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Sound Processing in an Emulator of Cochlear Implant
Tóth, Peter ; Maršálek, Petr (advisor) ; Hric, Jan (referee)
The time accuracy of the auditory neuronal pathway in its sound localization branch is high, compared to other sensory systems. The time differences in the sound arrival between the left and right ear are distinguished by the neural circuit in this branch. The accuracy achieved here is in the order of tens of microseconds. This phenomenon has not yet been definitively clarified. In this master thesis, a model of a neuron central to this neural circuit is presented. This neuron is called binaural (neuron of the two ears) and is located in the medial superior olive (MSO) neural nucleus. The properties of the MSO neuron are described. Specifically, the neuron acts as a coincidence detector, and this is necessary for the circuit functioning. Main result of the thesis is the theory explaining how the function of the coincidence detector can be described based on the interaction of the post-synaptic potentials on the spike-response model neuron. Generality and implications for the auditory pathway are then discussed.
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Models of binaural hearing
Drápal, Marek ; Maršálek, Petr (advisor) ; Wünsch, Zdeněk (referee) ; Lánský, Petr (referee)
In this work is presented stochastic model of binaural hearing in context of another alternative models. According to latest experimental data on mammals, inhibition plays a role in interaural time difference recognition, which is a key for low frequency sound source localization. The outputs of experiments may lead to the conclusion that the binaural hearing works differently in mammals compared to birds. Nowadays there are a few theoretical works addressing this new phenomena, but all of them are relaying on a very precise inhibition timing, which was never proved as physiologically valid. On the other hand, models described in this work are based on the fact, that every neuron has a random delay when reacting to an excitation. If this time jitter is taken into account and combined with inhibitory signal, delay in the neuronal circuit and coincidence detection, then the output firing rate corresponds to the azimuth of the sound source. In this work it is shown, that such a neuronal circuits are giving the same output results compared to experimental data. The models are supported by analytical computations and numerical simulations including simulation of cochlear implant.
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Modeling of Binaural Hearing.
Tóth, Peter ; Maršálek, Petr (advisor) ; Košťál, Lubomír (referee) ; Hromádka, Tomáš (referee)
The central theme of this thesis is a description of information processing in the sound localization circuit of the auditory pathway. The focus is on principal neurons of the medial superior olive (MSO), the first major convergence point for binaural information. Selected properties and relations of MSO neurons are derived and expressed through models. In the thesis we present three modeling studies. The first one clarifies a relation- ship between biophysical parameters of the MSO neuron and its ability to detect coincidental spikes from the left and the right ear. The second study describes the statistical behavior of spike trains on the input and output of the MSO neuron. In the third work, we studied how interaural coherence could guide localization of sound sources in complex listening situations with multiple sound sources in reverberant environments. The main results are analytical and numerical models describing the aforemen- tioned relations and behaviors. Secondary results include that inhibitory input to the MSO neuron narrows and shifts the time range of coincidence detection, that ergodic assumption from statistical physics and circular statistics are beneficial in the description of spike trains in the auditory pathway, and that interaural level difference of parts of the signal with...
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Sound Processing in an Emulator of Cochlear Implant
Tóth, Peter ; Maršálek, Petr (advisor) ; Hric, Jan (referee)
The time accuracy of the auditory neuronal pathway in its sound localization branch is high, compared to other sensory systems. The time differences in the sound arrival between the left and right ear are distinguished by the neural circuit in this branch. The accuracy achieved here is in the order of tens of microseconds. This phenomenon has not yet been definitively clarified. In this master thesis, a model of a neuron central to this neural circuit is presented. This neuron is called binaural (neuron of the two ears) and is located in the medial superior olive (MSO) neural nucleus. The properties of the MSO neuron are described. Specifically, the neuron acts as a coincidence detector, and this is necessary for the circuit functioning. Main result of the thesis is the theory explaining how the function of the coincidence detector can be described based on the interaction of the post-synaptic potentials on the spike-response model neuron. Generality and implications for the auditory pathway are then discussed.
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Models of binaural hearing
Drápal, Marek ; Maršálek, Petr (advisor) ; Wünsch, Zdeněk (referee) ; Lánský, Petr (referee)
In this work is presented stochastic model of binaural hearing in context of another alternative models. According to latest experimental data on mammals, inhibition plays a role in interaural time difference recognition, which is a key for low frequency sound source localization. The outputs of experiments may lead to the conclusion that the binaural hearing works differently in mammals compared to birds. Nowadays there are a few theoretical works addressing this new phenomena, but all of them are relaying on a very precise inhibition timing, which was never proved as physiologically valid. On the other hand, models described in this work are based on the fact, that every neuron has a random delay when reacting to an excitation. If this time jitter is taken into account and combined with inhibitory signal, delay in the neuronal circuit and coincidence detection, then the output firing rate corresponds to the azimuth of the sound source. In this work it is shown, that such a neuronal circuits are giving the same output results compared to experimental data. The models are supported by analytical computations and numerical simulations including simulation of cochlear implant.
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