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Age-related hearing loss, presbyacusis, is becoming one of the most common health disabilities in elderly people. Despite intensive research, age-related changes are still poorly understood and, given the continuous aging of the population, it is desirable to improve our knowledge of the mechanisms of presbyacusis. Consequently we decided to study age-related changes that appear in the structure and function of the central auditory system in the brain of experimental animals. In the first experiment we tested the hypothesis that during aging there is substantial decline of GABA-mediated inhibition in the central auditory system of the rat. We evaluated levels of both isoforms of glutamatedecarboxylase (GAD65, GAD67), a key enzyme in GABA synthesis. Western blot analysis revealed an overall decrease in levels of both isoforms in the inferior colliculus as well as the auditory cortex in aged rats. The same pattern was found when we used immunohistochemistry analysis; there was a decrease in the number of GAD65 and GAD67-ir neuronal bodies and a decrease in the density of the labeling. The results were similar for both GAD isoforms and both studied strains - the normally aging Long Evans strain (LE) and the Fischer 344 (F344) strain known for accelerated aging. In the next experiment we evaluated...

Neurons communicate by action potentials. This process can be described by very detailed biochemical models of neuronal membrane and its channels, or by simpler phenomenological models of membrane potential (integrate-and- fire models) or even by very abstract models when only time of spikes are considered. We took one particular description - stochastic leaky integrate-and-fire model - and compared it with recorded in-vivo intracellular activity of the neuron. We estimated parameters of this model, compared how the model simulation corresponds with a real neuron. It can be concluded that the data are generally consistent with the model. At a more abstract level of description, the spike trains are analyzed without considering exact membrane voltage and one asks how the external stimulus is encoded in the spike train emitted by neurons. There are many neuronal codes described in literature and we focused on the open problem of neural code responsible for spatial hearing in mammals. Several theories explaining the experimental findings have been proposed and we suggest a specific variant of so called slope-encoding model. Neuronal circuit mimick- ing auditory pathway up to the first binaural neuron was constructed and experimental results were reproduced. Finally, we estimated the minimal number of such...

ln my the:!i" I aimed to dwal:teriu t.hc dumges in neuronil mvi'Y in tbe tenUlll nucleus of !hl' inferior coIlleulus (CIC) in ..:Iult fllI who ..ffertd fium a lack ohuditory stimulatiOll dl.lling their postnatal dcvdopment ""'..... by the Illmponry i~ase of auditory bearing thresholds after bOef noise e:o:poawe Oll postnItaJ day 14 (broad-bllrKl noise, US dB SPL., 11 min). AI the age of 3-6 IJlOI\tbs, lhe rtSpon5eII ofindividual neurons in tbc CIC 10 :taJnd wtre rcoordod in tb_ animall .nd eompared witb thoseoh~a\l;hcd eontrols. We foood lhal tbe neuronal response tbresholds were sinůlll" in tbe exposed and eontrol animals. However, tbe responJe propenies of high-frequtnCy neuronJ in the exposed rau had characteristic.s typical of the immature auditory system, Le. significantly widtr excitatory response II"talI (which indicatel impairod frcquoncy selectivity), a loogcr fil"Jl-spikc latcfJ(:y, a u.rrower dynamie range, lower maximum rcspon.