OBJECTIVES: Asymmetric or unilateral hearing loss (AHL) may cause irreversible changes in the processing of acoustic signals in the auditory system. We aim to provide a comprehensive view of the auditory processing abilities for subjects with acquired AHL, and to examine the influence of AHL on speech perception under difficult conditions, and on auditory temporal and intensity processing. DESIGN: We examined peripheral and central auditory functions for 25 subjects with AHL resulting from vestibular schwannoma, and compared them to those from 24 normal-hearing controls that were matched with the AHL subjects in mean age and hearing thresholds in the healthy ear. Besides the basic hearing threshold assessment, the tests comprised the detection of tones and gaps in a continuous noise, comprehension of speech in babble noise, binaural interactions, difference limen of intensity, and detection of frequency modulation. For the AHL subjects, the selected tests were performed separately for the healthy and diseased ear. RESULTS: We observed that binaural speech comprehension, gap detection, and frequency modulation detection abilities were dominated by the healthy ear and were comparable for both groups. The AHL subjects were less sensitive to interaural delays, however, they exhibited a higher sensitivity to sound level, as indicated by lower difference limen of intensity and a higher sensitivity to interaural intensity difference. Correlations between the individual test scores indicated that speech comprehension by the AHL subjects was associated with different auditory processing mechanisms than for the control subjects. CONCLUSIONS: The data suggest that AHL influences both peripheral and central auditory processing abilities and that speech comprehension under difficult conditions relies on different mechanisms for the AHL subjects than for normal-hearing controls.
- MeSH
- dospělí MeSH
- jednostranná nedoslýchavost * patofyziologie MeSH
- lidé středního věku MeSH
- lidé MeSH
- percepce řeči * fyziologie MeSH
- senioři MeSH
- sluchová percepce fyziologie MeSH
- sluchový práh * MeSH
- studie případů a kontrol MeSH
- vestibulární schwannom * patofyziologie komplikace MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
It has long been known that environmental conditions, particularly during development, affect morphological and functional properties of the brain including sensory systems; manipulating the environment thus represents a viable way to explore experience-dependent plasticity of the brain as well as of sensory systems. In this review, we summarize our experience with the effects of acoustically enriched environment (AEE) consisting of spectrally and temporally modulated complex sounds applied during first weeks of the postnatal development in rats and compare it with the related knowledge from the literature. Compared to controls, rats exposed to AEE showed in neurons of several parts of the auditory system differences in the dendritic length and in number of spines and spine density. The AEE exposure permanently influenced neuronal representation of the sound frequency and intensity resulting in lower excitatory thresholds, increased frequency selectivity and steeper rate-intensity functions. These changes were present both in the neurons of the inferior colliculus and the auditory cortex (AC). In addition, the AEE changed the responsiveness of AC neurons to frequency modulated, and also to a lesser extent, amplitude-modulated stimuli. Rearing rat pups in AEE leads to an increased reliability of acoustical responses of AC neurons, affecting both the rate and the temporal codes. At the level of individual spikes, the discharge patterns of individual neurons show a higher degree of similarity across stimulus repetitions. Behaviorally, rearing pups in AEE resulted in an improvement in the frequency resolution and gap detection ability under conditions with a worsened stimulus clarity. Altogether, the results of experiments show that the exposure to AEE during the critical developmental period influences the frequency and temporal processing in the auditory system, and these changes persist until adulthood. The results may serve for interpretation of the effects of the application of enriched acoustical environment in human neonatal medicine, especially in the case of care for preterm born children.
- MeSH
- akustická stimulace * MeSH
- akustika MeSH
- colliculus inferior růst a vývoj fyziologie MeSH
- krysa rodu rattus MeSH
- lidé MeSH
- neurony fyziologie MeSH
- neuroplasticita * fyziologie MeSH
- novorozená zvířata MeSH
- sluchová dráha * růst a vývoj fyziologie MeSH
- sluchová percepce MeSH
- sluchové korové centrum * růst a vývoj fyziologie MeSH
- věkové faktory MeSH
- životní prostředí MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
INTRODUCTION: Aging negatively influences the structure of the human brain including the white matter. The objective of our study was to identify, using fixel-based morphometry, the age induced changes in the pathways connecting several regions of the central auditory system (inferior colliculus, Heschl's gyrus, planum temporale) and the pathways connecting these structures with parts of the limbic system (anterior insula, hippocampus and amygdala). In addition, we were interested in the extent to which the integrity of these pathways is influenced by hearing loss and tinnitus. METHODS: Tractographic data were acquired using a 3 T MRI in 79 volunteers. The participants were categorized into multiple groups in accordance with their age, auditory thresholds and tinnitus status. Fixel-based analysis was utilized to identify alterations in the subsequent three parameters: logarithm of fiber cross-section, fiber density, fiber density and cross-section. Two modes of analysis were used: whole brain analysis and targeted analysis using fixel mask, corresponding to the pathways connecting the aforementioned structures. RESULTS: A significantly negative effect of aging was present for all fixel-based metrics, namely the logarithm of the fiber cross-section, (7 % fixels in whole-brain, 14% fixels in fixel mask), fiber density (5 % fixels in whole-brain, 15% fixels in fixel mask), fiber density and cross section (7 % fixels in whole-brain, 19% fixels in fixel mask). Expressed age-related losses, exceeding 30% fixels, were particularly present in pathways connecting the auditory structures with limbic structures. The effect of hearing loss and/or tinnitus did not reach significance. CONCLUSIONS: Our results show that although an age-related reduction of fibers is present in pathways connecting several auditory regions, the connections of these structures with limbic structures are even more reduced. To what extent this fact influences the symptoms of presbycusis, such as decreased speech comprehension, especially in noise conditions, remains to be elucidated.
- Publikační typ
- časopisecké články MeSH
Presbycusis and tinnitus are the two most common hearing related pathologies. Although both of these conditions presumably originate in the inner ear, there are several reports concerning their central components. Interestingly, the onset of presbycusis coincides with the highest occurrence of tinnitus. The aim of this study was to identify age, hearing loss, and tinnitus related functional changes, within the auditory system and its associated structures. Seventy-eight participants were selected for the study based on their age, hearing, and tinnitus, and they were divided into six groups: young controls (Y-NH-NT), subjects with mild presbycusis (O-NH-NT) or expressed presbycusis (O-HL-NT), young subjects with tinnitus (Y-NH-T), subjects with mild presbycusis and tinnitus (O-NH-T), and subjects with expressed presbycusis and tinnitus (O-HL-T). An MRI functional study was performed with a 3T MRI system, using an event related design (different types of acoustic and visual stimulations and their combinations). The amount of activation of the auditory cortices (ACs) was dependent on the complexity of the stimuli; higher complexity resulted in a larger area of the activated cortex. Auditory stimulation produced a slightly greater activation in the elderly, with a negative effect of hearing loss (lower activation). The congruent audiovisual stimulation led to an increased activity within the default mode network, whereas incongruent stimulation led to increased activation of the visual cortex. The presence of tinnitus increased activation of the AC, specifically in the aged population, with a slight prevalence in the left AC. The occurrence of tinnitus was accompanied by increased activity within the insula and hippocampus bilaterally. Overall, we can conclude that expressed presbycusis leads to a lower activation of the AC, compared to the elderly with normal hearing; aging itself leads to increased activity in the right AC. The complexity of acoustic stimuli plays a major role in the activation of the AC, its support by visual stimulation leads to minimal changes within the AC. Tinnitus causes changes in the activity of the limbic system, as well as in the auditory AC, where it is bound to the left hemisphere.
- Publikační typ
- časopisecké články MeSH
AUT00063 and AUT00202 are novel pharmaceutical modulators of the Kv3 subfamily of voltage-gated K+ channels. Kv3.1 channels, which control fast firing of many central auditory neurons, have been shown to decline with age and this may contribute to age-related deficits in central auditory processing. In the present study, the effects of the two novel compounds that specifically modulate Kv3 channels on auditory temporal processing were examined in aged (19-25-month-old) and young-adult (3-5 month-old) Fischer 344 rats (F344) using a behavioral gap-prepulse inhibition (gap-PPI) paradigm. The acoustic startle response (ASR) and its inhibition induced by a gap in noise were measured before and after drug administration. Hearing thresholds in tested rats were evaluated by the auditory brainstem response (ABR). Aged F344 rats had significantly higher ABR thresholds, lower amplitudes of ASR, and weaker gap-PPI compared with young-adult rats. No influence of AUT00063 and AUT00202 administration was observed on ABR hearing thresholds in rats of both age groups. AUT00063 and AUT00202 had suppressive effect on ASR of F344 rats that was more pronounced with AUT00063. The degree of suppression depended on the dose and age of the rats. Both compounds significantly improved the gap-PPI performance in gap detection tests in aged rats. These results indicate that AUT00063 and AUT00202 may influence intrinsic firing properties of neurons in the central auditory system of aged animals and have the potential to treat aged-related hearing disorders.
- MeSH
- akustická stimulace MeSH
- draslíkové kanály Shaw MeSH
- krysa rodu rattus MeSH
- potkani inbrední F344 MeSH
- prepulsní inhibice MeSH
- sluchová percepce * MeSH
- sluchové kmenové evokované potenciály * MeSH
- sluchový práh MeSH
- úleková reakce MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- lidé MeSH
- presbyakuze * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- úvodní články MeSH
- úvodníky MeSH
Previous experiments have acknowledged that inappropriate or missing auditory inputs during the critical period of development cause permanent changes of the structure and function of the auditory system (Bures et al., 2017). We explore in this study how developmental noise exposure influences the coding of temporally structured stimuli in the neurons of the primary auditory cortex (AC) in Long Evans rats. The animals were exposed on postnatal day 14 (P14) for 12 minutes to a loud (125 dB SPL) broad-band noise. The responses to an amplitude-modulated (AM) noise, frequency-modulated (FM) tones, and click trains, were recorded from the right AC of rats of two age groups: young-adult (ca. 6 months old) and adult (ca. 2 years old), both in the exposed animals and in control unexposed rats. The neonatal exposure resulted in a higher synchronization ability (phase-locking) of the AC neurons for all three stimuli; furthermore, the similarity of neuronal response patterns to repetitive stimulation was higher in the exposed rats. On the other hand, the exposed animals showed a steeper decline of modulation-transfer functions towards higher modulation frequencies/repetition rates. Differences between the two age groups were also apparent; in general, aging had qualitatively the same effect as the developmental exposure. The current results demonstrate that brief noise exposure during the maturation of the auditory system influences both the temporal and the rate coding of periodically modulated sounds in the AC of rats; the changes are permanent and observable up to late adulthood.
- MeSH
- akustická stimulace MeSH
- hluk škodlivé účinky MeSH
- krysa rodu rattus MeSH
- potkani Long-Evans MeSH
- sluchová percepce MeSH
- sluchové korové centrum * MeSH
- vnímání času MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Age-related hearing loss is manifested primarily by a decreased sensitivity to faint sounds, that is, by elevation of the hearing thresholds. Nevertheless, aging also affects the ability of the auditory system to process temporal parameters of the sound stimulus. To explore the precision and reliability of auditory temporal processing during aging, responses to several types of sound stimuli were recorded from neurons of the auditory cortex (AC) of young and aged anaesthetized Fischer 344 rats. In response to broad-band noise bursts, the aged rats exhibited larger response magnitudes, a higher proportion of monotonic units, and also a larger variability of response magnitudes, suggesting a lower stability of the rate code. Of primary interest were the responses to temporally structured stimuli (amplitude-modulated (AM) noise, frequency-modulated (FM) tones, and click trains) recorded separately in the right and left AC. Significant differences of temporal processing were already found between the neuronal responses in the left and right AC in the young animals: for the click trains, the left hemisphere exhibited a greater responsiveness to higher repetition rates, lower vector strength values, and a lower similarity of responses. The two hemispheres were also affected differently by aging. In the right hemisphere, neurons in the aged animals displayed worse synchronization with the AM noise and clicks, but better synchronization with the FM tone. In the left hemisphere, neuronal synchronization with the stimulus modulation improved at a higher age for all three stimuli. The results show that the ability of the aging auditory system to process temporal parameters of the stimulus strongly depends on the stimulus type and on laterality. Furthermore, the commonly reported age-related decline in the temporal processing ability cannot be regarded as general as, at least at the neuronal level in the AC, objective measures of the temporal representation often exhibit age-related improvement instead of deterioration.
We used two-photon calcium imaging with single-cell and cell-type resolution. Fear conditioning induced heterogeneous tuning shifts at single-cell level in the auditory cortex, with shifts both to CS+ frequency and to the control CS- stimulus frequency. We thus extend the view of simple expansion of CS+ tuned regions. Instead of conventional freezing reactions only, we observe selective orienting responses towards the conditioned stimuli. The orienting responses were often followed by escape behavior.
- MeSH
- akustická stimulace MeSH
- chování zvířat MeSH
- elektrický šok MeSH
- interneurony fyziologie MeSH
- klasické podmiňování fyziologie MeSH
- myši inbrední C57BL MeSH
- myši MeSH
- neuroplasticita fyziologie MeSH
- sluchové korové centrum fyziologie MeSH
- strach psychologie MeSH
- učení fyziologie MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
The LIM homeodomain transcription factor ISL1 is essential for the different aspects of neuronal development and maintenance. In order to study the role of ISL1 in the auditory system, we generated a transgenic mouse (Tg) expressing Isl1 under the Pax2 promoter control. We previously reported a progressive age-related decline in hearing and abnormalities in the inner ear, medial olivocochlear system, and auditory midbrain of these Tg mice. In this study, we investigated how Isl1 overexpression affects sound processing by the neurons of the inferior colliculus (IC). We recorded extracellular neuronal activity and analyzed the responses of IC neurons to broadband noise, clicks, pure tones, two-tone stimulation and frequency-modulated sounds. We found that Tg animals showed a higher inhibition as displayed by two-tone stimulation; they exhibited a wider dynamic range, lower spontaneous firing rate, longer first spike latency and, in the processing of frequency modulated sounds, showed a prevalence of high-frequency inhibition. Functional changes were accompanied by a decreased number of calretinin and parvalbumin positive neurons, and an increased expression of vesicular GABA/glycine transporter and calbindin in the IC of Tg mice, compared to wild type animals. The results further characterize abnormal sound processing in the IC of Tg mice and demonstrate that major changes occur on the side of inhibition.
- MeSH
- colliculus inferior metabolismus fyziologie MeSH
- exprese genu genetika MeSH
- lidé MeSH
- mozek fyziologie MeSH
- myši transgenní MeSH
- myši MeSH
- neurony fyziologie MeSH
- promotorové oblasti (genetika) genetika MeSH
- proteiny s homeodoménou LIM genetika metabolismus MeSH
- sluch MeSH
- sluchová percepce genetika fyziologie MeSH
- sluchové kmenové evokované potenciály fyziologie MeSH
- sluchový práh fyziologie MeSH
- transkripční faktor PAX2 genetika MeSH
- transkripční faktory genetika metabolismus MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- myši MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
