The lower brain may take the higher brain hostage. When this happens emotional intelligence may be lowered. (Pearsall, Paul, PhD. The Heart’s Code. NY: Broadway Books, 1998, pp 26-27)
Driver-training car metaphor: Normally the cortex does all the steering, When anxiety reaches certain thresholds, the reptilian systems can take over the other set of controls and override the steering of the cortex. Of course the problem is that even after the reptilian brain takes over, the cortex continues steering, assuming it is still in charge. (Friedman, Edwin H. A Failure of Nerve: Leadership in the Age of the Quick Fix. NY: Seabury Books, 2007. p. 120-121.