I assume that a rich inner presentation of my grandmother includes simultaneously imagining parts of her look, her voice, her smell, characteristics of her speech, behaviour and personality, her name. All this represented somehow by distributed neuron assemblies spread over the cortex, in modality specific areas (modality in a wide sense).
Each such assembly is somehow capable of activating other grandmother related assemblies, so if I read only the name of my grandmother (or e.g. a description of something she did in her characteristic way, or have a glance at a letter hand-written by her) a more or less rich inner representation of her arises.
This could happen in two quite different ways: those different modality specific assemblies activate each other in intricate ways directly, or they all activate a central small assembly (the grandmother assembly) which in turn activates the others. This assembly would work as (and have the function of) a hub. Its function would be both that of spreading and of integration of information. It would be used both for creating the global representation and for maintaining/stabilizing it.
For this hub to work, it must consist of different neurons, at least one for each modality - otherwise it would respond to rather arbitrary global patterns (summing up all excitatory inputs at once). But given that, it might work.
The truth (in the brain) will probably lie inbetween these two extremes: "no hub at all" and "very small hubs". And the hubs can be more or less important (because there are neuronal pathways bypassing them). And the hubs can be more or less specific (with respect to the cognitive item they are responsible for).
Is there a majority opinion among cognitive neuroscientists concerning these questions (existence/number and size of such hubs and their specificity and importance)?