RT Journal Article
SR Electronic
T1 Multiple spin echos in cerebral dynamics: Evidence for spontaneous symmetry breaking during pulsation
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 219931
DO 10.1101/219931
A1 Christian Kerskens
A1 David López Pérez
YR 2017
UL http://biorxiv.org/content/early/2017/11/15/219931.abstract
AB Brain functions depend on cerebral transport mechanisms which are evidently propelled and regulated throughout the entire brain [1]. It is generally believed that the main driving force is the cardiac pulse [2] which, after arrival in the brain, travels effortlessly from the arterial into the veinous system seemingly leaving out what is in-between: namely the capillaries and the tissue, which both consist of a flow volume many magnitudes larger with a higher flow resistance than that of the blood vessels. If a pulsatile flow hits both the capillaries and the tissue [3], which are non-pulsatile regimes without vascular smooth musculature, then it should react like a small wave hitting a big inert mass. As a result, the wave should lose energy in a scattering process leading to damping, dispersion and reflection. However, the pulse exits the brain un-scattered [4] leaving us with the open question of what then drives cerebral dynamics. Here, we wanted to shed light on this mystery by studying microscopic parameters of cerebral dynamics. As such, we aimed to observe variations in Landau’s order parameter [5] which may be accessible via multiple spin echos (MSE) [6]. We found MSE oscillations which appeared in brain tissue simultaneously with the arterial pulse. Those oscillations showed remarkable time pattern which revealed the spontaneous character of the underlying physiological mechanism. Our finding can be interpreted as a spontaneous symmetry breaking of the order parameter [7]; a phenomenon also occurring in superfluids. Superfluidity in cerebral dynamics has been recently discussed [8] as a possible answer to what may drive cerebral flow. It would give an eloquent explanation for the still controversially discussed cerebral autoregulation [9] because in superfluidity, heat would drive the flow [10] and not the cardiac pulse. Furthermore, a superfluid would flow dispersion-free whereby membranes would be of no obstacle because superfluids leak through every pore [11, 12].