Assessment of neurofunctional activity in patients with vibration disease caused by combined effects of local and general vibration

Introduction. The authors note insufficient knowledge of pathophysiological mechanisms, the cumulative role of cerebral functioning disorders in the formation of sensorineural deficit in vibration disease (VD). The study aims to identify changes in indicators characterizing neurofunctional activity in patients with VD due to the combined effects of local and general vibration. Materials and methods. The study involved 42 patients with VD (group I), 35 healthy men (comparison group). Researchers used methods of electroneuromyography, neuroenergic mapping, and neuropsychological testing. Results. In group I, when compared with the comparison group, we have detected an increase in latency N9, N10, N11, N13, N25, N30, the duration of the peak interval N10-N13 (p=0,002; 0,0001; 0,0002; 0,0001; 0,0023; 0,005; 0,01 respectively); an increase in local levels of constant potential (LCP) in the frontal, central, right parietal, occipital, right temporal parts of the brain (p=0.037; 0.0007; 0,0005; 0,01; 0,0004; 0,014; 0,029; 0,028; 0,001 respectively). Cognitive impairments in patients with VD correspond to an easily expressed disorder of analytical-synthetic and conceptual thinking, short-term (auditory-speech), visual imagery, long-term memory, dynamic praxis, joint coordination, impressive and expressive speech. The revealed conjugacy of the indicators of the LCP of the frontal left abduction, and the latency of the peak N30, duration N13-N20, and the hand of analytical and synthetic thinking (r=0.51, p=0.004; r=0.50, p=0.005, respectively) indicates the pathogenetic significance in the violation of neurofunctional activity of a decrease in cortical activation as a result of the arrival of a sensory message from the brain stem to the cortex, increased energy exchange in the frontal part of the left hemisphere. Conclusions. A sign of impaired neurofunctional activity in VB from the combined effects of local and general vibration is a decrease in the postsynaptic action of neurons, the time of signal passage through afferent pathways at the level of the cervical spinal cord, dynamic praxis, short-term (auditory-speech) memory, increased energy metabolism in the temporal right and left frontal brain.

Endurance Trained Athletes Do Not per se Have Higher Hoffmann Reflexes Than Recreationally Active Controls

The impact of endurance training on spinal neural circuitries remains largely unknown. Some studies have reported higher H-reflexes in endurance trained athletes and therefore, adaptations within the Ia afferent pathways after long term endurance training have been suggested. In the present study we tested the hypothesis that cyclists (n = 12) demonstrate higher Hoffmann reflexes (H-reflexes) compared to recreationally active controls (n = 10). Notwithstanding, highly significant differences in endurance performance (VO2peak: 60.6 for cyclists vs. 46.3 ml/min/kg for controls (p < 0.001) there was no difference in the size of the SOL H-reflex between cyclists and controls (Hmax/Mmax ratio 61.3 vs. 60.0%, respectively (p = 0.840). Further analyses of the H and M recruitment curves for SOL revealed a significant steeper slope of the M recruitment curve in the group of cyclists (76.2 ± 3.8° vs. 72.0 ± 4.4°, p = 0.046) without a difference in the H-recruitment curve (84.6 ± 3.0° vs. 85.0 ± 2.8°, p = 0.784) compared to the control group. Cycling is classified as an endurance sport and thus the findings of the present study do not further support the assumption that long-term aerobic training leads to a general increase of the H-reflex. Amongst methodological differences in assessing the H-reflex, the training-specific sensorimotor control of the endurance sport itself might differently affect the responsiveness of spinal motoneurons on Ia-afferent inputs.

The Auditory Afferent Pathway as a Clinical Marker of Alzheimer’s Disease

Brain stem neural tracts and nuclei may be disturbed prior to observable neuronal atrophy in AD. In this perspective, we discuss the notion of functional deficits presenting prior to structural abnormalities in Alzheimer’s disease (AD). Imaging of inferior colliculi using magnetic resonance spectroscopy (MRS) shows significant decrease in the neuronal markers, N acetyl aspartate/creatine ratio and increase in the glial marker myo-Inositol, in subjects with Mini-Mental State Examination scores greater than 24 and with no signs of atrophy in their MRI of the medial temporal lobe. Abnormalities in components of the auditory event-related potentials (ERPs) are described in cognitive impairment including AD. We observed a significant decrease in amplitude and increase in latency during the first 10 ms of auditory evoked potentials measured on electroencephalography (EEG) indicating slow auditory response of the brainstem. EEG spectral power recorded at the cortex is also associated with neural activity at the level of the inferior colliculi. We postulate that a functional examination of auditory afferent pathways, using non-invasive techniques, such as MRS, brain stem auditory evoked potentials (BAEPs) and ERPs may improve diagnostic accuracy of AD. Functional changes precede structural changes and it is important to further understand the relationship between biochemical and electrophysiological measures such as MRS, BAEPs and EEG.

Electroencephalogram-Electromyogram Functional Coupling and Delay Time Change Based on Motor Task Performance

Synchronous correlation brain and muscle oscillations during motor task execution is termed as functional coupling. Functional coupling between two signals appears with a delay time which can be used to infer the directionality of information flow. Functional coupling of brain and muscle depends on the type of muscle contraction and motor task performance. Although there have been many studies of functional coupling with types of muscle contraction and force level, there has been a lack of investigation with various motor task performances. Motor task types play an essential role that can reflect the amount of functional interaction. Thus, we examined functional coupling under four different motor tasks: real movement, intention, motor imagery and movement observation tasks. We explored interaction of two signals with linear and nonlinear information flow. The aim of this study is to investigate the synchronization between brain and muscle signals in terms of functional coupling and delay time. The results proved that brain–muscle functional coupling and delay time change according to motor tasks. Quick synchronization of localized cortical activity and motor unit firing causes good functional coupling and this can lead to short delay time to oscillate between signals. Signals can flow with bidirectionality between efferent and afferent pathways.

Influence of wide-pulse neuromuscular electrical stimulation frequency and superimposed tendon vibration on occurrence and magnitude of extra torque

Low-frequency and high-frequency wide-pulse neuromuscular electrical stimulation (NMES) can generate extra-torque (ET) via afferent pathways. Superimposing tendon vibration (TV) to NMES can increase the activation of these afferent pathways and favour ET generation. Knowledge of the characteristics of ET is essential to implement these stimulation paradigms in clinical practice. Thus, we aimed at investigating the effects of frequency and TV superimposition on the occurrence and magnitude of ET in response to wide-pulse NMES. NMES-induced isometric plantar flexion torque was recorded in 30 healthy individuals who performed five NMES protocols: wide-pulse low-frequency (1 ms; 20 Hz; WPLF) and wide-pulse high-frequency (1 ms; 100 Hz; WPHF) without and with superimposed TV (1 mm; 100 Hz) and conventional NMES (50 µs; 20 Hz; reference protocol). Each NMES protocol began with an adjustment of NMES intensity in order to reach 10% of maximal voluntary contraction then consisted of three 20-s trains interspersed by 90 s of rest. The ET occurrence was similar for WPLF and WPHF (p=0.822). In the responders, the ET magnitude was greater for WPHF than WPLF (p<0.001). There was no effect of superimposed TV on ET characteristics. This study reported an effect of NMES frequency on ET magnitude, whereas TV superimposition did not affect this parameter. In the context of our experimental design decisions, the present findings question the clinical use of wide-pulse NMES and its combination with superimposed TV. Yet, further research is needed in order to maximize force production through the occurrence and magnitude of ET.

Fibromyalgia-Associated Hyperalgesia and Psychopathological Alterations are Unrelated to Gut Microbiome Diversity

Fibromyalgia-syndrome (FMS) is a complex disease characterized by chronic widespread pain and additional symptoms including depression, cognitive dysfunction (“fibro-fog”) and maldigestion. We examined whether FMS-related pain parameters assessed by quantitative sensory testing (QST) are related to changes of microbial diversity.We recruited 25 patients with FMS and 26 age- and sex-matched healthy controls. Medical background, food habits, psychopathology and quality of life were assessed with questionnaires. Stool samples were analyzed by 16S rRNA gene amplification and sequencing. QST was performed according to the protocol of the German Network for Neuropathic Pain.QST showed that both lemniscal and spinothalamic afferent pathways are altered in FMS patients relative to healthy controls and that peripheral as well as central pain sensitization processes are manifest. Psychometric assessment revealed enhanced scores of depression, anxiety and stress. In contrast, neither the composition nor the alpha- and beta-diversity of the fecal microbiome was changed in FMS patients.FMS patients segregate from healthy controls in various parameters of QST and psychopathology, but not in terms of composition and diversity of the fecal microbiome. Despite consideration of several confounding factors we conclude that the impact of the gut microbiome on the pathophysiology of FMS is limited.

Intraperitoneal injection of lithium chloride induces lateralized activation of the insular cortex in adult mice

Insular cortex is a critical brain region that participates in the interoceptive sensations. Here, we combined the iDISCO + method and Fos immunostaining to confirm that the middle part of the right-side, but not the left-side, insular cortex in adult male mice is activated by intraperitoneal injection of lithium chloride. Lateralized activation of the insular cortex is also observed in adult female mice, but not in young or aged male mice. Furthermore, asymmetrical activation of the insular cortex was completely blocked when both sides of the vagal nerve are transected, whereas intravenous injection of lithium chloride has no effect on the insular activation. Combined together, these results indicate that the insular cortex unilaterally responds to aversive visceral stimuli in an age-dependent way and this process depends on the vagal afferent pathways.

Adaptive Balance in Posterior Cerebellum

Vestibular and optokinetic space is represented in three-dimensions in vermal lobules IX-X (uvula, nodulus) and hemisphere lobule X (flocculus) of the cerebellum. Vermal lobules IX-X encodes gravity and head movement using the utricular otolith and the two vertical semicircular canals. Hemispheric lobule X encodes self-motion using optokinetic feedback about the three axes of the semicircular canals. Vestibular and visual adaptation of this circuitry is needed to maintain balance during perturbations of self-induced motion. Vestibular and optokinetic (self-motion detection) stimulation is encoded by cerebellar climbing and mossy fibers. These two afferent pathways excite the discharge of Purkinje cells directly. Climbing fibers preferentially decrease the discharge of Purkinje cells by exciting stellate cell inhibitory interneurons. We describe instances adaptive balance at a behavioral level in which prolonged vestibular or optokinetic stimulation evokes reflexive eye movements that persist when the stimulation that initially evoked them stops. Adaptation to prolonged optokinetic stimulation also can be detected at cellular and subcellular levels. The transcription and expression of a neuropeptide, corticotropin releasing factor (CRF), is influenced by optokinetically-evoked olivary discharge and may contribute to optokinetic adaptation. The transcription and expression of microRNAs in floccular Purkinje cells evoked by long-term optokinetic stimulation may provide one of the subcellular mechanisms by which the membrane insertion of the GABAA receptors is regulated. The neurosteroids, estradiol (E2) and dihydrotestosterone (DHT), influence adaptation of vestibular nuclear neurons to electrically-induced potentiation and depression. In each section of this review, we discuss how adaptive changes in the vestibular and optokinetic subsystems of lobule X, inferior olivary nuclei and vestibular nuclei may contribute to the control of balance.