Exagerated standing and other abnormal posturing is a phenomena
analogous to the heightened muscle tone and hyper-reflexia seen in upper
motor neuron lesions. Descending motor pathways from the cortex are
primarily inhibatory. In a healthy nervous system descending cortical
motor systems continuosly inhibit hyperactive lower motor reflexes. It
is like keeping your car from moving by applying the brakes despite the
fact that the engine is running and the transmission is engaged. Many
fairly complex behaviors including posture are handled by subcortical
regions of the nervous system. The primary role of the cortex in these
reflexes is to shut them down when they interefere with directed motor
activity or are in some other way inappropriate. When the cortex is
removed exagerated and uncoordinated reflex programs emerge.