> Brian S
>Since we have many people knowledgeable on the subject
>of how the brain works or at least semi-knowledgeable.
>I thought I'd ask a few questions about sleep.
There are some good references available. Consider
Hobson, J. Allan. _Sleep_. _Scientific American_ Library series.
Hobson, J. Allan. 1994. _The Chemistry of Conscious States_. Boston: Little, Brown and Company.
Anch, A. Michael | Browman, Carl P. | Mitler, Merrill M. | Walsh, James K.
Michel Jouvet and William Dement (sleep research pioneers) have recently come out with popular works.
>3) Would an uploaded person need to sleep? an SI? Why
>or why not?
This is an excellent question. There are several theories as to why we sleep; they are not all necessarily mutually exclusive---sleep most likely offers several benefits. Since we don't really know the exact purpose of sleep we can't be entirely sure whether animal-level intelligence requires it or not. I suspect that sleep is not required for certain kinds of (human-level or above) intelligence. There is probably more than one way to solve certain processing requirements, for one thing, and there may be architectures which simply have designs which do not require the sort of processing that occurs during sleep. (Such minds might not closely resemble the human mind in some ways.)
This sort of question is useful because it encourages us to organize our observations in a systematic way. Arranging known systems in a meaningful way can tell us which systems might be possible if not currently observed or extant and can provide insight into the internal structure of systems which are not fully understood. The periodic table is a model for this notion.