| Purpose: 1) This study will investigate responses of the central auditory system in hearing impaired patients with and without tinnitus. 2) The proposed project will also investigate whether variations in patient characteristics, as evaluated in a comprehensive diagnostic protocol, correlate with variations of the neural response. Description: Every sound we hear, including tinnitus, is related to some pattern of activity in the brain. Tinnitus is a sound percept that is not related to an acoustic sound from outside the body. People with tinnitus may continuously hear a tone for which no sound source can be identified. This tinnitus may be mild, but may also have a devastating impact on the ability to function in daily life. An increasing amount of evidence suggests that mechanisms in the central auditory system play a key role in the generation of tinnitus. Many (but not all) patients with tinnitus have some form of hearing loss. Hearing loss usually has a peripheral origin, but the tinnitus activity can most of all not originate from the cochlea. Consequently, mechanisms in the central auditory system must be responsible for these forms of tinnitus. In a previous study, Lanting et al. (2007) studied fMRI-responses of the inferior colliculus and other auditory brainstem, thalamic and cortical regions in patients with normal audiometric thresholds and unilateral tinnitus. They showed that the response of the inferior colliculus in tinnitus patients was significantly enhanced relative to that in normal hearing subjects. A similar enhancement of the response is also present in the cochlear nucleus, the superior olivary complex and the medical geniculate body. The proposed fMR-study compares hearing impaired patients with and without tinnitus. This is expected to clarify why some hearing impaired patients hear tinnitus, while others do not. The project aims to answer two main questions. The preliminary aim is to investigate which brain activity patterns are specific to tinnitus. Since, there is a relation between tinnitus and hearing loss, we aim to answer this question in subjects with a hearing loss. We will investigate whether patients with a hearing loss and tinnitus also have an enlarged response to sound in comparison to patients with only hearing loss. A secondary aim is to investigate whether there is a relation between activity in the brain and tinnitus-related patient characteristics. For example, it is conceivable that there is a relation between experienced tinnitus handicap and neural patterns. Therefore, we will also perform a number of psycho-acoustical and physiological tests and administer a number of questionnaires. This is expected to clarify whether there are subgroups of tinnitus and whether these subgroups have specific neural activation patterns. |
