PT  - JOURNAL ARTICLE
AU  - Christian Kerskens
AU  - David López Pérez
TI  - Evidence of inverse energy cascades in cerebral dynamics
AID  - 10.1101/219931
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 219931
4099  - http://biorxiv.org/content/early/2018/06/10/219931.short
4100  - http://biorxiv.org/content/early/2018/06/10/219931.full
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 cardiac pulse wave is the main driving force [2]which, after arrival in the brain, seems to travel effortlessly from the arterial into the venous system without any delay. Paradoxically, the arterial and venous system are not directly connected to allow such a smooth transfer [3]. Instead, cerebral pulsation decays from large scales (arteries) to small scales (capillaries, tissue) [2, 3] in a heart beat. The paradox reverse outflow starting from small scales towards the veins [4] may then only be realized by backward energy cascades, so-called inverse cascades [5]. However, inverse cascades in three dimensions are considered to be a rare phenomenon which, if existing, are most likely accompanied by spontaneously broken mirror-symmetries [6, 7, 8]. Here, we focused on the latter utilizing multiple spin echos (MSE)s [9, 10, 11] to detect symmetry breaking in the human brain at rest. For every heart cycle, we found broken symmetries during the arterial pulsation. From our findings, we conclude a flow cycle separated into two phases. In the first, the arterial pulsation (decaying cascade) injects energy to start reverse flow from tissue level toward the veins (inverse cascade). In the following phase, the outflow continues in the vein while inflow from the arteries flows unhindered into tissue (decaying cascade). This interplay of decaying and inverse cascades explains how the illusive pulse wave traveling through the brain emerges.