The intrinsic plasticity of medial vestibular nucleus neurons during vestibular compensation-a systematic review and meta-analysis

A convolutional neural network model detecting lasting behavioral changes in mice with kanamycin-induced unilateral inner ear dysfunction

In acute aminoglycoside ototoxicity of the unilateral inner ear, physical abnormalities, such as nystagmus and postural alteration, are relieved within a few days by neural compensation. To examine exploratory behavior over an extended period, behaviors of freely moving mice after unilateral kanamycin injection into the inner ear were recorded in a home cage environment. The tail was excluded from deep learning-mediated object detection because of its delayed movement relative to the body. All detection results were confirmed using a convolutional neural network classification model. In kanamycin-injected mice, the total distance moved in 15 min increased on postoperative day 3. Furthermore, injured mice turned more frequently toward the healthy side up to 17 days after the surgery. This tendency resulted in increased clockwise movements in home cage recordings. Moreover, tail suspension and twisting toward the healthy side induced a physical sign for up to 14 days after the injury; the mice rapidly rotated with dorsal bending. Our analysis strategy employing deep learning helps to evaluate neuronal compensatory processes for an extended period and is useful for assessing the efficacy of therapeutic interventions.

Vestibulo-Ocular Reflex Suppression: Clinical Relevance and Assessment in the Digital Age

Background

Visual acuity and image stability are crucial for daily activities, particularly during head motion. The vestibulo-ocular reflex (VOR) and its suppression (VORS) support stable fixation of objects of interest. The VOR drives a reflexive eye movement to counter retinal slip of a stable target during head motion. In contrast, VORS inhibits this countermovement when the target stimulus is in motion. The VORS allows for object fixation when it aligns with the direction of the head's movement, or when an object within or outside the peripheral vision needs to be focused upon.

Summary

Deficits of the VORS have been linked to age-related diseases such as balance deficits associated with an increased fall risk. Therefore, the accurate assessment of the VORS is of particular clinical relevance. However, current clinical assessment methods for VORS are mainly qualitative and not sufficiently standardised. Recent advances in digital health technology, such as smartphone-based videooculography, offer a promising alternative for assessing VORS in a more accessible, efficient, and quantitative manner. Moreover, integrating mobile eye-tracking technology with virtual reality environments allows for the implementation of controlled VORS assessments with different visual inputs. These assessment approaches allow the extraction of novel parameters with potential pathomechanistic and clinical relevance.

Key Messages

We argue that researchers and clinicians can obtain a more nuanced understanding of this ocular stabilisation reflex and its associated pathologies by harnessing digital health technology for VORS assessment. Further research is warranted to explore the technologies' full potential and utility in clinical practice.

What can the citations of systematic reviews of ethical literature tell us about their use?-an explorative empirical analysis of 31 reviews

Background

Systematic reviews of ethical literature (SREL) aim at providing an overview of ethical issues, arguments, or concepts on a specific ethical topic. As SREL are becoming more common, their methodology and possible impact are increasingly subjected to critical considerations. Because they analyse and synthetise normative literature, SREL are likely to be used differently than typical systematic reviews. Still, the uses and the expected purposes of SREL were, to date, mainly theoretically discussed. Our explorative study aimed at gaining preliminary empirical insights into the actual uses of SREL.

Methods

Citations of SREL in publications, both scientific and non-scientific, were taken as proxy for SREL uses. The citations of 31 published SREL were systematically searched on Google Scholar. Each citation was qualitatively analysed to determine its function. The resulting categorisation of SREL citations was further quantitatively investigated to unveil possible trends.

Results

The analysis of the resulting sample of SREL citations (n=1812) showed that the selected SREL were mostly cited to support claims about ethical issues, arguments, or concepts, but also to merely mention the existence of literature on a given topic. In this sample, SREL were cited predominantly within empirical publications in journals from various academic fields, indicating a broad, field-independent use of such systematic reviews. The selected SREL were also used as methodological orientations either for the conduct of SREL or for the practical and ethically sensitive conduct of empirical studies.

Conclusions

In our sample, SREL were rarely used to develop guidelines or to derive ethical recommendations, as it is often postulated in the theoretical literature. The findings of this study constitute a valuable preliminary empirical input in the current methodological debate on SREL and could contribute to developing strategies to align expected purposes with actual uses of SREL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13643-023-02341-y.

Vestibular rehabilitation improves spontaneous nystagmus normalization in patients with acute unilateral vestibulopathy

Introduction

Spontaneous nystagmus (SN) can be observed after acute unilateral vestibulopathy (AUVP). The slow phase eye velocity of the SN progressively decreases in darkness as the result of rebalanced neurophysiological activity between both vestibular nuclei, a process that can take several months. Although this compensatory process can occur spontaneously, there is poor evidence that vestibular rehabilitation (VR) can facilitate the process.

Methods

We documented the natural time course of SN reduction in patients with AUVP, as well as the effects of VR by means of a unilateral rotation paradigm. In a retrospective study (Study 1: n = 126 AUVP patients), we compared the time course of the SN reduction in patients with VR (n = 33) and without VR (n = 93). In a prospective study (Study 2: n = 42 AUVP patients), we compared the effects of early VR (n = 22; initiated within the first two weeks of symptoms onset) or late VR (n = 20; initiated after the second week of symptoms onset) on the time course of the SN reduction.

Results

Study 1 showed shorter median time of SN normalization in patients with VR compared to patients without VR (14 days and 90 days, respectively). Study 2 showed that AUVP patients with early and late VR had a similar median time of SN normalization. The SN slow phase eye velocity was significantly decreased as early as the end of the first VR session in both groups, and kept decreasing at each subsequent VR session. In the early VR group, 38% of the patients had slow phase eye velocity below 2°/s after the first VR session, 100% after the fifth session. Similar findings were observed in the late VR group.

Discussion

Taken together, these results indicate that VR with a unidirectional rotation paradigm speeds up the normalization of SN. This effect seems independent of the time between symptoms onset and commencement of VR, but early intervention is recommended to speed up the SN reduction.

Galvanic vestibular stimulation down-regulated NMDA receptors in vestibular nucleus of PD model

Parkinsonian symptoms relief by electrical stimulation is constructed by modulating neural network activity, and Galvanic vestibular stimulation (GVS) is known to affect the neural activity for motor control by activating the vestibular afferents. However, its underlying mechanism is still elusive. Due to the tight link from the peripheral vestibular organ to vestibular nucleus (VN), the effect by GVS was investigated to understand the neural mechanism. Using Sprague Dawley (SD) rats, behavioral response, extracellular neural recording, and immunohistochemistry in VN were conducted before and after the construction of Parkinson's disease (PD) model. Animals' locomotion was tested using rota-rod, and single extracellular neuronal activity was recorded in VN. The immunohistochemistry detected AMPA and NMDA receptors in VN to assess the effects by different amounts of electrical charge (0.018, 0.09, and 0.18 coulombs) as well as normal and PD with no GVS. All PD models showed the motor impairment, and the loss of TH⁺ neurons in medial forebrain bundle (mfb) and striatum was observed. Sixty-five neuronal extracellular activities (32 canal & 33 otolith) were recorded, but no significant difference in the resting firing rates and the kinetic responding gain were found in the PD models. On the other hand, the numbers of AMPA and NMDA receptors increased after the construction of PD model, and the effect by GVS was significantly evident in the change of NMDA receptors (p < 0.018). In conclusion, the increased glutamate receptors in PD models were down-regulated by GVS, and the plastic modulation mainly occurred through NMDA receptor in VN.

How Does the Central Nervous System for Posture and Locomotion Cope With Damage-Induced Neural Asymmetry?

In most vertebrates, posture and locomotion are achieved by a biomechanical apparatus whose effectors are symmetrically positioned around the main body axis. Logically, motor commands to these effectors are intrinsically adapted to such anatomical symmetry, and the underlying sensory-motor neural networks are correspondingly arranged during central nervous system (CNS) development. However, many developmental and/or life accidents may alter such neural organization and acutely generate asymmetries in motor operation that are often at least partially compensated for over time. First, we briefly present the basic sensory-motor organization of posturo-locomotor networks in vertebrates. Next, we review some aspects of neural plasticity that is implemented in response to unilateral central injury or asymmetrical sensory deprivation in order to substantially restore symmetry in the control of posturo-locomotor functions. Data are finally discussed in the context of CNS structure-function relationship.

Stochastic and sinusoidal electrical stimuli increase the irregularity and gain of Type A and B medial vestibular nucleus neurons, in vitro

Galvanic vestibular stimulation (GVS) has been shown to improve vestibular function potentially via stochastic resonance, however, it remains unknown how central vestibular nuclei process these signals. In vivo work applying electrical stimuli to the vestibular apparatus of animals has shown changes in neuronal discharge at the level of the primary vestibular afferents and hair cells. This study aimed to determine the cellular impacts of stochastic, sinusoidal, and stochastic + sinusoidal stimuli on individual medial vestibular nucleus (MVN) neurons of male and female C57BL/6 mice. All stimuli increased the irregularity of MVN neuronal discharge, while differentially affecting neuronal gain. This suggests that the heterogeneous MVN neuronal population (marked by differential expression of ion channels), may influence the impact of electrical stimuli on neuronal discharge. Neuronal subtypes showed increased variability of neuronal firing, where Type A and B neurons experienced the largest gain changes in response to stochastic and sinusoidal stimuli. Type C neurons were the least affected regarding neuronal firing variability and gain changes. The membrane potential (MP) of neurons was altered by sinusoidal and stochastic + sinusoidal stimuli, with Type B and C neuronal MP significantly affected. These results indicate that GVS-like electrical stimuli impact MVN neuronal discharge differentially, likely as a result of heterogeneous ion channel expression.

Comparison of Activity-Based Home Program and Cawthorne-Cooksey Exercises in Patients With Chronic Unilateral Peripheral Vestibular Disorders

OBJECTIVE

This study aimed to investigate the effects of an activity-based home program and an exercise-based home program on dizziness severity, balance, and independent level of daily life activities in patients with dizziness due to chronic unilateral peripheral vestibular disorders.

DESIGN

A single-blind randomized controlled trial.

SETTING

University dizziness management clinics.

PARTICIPANTS

Individuals (N=75) between 18 and 65 years of age who had chronic unilateral peripheric vestibular disorders and vestibular rehabilitation indication.

INTERVENTION

Participants were randomly divided into 3 groups: an activity-based home program (group 1/activity group), an exercise-based home program (group 2/exercise group), and a control group (group 3). After an initial assessment, all groups participated in the patient education program. In addition, the activity-based home program was administered to the first group, while the Cawthorne-Cooksey home exercise program was administered to the second group.

MAIN OUTCOME MEASURES

Visual analog scale (VAS), Vestibular Disorders Activities of Daily Living Scale (VADL), and computerized dynamic posturography before and immediately after the treatment program.

RESULTS

A statistically significant improvement was found in the activity and exercise groups in terms of VAS, VADL, Sensory Organization Test (SOT) 5, SOT 6, and SOT (composite) scores compared with the control group (P<.05). A statistically significant improvement was found in the activity group in terms of the instrumental subscale of VADL, SOT 5, SOT 6, and SOT (composite) scores compared with the exercise group.

CONCLUSIONS

The activity-based home program was more effective in improving the home management task, the occupational task, and balance than the exercise-based home treatment program in patients with chronic peripheral vestibular disorders.