Intervention: Device (transcranial electrical stimulation, TES)

Intervention: Device (transcranial electrical stimulation, TES)

Intervention: none

Transcranial electrical stimulation (tES) is a noninvasive brain stimulation technique that passes an electrical current through the cortex of the brain to alter brain function. The electrical current is applied to an individual's scalp usually via two or more electrodes, and whilst a large amount of the current is conducted between electrodes through soft tissue and skull (Vöröslakos et al. 2018), a portion of the current penetrates the scalp and is conducted through the brain, where it can alter neuronal excitability. By altering the activity of brain regions involved with a behaviour of interest, investigators can observe the resulting behavioral changes and so establish a causal link between the two (Reed et al. 2018).

The THI consists of 25 items, each with the 3 response options-yes (4 points), sometimes (2 points), and no (0 points)-resulting in a total score range from 0 to 100. A higher score denotes a higher tinnitus-related handicap.

EEG activities in certain cortical regions within all 8 frequency bands will be compared. Specifically, as for the source localization analysis, standardized low-resolution brain electromagnetic tomography (sLORETA) will be employed to estimate the scalp-recorded electrical activity in each of the eight frequency bands (i.e., intracerebral sources). We will identify the cortical sources that generate the activities recorded by the scalp electrodes in each of the following eight frequency bands: delta (2-3.5Hz), theta (4-7.5Hz), alpha 1 (8-10Hz), alpha 2 (10-12Hz), beta 1 (13-18Hz), beta 2 (18.5-21Hz), beta 3 (21.5-30Hz), and gamma (30.5-44Hz). sLORETA computes neuronal electrical activity as current density (A/m2) without assuming a predefined number of active sources.