Can observing neutral objects prime the brain to integrate them into new ideas in the waking state?
There is some support for a short-term day residue effect in the literature, but no support for a more extended dream-lag effect.

Nielsen and Powell (1992) published a test of the day residue effect (incorporation of material from the immediately preceding day) and the dream-lag effect (incorporation of material from 6–8 days prior). Based on dream journals and self-reports of daily events, they found evidence to support the day residue effect, but not the dream-lag effect.

A short 2005 Nature article by the same first author provides a review of the literature for memory's general relationship to dreaming, and includes a very nice summary of the different theories that are in play right now (Nielsen and Stenstrom, 2005).

References


Nielsen, T. A., &amp; Powell, R. A. (1992). The day-residue and dream-lag effects: A literature review and limited replication of two temporal effects in dream formation. Dreaming, 2(2), 67.
Nielsen, T. A., &amp; Stenstrom, P. (2005). What are the memory sources of dreaming?. Nature, 437(7063), 1286-1289.