Effect heart rate variability biofeedback on autonomic function and functional connectivity of the prefrontal cortex

Heart rate variability (HRV) has been associated to cognitive and executive function. There is increasing evidence that prefrontal control over limbic structures determines HRV. Whether this connection might be modulated by vagal cardiac function is still illusive. In this study, an eight-week HRV-biofeedback intervention was applied in order to increase HRV in 14 healthy subjects (7 females; 30.4±9.3y). Participants' heart rates (HR) were recorded by a chest belt (H10; Polar Electro) and displayed on their smartphones (EliteHRV 4.2.1, Elite HRV LLC). In five sessions per week, participants trained to maximize HRV. A control group (5 males, 5 females; 30.0±12.6 y) played jump'n'run games instead of biofeedback training. Functional magnetic resonance imaging sessions were conducted before and after the intervention. Resting state functional connectivity (RSFC) to a seed region in the ventromedial prefrontal cortex (PFC) were compared before and after intervention. Cardiac autonomic indices were significantly affected by biofeedback training when compared to the control group. HR dropped by 5.5 beats/min and vagal HRV improved by 10.1ms (22%). Increases of the prefrontal connectivity mainly to the right anterior insula, the dorsal anterior cingulate cortex and dorsolateral PFC were significantly higher in the training than in the control group. HRV-biofeedback has a beneficial effect on cardiac autonomic function and might as well influence brain organization and function.