We have lots of miscellaneous items in our minds: streams of sensory input, memories, hypothesese. We can be concious of any combination of these while ignoring others. How about a distributed search, where the search algorithm is embedded in a dynamic propagating pattern, like an entity in Conway's Life? The search replicates, bouncing around the brain. When it finds a local pattern that matches its criteria, it stimulates this region to fire at a frequency unique to this current search pattern.
Conciousness integrates all the elements synced to the same frequency. An integration mechanism was described by Terrence J. Sejnowski at a talk I attended in Zurich, the gist is described here and in detail in the article “Selective attention through phase relationship of excitatory and inhibitory input synchrony in a model cortical neuron”.
The authors of this article go further, saying that not only are we concious of trains of thought when enough patterns fall into sync, but that we can only be concious at all if we have the capacity for enough patterns fall into sync.