1,721,161 research outputs found
On sound and silence: Neurophysiological and behavioral consequences of acoustic trauma
Get PDFNext to elevated hearing thresholds, noise exposure can also cause ringing in the ears (tinnitus) and hyperacusis, a condition in which normal sounds are being perceived as too loud. At present there are no treatments available that consistently cure tinnitus and hyperacusis, partly because the underlying mechanisms of these conditions are not yet completely understood. In this dissertation, the neurophysiological consequences of acoustic trauma are studied. The balance between excitation and inhibition in the central auditory nervous system is disrupted as a result of acoustic trauma. In particular, a decreased inhibition in neurons that respond to frequencies below the trauma frequency are responsible for this. Further, acoustic trauma causes an increased amplification of the signal in the brain. This is both determined by measuring the auditory brain stem response as well as by measuring neural responses to amplitude modulated sound. The disrupted balance between excitation and inhibition, and the amplification of the signal in the brain may underlie neuropathology of tinnitus and hyperacusis. To investigate this, the present thesis describes a possible new method to demonstrate whether an animal experiences tinnitus or hyperacusis. These results could contribute to the development of an animal model in which a direct relationship can be established between the neurophysiological consequences of acoustic trauma and the presence of tinnitus or hyperacusis. Such an animal model can be used for the development of new treatments
Auditory and cognitive mechanisms of top-down restoration of degraded speech: Implications for cochlear implant users
Get PDFEen van de hoofdredenen dat normaal horenden in staat zijn om een gesprek te voeren in achtergrondrumoer is dat ze gebruik kunnen maken van verschillende cognitieve herstelmechanismen die de gedegradeerde auditieve input herstellen tot betekenisvolle spraak. De hersenen zijn in staat om de door ruis onhoorbare stukken spraak te reconstrueren zodat het verstaanbaar wordt. Dit phonemic restoration effect kan gedemonstreerd worden doordat onderbroken spraak beter verstaanbaar wordt als de stilte intervallen opgevuld zijn met ruis. Een gesprek voeren in achtergrondrumoer is zeer lastig voor slechthorenden; het te verwerken auditieve signaal zo slecht is dat compensatiemechanismen niet altijd de problemen oplossen die ze dagelijks ondervinden. Dit onderzoek bestudeert onderliggende mechanismes van top-down herstel van spraak, een voorheen slecht begrepen fenomeen, als spraak gedegradeerd is zoals in cochleaire implantaten (CI, implanteerbaar hoorhulpmiddel voor ernstig slechthorenden). De resultaten geven weer dat het verstaan van onderbroken spraak geleerd kan worden door training, waarschijnlijk door mensen te leren beter gebruik te maken van hun cognitieve herstelmechanismen. We hebben aangetoond dat top-down ¬cognitieve herstelmechanismen minder effectief zijn als het bottom-up auditieve signaal van onvoldoende kwaliteit is (zoals in spraakbewerking in CI’s). Zowel cognitieve als auditieve processen spelen een belangrijke rol in het herstellen van onderbroken spraak. Met name high-level linguïstische mechanismen lijken erg belangrijk in het herstel van onderbroken spraak; woordenschat en verbaal begrip zijn significante voorspellers voor succesvol herstel van onderbroken spraak. Omdat linguïstische vaardigheden een belangrijke rol spelen in het herstel van gedegradeerde spraak, kunnen CI gebruikers mogelijk getraind worden deze vaardigheden te verbeteren
Listening difficulties in children:auditory processing and beyond
Get PDFThere are children who seem to have difficulty in hearing and understanding speech despite normal peripheral hearing. After hearing the sound, something seems to go wrong with the processing of the auditory information. Such problems in listening are known as (unexplained) listening difficulties or auditory processing disorder (APD). Children with such problems have difficulties with understanding speech in complex listening situations, such as in a busy classroom with a lot of background noise. The overall aim of this thesis was to investigate which behavioral characteristics are associated with listening difficulties and whether APD must be considered as distinct and unique construct. The aim was four-fold. Firstly, to investigate which behavioral characteristics are associated with (suspected) APD. Secondly, to investigate the relationship between APD and other neurological developmental disorders. Thirdly, to explore the role of cognitive processes in children with unexplained listening difficulties. Finally, to achieve, in collaboration with professionals from Dutch audiological centers, a practice-oriented definition and method for children with listening difficulties. Based on the results, it can be concluded that listening difficulties in children are multifactorial in nature and may be a consequence of cognitive (intelligence, attention, and working memory), language, and auditory capacities rather than being uniquely limited to the auditory system. APD cannot be considered as an isolated disorder that can be differentiated from other neurodevelopmental disorders, such as language development disorders, dyslexia and ADHD. The diagnostic label APD is therefore not suitable for classifying listening difficulties in children
Characteristcs and mechanics of spontaneous otoacoustic emissions
Get PDFDit proefschrift beschrijft spontane otoakoestische emissies van mensen en kikkers. Met een gevoelige microfoon, aangesloten op een oor van b.v. een mens, kunnen in veel gevallen zachte fluittoontjes worden geregistreerd. De frequenties van deze spontane otoakoestische emissies liggen doorgaans tussen de 1 en 3 kHz, terwijl het geluidsniveau van emissies rond de gehoordrempel ligt. De meest gangbare opvatting over het ontstaan van een emissie is, dat deze gegenereerd wordt door een actief auditief fllter. Instabiliteit van een dergelijk filter zou de oorzaak zijn van een mechanische oscillatie in het binnenoor, die een akoestische emissie in de gehoorgang tot gevolg heeft. ... Zie: Samenvattin
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Adaptive Deep Brain Stimulation for Parkinson’s Disease and Dystonia
Get PDFDeep brain stimulation (DBS) is a neurosurgical treatment, in which electrodes are implanted in deep regions of the brain. This procedure can be used to treat patients with movement disorders, such as Parkinson’s disease (PD) and dystonia. The implanted electrodes deliver electrical pulses, that help to control the main disease symptoms. Until recently, stimulation could only be continuously applied, without taking into account daily symptom fluctuations.Adaptive DBS (aDBS) is an upgrade of this treatment. With aDBS, the stimulation delivered is regulated (in real time), based on the severity of symptoms. To indicate when and how stimulation should be delivered, brain oscillations are used as feedback signal. These oscillations are able to reflect the clinical state of the patients. By dynamically adjusting the stimulation according to the needs of each patient, aDBS might be able to provide a better symptom control. In addition to this, aDBS could prevent the occurrence of side effects caused by excessive stimulation. This thesis investigates the intraoperative efficacy of aDBS in patients with PD and dystonia at the University Medical Center Groningen, The Netherlands. The first part of this thesis describes the characteristics of the signals that can be used to estimate the severity of symptoms in these patients. The second and third parts of the thesis evaluate the immediate effects of aDBS in patients with PD and dystonia, respectively. The main conclusions are that aDBS is effective for PD, and feasible for dystonia. This opens the possibility to further investigate aDBS outside the hospital
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