0.39, respectively, with significant differences (P<0.001). There was no significant difference in the membrane potential response to step currents among the three firing pattern types (P>0.05). The action potential amplitudes were (60.45±12.22), (53.67±13.20), and (44.04± 12.92) mV, and the afterhyperpolarization amplitudes were (13.45±13.79), (12.02±13.11), and (20.75±2.85) mV, respectively. The maximum rising slopes were (171.29±77.46), (130.14±61.83), and (78.89±37.08) V/s, and the maximum falling slopes were (-76.33±33.61), (-68.17±31.65), and (-47.97±13.92) V/s, respectively, with all differences being statistically significant (all P<0.05). There were no significant differences in the resting membrane potential, action potential threshold, half-width, and afterhyperpolarization duration among the three firing pattern types (all P>0.05). Conclusions: In the early postnatal mice, neurons in the visual sensory layers of the superior colliculus exhibit three distinct firing patterns: tonic, phasic, and single firing. These firing pattern types show significant differences in action potential amplitude, afterhyperpolarization amplitude, maximum rising slopes, and maximum falling slopes.

Temperature control during pars plana vitrectomy.

To evaluate the impact of temperature-controlled pars plana vitrectomy (PPV) on structural and functional outcomes in a rabbit eye model in vivo. Ten healthy New Zealand White rabbits underwent temperature-controlled PPV in the right eye (group A), using a device specifically designed to heat the infusion fluid/air and integrated into the vitrectomy machine, and conventional PPV in the left eye (group B). Both eyes received ophthalmic examination and electroretinography (ERG) before and 1week postoperatively. After 1-week ERG, rabbits were enucleated and then sacrificed. Histological and immunohistochemical examinations were performed on enucleated eyes and expression of glial fibrillary acidic protein (GFAP) and vimentin investigated. Postoperatively, only group B showed significantly decreased amplitude and increased latency of a-wave at 3cd·s/m2 (p = 0.001 and 0.005, respectively). Significant increase of b-wave latency at 0.01cd·s/m2 was detected in both groups (p = 0.019 and 0.023, respectively). Postoperatively, amplitude of oscillatory potentials (OPs) increased significantly in group A (p = 0.023) and decreased in group B. In both groups, OPs latency significantly increased at 1-week test (P < 0.05). A greater number of eyes without structural retinal alterations was detected in group A compared to group B (6 vs 5, respectively). GFAP expression was higher in group B than group A, even if the difference was not statistically significant. Temperature-controlled PPV resulted in more favorable functional and structural outcomes in rabbit eyes compared with conventional PPV, supporting the potential beneficial role of the intraoperative management of intraocular temperature in vitreoretinal surgery.

Fluorescein Angiography for Monitoring Neural Blood Flow in Chronic Nerve Compression Neuropathy: Experimental Animal Models and Preliminary Clinical Observations.

Pathologies associated with neural blood disturbance have been reported in patients with chronic nerve compression (CNC) neuropathy. Fluorescein angiography (FAG) and laser Doppler flowmetry (LDF) are effective for real-time peripheral nerve blood flow assessment. However, their reliability in severe neuropathy models in large animals or clinical conditions remains unclear. Initially, we aim to apply FAG to two different CNC animal models and evaluate their characteristics in comparison with those of LDF. In FAG, we quantified the peak luminance at the compression site following fluorescein injection. Then, we positioned the LDF probe at the center of the compression site and recorded the blood flow. Subsequently, we analyzed whether the FAG characteristics obtained in this animal experiment were consistent with those of clinical studies in patients with severe carpal tunnel syndrome (CTS). In the CNC rat model, FAG and LDF effectively monitored reduced neural blood flow over time. We observed significant blood flow reduction using both techniques in a newly developed severe CNC rabbit model. Notably, FAG correlated strongly with the compound muscle action potential (CMAP) amplitude in electrodiagnostic findings, unlike LDF. As a next step, we performed FAG after open carpal tunnel release in clinical cases of CTS. FAG correlated significantly with preoperative CMAP amplitude. This indicates FAG's importance for assessing nerve blood flow during surgery, potentially improving diagnostic accuracy and surgical outcomes.

Sensory dysfunction in SMA type 2 and 3 - adaptive mechanism or concomitant target of damage?

BackgroundThe motor neuron survival protein performs numerous cellular functions; hence, spinal muscular atrophy (SMA) is considered to be a multi-organ disease with possible sensory system damage. The controversy surrounding the presence of sensory disturbances, prompted us to conduct standard electrophysiological studies and assess the sensory thresholds for different modalities in adults with SMA types 2 and 3. The study group consisted of 44 adult SMA patients (types 2 and 3). All patients underwent neurological examination using the Hammersmith Functional Motor Scale – Expanded (HFMSE). Standard sensory electrophysiological studies in the ulnar nerve and the estimation of vibratory, temperature, and warm- and cold-induced pain thresholds with temperature dispersion assessment were performed using quantitative sensory testing (QST).ResultsThe most repeatable result was the high amplitude of the sensory nerve action potentials (SNAP) in SMA patients compared to controls. This was higher in type 2 patients compared to type 3a and 3b patients and patients with low HFSME scores. Patients with SMA, especially type 3b presented a longer sensory latency and slower conduction velocity than did controls. Cold pain threshold was higher and warm dispersion larger in SMA. The vibratory limit was higher in patients with high HFSME scores.ConclusionsA high SNAP amplitude suggests sensory fibre hyperactivity, which may be based on overactivation of metabolic pathways as an adaptive mechanism in response to SMN protein deficiency with additionally coexisting small C- and A-delta fibre damage. SMA patients seem to have a concomitant, mild demyelinating process present at the early SMA stage.

Abstract P436: Prorenin Increases the Firing Activity of Hypothalamic Arcuate Nucleus AgRP Neurons

The arcuate nucleus of the hypothalamus (ARC) serves as a key regulator of the cardiovascular and sympathetic regulating center. While neurons in the ARC expressing agouti-related peptide (AgRP) are implicated in the regulation of energy- and glucose homeostasis, our recent findings show that acute chemogenic activation of ARC AgRP neurons reduces blood pressure (BP), whereas inhibition of these neurons has the opposite effect. Together, these observations indicate ARC AgRP neuronal activity as a determinant of basal BP and suggest that tonic activity of these neurons may be required to maintain BP in the normal range. Importantly, most AgRP neurons express the (pro)renin receptor (PRR), a pivotal component of the brain renin-angiotensin system critical for BP regulation. Accordingly, we hypothesized that prorenin may regulate AgRP neuron activity through PRR, and thereby contributing to the autonomic regulation of BP. This study employed whole-cell patch clamp methodology in brain slices of ARC to investigate the effect of prorenin on AgRP neuron firing activity and understand mechanisms. Male and female mice expressing tdTomato in the AgRP neurons were used. Prorenin (2.5 nM) depolarized the resting membrane potential (-41.9 ± 8.7 mV vs. -47.2 ± 7.8 mV, P &lt; 0.001) and increased the frequency of action potential (AP) (2.3 ± 1.3 Hz vs. 1.2 ± 0.8 Hz, P &lt; 0.001) compared with the control (artificial cerebrospinal fluid (aCSF), n=10 neurons from 7mice). Analysis of AP waveforms revealed that prorenin decreased the amplitude of AP (61.0 ± 14.4 mV vs. 70.2 ± 14.3 mV, P &lt; 0.001) and threshold potential (-31.8 ± 6.0 mV vs. -35.5 ± 4.8 mV, P &lt; 0.001), and increased the rise time (2.3 ± 0.7 ms vs. 1.9 ± 0.6 ms, P &lt; 0.001), decay time (2.6 ± 1.1 ms vs. 2.0 ± 0.9 ms, P &lt; 0.01) and half-width (2.2 ± 0.7 ms vs. 1.8 ± 0.6 ms, P &lt;0.01) compared with the control. These changes suggest that alterations in the intrinsic conductance underlying the AP waveform likely coincide with the observed decrease in resting membrane potentials, while the ion channels involved remained to be determined. In summary, prorenin increases the firing activity of the ARC AgRP neurons by depolarizing the resting membrane potential, implicating that activation of PRR in the ARC AgRP neurons may reduce BP and protect against hypertension development.

Long-term impact of nusinersen on motor and electrophysiological outcomes in adolescent and adult spinal muscular atrophy: insights from a multicenter retrospective study.

5q spinal muscular atrophy (SMA) is a progressive autosomal recessive motor neuron disease. We aimed to assess the effects of nusinersen on motor function and electrophysiological parameters in adolescent and adult patients with 5q SMA. Patients with genetically confirmed 5q SMA were eligible for inclusion, and clinical data were collected at baseline (V1), 63days (V4), 180days (V5), and 300days (V6). The efficacy of nusinersen was monitored by encompassing clinical assessments, including the Revised Upper Limb Module (RULM), Hammersmith Functional Motor Scale Expanded (HFMSE), 6-Minute Walk Test (6MWT), and percent-predicted Forced Vital Capacity in sitting position (FVC%) and Compound Muscle Action Potential (CMAP) amplitude. The patients were divided into "sitter" and "walker" subgroups according to motor function status. 54 patients were screened, divided into "sitter" (N = 22) and "walker" (N = 32), with the mean age at baseline of 27.03years (range 13-53years). The HFMSE in the walker subgroup increased significantly from baseline to V4 (mean change +2.32-point, P = 0.004), V5 (+3.09, P = 0.004) and V6 (+4.21, P = 0.005). The patients in both the sitter and walker subgroup had no significant changes in mean RULM between V1 and the following time points. Significant increases in CMAP amplitudes were observed in both upper and lower limbs after treatment. Also, patients with RULM ≥ 36 points showed significant CMAP improvements. Our analysis predicted that patients with CMAP amplitudes of trapezius ≥ 1.76mV were more likely to achieve significant motor function improvements. Nusinersen effectively improves motor function and electrophysiological data in adolescent and adult patients with SMA. This is the first report on the CMAP amplitude changes in the trapezius after treatment in patients with SMA. The CMAP values effectively compensate for the ceiling effect observed in the RULM, suggesting that CMAP could serve as an additional biomarker for evaluating treatment efficacy.

Exploring the translational impact of type 1 diabetes on cerebral neurovascular function through ECoG-LSCI.

Type 1 diabetes mellitus (T1DM) can result in complications such as retinopathy, nephropathy, and peripheral neuropathy, which can lead to brain dysfunction. In this study, we investigated the effects of T1DM on cerebral neurovascular function in mice. Streptozotocin (STZ) is known to induce T1DM in animals; thus, we used an STZ-induced diabetes model to evaluate the effects of hyperglycemia on brain morphology and neurovascular tissue. Neurovascular coupling is the connection between neuronal activity and cerebral blood flow that maintains brain function. The ECoG-LSCI technique combines electrocorticography (ECoG) and laser speckle contrast imaging (LSCI) to detect cortical spreading depression (CSD) as a marker of neurovascular coupling and measure corresponding neurovascular function. Our results suggested that in the STZ group, hyperglycemia affected excitatory neurotransmission and metabolism, leading to reductions in intercellular signaling, somatosensory evoked potential (SSEP) amplitudes, and CSD transmission rates. Western blot data further revealed that brain-derived neurotrophic factor (BDNF) and neuronal nuclear antigen levels were reduced in the STZ group. Abnormalities in glucose metabolism in the brain and increased phosphorylation of AKT and GSK3 are hypothesized to be responsible for these decreases. Overall, this study highlights the importance of glucose metabolism in normal brain physiology and demonstrates that hyperglycemia disrupts neurovascular coupling and affects cerebral neurovascular function and that the degree of CSD is positively correlated with the extent of brain tissue damage. Further research is essential to gain a complete understanding of the related mechanisms and the implications of these findings.

The importance of medial plantar nerve conduction study in detectıon of polyneuropathy in inflammatory bowel disease

Background &amp; Objective: Peripheral neuropathy is the most frequent neurologic complication of inflammatory bowel disease (IBD). We aimed to evaluate the clinical utility of medial plantar nerve conduction study (NCS) in the detection of distal sensory polyneuropathy in IBD patients. Methods: The study was performed with 21 Crohn’s disease (Group 1) patients, 24 Ulcerative Colitis (Group 2) patients without clinical peripheral neuropathy and 28 healthy participants (Group 3). Each patient group underwent electrophysiological conduction studies. The findings were analyzed statistically. Results: Abnormal medial plantar nerve conduction was present on both sides in 11 (24.4 %) patients with IBD; 5 (11.1 %) patients had low sural nerve amplitude, and 5 (11.1 %) had low superficial peroneal nerve amplitude bilaterally. There were significant differences between the IBD groups (Group 1 and 2) and Group 3 in the mean sensory nerve action potential amplitude of the right medial plantar nerve (p&lt;0.024), and in the mean sensory nerve action potential amplitude of the left medial plantar nerve (p&lt;0.025). The polyneuropathy pattern was mostly of the sensory axonal type in patients with IBD. Conclusions: These electrophysiologic findings indicate that peripheral neuropathy is more prevalent in IBD. In IBD patients the amplitudes of the medial plantar nerve were abnormal more than in the sural and superficial peroneal nerves.

Motor unit number index in Bell's palsy: A potential electrophysiological biomarker for early evaluation.

Reliable, noninvasive early diagnostics of neuromuscular function in Bell's palsy, which causes facial paralysis and reduced quality of life, remain to be established. Here, we aimed to evaluate the utility of the motor unit number index (MUNIX) for the quantitative electrophysiological assessment of early-stage Bell's palsy, its correlation with clinical assessments, changes following treatment, and association with clinical prognosis. MUNIX measures were recorded from the bilateral zygomaticus, orbicularis oculi, and orbicularis oris muscles of 10 healthy individuals and 64 patients with Bell's palsy. The patients were assessed by two specialist neurologists using the House-Brackmann and Sunnybrook Facial Grading Systems. Repeat assessments were performed on 20 patients with Bell's palsy who received treatment. Additionally, the 64 patients were reassessed using clinical scales after a 1-month interval. The MUNIX values of the main affected muscles on the affected side were lower than those on the healthy side in patients with Bell's palsy (p<.05). The MUNIX measurements significantly correlated with the clinical facial nerve palsy scale scores (p<.05). Significant improvements were observed in the MUNIX values on repeat testing following treatment (p<.05). The baseline motor unit size index (the compound muscle action potential amplitude divided by MUNIX) was positively associated with improved clinical presentation after 1 month (p<.05). MUNIX can be used as an electrophysiological biomarker for the quantitative assessment of facial nerve palsy and treatment response, and as a prognostic biomarker, in patients with early Bell's palsy, and is recommended as a complement to conventional neurophysiological examinations.

Ethambutol-induced optic neuropathy: Another conundrum

Purpose: The purpose was to study the effect of ethambutol (EMB) and cause for optic neuropathy in the hope that better understanding of the condition will help us to reduce the burden of visual loss. Materials and Methods: A retrospective analysis of patients with EMB-induced optic neuropathy was done, which included 30 patients attending our outpatient department from January 2022 to March 2022. Results: The mean age was 53.73 with male (70%) preponderance. Visual fields showed bitemporal hemianopia in 43% (13), temporal field defects in 26% (8), centrocecal scotoma in 17% (5), and low reliability in 10% (3). Visual evoked potential amplitude was reduced in 87% (26). Magnetic resonance imaging showed enhancement of optic chiasma in 40% (12). After discontinuing and replacing EMB, with Vitamin B complex and zinc supplements, 53% (16) had visual improvement on 1-month follow-up. Conclusion: India has launched the Pradhan Mantri TB Mukt Bharat Abhiyan “Ni-kshay 2.0” portal to eradicate tuberculosis by 2025. Hence, aggressive treatment protocols are underway. The increased duration of EMB in new directly observed therapy short-course regimen has caused increased incidence of EMB optic neuropathy. Regular screening is needed to diagnose and prevent further visual deterioration in these patients. Timely replacement of the drug with another drug is a key in visual recovery of these patients. Further studies are needed to assess if the genetic predisposition is responsible for optic nerve damage.

Two-dimensional Diffusion with a Transverse Gravitational Force: Analytical, Numerical and Simulations Results

Abstract Using the Kalinay and Percus projection method a new effective diffusion coefficient is found. This diffusivity generalizes the well-known results previously reported in the literature. Specifically, it is a coefficient that can be applied to two-dimensional asymmetrical channels under an external gravitational-like potential. Furthermore, Brownian Dynamics simulations are performed, and their agreement with the theoretical results is shown. Also, the Mean First-Passage Time is studied for two-dimensional straight conical channels, where the analytical results are analyzed to understand its applicability range using numerical methods, which are compared with Brownian Dynamics simulations. A remarkable result is also presented: the Mean First-Passage Time assumes a minimum at finite values of the external potential amplitude.

Pilot study of using transcranial temporal interfering theta-burst stimulation for modulating motor excitability in rat

Transcranial temporal interference stimulation (tTIS) is a promising brain stimulation method that can target deep brain regions by delivering an interfering current from surface electrodes. Most instances of tTIS stimulate the brain with a single-frequency sinusoidal waveform generated by wave interference. Theta burst stimulation is an effective stimulation scheme that can modulate neuroplasticity by generating long-term potentiation- or depression-like effects. To broaden tTIS application, we developed a theta burst protocol using tTIS technique to modulate neuroplasticity in rats. Two cannula electrodes were unilaterally implanted into the intact skull over the primary motor cortex. Electrical field of temporal interference envelopes generated by tTIS through cannula electrodes were recorded from primary motor cortex. Theta burst schemes were characterized, and motor activation induced by the stimulation was also evaluated simultaneously by observing electromyographic signals from the corresponding brachioradialis muscle. After validating the stimulation scheme, we further tested the modulatory effects of theta burst stimulation delivered by tTIS and by conventional transcranial electrical stimulation on primary motor cortex excitability. Changes in the amplitude of motor evoked potentials, elicited when the primary motor cortex was activated by electrical pulses, were measured before and after theta burst stimulation by both techniques. Significant potentiation and suppression were found at 15 to 30 min after the intermittent and continuous theta burst stimulation delivered using tTIS, respectively. However, comparing to theta burst stimulations delivered using conventional form of transcranial electrical stimulation, using tTIS expressed no significant difference in modulating motor evoked potential amplitudes. Sham treatment from both methods had no effect on changing the motor evoked potential amplitude. The present study demonstrated the feasibility of using tTIS to achieve a theta burst stimulation scheme for motor cortical neuromodulation. These findings also indicated the future potential of using tTIS to carry out theta burst stimulation protocols in deep-brain networks for modulating neuroplasticity.

Short-latency afferent inhibition is reduced with cold-water immersion of a limb and remains reduced after removal from the cold stimulus.

The experience of pain that is induced by extremely cold temperatures can exert a modulatory effect on motor cortex circuitry. Although it is known that immersion of a single limb in very cold water can increase corticomotor excitability it is unknown how afferent input to the cortex shapes excitatory and inhibitory processes. Therefore, the purpose of this study was to examine motor-evoked potentials (MEP), short-latency afferent inhibition (SAI) and long-latency afferent inhibition (LAI) in response to immersion of a single hand in cold water. Transcranial magnetic stimulation (TMS) was used to assess MEPs, and peripheral nerve stimulation of the median nerve paired with TMS was used to measure SAI and LAI in motor circuits of the ipsilateral hemisphere. Measurements were obtained from electromyography (EMG) of the first dorsal interosseous (FDI) at baseline, during cold-water immersion, and during recovery from cold-water immersion. The intervention caused unconditioned MEPs to increase during exposure to the cold stimulus (P=0.008) which then returned to baseline levels once the hand was removed from the cold water. MEP responses were decoupled from SAI responses, where SAI was reduced during exposure to the cold stimulus (P=0.005) and remained reduced compared to baseline when the hand was removed from the cold water (P=0.002). The intervention had no effect on LAI. The uncoupling of SAI from MEPs during the recovery period suggests that the mechanisms underlying the modulation of corticospinal excitability by sensory input may be distinct from those affecting intracortical inhibitory circuits. HIGHLIGHTS: What is the central question of this study? Does immersion of a limb in very cold water influence corticospinal excitability and the level of afferent inhibition exerted on motor cortical circuits? What is the main finding and its importance? In additional to perception of temperature, immersion in 6°C water also induced perceptions of pain. Motor evoked potential (MEP) amplitude increased during immersion, and short-latency afferent inhibition (SAI) of the motor cortex was reduced during immersion; however, these responses differed after the limb was removed from the cold stimulus, as MEPs returned to normal levels while SAI remained suppressed.

Effects of Motor Learning on Corticospinal Tract Excitability During Motor Imagery.

We aimed to examine the effects of motor performance improvements produced by practice on corticospinal tract excitability during motor imagery (MI) of identical movements. Participants performed a motor task with no guidelines displayed on the monitor (performance test); the participants only imagined performing the task without performing the movement (MI test), and the participants performed the power output and then adjusted it (exercise). The output force conditions were 20, 40, and 60% of the maximum voluntary contraction, and the objective was for 21 participants to learn each output force condition. The outcome of the performance test was calculated as the difference between the actual motor output and the target. During the MI test, we applied a single transcranial magnetic stimulation during imagery, assessed the corticospinal tract excitability of the right first dorsal interosseous by motor-evoked potential (MEP) amplitude, and recorded the vividness of the MI in each trial. We evaluated performance and MI before practice (Pre-test), after 150 practice sessions (Post-test 1), and after another 150 practice sessions (Post-test 2). The MEP amplitude was significantly reduced at Post-test 2 compared to Pre-test. The vividness of the MI improved with practice. Corticospinal tract excitability during MI decreased as motor performance improved. Thus, actual motor practice was also reflected in the MI of the exercise. Performance improvement was accompanied by a decrease in redundant activity, enhancing the efficiency and appropriateness of the exercise.

Immediate Effects of Preconditioning Intermittent Theta Burst Stimulation on Lower Extremity Motor Cortex Excitability in Healthy Participants.

Previous studies have found that inhibitory priming with continuous theta burst stimulation (cTBS) can enhance the effect of subsequent excitatory conditioning stimuli with intermittent theta burst stimulation (iTBS) in the upper limbs. However, whether this combined stimulation approach elicits a comparable compensatory response in the lower extremities remains unclear. This study aimed to investigate how cTBS preconditioning modulated the effect of iTBS on motor cortex excitability related to the lower limb in healthy individuals. Using a randomised cross-over design, a total of 25 healthy participants (19 females, mean age = 24.80 yr) were recruited to undergo three different TBS protocols (cTBS + iTBS, sham cTBS + iTBS, sham cTBS + sham iTBS) in a random order. Each TBS intervention was administered with one-week intervals. cTBS and iTBS were administered at an intensity of 80% active motor threshold (AMT) delivering a total of 600 pulses. Before intervention (T0), immediately following intervention (T1), and 20 min after intervention (T2), the corticomotor excitability was measured for the tibialis anterior muscle of participants' non-dominant leg using a Magneuro100 stimulator and matched double-cone coil. The average amplitude of the motor-evoked potential (MEP) induced by applying 20 consecutive monopulse stimuli at an intensity of 130% resting motor threshold (RMT) was collected and analysed. Compare with T0 time, the MEP amplitude (raw and normalised) at T1 and T2 showed a statistically significant increase following the cTBS + iTBS protocol (p < 0.01), but no significant differences were observed in amplitude changes following other protocols (sham cTBS + iTBS and sham cTBS + sham iTBS) (p > 0.05). Furthermore, no statistically significant difference was found among the three protocols at any given time point (p > 0.05). Preconditioning the lower extremity motor cortex with cTBS prior to iTBS intervention can promptly enhance its excitability in healthy participants. This effect persists for a minimum duration of 20 min. No: ChiCTR2300069315. Registered 13 March, 2023, https://www.chictr.org.cn.

CAMP reduces action potential amplitude and conduction velocity over long axonal distance.

cAMP reduces action potential amplitude and conduction velocity over long axonal distance.

Association of the Achondroplasia Foramen Magnum Score and intraoperative neuromonitoring

IntroductionForamen magnum stenosis in achondroplasia carries a risk of sudden death. A proportion of these patients benefit from foramen magnum decompression (FMD). The Achondroplasia Foramen Magnum Score (AFMS) was developed...

Altered somatosensory processing in adult attention deficit hyperactivity disorder

BackgroundTactile sensitivity and sensory overload in ADHD are well-documented in clinical-, self-, and parent- reports, but empirical evidence is scarce and ambiguous and focuses primarily on children. Here, we compare both empirical and self-report tactile sensitivity and ADHD symptomatology in adults with ADHD and neurotypical controls. We evaluate whether tactile sensitivity and integration is more prevalent in ADHD and whether it is related to ADHD symptom severity.MethodsSomatosensory evoked potential (SEP) amplitudes were measured in 27 adults with ADHD and 24 controls during four conditions (rest, stroking of the own arm, stroking of the arm by a researcher, and stroking of an object). Participants also filled out questionnaires on tactile sensitivity and ADHD symptoms and performed a Qb-test as an objective measure of ADHD symptom severity.ResultsParticipants with ADHD self-reported greater tactile sensitivity and ADHD symptom severity than controls and received higher scores on the Qb-test. These values correlated with one another. ADHD participants showed lower tolerable threshold for electrical radial nerve stimulus, and greater reduction in cortical SEP amplitudes during additional tactile stimuli which was correlated with ADHD symptoms.ConclusionsWe find that ADHD symptomatology and touch sensitivity are directly linked, using both self-reports and experimental measures. We also find evidence of tactile sensory overload in ADHD, and an indication that this is linked to inattention specifically. Tactile sensitivity and sensory overload impact the functioning and life quality of many people with ADHD, and clinicians should consider this when treating their patients.

Hebbian plasticity induced by temporally coincident BCI enhances post-stroke motor recovery

Functional electrical stimulation (FES) can support functional restoration of a paretic limb post-stroke. Hebbian plasticity depends on temporally coinciding pre- and post-synaptic activity. A tight temporal relationship between motor cortical (MC) activity associated with attempted movement and FES-generated visuo-proprioceptive feedback is hypothesized to enhance motor recovery. Using a brain–computer interface (BCI) to classify MC spectral power in electroencephalographic (EEG) signals to trigger FES-delivery with detection of movement attempts improved motor outcomes in chronic stroke patients. We hypothesized that heightened neural plasticity earlier post-stroke would further enhance corticomuscular functional connectivity and motor recovery. We compared subcortical non-dominant hemisphere stroke patients in BCI-FES and Random-FES (FES temporally independent of MC movement attempt detection) groups. The primary outcome measure was the Fugl-Meyer Assessment, Upper Extremity (FMA-UE). We recorded high-density EEG and transcranial magnetic stimulation-induced motor evoked potentials before and after treatment. The BCI group showed greater: FMA-UE improvement; motor evoked potential amplitude; beta oscillatory power and long-range temporal correlation reduction over contralateral MC; and corticomuscular coherence with contralateral MC. These changes are consistent with enhanced post-stroke motor improvement when movement is synchronized with MC activity reflecting attempted movement.