Toward illuminating the structure of Llewellyn's dream theory, I compare it in formal terms to Freud's dream theory. An alternative to both of these dream machines, grounded in the distribution of cholinergic activation in the central nervous system, is presented. It is suggested that neither nor dream theory is sufficient to account for the properties of dreams.

Certain features of Stage NREM sleep – for example, rhythmic voltage oscillation in thalamic neurons – are physiologically inhospitable to “REM sleep processes.” In Stage 2, the sleep spindle and its refractory period must limit the incursion of “covert REM,” and thus the extent of REM-like cognition. If these hyperpolarization-dependent events also inform Stage NREM cognition, does a “1-gen” model suffice to account for REM-NREM differences? [Nielsen].

This commentary implicates the neostriatum in the production of the EEG sleep spindle and in the processing of motor procedural learning in sleep. Whether the sleep spindle may implement not only the consolidation-based enhancement of procedural learning, but also its initial consolidation, is considered; as is the fit between (1) corticostriatal anatomy and physiology, and (2) the physical properties of the sleep spindle.