Exploring the effect of the nerve conduction distance on the MScanFit method ofmotor unit number estimation (MUNE).

OBJECTIVE: MScanFit motor unit number estimation (MUNE) is a sensitive method for detecting motor unit loss and has demonstrated high reproducibility in various settings. In this study, our aim was to assess the outputs of this method when the nerve conduction distance is increased. METHODS: MScanFit recordings were obtained from the abductor digiti minimi muscle of 20 healthy volunteers. To evaluate the effect of nerve conduction distance, the ulnar nerve was stimulated from the wrist and elbow respectively. Reproducibility of MUNE, compound muscle action potential (CMAP), and other motor unit parameters were assessed using intraclass correlation coefficients (ICCs). RESULTS: Motor unit numbers obtained from stimulation at the wrist and elbow did not significantly differ and exhibited strong consistency in the ICC test (120.3 ± 23.7 vs. 118.5 ± 27.9, p > 0.05, ICC: 0.88). Similar repeatability values were noted for other parameters. However, the Largest Unit (%) displayed notable variability between the two regions and exhibited a negative correlation with nerve conduction distance. CONCLUSION: Our findings indicate that MScanFit can consistently calculate motor unit numbers and most of its outputs without substantial influence from nerve conduction distance. Exploring MScanFit's capabilities in various settings could enhance our understanding of its strengths and limitations for extensive use in clinical practice.

Excitability of somatosensory cortex is increased in ALS: A SEP recovery function study.

OBJECTIVE: Neuronal loss in the somatosensory, as well as the motor cortex in amyotrophic lateral sclerosis (ALS), indicative of a structural abnormality has been reported. Previously we have shown that afferent inhibition was impaired in ALS, suggestive of sensory involvement. In this study, we aimed to evaluate excitability changes in the somatosensory cortex of ALS patients. METHODS: ALS patients underwent a paired pulse somatosensory evoked potential (SEP) paradigm at various interstimulus intervals (ISI). The amplitude ratio obtained by dividing the amplitude of paired pulse SEP stimulation S2 (paired pulse stimulation) to S1 (the single pulse stimulation) was considered the somatosensory cortex excitability parameter. Findings were compared to the results obtained from healthy controls. Resting motor threshold (RMT) was also assessed in the ALS group. RESULTS: An increased S2/S1 ratio was found in the ALS group in every ISI examined. Additionally, the reduced inhibition correlated negatively with forced vital capacity, Medical Research Council sum score, median nerve compound muscle action potential amplitude, while there was a positive association with Penn upper motor neuron score and sural nerve conduction velocity. No correlation existed with RMT. CONCLUSIONS: Our findings demonstrated increased somatosensory cortical excitability in ALS, which was associated with clinical parameters such as reduced pulmonary function and motor strength. SIGNIFICANCE: Somatosensory cortical excitability is impaired in ALS. Whether this is associated with increased motor cortical excitability requires further studies.

Mirror neuron activity depending on the content and stage of the observed action: a TMS study.

Background/aim: The firing rate of the mirror neuron system in monkeys decreases systematically with more repetitions. The aim of this study is to investigate whether the activity of the mirror neuron system varies based on the observed movement and the contents of the action, as well as whether there is inhibition in the mirror neuron system when humans observe repeated actions. If inhibition is present, the second question of the study is whether it is related to the organization of the observed action. Materials and methods: Fourteen healthy volunteers participated in the study. Transcranial magnetic stimulation was applied to the left primary motor cortex and motor evoked potentials (MEPs) were recorded from the right first dorsal interosseous and abductor pollicis brevis muscles while the participants were watching videos specially prepared for the study. Results: There were no significant changes in MEP amplitudes compared to baseline MEPs while observing aimless action. However, while participants watched the repeated action video, the mean MEP amplitude increased at the beginning of the movement, but neither facilitation nor inhibition was detected when the participants watched the phase of grasping the object of the action compared to the baseline MEP amplitude. On the other hand, while participants were watching different activities, an increased MEP amplitude was observed at the beginning of the movement and in the grasping of the object of the action. Additionally, there was no significant reduction in MEP amplitude during any movement stages while observing the repeated action video. Conclusion: The findings of this study suggest that the activation of the mirror neuron system in humans depends on the content and stages of the observed movement. Additionally, there was no inhibition or systematic reduction in MEP amplitudes while watching a repeated action.

Estimating the motor unit number of the flexor carpi ulnaris muscle with MScanFit MUNE.

INTRODUCTION/AIMS: MScanFit motor unit number estimation (MUNE) is a promising method for motor unit estimation and is reported to have good reliability in distal and small muscles. In this study, we investigated the reliability of MScanFit MUNE in a proximal forearm muscle, the flexor carpi ulnaris. METHODS: Twenty healthy volunteers were included in this study, and 15 participants were re-evaluated in a second session. The ulnar nerve was stimulated at the elbow and a compound muscle action potential (CMAP) scan from the flexor carpi ulnaris (FCU) muscle was recorded from each arm. CMAP, MUNE, and other motor unit parameters were obtained. Reproducibility was evaluated using intraclass correlation coefficients (ICCs). RESULTS: The average MUNE from 40 FCU muscles was 90.9 (standard deviation: 16.4). MScanFit MUNE and CMAP were not significantly different between the dominant and non-dominant sides. The ICC indicated good reliability between sessions for each side (0.81 and 0.8, respectively). DISCUSSION: Our results indicate that MScanFit MUNE is a feasible method with good reproducibility for MUNE of the FCU muscle.

Short latency afferent inhibition: comparison between threshold-tracking and conventional amplitude recording methods.

Short-latency afferent inhibition (SAI), which is conventionally measured as a reduction in motor evoked potential amplitude (A-SAI), is of clinical interest as a potential biomarker for cognitive impairment. Since threshold-tracking has some advantages for clinical studies of short-interval cortical inhibition, we have compared A-SAI with a threshold-tracking alternative method (T-SAI). In the T-SAI method, inhibition was calculated by tracking the required TMS intensity for the targeted MEP amplitude (200 uV) both for the test (TMS only) and paired (TMS and peripheral stimulation) stimuli. A-SAI and T-SAI were recorded from 31 healthy subjects using ten stimuli at each of 12 inter-stimulus intervals, once in the morning and again in the afternoon. There were no differences between morning and afternoon recordings. When A-SAI was normalized by log conversion it was closely related to T-SAI. Between subjects, variability was similar for the two techniques, but within-subject variability was significantly smaller for normalized A-SAI. Conventional amplitude measurements appear more sensitive for detecting changes within-subjects, such as in interventional studies, but threshold-tracking may be as sensitive as detecting abnormal SAI in a patient.

CGRP receptor antagonist MK-8825 attenuates cortical spreading depression induced pain behavior.

BACKGROUND AND OBJECTIVE: The present study aimed to investigate the effects of selective calcitonin gene related peptide (CGRP) receptor antagonist (MK-8825) on cortical spreading depression (CSD) induced pain behavior and anxiety in freely-moving rats, and neuronal activation in the correlated anatomical regions. METHODS: CSD was induced while keeping all meningeal layers and BBB intact and MK-8825 was administered in two different doses. Regional cerebral blood flow (rCBF), arterial pressure and DC shift were recorded. Behavioral studies were conducted in freely-moving rats. Spontaneous behavior, mechanical allodynia, ultrasonic vocalization, and anxiety were evaluated. Immunohistochemistry of c-fos, CGRP, calcitonin receptor like-receptor (CLR) and receptor activity modifying protein 1 (RAMP1) were studied. RESULTS: MK-8825 did not block DC shifts in the cerebral cortex and accompanied hemodynamic response. CSD significantly induced freezing and grooming behavior in freely-moving rats. MK-8825 reversed increased episodes of freezing, grooming, wet dog shake and head shake behavior. MK-8825 increased CSD-induced reductions in von Frey thresholds, but did not change elevated plus maze results. MK-8825 blocked c-fos induction by CSD in the brainstem trigeminal nucleus caudalis (TNC) and reticular nucleus of thalamus (TRN) but not in the amygdala. Immunofluorescence analysis showed no co-localization of CGRP, CLR or RAMP1 with c-fos positive cells. CONCLUSION: CGRP receptor antagonist MK-8825 dose dependently attenuated CSD-induced trigeminal nerve mediated pain response without altering CSD waves and accompanied rCBF response. While blocking TNC activation, MK-8825 did not exert any effect on amygdala and anxiety behavior. CGRP receptor antagonists may also modulate thalamo-cortical gating.

Somatosensory temporal discrimination remains intact in tension-type headache whereas it is disrupted in migraine attacks.

Background and objective Somatosensory temporal discrimination was recently reported as prolonged during migraine attacks, which is consistent with disrupted sensorial perception in migraine. However, knowledge about central sensory processing in tension-type headache is still lacking. This prospective, controlled study aimed to investigate somatosensory temporal discrimination thresholds in tension-type headache. Methods The study included 10 tension-type headache patients, 10 migraine patients and 10 healthy volunteers without headache. Somatosensory temporal discrimination thresholds were evaluated during the headache attacks of tension-type headache and migraine patients. Results Somatosensory temporal discrimination thresholds of tension-type headache patients (39.0 ± 5.5 ms for the right hand and 40.6 ± 4.6 ms for the left hand) were significantly lower than those of episodic migraine patients (137.1 ± 35.8 ms for the right hand and 118.4 ± 34.3 ms for the left hand, p < 0.0001 and p < 0.0001 respectively), and comparable to those of healthy volunteers (38.6 ± 5.3 ms for the right hand and 38.3 ± 7.2 ms for the left hand, p = 0.79 and p = 0.45 respectively). Conclusion Central sensory processing, as tested by somatosensory temporal discrimination, was remarkably disrupted during the headache attacks in migraineurs, whereas it remained intact in the tension-type headache patients.

Chronic Migraine Is Associated With Sustained Elevation of Somatosensory Temporal Discrimination Thresholds.

BACKGROUND AND OBJECTIVE: Migraine headache attacks have been shown to be accompanied by significant prolongation of somatosensory temporal discrimination threshold values, supporting signs of disrupted sensorial processing in migraine. Chronic migraine is one of the most debilitating and challenging headache disorders with no available biomarker. We aimed to test the diagnostic value of somatosensory temporal discrimination for chronic migraine in this prospective, controlled study. METHODS: Fifteen chronic migraine patients and 15 healthy controls completed the study. Chronic migraine patients were evaluated twice, during a headache and headache-free period. Somatosensory temporal discrimination threshold values were evaluated in both hands. Duration of migraine and chronic migraine, headache intensity, clinical features accompanying headache such as nausea, photophobia, phonophobia and osmophobia, and pressure pain thresholds were also recorded. RESULTS: In the chronic migraine group, somatosensory temporal discrimination threshold values on the headache day (138.8 ± 21.8 ms for the right hand and 141.2 ± 17.4 ms for the left hand) were significantly higher than somatosensory temporal discrimination threshold values on the headache free day (121.5 ± 13.8 ms for the right hand and 122.8 ± 12.6 ms for the left hand, P = .003 and P < .0001, respectively) and somatosensory temporal discrimination thresholds of healthy volunteers (35.4 ± 5.5 ms for the right hand and 36.4 ± 5.4 ms for the left hand, P < .0001 and P < .0001, respectively). Somatosensory temporal discrimination threshold values of chronic migraine patients on the headache free day were significantly prolonged compared to somatosensory temporal discrimination threshold values of the control group (121.5 ± 13.8 ms vs 35.4 ± 5.5 ms for the right hand, P < .0001 and 122.8 ± 12.6 ms vs 36.4 ± 5.4 ms for the left hand, P < .0001). Somatosensory temporal discrimination threshold values of the hand contralateral to the headache lateralization (153.3 ± 13.7 ms) were significantly higher (P < .0001) than the ipsilateral hand (118.2 ± 11.9 ms) in chronic migraine patients when headache was lateralized. The headache intensity of chronic migraine patients rated with visual analog score was positively correlated with the contralateral somatosensory temporal discrimination threshold values. CONCLUSION: Somatosensory temporal discrimination thresholds persist elevated during the headache-free intervals in patients with chronic migraine. By providing evidence for the first time for unremitting disruption of central sensory processing, somatosensory temporal discrimination test stands out as a promising neurophysiological biomarker for chronic migraine.

The role of the cerebellum in motor imagery.

OBJECTIVE: Although it is well documented that the cerebellum plays a role in motor imagery (MI), its exact role in MI is still obscure. Since motor imagery and execution of movement share common pathways, and the cerebellum has an inhibitory effect on the motor cortex, we speculated that the cerebellum also has an inhibitory role on MI. METHODS: To test this hypothesis, 12 healthy individuals aged 27-47 years (mean age 33.3 years) were enrolled in the study. Subjects were asked to imagine two different tasks, one complex (MI-c) and one simple (MI-s) motor task. The intensity of anodal cerebellar transcranial direct current stimulation (ctDCS) was set at 2 mA for 20 min. Sham ctDCS consisted of 30s current stimulation. RESULTS: MI-s resulted in significantly increased log MEP amplitude during MI, compared with control MEP amplitude,(p=0.000). The increase in log MEP amplitude during MI disappeared after anodal ctDCS. Before sham ctDCS, both MI-s and MI-c resulted in log MEP amplitude increases (p=0.000). This facilitator effect of both MI-c and MI-s on log MEP amplitude was also persistent after sham ctDCS (p=0.000). CONCLUSIONS: The study demonstrates for the first time that the cerebellum has an inhibitory effect on MI. SIGNIFICANCE: Combining ctDCS with MI significantly modulates corticomotor excitability.

Somatosensory temporal discrimination is prolonged during migraine attacks.

BACKGROUND AND OBJECTIVE: Symptoms and signs of sensorial disturbances are characteristic features of a migraine headache. Somatosensory temporal discrimination measures the temporal threshold to perceive two separate somaesthetic stimuli as clearly distinct. This study aimed to evaluate somaesthetic perception in migraine patients by measuring the somatosensory temporal discrimination thresholds. METHODS: The study included 12 migraine patients without aura and 12 volunteers without headache. Somatosensory temporal discrimination threshold (STDT) values were measured in the face (V3) and hands (C7) during a lateralized headache attack and the headache-free interictal period. The disease duration, pain intensity, phonophobia, photophobia, nausea, vomiting, and brush allodynia were also recorded during the migraine attack. RESULTS: STDT values were within normal limits and not different between the control group and the interictal period in migraine patients. Compared to the headache-free period, STDT values during the attack were significantly prolonged in the contralateral hand (C7) (155.7 ± 84.2 vs 40.6 ± 16.1 ms [P < .001]), ipsilateral hand (C7) (88.6 ± 51.3 vs 31.4 ± 14.2 ms [P < 0.001]), contralateral face (V3) (65.5 ± 35.4 vs 37.6 ± 22.2 ms [P = .006]) and ipsilateral face (V3) (104.1 ± 44.5 vs 37.5 ± 21.4 ms [P < 0.001]) according to the lateralization of the headache. Ictal STDT values of the contralateral hand and ipsilateral face were significantly increased compared to that of the ipsilateral hand and contralateral face (155.7 ± 84.2 ms vs 88.6 ± 5.1.3 ms [P = .001], 104.1 ± 44.5 ms vs 65.5 ± 35.4 ms [P = 0.001]). No allodynia was detected in the areas that were tested for somatosensory temporal discrimination. The visual analog scale scores were correlated with the somatosensory temporal discrimination thresholds of the contralateral hand (r = 0.602, P = .038), whereas no correlation was detected between the somatosensory temporal discrimination thresholds and disease duration, brush allodynia in the forehead, phonophobia, photophobia, nausea and vomiting. CONCLUSION: The study demonstrates for the first time that somatosensory temporal discrimination thresholds are elevated during migraine attacks. A transient disruption of the central processing of somaesthetic stimuli during the lateralized migraine attack may provide additional information to understand the mechanisms of the cognitive and sensory perception impairment associated with migraine headache and may have diagnostic value.

Impacts of chloramine-T treatment on antioxidant enzyme activities and genotoxicity in rainbow trout, Oncorhynchus mykiss (Walbaum).

Juvenile rainbow trout Oncorhynchus mykiss (Walbaum) were exposed to therapeutic, and higher concentrations of chloramine-T (Cl-T) to assess the effects of this chemical on the antioxidant enzyme system and genetic structure. Red blood cells acetylcholinesterase, ∆-aminolevulinic acid dehydratase, paraoxonase and liver glutathione S-transferase activity were increased at 10 and 20 mg L(-1) Cl-T-exposed fish, while they were decreased at 30 mg L(-1) Cl-T-exposed fish. On the other hand, liver catalase activity and liver protein levels increased at 10 mg L(-1) and decreased at 20 and 30 mg L(-1) concentrations of Cl-T. Liver super-oxide dismutase activity decreased at 10 mg L(-1) and 20 mg L(-1) Cl-T and increased at 30 mg L(-1) of Cl-T. Compared to control, comet assay indicated that Cl-T did not cause significant DNA damage to red blood cells of the fish. Results indicate that 10 or 20 mg L(-1) Cl-T can be safely used to prevent or treat external parasitic and bacterial infection of rainbow trout.

Pathophysiology of Migraine.

Migraine is a serious health problem which impair quality of life. It is the second most common primary headache that affects approximately more than %10 people in general population. Migraine pathophysiology is still unclear. Increasing results of studies suggest to migraine pathophysiology is related with primary neuronal mechanisms. Migraine pain starts in which region of brain and what brain regions are activated in different stages is unenlightened. There is evidences that growing number of studies which using new imaging techniques as positron emission tomography (PET) and functional magnetic resonans imaging (fMRI) show that migraine and cluster headaches are related with neuronal structures and vasodilatation. There are four phases to a migraine. The prodrome phase, aura, the attack, and the postdrome phase. Some datas obtained from last ten years indicate that cortical excitability has increased in interictal phase too. For many years, studies in rodents show trgimenial nerve is activated and it leads to vasodilatation and neurogenic inflammation in the headache phase. Although the majority of patients encountered in clinical practice are migraine without aura or chronic migraine, experimental studies of the migraine pathophysiology are focusing on the aura model which is used cortical spreading depression.