Fast temporal processing and ,central auditory disorder`: subcortical mechanisms

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The ability to follow the temporal structure of sounds at high frequencies is required for discrimination of complex sounds and sound localization. The central auditory disorder (CAPD) is characterized by normal cochlear thresholds, but affected recognition, discrimination, separation, grouping, localization or ordering of sounds. To investigate the pathophysiology of CAPD and develop a clinically-exploitable method for differential diagnosis of the causes, transgenic mice with an induced Cav1.3-deficiency in the brainstem will be used. Preliminary results show that these animals have normal hearing thresholds, abnormal brainstem evoked responses (ABRs) and structural changes in the brainstem, corresponding to the definition of CAPD. In the present project, responses of neurons to simple tones, complex sounds and binaural stimuli will be investigated in the inferior colliculus of these animals. The inferior colliculus is the most central auditory structure showing a high precision in temporal synchrony with the acoustic input and receiving inputs from the structures affected in the transgenic animals used. We want to test the ability of neurons to follow the temporal envelope of the sounds. Also, the cues of azimuthal locations will be investigated. Finally, ABRs will be recorded during stimulation with temporally complex sounds. After determining the neuronal signature of the deficit in the midbrain, a stimulus will be designed that can allow to detect the described deficits using ABRs in human subjects.