An Auditory Evoked Potential Measurement System to Study Tinnitus Maroof H. Choudhury Biomedical Engineering Department Florida International University mchou001@fiu.edu Armando Barreto Electrical & Computer Engineering Department and Biomedical Engineering Department Florida International University barretoa@fiu.edu Miguel Alonso Electrical & Computer Engineering Department Florida International University malons05@fiu.edu Abstract Tinnitus is a consciously experienced ‘ringing’ sensation in the auditory system, which, so far can only be diagnosed by behavioral response. The study of Tinnitus has resulted in a number of speculated mechanisms and suspected origins within the human auditory pathway. A definitive model for this phenomenon is yet to be formulated. The tinnitus sensation is typically reported to be prominent during silence. In addition, the complete withdrawal of auditory stimulus usually precedes the onset of the tinnitus sensation. Therefore, the objective of our research is to facilitate the study of the Auditory Evoked Potential (AEP) response during the silent period that ensues simulation, as well as to observe the transitional nature of the AEP. This paper describes the conceptualization, integration and testing of an experimental instrument setup for observing AEP, in order to identify possible EEG correlates of tinnitus. 1. Introduction Tinnitus is described as a disorder by which a person perceives a spontaneous auditory sensation in the absence of a true acoustic stimuli. A temporary presence of Tinnitus may be experienced from sudden acoustic, mechanical or barometric trauma. Persisting forms of Tinnitus are most commonly associated with disorders or damage in the inner ear or auditory-neural pathway [10]. Symptomatic expressions of Tinnitus have been associated with neural or otological dysfunctions or degenerations such as, Age Related Hearing Loss[1], Noise Induced Hearing Loss[1], Meniere’s disease, Multiple Sclerosis and Acoustic Neuroma. Tinnitus occurrences can be classified into two groups: Peripheral Tinnitus and Central Tinnitus. There is noticeable difference in the perception of these two types of Tinnitus. Peripheral Tinnitus is assumed to originate from the peripheral nervous system and cochlea, while Central Tinnitus is assumed to originate in segments of the auditory neural pathways beyond the cochlea. 2. Neurological Activity and Tinnitus Previous research in the study and modeling of Tinnitus suggests that it is reasonable to consider that the generation of tinnitus involves several structures, which might be widely distributed over the whole auditory system. The neurological aspects of Tinnitus have been investigated by different groups. The pitch of tinnitus in noise induced hearing loss frequently correlates with the characteristic frequency of the firing rate of neurons innervating the inner hair cells of noise damaged regions[3]. Tinnitus has been reported following surgery of the eighth nerve [2,11]. Different types of destructive surgery including neurectomy failed to improve or abolish Tinnitus [7]. Studies related to the efferent nervous system controlling the inner hair cells [8] show sufficient evidence of Tinnitus being related to spontaneous neural activity. 3. Research Goals The instrument described in this paper has been developed in order to identify neural activity that might be correlated with Tinnitus, by analyzing the Auditory Evoked Response. The skin measurements of Electroencephalogram (EEG) potentials are contributed by the superposition of numerous synaptic potentials originating in different regions of the brain. The contributors in scalp EEG measurements are classified according to their spectral significance as the alpha, beta and gamma components. Typical scalp EEG magnitudes range between 0.5-4 mV. Evoked potentials are electrical signals reflecting neural activity that occurs in response to an experimental stimulus. Auditory Evoked Potentials (AEPs) originate along the neural pathway in response to appropriate acoustic stimuli. AEP magnitudes are typically below 10 µV, with a characteristic wave shape composed of several peaks. The AEP signals are considerably smaller in magnitude than other background EEG components. Therefore a synchronized averaging technique is utilized to enhance the AEP responses in contrast to the background EEG. AEPs are commonly used for basic audiometric evaluation. This type of general study of Auditory Brainstem Response