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<p> We undertook a detailed analysis of population spike rate and LFP power in the Zebra finch auditory system. Utilizing the full range of Zebra finch vocalizations and dual-hemisphere multielectrode recordings from auditory neurons, we used encoder models to show how intuitive acoustic features such as amplitude, spectral shape and pitch drive the spike rate of individual neurons and LFP power on electrodes. Using ensemble decoding approaches, we show that these acoustic features can be successfully decoded from the population spike rate vector and the power spectra of the multielectrode LFP with comparable performance. In addition we found that adding pairwise spike synchrony to the spike rate decoder boosts performance above that of the population spike rate alone, or LFP power spectra. We also found that decoder performance grows quickly with the addition of more neurons, but there is notable redundancy in the population code. Finally, we demonstrate that LFP power on an electrode can be well predicted by population spike rate and spike synchrony. High frequency LFP power (80-190Hz) integrates neural activity spatially over a distance of up to 250 microns, while low frequency LFP power (0-30Hz) can integrate neural activity originating up to 800 microns away from the recording electrode. </p><p> To understand how an auditory system processes complex sounds, it is essential to understand how the temporal envelope of sounds, i.e. the time-varying amplitude, is encoded by neural activity. We studied the temporal envelope of Zebra finch vocalizations, and show that it exhibits modulations in the 0-30Hz range, similar to human speech. We then built linear filter models to predict 0-30Hz LFP activity from the temporal envelopes of vocalizations, achieving surprisingly high performance for electrodes near thalamorecipient areas of Zebra finch auditory cortex. We then show that there are two spatially-distinct subnetworks that resonate at different frequency bands, one subnetwork that resonates around 19Hz, and another subnetwork that resonates at 14Hz. These two subnetworks are present in every anatomical region. Finally we show that we can improve predictive performance with recurrent neural network models. </p>

<p>King-Kopetzkys syndrom (KKS) beskrivs som när en person upplever svårigheter med att uppfatta tal, speciellt i bullriga miljöer, men har normala tontrösklar. Orsaken till syndromet är fortfarande oviss och detta gör att de som jobbar inom hörselvården ställs inför ett val då de möter dessa patienter. Patienten kan antingen avfärdas då denne anses höra normalt, eller så tas problemet på allvar och vidare utredning utförs.</p><p>Genom att göra en systematisk litteraturstudie belyses och förklaras syndromet och syftet har varit att göra en sammanställning och ge en översikt över KKS utifrån de vetenskapliga artiklar som berör ämnet. Målet med detta arbete är att öka förståelsen för KKS.</p><p>Resultatet pekar på att det är fler kvinnor än män som drabbas och att medelåldern för de med syndromet är ganska låg, runt 32 år. Det finns många olika teorier till orsaken och ingen är i dagsläget mer rätt än den andra. Detsamma gäller mätningar som använts för att försöka utreda syndromet, här framkommer många olika förslag på vägen till diagnostisering. Slutsatsen som dras är att mer forskning kring ämnet är nödvändigt för att få en förklaring och ett tillvägagångssätt för diagnostisering av syndromet.</p>

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<p>Normal audiometric thresholds following noise exposure have generally been considered as an indication of a recovered cochlea and intact peripheral auditory system, yet recent animal work has challenged this classic assumption. Moderately noise-exposed animals have been shown to have permanent loss of synapses on inner hair cells (IHCs) and permanent damage to auditory nerve fibers (ANFs), specifically the low-spontaneous rate fibers (low-SR), despite normal electrophysiological thresholds. Loss of cochlear synapses, known as cochlear synaptopathy, disrupts auditory-nerve signaling, which may result in perceptual speech deficits in noise despite normal audiometric thresholds. Perceptual deficit studies in humans have shown evidence consistent with the idea of cochlear synaptopathy. To date, there has been no direct evidence linking cochlear synaptopathy and perceptual deficits. Our research aims to develop a cochlear synaptopathy model in chinchilla, similar to previously established mouse and guinea pig models, to provide a model in which the effects of cochlear synaptopathy on behavioral and physiological measures of low-frequency temporal coding can be explored. </p><p> Positive-reinforcement operant-conditioning was used to train animals to perform auditory detection behavioral tasks for four frequencies: 0.5, 1, 2, and 4 kHz. Our goal was to evaluate the detection abilities of chinchillas for tone-in-noise and sinusoidal amplitude modulated (SAM) tone behavioral tasks, which are tasks thought to rely on low-SR ANFs for encoding. Testing was performed before and after exposure to an octave-band noise exposure centered at 1 kHz for 2 hours at 98.5 dB SPL. This noise exposure produced the synaptopathy phenotype in na&iuml;ve chinchillas, based on auditory-brainstem responses (ABRs), otoacoustic emissions (OAEs) and histological analyses. Threshold shift and inferred synaptopathy was determined from ABR and OAE measures in our behavioral animals. </p><p> Overall, we have shown that chinchillas, similar to mice and guinea pigs, can display cochlear synaptopathy phenotype following moderate-level sound exposure. This finding was seen in na&iuml;ve exposed chinchillas, but our results suggest the susceptibility to noise can vary between na&iuml;ve and behavioral cohorts because minimal physiological evidence for synaptopathy was observed in the behavioral group. Hearing sensitivity determined by a tone-in-quiet behavioral task on normal hearing chinchillas followed trends reported previously, and supported the lack of permanent threshold shift following moderate noise exposure. As we expected, thresholds determined in a tone-in-noise behavioral task were higher than thresholds measured in quiet. Behavioral thresholds measured in noise after moderate noise exposure did not show threshold shifts relative to pre-exposure thresholds in noise. As expected, chinchillas were more sensitive at detecting fully modulated SAM-tone signals than less modulated, with individual modulation depth thresholds falling within previously reported mammalian ranges. </p><p> Although we have only been able to confirm cochlear synaptopathy in pilot assays with na&iuml;ve animals so far (i.e., not in the pilot behavioral animals), this project has developed an awake protocol for moderate-level noise exposure, an extension to our lab&rsquo;s previous experience with high-level permanent damage noise exposure under anesthesia. Also, we successfully established chinchilla behavioral training and testing protocols on several auditory tasks, a new methodology to our laboratory, which we hope will ultimately allow us to identify changes in auditory perception resulting from moderate-level noise exposure. </p>

Fourteen percent of the Swedish population report subjective hearing loss. The number of persons suffering from hearing loss is expected to increase in accordance with the increased length of the average life span, causing an associated increase in the demand for hearing health care services as new patient groups who expect a higher quality of life begin to request hearing care. The main goal of this thesis was to develop new approaches in audiological rehabilitation to meet these demands and achieve user satisfaction. Two randomized controlled trials including 39 and 38 subjects, respectively were performed that evaluated two interventions, user-controlled adjustment and sound awareness training, which were performed prior to a hearing aid fitting. The new approaches focused on increasing user participation and activity. To evaluate the goals of audiological rehabilitation, e.g., reducing auditory impairment, optimizing auditory activities and minimizing participation restrictions, several standardized self-reporting instruments were used to assess activity limitations, participation restriction, satisfaction and psychosocial well-being. Several of the instruments were validated for a Swedish population in a postal survey including 162 subjects. Furthermore, an interview instrument that was appropriate for telephone interviews and a categorization rating scale were developed for assessing the global clinical impression of the audiological rehabilitation. Few significant differences in outcomes were found between the treatment and control groups in the short term, and the interventions did not achieve additional or more successful hearing aid users in the long term. Thus, it was concluded that the hearing aid rehabilitation was effective in and of itself, as both the treatment and control groups showed significant improvements in psychosocial well-being and reduced activity limitation and participation restriction. The self-report instruments were found to be valid, and a factor analysis indicated that the number of questionnaires could be reduced with a recommendation for further clinical use. The telephone interviews evaluating the clinical global impression of the audiological rehabilitation were found to be effective and showed success in a vast majority of the users. Advantages such as simpler administration and less time consumption warrant their continued use in additional audiological settings. The pre-interventions in these studies need to be further investigated before they could be recommended for clinical use also in a Swedish context. The international standardized self reports, however, can already be recommended for clinical use. A first attempt to evaluate global clinical impression by telephone interviews was found to be effective and further validations are suggested.