Study Protocol for a Single-blind Randomized Controlled Trial, Assessing the Specificity of an Alpha/Delta Ratio Neurofeedback Training Protocol in Chronic Tinnitus.

Tinnitus is hypothesized to originate as a result of a disturbance in the balance of excitatory and inhibitory neurons in central auditory structures. More specifically, inhibitory neurons hyperpolarize, by which their functional role is weakened . Consequently, this allows auditory neurons, deprived of input from a lesioned auditory system, to spontaneously synchronize their activity, resulting in the tinnitus percept.

In the normal functioning auditory system, neurons firing synchronously in the alpha frequency region (8 - 12 Hz) have a gating function of inhibiting task-irrelevant regions in the brain. In people with chronic tinnitus, it has been observed, that alpha activity over temporal regions is weakened, thus leading to the spontaneous activity characterizing the condition. By upregulating alpha activity with neurofeedback training, it is hypothesized that the excitatory/inhibitory balance in temporal regions can be restored, thus minimizing the tinnitus percept.

The coupling or exchange of information of distinct brain regions, leading to an integrated conscious perception, is assumed to be mediated by delta oscillations. In tinnitus, the distress associated with the condition arises as a consequence of coupling prefrontal areas, responsible for allocation of attentional resources with limbic (arousal) and temporal (auditory processing) regions. In neurofeedback, the downregulation of delta activity is hypothesized to lead to a de-coupling of the communication between the areas associated with the distress.

No studies to date have tested the specific role of alpha and delta in the origin and perpetuation of tinnitus distress and intrusiveness. The present study seeks to compensate for this, by comparing an alpha and delta neurofeedback ratio training protocol with one assumed to have no direct association with the pathophysiology of tinnitus.

In addition to the ten neurofeedback training sessions, all participants undergo diagnostic assessments at three time points throughout the trial (pre-neurofeedback training, post-neurofeedback training and at three months follow-up). For the first 40 participants, electroencephalographic (EEG) activity is recorded and cognitive capacity assessed with two attention tests, the Attention Network Test and Sustained Attention Response Task, respectively at all three time points. For the remaining 80 participants, the EEG recording is abandoned, and only cognitive capacity assessed in the pre- post, and follow-up phase of the study.