Creativity can be negatively impacted when the brain is in a downshifted state. (Caine, Renate Nummela, and Geoffrey Caine. Making Connections: Teaching and the Human Brain. VA: ASCD, 1991, pp 71-73)
Definition: the psychophysiological response to threat, accompanied by a sense of helplessness or fatigue. Downshifting is everywhere in schools. Some memorization can occur when the brain is in a downshifted state but real learning (e.g., creativity, higher-order learning) is incompatible with a downshifted state. (Poole, Carolyn.Maximizing Learning: A Conversation with Renate Nummela Caine. Educational Leadership, Vol 54, No 6 March 1997. Article.)
Refer to Downshifting and the Brain for additional information.