true of both visceral and cutaneouspain. The HeartMath system is currently employed by numerous clinicians as a pain managementaid, and has proven effective in patients with a wide range of conditions, including chronic jointpain, serious burns, and traumatic brain injury. The generation of increased vagal afferentactivity during the coherence mode provides a likely mechanism to account for the reduction ofpain associated with increased heart rhythm coherence.Several mechanisms have been identified that explain how increased vagal afferent activitydecreases pain sensitivity and increases pain threshold. Nociceptive information (pain signals)from the skin and internal organs is carried to cell bodies located in the dorsal root ganglia of thespinal cord. Axons from neurons in the dorsal root ganglia penetrate the spinal cord and conveyafferent pain information to localized regions of the gray matter in the cord. From there, afferentinformation ascends in pathways to both the lateral and medial thalamus. Cells of the lateralthalamus in turn project to the primary somatosensory cortex, where the location, intensity, andduration of the painful stimulus are analyzed. Information is sent from the medial thalamus to theinsular cortex, amygdala, and cingulate gyrus, where motivational-affective components of pain,including autonomic adjustments, occur. This pathway is called the spinothalamic tract (STT)and, although not the only pain pathway, it is the main and most studied system that transmitsvisceral sympathetic afferent pain information to the brain (Foreman, 1989).Afferent fibers in the vagus nerve participate in the modulation of pain partly by modulatingthe flow of pain signals in the STT. An increase in afferent vagal activity causes a generalinhibitory effect at most levels of the spinal cord on neurons that transmit nociceptiveinformation to the thalamus and then to areas of the brain involved in pain perception. Vagalafferent fibers terminate primarily in the caudal medulla of the brain stem and nucleus tractussolitarius (NTS), and evidence shows that suppression of spinal neuronal activity is dependentupon the NTS connections. It has been demonstrated that the cardiac branch of the vagus nervemakes up the major contribution for the inhibitory responses on the spinal pain signals and thatleft vagal stimulation suppresses approximately 60% of the STT cells. Thus, the predominanteffect of increased vagal afferent activity, which is associated with increased coherence, is thesuppression of somatic and visceral input to STT cells, which provides a mechanism fordecreasing pain (Foreman, 1994, 1997).It is well known that the respiratory rhythm modulates the pattern of the heart rhythm. Thisbreath-related modulation of the heart rhythm is called respiratory sinus arrhythmia (RSA)(Hirsh & Bishop, 1981). RSA reflects the complex interaction of central respiratory drive,autonomic afferent signals, efferent outflow from the brain stem, and respiratory mechanicsINTEGRAL REVIEWDecember 2009Vol. 5, No. 2within the thorax. The phenomenon is dependent on the frequency and amplitude of respirationas well as on the underlying autonomic state of the organism.11Since we have conscious control over our breathing, cognitively-directed breathing exercisescan be used to impose a breathing rhythm on the heart rhythms. Thus, when we breathe at a slow,rhythmic rate (five seconds in and then five seconds out), we can facilitate coherence andentrainment. However, we do not normally think about our breathing. It is automatic; ourbreathing depth