In considering 2 objects in an imaginary senses you are using a serial process. Also, this mental manipulation is using maps/areas very far away from the sensory receptors areas, in the areas by the posterior temporal lobe.
These “high level” areas process things in serial order, using the same cortical areas with other related maps holding parts of the process as placeholders. I maintain that these serial processes are performed at the “loop of consciousness“ level and are outside of the scope of the basic operations performed at the individual map/area level.