scholarly journals Neural Plastic Changes in the Subcortical Auditory Neural Pathway after Single-Sided Deafness in Adult Mice: A MEMRI Study

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
So Young Kim ◽  
Hwon Heo ◽  
Doo Hee Kim ◽  
Hyun Jin Kim ◽  
Seung-ha Oh
Keyword(s):  
Medial Geniculate Body ◽  
Neural System ◽  
Contralateral Side ◽  
Superior Olivary Complex ◽  
Control Group ◽  
Adult Mice ◽  
Medial Geniculate ◽  
Plastic Changes ◽  
Interaural Differences ◽  
Single Sided Deafness

Single-sided deafness (SSD) induces cortical neural plastic changes according to duration of deafness. However, it is still unclear how the auditory cortical changes accompany the subcortical neural changes. The present study aimed to find the neural plastic changes in the cortical and subcortical auditory system following adult-onset single-sided deafness (SSD) using Mn-enhanced magnetic resonance imaging (MEMRI). B57BL/6 mice (postnatal 8-week-old) were divided into three groups: the SSD-4-week group (postnatal 12-week-old, n = 11), the SSD-8-week group (postnatal 16-week-old, n = 11), and a normal-hearing control group (postnatal 8-week-old, n = 9). The left cochlea was ablated in the SSD groups. White Gaussian noise was delivered for 24 h before MEMRI acquisition. T1-weighted MRI data were analyzed from the cochlear nucleus (CN), superior olivary complex (SOC), lateral lemniscus (LL), inferior colliculus (IC), medial geniculate body (MG), and auditory cortex (AC). The differences in relative Mn2+-enhanced signal intensities (Mn2+SI) and laterality were analyzed between the groups. Four weeks after the SSD procedure, the ipsilateral side of the SSD showed significantly lower Mn2+SI in the CN than the control group. On the other hand, the contralateral side of the SSD demonstrated significantly lower Mn2+SI in the SOC, LL, and IC. These decreased Mn2+SI values were partially recovered at 8 weeks after the SSD procedure. The interaural Mn2+SI differences representing the interaural dominance were highest in CN and then became less prominently higher in the auditory neural system. The SSD-8-week group still showed interaural differences in the CN, LL, and IC. In contrast, the MG and AC did not show any significant intergroup or interaural differences in Mn2+SI. In conclusion, subcortical auditory neural activities were decreased after SSD, and the interaural differences were diluted in the higher auditory nervous system. These findings were attenuated with time. Subcortical auditory neural changes after SSD may contribute to the change in tinnitus severity and the outcomes of cochlear implantation in SSD patients.

scholarly journals Three-dimensional assessment of enamel and dentine in mouse molar teeth during masseter muscle hypofunction

2019 ◽  
Vol 26 (2) ◽  
pp. 30-37 ◽  
Author(s):  
Julián Balanta-Melo ◽  
Maximilian Bemmann ◽  
Viviana Toro Ibacache ◽  
Kornelius Kupczik ◽  
Sonja Buvinic
Keyword(s):  
Root Length ◽  
Ex Vivo ◽  
Botulinum Toxin Type A ◽  
Three Dimensional ◽  
Botulinum Toxin Type ◽  
Contralateral Side ◽  
Control Group ◽  
Adult Mice ◽  
Molar Teeth ◽  
The Right

Background: Mouse molar is a widely used model for teeth development. However, the effect of masticatory function on enamel and dentine in adult individuals remains poorly understood. As reported, the unilateral masseter hypofunction induced by botulinum toxin type A (BoNTA) resulted in mandibular bone damage and signs of unilateral chewing in adult mice. Objective: We aimed to assess the amount of enamel and dentine in the first molar (M1) during the unilateral masseter hypofunction in mice, using high-resolution X-ray microtomography (μCT) as threedimensional approach. Materials and methods: Mandibles of adult BALB/c mice, located either in a Control-group (without intervention) or a BoNTA-group, were ex-vivo scanned using μCT. Treated individuals received each one BoNTA intervention in the right masseter, and saline solution in the left masseter (intra-individual control). Enamel and dentine from M1 were segmented, and volume, thickness and mesial root length were quantified. Results: Enamel volume from treated side resulted unchanged after 2 weeks of unilateral masseter hypofunction. No differences for enamel volume were found between both sides of control individuals, and between these and samples from hypofunctional side in BoNTA-group. Enamel volume from saline-injected side was reduced when compared with experimental side (p<0,01). No differences in dentine volume, thickness of enamel and dentine, and mesial root length were found for any group. Conclusion: The amount of enamel in hypofunctional molars remains unaffected after unilateral BoNTA intervention in the masseter, but contralateral side showed reduced enamel volume. Therefore, increased functional wearing during unilateral chewing after BoNTA intervention should be considered.

scholarly journals Noise-induced neurophysiological alterations in the rat medial geniculate body and thalamocortical desynchronization by deep brain stimulation

2021 ◽  
Author(s):  
Gusta van Zwieten ◽  
Mark J. Roberts ◽  
Frédéric LVW Schaper ◽  
Jasper V Smit ◽  
Yasin Temel ◽  
...  
Keyword(s):  
Deep Brain Stimulation ◽  
Brain Stimulation ◽  
High Frequency ◽  
Noise Exposure ◽  
Medial Geniculate Body ◽  
Single Units ◽  
Control Group ◽  
Sprague Dawley ◽  
Medial Geniculate ◽  
Deep Brain

The thalamic medial geniculate body (MGB) is uniquely positioned within the neural tinnitus networks. Deep brain stimulation (DBS) of the MGB has been proposed as a possible novel treatment for tinnitus, yet mechanisms remain elusive. The aim of this study was to characterize neurophysiologic hallmarks in the MGB after noise-exposure and to assess the neurophysiological effects of electrical stimulation of the MGB. Fourteen male Sprague Dawley rats were included. Nine subjects were unilaterally exposed to a 16 kHz octave-band noise at 115 dB for 90 minutes, five received sham exposure. Single units were recorded from the contralateral MGB where spontaneous firing, coefficient of variation, response type, rate-level functions and thresholds were determined. Local field potentials and electroencephalographical (EEG) recordings were performed before and after high frequency DBS of the MGB. Thalamocortical synchronization and power were analyzed. In total, 214 single units were identified (n = 145 in noise-exposed group, n = 69 in control group). After noise-exposure, fast-responding neurons become less- or non-responsive without change to their spontaneous rate, while sustained and suppressed type neurons exhibit enhanced spontaneous activity without change to their stimulus driven activity. MGB DBS suppressed thalamocortical synchronization in the beta and gamma bands, supporting suppression of thalamocortical synchronization as an underlying mechanism of tinnitus suppression by high frequency DBS. These findings contribute to our understanding of the neurophysiologic consequences of noise-exposure and the mechanism of potential DBS therapy for tinnitus.

Efferent Innervation to the Cochlea

2018 ◽  
pp. 58-94
Author(s):  
Ana Belén Elgoyhen ◽  
Carolina Wedemeyer ◽  
Mariano N. Di Guilmi
Keyword(s):  
Auditory System ◽  
Cochlear Nucleus ◽  
Medial Geniculate Body ◽  
Superior Olivary Complex ◽  
Auditory Neurons ◽  
Olivocochlear System ◽  
System P ◽  
Medial Geniculate ◽  
Central Auditory Neurons ◽  
The Brain

The auditory system consists of ascending and descending neuronal pathways. The best studied is the ascending pathway, whereby sounds that are transduced in the cochlea into electrical signals are sent to the brain via the auditory nerve. Before reaching the auditory cortex, auditory ascending information has several central relays: the cochlear nucleus and superior olivary complex in the brainstem, the lateral lemniscal nuclei and inferior colliculus in the midbrain, and the medial geniculate body in the thalamus. The function(s) of the descending corticofugal pathway is less well understood. It plays important roles in shaping or even creating the response properties of central auditory neurons and in the plasticity of the auditory system, such as reorganizing cochleotopic and computational maps. Corticofugal projections are present at different relays of the auditory system. This review focuses on the physiology and plasticity of the medial efferent olivocochlear system.

The Effect of Nonlinear Amplitude Growth on the Speech Perception Benefits Provided by a Single-Sided Vocoder

2019 ◽  
Vol 62 (3) ◽  
pp. 745-757 ◽  
Author(s):  
Jessica M. Wess ◽  
Joshua G. W. Bernstein
Keyword(s):  
Transfer Functions ◽  
Spatial Configuration ◽  
Free Field ◽  
Spatial Separation ◽  
Compression And Expansion ◽  
Interaural Difference ◽  
Interaural Differences ◽  
Single Sided Deafness ◽  
Perceptual Separation ◽  
Loudness Growth

PurposeFor listeners with single-sided deafness, a cochlear implant (CI) can improve speech understanding by giving the listener access to the ear with the better target-to-masker ratio (TMR; head shadow) or by providing interaural difference cues to facilitate the perceptual separation of concurrent talkers (squelch). CI simulations presented to listeners with normal hearing examined how these benefits could be affected by interaural differences in loudness growth in a speech-on-speech masking task.MethodExperiment 1 examined a target–masker spatial configuration where the vocoded ear had a poorer TMR than the nonvocoded ear. Experiment 2 examined the reverse configuration. Generic head-related transfer functions simulated free-field listening. Compression or expansion was applied independently to each vocoder channel (power-law exponents: 0.25, 0.5, 1, 1.5, or 2).ResultsCompression reduced the benefit provided by the vocoder ear in both experiments. There was some evidence that expansion increased squelch in Experiment 1 but reduced the benefit in Experiment 2 where the vocoder ear provided a combination of head-shadow and squelch benefits.ConclusionsThe effects of compression and expansion are interpreted in terms of envelope distortion and changes in the vocoded-ear TMR (for head shadow) or changes in perceived target–masker spatial separation (for squelch). The compression parameter is a candidate for clinical optimization to improve single-sided deafness CI outcomes.

Cell types and response properties of neurons in the ventral division of the medial geniculate body of the rabbit

2002 ◽  
Vol 445 (1) ◽  
pp. 78-96 ◽  
Author(s):  
Justin S. Cetas ◽  
Robin O. Price ◽  
David S. Velenovsky ◽  
Jennifer J. Crowe ◽  
Donal G. Sinex ◽  
...  
Keyword(s):  
Medial Geniculate Body ◽  
Cell Types ◽  
Response Properties ◽  
Medial Geniculate

scholarly journals Lack of WWC2 Protein Leads to Aberrant Angiogenesis in Postnatal Mice

2021 ◽  
Vol 22 (10) ◽  
pp. 5321
Author(s):  
Viktoria Constanze Brücher ◽  
Charlotte Egbring ◽  
Tanja Plagemann ◽  
Pavel I. Nedvetsky ◽  
Verena Höffken ◽  
...  
Keyword(s):  
Signalling Pathway ◽  
Control Group ◽  
Knock Out ◽  
Ocular Angiogenesis ◽  
Sprouting Angiogenesis ◽  
Adult Mice ◽  
Upstream Regulator ◽  
Knock Out Mice ◽  
Hippo Signalling

The WWC protein family is an upstream regulator of the Hippo signalling pathway that is involved in many cellular processes. We examined the effect of an endothelium-specific WWC1 and/or WWC2 knock-out on ocular angiogenesis. Knock-outs were induced in C57BL/6 mice at the age of one day (P1) and evaluated at P6 (postnatal mice) or induced at the age of five weeks and evaluated at three months of age (adult mice). We analysed morphology of retinal vasculature in retinal flat mounts. In addition, in vivo imaging and functional testing by electroretinography were performed in adult mice. Adult WWC1/2 double knock-out mice differed neither functionally nor morphologically from the control group. In contrast, the retinas of the postnatal WWC knock-out mice showed a hyperproliferative phenotype with significantly enlarged areas of sprouting angiogenesis and a higher number of tip cells. The branching and end points in the peripheral plexus were significantly increased compared to the control group. The deletion of the WWC2 gene was decisive for these effects; while knocking out WWC1 showed no significant differences. The results hint strongly that WWC2 is an essential regulator of ocular angiogenesis in mice. As an activator of the Hippo signalling pathway, it prevents excessive proliferation during physiological angiogenesis. In adult animals, WWC proteins do not seem to be important for the maintenance of the mature vascular plexus.

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