The thermodynamic brain and the evolution of intellect: the role of mental energy.The living state is low entropy, highly complex organization, yet it is part of the energy cycle of the environment.  Due to the recurring presence of the resting state, stimulus and its response form a thermodynamic cycle of perception that can be modeled by the Carnot engine.  The endothermic reversed Carnot engine relies on energy from the environment to increase entropy (i.e., the synaptic complexity of the resting state).  The Carnot engine can model exothermic, negative emotional states, which direct the focus on the past. 
THERM