sleep

[Mark R. Opp, Ph.D.]

If I may jump in with a slightly different perspective (forgive the 
breach of etiquette, but I am a newby).  The question of sleep function, 
whether energetic, or for cooling the brain, or for memory 
consolidation,etc is complicated by the fact that sleep is evolutionary 
an old behavior that may have evolved at least twice.  The benefits of 
sleep differ from one species to the next, and differ within species 
depending on current ecological conditions, etc.  This makes the 
development of unitary hypotheses for sleep function very difficult, to 
say the least.  One of the newer theories for sleep function is couched 
within the context of the neuronal group selection hypothesis.  This 
hypothesis (based largely on work of Edelman) emphasizes that neuronal 
groups compete for neurons via use-dependent synaptic formation and 
atrophy.  Sleep serves to stabilize these competitive processes by 
providing a pattern of stimulation that serves to maintain a synaptic 
infrastructure upon which wakefulness-driven sunaptic changes are 
superimposed.  As such, sleep is "quantal" in that it is a statistical 
property of a population of neuronal groups in different states.  This 
theory is proposed by Krueger and Obal, and the initial formulation 
appears in the Journal of Sleep Research 2:63-69, 1993.