Improving Speech in Noise Using Noninvasive Stimulation

Inclusion Criteria:

* 25-55 years old
* Proficiency in English
* TBI group: history of traumatic brain injury by blast or physical trauma
* Normal hearing group: no history of traumatic brain injury

Exclusion Criteria:

* Other neurological diseases or related conditions will be excluded (e.g., large vessel stroke, seizures). We will exclude patients with severe medical diseases that may be associated with impaired cognition (e.g., heart failure, dialysis dependent kidney disease, brain cancer). Further, psychiatric diseases that are unlikely to be related to trauma will be excluded (e.g., schizophrenia).

Patients with histories of severe psychiatric disease prior to trauma exposure will be excluded.

* Current illicit or prescription drug abuse (within the last two months)
* Any taVNS contraindication, including but not limited to the presence of unremovable metal in the left ear, known heart conditions, medications that influence neurotransmitters thought to be critical for vagus nerve stimulation (norepinephrine, acetylcholine, and serotonin), or implanted medical devices such as a pacemaker.