Introduction
traumatic brain injury, Brain injury, TBI, nervous system damage, concussion
POST-CONCUSSION SYNDROME, DISORDERS, CORTEX
The term traumatic brain injury (TBI) refers to a direct or indirect force that causes an injury to the brain, and this injury can occur as a result of direct blows to the head, face, neck, or any other location on the body accompanied by an impulsive force (Lezak et al., Brain injury results in central nervous system damage and also impacts the peripheral nervous system (Blennow et al., One intervention that targets autonomic function is vagal nerve stimulation (VNS) (Mondal et al., In a manner similar to VNS, based on the heart-brain integration in HRV, the intervention of HRV-BF can validate the neurovisceral relationship and improve the interaction between top-down and bottom-up processes. HRV-BF also referred to as resonance frequency (RFF) biofeedback applies heart rate variation that accompany breathing, and diaphragmatic breathing to stimulate afferent and efferent vagal pathways to influence brain areas (locus coeruleus, orbitofrontal cortex, insula, hippocampus, and amygdala) (Lehrer et al., Few previous studies have addressed the treatment outcomes of HRV-BF in TBI, and such studies were mostly limited to pilot studies or case reports. For example, a case study with a 42-year-old athlete who sustained a concussion and severe post-concussion syndrome (Lagos et al., Several studies have demonstrated the effectiveness of psychoeducational interventions in treating mTBI as well as supplementing mental health disorders in the acute and chronic phases (Comper et al., 