A relevant development in the study of brain-behavior relations comes from experiments that measure neural activity using Electroencephalography (EEG). In a technique called Event Related Potentials (ERPs), EEG activity is time-locked to experimentally relevant events, such as stimuli presented to the subject, thereby isolating specific neural responses of interest. A brain response distributed anteriorly on the human scalp, has been described as the P3A. The label derives from the response consisting of a positive peak, occurring at approximately 300ms post stimulus presentation. The P3A response is typically obtained in a discrete trial three stimulus oddball in which a frequent stimulus occasioning a response (target) is alternated with an infrequent stimulus (nontarget). A third kind of stimulus – unrelated to the task (e.g. a dog barking) is presented, originating a P3A response. The P3A has been interpreted in the past as a response indicative of “novelty processing” or of an orienting response (e.g. Wetzel, N., Schröger, E., & Widmann, A. 2013). While previous research on the P3A was carried out in discrete trial procedures, we opted for a a free operant procedure consisting of alternation of FR5 and VR5 schedules of reinforcement.

Subjective tinnitus is a condition that is not fully understood, and as a result there are no diagnostic tests or completely efficacious treatments that can be used. The financial implications of this are particularly evident in the VA, where tinnitus is one of the top two service-connected disabilities, behind hearing loss, costing hundreds of millions of dollars annually. The test battery utilized in this study examines both exogenous and endogenous potentials to search for differences between tinnitus and matched non-tinnitus controls. This allows for a more complete evaluation of the auditory system, starting with the early evoked cortical potential, P1, and ending with the endogenous P300 potential. Identification of differences along the central auditory pathway, beginning at the cortical level, could also inspire research for treatment methods that target the cortical regions where differences exist. We hypothesize that individuals with tinnitus, compared to their matched controls without tinnitus, will exhibit differences in their ALR, MMN responses, and P300 responses when their pitch matched tinnitus frequency is incorporated into the test paradigm due to their inability to completely disengage from their perceived tinnitus. Specifically, an inability to completely disengage from their tinnitus is expected to result in reduced amplitudes.