The yin and yang of cardiac autonomic control: Vago-sympathetic interactions revisited

Baroreflex mechanisms in major depression

“…In contrast, during reciprocal control of both autonomic limbs, both the range and gain are massively increased in either direction (Paton et al, 2005). In the present study, this mode of autonomic control was related to decoupling of the 'double' product from a narrow baroreflex operating range and to baroreflex sensitivity regulation by reciprocal control from both afferent and efferent components of the loop.…”

“…The importance of the operating ranges and autonomic modes in relation to gain, gating, and phase mechanisms of baroreflex regulation needs to be evaluated more intensively in future studies. Paton et al (2005) stated that simultaneous co-activation of cardiac sympathetic and parasympathetic branches of the autonomic nervous system (sympathetic-parasympathetic 'compensation' or co-activation mode in baroreflex mechanism in our case) allows precise control of response direction, but restricts the dynamic range and gain of the response. In depressed patients, this condition appears to restrict the ability to cope with physical and cognitive challenges (Davydov, 2000;Shapiro et al, unpublished).…”

“…The higher gain of the afferent component of the baroreflex is a result of strain in cardiac work and metabolism, as estimated by the affected heart rate and blood pressure double product, via a tonic increase in ventricular contractility (inotropic activity) caused by an increase in sympathetic outflow to the ventricular myocardium (Paton et al, 2005). Thus, peripheral norepinephrine hyperactivity in depressed patients may lead to increased sympathetic cardiac tone.…”

Cardiac arrhythmias during or after epileptic seizures

“…27 In the context of postictal coma, the arousal effect may be blocked and thus not result in resumption of normal ventilation, thus explaining why postictal asystole can be fatal. PGES has been linked to postictal coma.…”

Brain correlates of autonomic modulation: Combining heart rate variability with fMRI

“…While some controversy in interpretation remains, the spectral peak in a low frequency band (LF, 0.01-0.15Hz) is thought to be influenced by both cardiovagal and sympathetic activity, while the peak in a high frequency band (HF, 0.15-0.40Hz) is influenced solely by cardiovagal activity (Malik et al 1996). Cardiovagal and sympathetic activity are not necessarily reciprocal or antagonistic (Berntson et al 1991;Paton et al 2005) and cannot be inferred from heart rate changes alone. For example, tachycardia may be produced by either increased sympathetic activity, decreased parasympathetic activity, both, or even peripheral chemoreflexes.…”