The mechanism of the REM state is more than a sum of its parts

Nielsen has not demonstrated that NREM dreams are regularly accompanied by fragments of the REM state. However, even if this hypothetical correlation could be demonstrated, its physiological basis would be indeterminate. The REM sate is a configuration of physiological variables, the basis of which is a control mechanism that recruits and coordinates multiple sub-mechanism s into a stereotyped pattern. The diverse sub-mechanisms underlying each in dividual component of the REM state do not have an intrinsic relationship w ith the REM state itself.