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Bureš Z, Svobodová Burianová J, Pysanenko K, Syka J. The effect of acoustically enriched environment on structure and function of the developing auditory system. Hear Res 2024; 453:109110. [PMID: 39278142 DOI: 10.1016/j.heares.2024.109110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 06/17/2024] [Accepted: 09/02/2024] [Indexed: 09/17/2024]
Abstract
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.
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Affiliation(s)
- Zbyněk Bureš
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Czech Academy of Sciences, Vídeňská 1083, 14220 Prague 4, Czech Republic; Department of Technical Studies, College of Polytechnics Jihlava, Tolstého 16, 58601, Jihlava, Czech Republic; Department of Otorhinolaryngology, Third Faculty of Medicine, University Hospital Královské Vinohrady, Charles University in Prague, Šrobárova 1150/50, 10034 Prague 10, Czech Republic.
| | - Jana Svobodová Burianová
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Czech Academy of Sciences, Vídeňská 1083, 14220 Prague 4, Czech Republic
| | - Kateryna Pysanenko
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Czech Academy of Sciences, Vídeňská 1083, 14220 Prague 4, Czech Republic
| | - Josef Syka
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Czech Academy of Sciences, Vídeňská 1083, 14220 Prague 4, Czech Republic
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Li Y, Zhang J. Binaural advantages in sound temporal information processing by neurons in the rat inferior colliculus. Front Neurosci 2023; 17:1308052. [PMID: 38125407 PMCID: PMC10731313 DOI: 10.3389/fnins.2023.1308052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 11/21/2023] [Indexed: 12/23/2023] Open
Abstract
Previous studies on the advantages of binaural hearing have long been focused on sound localization and spatial stream segregation. The binaural advantages have also been observed in speech perception in reverberation. Both human speech and animal vocalizations contain temporal features that are critical for speech perception and animal communication. However, whether there are binaural advantages for sound temporal information processing in the central auditory system has not been elucidated. Gap detection threshold (GDT), the ability to detect the shortest silent interval in a sound, has been widely used to measure the auditory temporal resolution. In the present study, we determined GDTs of rat inferior collicular neurons under both monaural and binaural hearing conditions. We found that the majority of the inferior collicular neurons in adult rats exhibited binaural advantages in gap detection, i.e., better neural gap detection ability in binaural hearing conditions compared to monaural hearing condition. However, this binaural advantage in sound temporal information processing was not significant in the inferior collicular neurons of P14-21 and P22-30 rats. Additionally, we also observed age-related changes in neural temporal acuity in the rat inferior colliculus. These results demonstrate a new advantage of binaural hearing (i.e., binaural advantage in temporal processing) in the central auditory system in addition to sound localization and spatial stream segregation.
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Affiliation(s)
| | - Jiping Zhang
- Key Laboratory of Brain Functional Genomics, Ministry of Education, NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai, School of Life Sciences, East China Normal University, Shanghai, China
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3
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Gay JD, Dangcil E, Nacipucha J, Botrous JE, Suresh N, Tucker A, Carayannopoulos NL, Khan MR, Meng R, Yao JD, Wackym PA, Mowery TM. An Animal Model of Neonatal Intensive Care Unit Exposure to Light and Sound in the Preterm Infant. Integr Comp Biol 2023; 63:585-596. [PMID: 37164937 PMCID: PMC10503467 DOI: 10.1093/icb/icad020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 04/19/2023] [Accepted: 04/21/2023] [Indexed: 05/12/2023] Open
Abstract
According to the World Health Organization, ∼15 million children are born prematurely each year. Many of these infants end up spending days to weeks in a neonatal intensive care unit (NICU). Infants who are born prematurely are often exposed to noise and light levels that affect their auditory and visual development. Children often have long-term impairments in cognition, visuospatial processing, hearing, and language. We have developed a rodent model of NICU exposure to light and sound using the Mongolian gerbil (Meriones unguiculatus), which has a low-frequency human-like audiogram and is altricial. To simulate preterm infancy, the eyes and ears were opened prematurely, and animals were exposed to the NICU-like sensory environment throughout the gerbil's cortical critical period of auditory development. After the animals matured into adults, auditory perceptual testing was carried out followed by auditory brainstem response recordings and then histology to assess the white matter morphology of various brain regions. Compared to normal hearing control animals, NICU sensory-exposed animals had significant impairments in learning at later stages of training, increased auditory thresholds reflecting hearing loss, and smaller cerebellar white matter volumes. These have all been reported in longitudinal studies of preterm infants. These preliminary results suggest that this animal model could provide researchers with an ethical way to explore the effects of the sensory environment in the NICU on the preterm infant's brain development.
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Affiliation(s)
- Jennifer D Gay
- Department of Otolaryngology—Head and Neck Surgery, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08854, USA
- Rutgers Brain Health Institute, New Brunswick, NJ, USA
| | - Evelynne Dangcil
- Department of Otolaryngology—Head and Neck Surgery, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08854, USA
| | - Jacqueline Nacipucha
- Department of Otolaryngology—Head and Neck Surgery, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08854, USA
| | - Jonathon E Botrous
- Department of Otolaryngology—Head and Neck Surgery, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08854, USA
| | - Nikhil Suresh
- Department of Otolaryngology—Head and Neck Surgery, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08854, USA
| | - Aaron Tucker
- Department of Otolaryngology—Head and Neck Surgery, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08854, USA
| | - Nicolas L Carayannopoulos
- Department of Otolaryngology—Head and Neck Surgery, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08854, USA
| | - Muhammad R Khan
- Department of Otolaryngology—Head and Neck Surgery, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08854, USA
| | - Raphael Meng
- Department of Otolaryngology—Head and Neck Surgery, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08854, USA
| | - Justin D Yao
- Department of Otolaryngology—Head and Neck Surgery, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08854, USA
- Rutgers Brain Health Institute, New Brunswick, NJ, USA
| | - P Ashley Wackym
- Department of Otolaryngology—Head and Neck Surgery, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08854, USA
- Rutgers Brain Health Institute, New Brunswick, NJ, USA
| | - Todd M Mowery
- Department of Otolaryngology—Head and Neck Surgery, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08854, USA
- Rutgers Brain Health Institute, New Brunswick, NJ, USA
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4
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Bures Z, Pysanenko K, Syka J. The influence of developmental noise exposure on the temporal processing of acoustical signals in the auditory cortex of rats. Hear Res 2021; 409:108306. [PMID: 34311267 DOI: 10.1016/j.heares.2021.108306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 06/01/2021] [Accepted: 06/30/2021] [Indexed: 11/19/2022]
Abstract
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.
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Affiliation(s)
- Zbynek Bures
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Czech Academy of Sciences, Vídeňská 1083, 14220 Prague 4, Czech Republic; Department of Cognitive Systems and Neurosciences, Czech Institute of Informatics, Robotics and Cybernetics, Czech Technical University, Jugoslávských partyzánů 1580/3, 160 00 Prague 6, Czech Republic.
| | - Kateryna Pysanenko
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Czech Academy of Sciences, Vídeňská 1083, 14220 Prague 4, Czech Republic
| | - Josef Syka
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Czech Academy of Sciences, Vídeňská 1083, 14220 Prague 4, Czech Republic
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Modifying the Adult Rat Tonotopic Map with Sound Exposure Produces Frequency Discrimination Deficits That Are Recovered with Training. J Neurosci 2020; 40:2259-2268. [PMID: 32024780 DOI: 10.1523/jneurosci.1445-19.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 12/04/2019] [Accepted: 12/06/2019] [Indexed: 11/21/2022] Open
Abstract
Frequency discrimination learning is often accompanied by an expansion of the functional region corresponding to the target frequency within the auditory cortex. Although the perceptual significance of this plastic functional reorganization remains debated, greater cortical representation is generally thought to improve perception for a stimulus. Recently, the ability to expand functional representations through passive sound experience has been demonstrated in adult rats, suggesting that it may be possible to design passive sound exposures to enhance specific perceptual abilities in adulthood. To test this hypothesis, we exposed adult female Long-Evans rats to 2 weeks of moderate-intensity broadband white noise followed by 1 week of 7 kHz tone pips, a paradigm that results in the functional over-representation of 7 kHz within the adult tonotopic map. We then tested the ability of exposed rats to identify 7 kHz among distractor tones on an adaptive tone discrimination task. Contrary to our expectations, we found that map expansion impaired frequency discrimination and delayed perceptual learning. Rats exposed to noise followed by 15 kHz tone pips were not impaired at the same task. Exposed rats also exhibited changes in auditory cortical responses consistent with reduced discriminability of the exposure tone. Encouragingly, these deficits were completely recovered with training. Our results provide strong evidence that map expansion alone does not imply improved perception. Rather, plastic changes in frequency representation induced by bottom-up processes can worsen perceptual faculties, but because of the very nature of plasticity these changes are inherently reversible.SIGNIFICANCE STATEMENT The potent ability of our acoustic environment to shape cortical sensory representations throughout life has led to a growing interest in harnessing both passive sound experience and operant perceptual learning to enhance mature cortical function. We use sound exposure to induce targeted expansions in the adult rat tonotopic map and find that these bottom-up changes unexpectedly impair performance on an adaptive tone discrimination task. Encouragingly, however, we also show that training promotes the recovery of electrophysiological measures of reduced neural discriminability following sound exposure. These results provide support for future neuroplasticity-based treatments that take into account both the sensory statistics of our external environment and perceptual training strategies to improve learning and memory in the adult auditory system.
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Wang X, Liu J, Zhang J. Chronic Unilateral Hearing Loss Disrupts Neural Tuning to Sound-Source Azimuth in the Rat Primary Auditory Cortex. Front Neurosci 2019; 13:477. [PMID: 31133797 PMCID: PMC6524417 DOI: 10.3389/fnins.2019.00477] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Accepted: 04/26/2019] [Indexed: 02/05/2023] Open
Abstract
Accurate sound localization requires normal binaural input and precise auditory neuronal representation of sound spatial locations. Previous studies showed that unilateral hearing loss profoundly impaired the sound localization abilities. However, the underlying neural mechanism is not fully understood. Here, we investigated how chronic unilateral conductive hearing loss (UCHL) affected the neural tuning to sound source azimuth in the primary auditory cortex (AI). The UCHL was manipulated by the removal of tympanic membrane and malleus in the right ear of young (P14) rats and adult (P57) rats. We recorded the azimuth tuning of neurons in the left AI contralateral to the operated ear in the two groups of rats that experienced 2 months of UCHL, and in the left AI of age-matched control rats. We found that AI neurons in control rats showed predominant preference to sound from contralateral azimuths. However, UCHL weakened the cortical neuronal representation of contralateral azimuths on the operated ear side and strengthened the cortical neuronal representation of ipsilateral azimuths on the intact ear side. This effect was stronger in rats with UCHL at young age than in rats with UCHL in adulthood. Moreover, UCHL degraded the azimuth selectivity and azimuth sensitivity of AI neurons, and this effect was stronger in rats with UCHL in adulthood than in rats with UCHL at young age. These findings highlight a remarkable age-related experience-dependent plasticity of neural tuning to sound source azimuth in AI, and imply a neural mechanism for the impacts of chronic UCHL on sound localization abilities.
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Affiliation(s)
- Xiuwen Wang
- Key Laboratory of Brain Functional Genomics, Ministry of Education, NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai, School of Life Sciences, East China Normal University, Shanghai, China
| | - Jing Liu
- Key Laboratory of Brain Functional Genomics, Ministry of Education, NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai, School of Life Sciences, East China Normal University, Shanghai, China
| | - Jiping Zhang
- Key Laboratory of Brain Functional Genomics, Ministry of Education, NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai, School of Life Sciences, East China Normal University, Shanghai, China
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7
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Wang F, Liu J, Zhang J. Early postnatal noise exposure degrades the stimulus-specific adaptation of neurons in the rat auditory cortex in adulthood. Neuroscience 2019; 404:1-13. [DOI: 10.1016/j.neuroscience.2019.01.064] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 01/09/2019] [Accepted: 01/30/2019] [Indexed: 12/11/2022]
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Acoustical Enrichment during Early Development Improves Response Reliability in the Adult Auditory Cortex of the Rat. Neural Plast 2018; 2018:5903720. [PMID: 30002673 PMCID: PMC5998158 DOI: 10.1155/2018/5903720] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 04/16/2018] [Accepted: 04/29/2018] [Indexed: 11/18/2022] Open
Abstract
It is well known that auditory experience during early development shapes response properties of auditory cortex (AC) neurons, influencing, for example, tonotopical arrangement, response thresholds and strength, or frequency selectivity. Here, we show that rearing rat pups in a complex acoustically enriched environment leads to an increased reliability of responses of AC neurons, affecting both the rate and the temporal codes. For a repetitive stimulus, the neurons exhibit a lower spike count variance, indicating a more stable rate coding. At the level of individual spikes, the discharge patterns of individual neurons show a higher degree of similarity across stimulus repetitions. Furthermore, the neurons follow more precisely the temporal course of the stimulus, as manifested by improved phase-locking to temporally modulated sounds. The changes are persistent and present up to adulthood. The results document that besides basic alterations of receptive fields presented in our previous study, the acoustic environment during the critical period of postnatal development also leads to a decreased stochasticity and a higher reproducibility of neuronal spiking patterns.
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Gao F, Chen L, Zhang J. Nonuniform impacts of forward suppression on neural responses to preferred stimuli and nonpreferred stimuli in the rat auditory cortex. Eur J Neurosci 2018; 47:1320-1338. [PMID: 29761576 DOI: 10.1111/ejn.13943] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 03/30/2018] [Accepted: 04/03/2018] [Indexed: 11/29/2022]
Abstract
In natural conditions, human and animals need to extract target sound information from noisy acoustic environments for communication and survival. However, how the contextual environmental sounds impact the tuning of central auditory neurons to target sound source azimuth over a wide range of sound levels is not fully understood. Here, we determined the azimuth-level response areas (ALRAs) of rat auditory cortex neurons by recording their responses to probe tones varying with levels and sound source azimuths under both quiet (probe alone) and forward masking conditions (preceding noise + probe). In quiet, cortical neurons responded stronger to their preferred stimuli than to their nonpreferred stimuli. In forward masking conditions, an effective preceding noise reduced the extents of the ALRAs and suppressed the neural responses across the ALRAs by decreasing the response strength and lengthening the first-spike latency. The forward suppressive effect on neural response strength was increased with increasing masker level and decreased with prolonging the time interval between masker and probe. For a portion of cortical neurons studied, the effects of forward suppression on the response strength to preferred stimuli was weaker than those to nonpreferred stimuli, and the recovery from forward suppression of the response strength to preferred stimuli was earlier than that to nonpreferred stimuli. We suggest that this nonuniform forward suppression of neural responses to preferred stimuli and to nonpreferred stimuli is important for cortical neurons to maintain their relative stable preferences for target sound source azimuth and level in noisy acoustic environments.
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Affiliation(s)
- Fei Gao
- Key Laboratory of Brain Functional Genomics, Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai, School of Life Sciences, East China Normal University, Shanghai, China
| | - Liang Chen
- Key Laboratory of Brain Functional Genomics, Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai, School of Life Sciences, East China Normal University, Shanghai, China
| | - Jiping Zhang
- Key Laboratory of Brain Functional Genomics, Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai, School of Life Sciences, East China Normal University, Shanghai, China
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Pysanenko K, Bureš Z, Lindovský J, Syka J. The Effect of Complex Acoustic Environment during Early Development on the Responses of Auditory Cortex Neurons in Rats. Neuroscience 2018; 371:221-228. [DOI: 10.1016/j.neuroscience.2017.11.049] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 11/29/2017] [Accepted: 11/30/2017] [Indexed: 01/12/2023]
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The effect of noise exposure during the developmental period on the function of the auditory system. Hear Res 2017; 352:1-11. [DOI: 10.1016/j.heares.2016.03.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 03/14/2016] [Indexed: 12/12/2022]
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12
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Brief Stimulus Exposure Fully Remediates Temporal Processing Deficits Induced by Early Hearing Loss. J Neurosci 2017; 37:7759-7771. [PMID: 28706081 DOI: 10.1523/jneurosci.0916-17.2017] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 06/24/2017] [Accepted: 07/08/2017] [Indexed: 12/30/2022] Open
Abstract
In childhood, partial hearing loss can produce prolonged deficits in speech perception and temporal processing. However, early therapeutic interventions targeting temporal processing may improve later speech-related outcomes. Gap detection is a measure of auditory temporal resolution that relies on the auditory cortex (ACx), and early auditory deprivation alters intrinsic and synaptic properties in the ACx. Thus, early deprivation should induce deficits in gap detection, which should be reflected in ACx gap sensitivity. We tested whether earplugging-induced, early transient auditory deprivation in male and female Mongolian gerbils caused correlated deficits in behavioral and cortical gap detection, and whether these could be rescued by a novel therapeutic approach: brief exposure to gaps in background noise. Two weeks after earplug removal, animals that had been earplugged from hearing onset throughout auditory critical periods displayed impaired behavioral gap detection thresholds (GDTs), but this deficit was fully reversed by three 1 h sessions of exposure to gaps in noise. In parallel, after earplugging, cortical GDTs increased because fewer cells were sensitive to short gaps, and gap exposure normalized this pattern. Furthermore, in deprived animals, both first-spike latency and first-spike latency jitter increased, while spontaneous and evoked firing rates decreased, suggesting that deprivation causes a wider range of perceptual problems than measured here. These cortical changes all returned to control levels after gap exposure. Thus, brief stimulus exposure, perhaps in a salient context such as the unfamiliar placement into a testing apparatus, rescued impaired gap detection and may have potential as a remediation tool for general auditory processing deficits.SIGNIFICANCE STATEMENT Hearing loss in early childhood leads to impairments in auditory perception and language processing that can last well beyond the restoration of hearing sensitivity. Perceptual deficits can be improved by training, or by acoustic enrichment in animal models, but both approaches involve extended time and effort. Here, we used a novel remediation technique, brief periods of auditory stimulus exposure, to fully remediate cortical and perceptual deficits in gap detection induced by early transient hearing loss. This technique also improved multiple cortical response properties. Rescue by this efficient exposure regime may have potential as a therapeutic tool to remediate general auditory processing deficits in children with perceptual challenges arising from early hearing loss.
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Abstract
UNLABELLED High temporal acuity of auditory processing underlies perception of speech and other rapidly varying sounds. A common measure of auditory temporal acuity in humans is the threshold for detection of brief gaps in noise. Gap-detection deficits, observed in developmental disorders, are considered evidence for "sluggish" auditory processing. Here we show, in a mouse model of gap-detection deficits, that auditory brain sensitivity to brief gaps in noise can be impaired even without a general loss of central auditory temporal acuity. Extracellular recordings in three different subdivisions of the auditory thalamus in anesthetized mice revealed a stimulus-specific, subdivision-specific deficit in thalamic sensitivity to brief gaps in noise in experimental animals relative to controls. Neural responses to brief gaps in noise were reduced, but responses to other rapidly changing stimuli unaffected, in lemniscal and nonlemniscal (but not polysensory) subdivisions of the medial geniculate body. Through experiments and modeling, we demonstrate that the observed deficits in thalamic sensitivity to brief gaps in noise arise from reduced neural population activity following noise offsets, but not onsets. These results reveal dissociable sound-onset-sensitive and sound-offset-sensitive channels underlying auditory temporal processing, and suggest that gap-detection deficits can arise from specific impairment of the sound-offset-sensitive channel. SIGNIFICANCE STATEMENT The experimental and modeling results reported here suggest a new hypothesis regarding the mechanisms of temporal processing in the auditory system. Using a mouse model of auditory temporal processing deficits, we demonstrate the existence of specific abnormalities in auditory thalamic activity following sound offsets, but not sound onsets. These results reveal dissociable sound-onset-sensitive and sound-offset-sensitive mechanisms underlying auditory processing of temporally varying sounds. Furthermore, the findings suggest that auditory temporal processing deficits, such as impairments in gap-in-noise detection, could arise from reduced brain sensitivity to sound offsets alone.
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Green DB, Ohlemacher J, Rosen MJ. Benefits of Stimulus Exposure: Developmental Learning Independent of Task Performance. Front Neurosci 2016; 10:263. [PMID: 27378837 PMCID: PMC4911416 DOI: 10.3389/fnins.2016.00263] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 05/24/2016] [Indexed: 12/22/2022] Open
Abstract
Perceptual learning (training-induced performance improvement) can be elicited by task-irrelevant stimulus exposure in humans. In contrast, task-irrelevant stimulus exposure in animals typically disrupts perception in juveniles while causing little to no effect in adults. This may be due to the extent of exposure, which is brief in humans while chronic in animals. Here we assessed the effects of short bouts of passive stimulus exposure on learning during development in gerbils, compared with non-passive stimulus exposure (i.e., during testing). We used prepulse inhibition of the acoustic startle response, a method that can be applied at any age, to measure gap detection thresholds across four age groups, spanning development. First, we showed that both gap detection thresholds and gap detection learning across sessions displayed a long developmental trajectory, improving throughout the juvenile period. Additionally, we demonstrated larger within- and across-animal performance variability in younger animals. These results are generally consistent with results in humans, where there are extended developmental trajectories for both the perception of temporally-varying signals, and the effects of perceptual training, as well as increased variability and poorer performance consistency in children. We then chose an age (mid-juveniles) that displayed clear learning over sessions in order to assess effects of brief passive stimulus exposure on this learning. We compared learning in mid-juveniles exposed to either gap detection testing (gaps paired with startles) or equivalent gap exposure without testing (gaps alone) for three sessions. Learning was equivalent in both these groups and better than both naïve age-matched animals and controls receiving no gap exposure but only startle testing. Thus, short bouts of exposure to gaps independent of task performance is sufficient to induce learning at this age, and is as effective as gap detection testing.
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Affiliation(s)
| | | | - Merri J. Rosen
- Department of Anatomy and Neurobiology, Northeast Ohio Medical UniversityRootstown, OH, USA
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15
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Noise exposure of immature rats can induce different age-dependent extra-auditory alterations that can be partially restored by rearing animals in an enriched environment. Brain Res 2016; 1636:52-61. [PMID: 26851548 DOI: 10.1016/j.brainres.2016.01.050] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Revised: 12/29/2015] [Accepted: 01/27/2016] [Indexed: 02/01/2023]
Abstract
It has been previously shown that different extra-auditory alterations can be induced in animals exposed to noise at 15 days. However, data regarding exposure of younger animals, that do not have a functional auditory system, have not been obtained yet. Besides, the possibility to find a helpful strategy to restore these changes has not been explored so far. Therefore, the aims of the present work were to test age-related differences in diverse hippocampal-dependent behavioral measurements that might be affected in noise-exposed rats, as well as to evaluate the effectiveness of a potential neuroprotective strategy, the enriched environment (EE), on noise-induced behavioral alterations. Male Wistar rats of 7 and 15 days were exposed to moderate levels of noise for two hours. At weaning, animals were separated and reared either in standard or in EE cages for one week. At 28 days of age, different hippocampal-dependent behavioral assessments were performed. Results show that rats exposed to noise at 7 and 15 days were differentially affected. Moreover, EE was effective in restoring all altered variables when animals were exposed at 7 days, while a few were restored in rats exposed at 15 days. The present findings suggest that noise exposure was capable to trigger significant hippocampal-related behavioral alterations that were differentially affected, depending on the age of exposure. In addition, it could be proposed that hearing structures did not seem to be necessarily involved in the generation of noise-induced hippocampal-related behaviors, as they were observed even in animals with an immature auditory pathway. Finally, it could be hypothesized that the differential restoration achieved by EE rearing might also depend on the degree of maturation at the time of exposure and the variable evaluated, being younger animals more susceptible to environmental manipulations.
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