Abstract . — Tinnitus is a consciously experienced ‘ringing’ sensation in the auditory system, which occurs without the presence of an actual auditory stimulation. The study of tinnitus has resulted in a number of speculated mechanisms and suspected origins in the auditory pathway, however a definite model for this phenomenon has not been confirmed. In the majority of cases, external acoustic stimulation masks the tinnitus sensation and the offset of tinnitus is preceded by the complete withdrawal of acoustic stimulus. This paper describes a research effort to study the neurological expressions of tinnitus by analyzing Auditory Evoked Potentials (AEP). The signals constituting the evoked response are many times smaller than the surrounding EEG signals. The paper describes the methodology and the instrument design to overcome this problem. The study concentrates in the analysis of AEP signals during silence, as well as the transitional nature of the AEP in order to identify possible EEG correlates of tinnitus. Index Terms—Auditory Brainstem Response (ABR), Auditory Evoked Potential (AEP), Tinnitus. I. INTRODUCTION Tinnitus is reported by many individuals as a ringing, buzzing or hissing noise experienced when located in a quiet environment. For many individuals this noise is loud enough to cause emotional stress, hearing impairment and even psychological trauma. Studies in this area have not been able to identify a definite location within the neuro-auditory pathway as responsible for the tinnitus perception. Several research studies suggest that the cause of tinnitus may be widely distributed within the auditory system. However, based on noticeable differences in the nature of perception of tinnitus experienced by many individuals, tinnitus occurrences can be classified into two groups: Peripheral Tinnitus and Central Tinnitus. Peripheral Tinnitus is assumed to originate from the peripheral nervous system and cochlea, while Central Tinnitus is assumed to originate in the Auditory Cortex. 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 neuro- . This work was sponsored by NSF grants IIS-0308155, HRD-0317692 and CNS-0426125. Fig. 1. A typical AEP waveform used for basic audiometric screening (courtesy of Intelligent Hearing Systems, http://www.ihsys.com ). auditory pathway [11]. 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. Neurological aspects of tinnitus have been extensively studied mostly through animal models. Studies related to the efferent nervous system controlling the inner hair cells [9] show sufficient evidence of Tinnitus being related to spontaneous neural activity. 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[4]. Tinnitus has been reported following surgery of the eighth nerve [3,12]. Different types of destructive surgery including neurectomy failed to improve or abolish Tinnitus [8]. II. 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 Brainstem 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 5-200 µV. Evoked potentials are electrical signals that result from neural activity which occurs in response to an experimental stimulus. Auditory Evoked Potentials (AEPs) originate along the neural pathway in response to appropriate acoustic stimuli. A Recording System for the Study of Tinnitus Through Auditory Evoked Potentials Maroof H. Choudhury and Armando Barreto Florida International University Miami, FL 33174, USA