(1) Evolutionary tendency for important functions of the nervous system to move forward in the brain. (2) Initiation and concentration of the growth tendency at the anterior end of the embryo. (3) The antigravitational redistribution of pulmonary blood flow that occurs with heart failure, caused by increased vascular resistance in the dependent part of the lung, a consequence of pulmonary venous hypertension; usually described on the basis of relative vascular size on chest radiography.