**6. Models of autonomic dysregulation and treatment of PTSD**

**Figure 2** is a model of HRV, orienting, and PTSD. The process begins in the upper left corner of the figure, when a stimulus in the environment is registered A normal OR is initiated in less than a second, and proceeds (blue arrow) to appraisal through cortical processing with an output of cardiac adjustment that depends on the appraisal: stimulus is not further perceived with return to baseline vigilance *or* appraisal of life threat with no escape (immobilization) *or* appraisal of affiliative engagement *or* appraisal of danger with freeze, fight, or flight response. Each of the latter appraisal outcomes is associated with an autonomic state, respectively: return to preregistration baseline, bradycardia modulated by dorsal vagal nucleus, bradycardia modulated by ventral vagus and nucleus ambiguus, cardiac acceleration modulated by withdrawal of rostroventral lateral medulla, and activation of sympathetic nervous system. This process is shown in schematized and highly simplified form in the right upper portion of **Figure 2** (for more detail of the vagal afferent and efferent neural circuits controlling cardiac function, see [19, 31]; see [96] for a thorough discussion of the centrally key role of the paraventricular nucleus of the hypothalamus in autonomic dysfunction). In the individual with PTSD, however, cortical appraisal is short‐circuited (red arrows) with repetitive activation of sympathetic nervous system and freeze of fight/flight. We propose that the beneficial effects of HRVB on PTSD symptoms, including attention bias, occur according to the model shown in **Figure 3**.

**Figure 2.** Model of HRV, orienting, and PTSD.

**Figure 3.** Dysregulation of heart rate deceleraton by PTSD and reduction if PTSD symptoms by HRVB.
