Self Comes to Mind

located in the next connectional level of the chain and receives return projections from them.
    CDZs are microscopic and are located within convergence-divergence regions (CDRegions), which are macroscopic. I envision the number of CDZs to be on the order of many thousands. On the other hand, CDRegions number in the dozens. CDZs are micronodes; CDRegions are macronodes.
    CDRegions are located at strategic areas in association cortices, areas toward which several major pathways converge. You can visualize CDRegions as hubs on an airline map. Think of Chicago, Washington, D.C., New York, Los Angeles, San Francisco, Denver, or Atlanta. Hubs receives airplanes along the spokes that come into the hub, and they return airplanes back along the same spokes. Importantly, hubs themselves are interconnected, though some are more peripheral than others. Finally, some hubs are bigger than others, which simply means that more CDZs are living under their umbrellas.
    We know from experimental neuroanatomical studies that such patterns of connectivity exist in the primate brain. 5 We also know from recent magnetic resonance neuroimaging studies using diffusion spectrum techniques that such patterns exist in humans. 6 We shall see, in the chapters ahead, that CDRegions play an important role in producing and organizing critical contents of the conscious mind, including those that make up the autobiographical self.
    Both CDRegions and CDZs come into existence under genetic control. As the organism interacts with the environment during development, synaptic strengthening or weakening modifies convergence regions significantly and massively modifies CDZs. Synaptic strengthening occurs when external circumstances match the survival needs of the organism.
    In brief, the job I envision for CDZs consists of re-creating separate sets of neural activity that were once approximately simultaneous during perception—that is, that coincided during the time window necessary for us to attend to them and be conscious of them. To achieve this, the CDZ would prompt an extremely fast sequence of activations that would make separate neural regions come online in some order, the sequence being imperceptible to consciousness.

     
Figure 6.2: Using the CD architecture to recall memories prompted by a specific visual stimulus. In panels a and b , a certain incoming visual stimulus (selective set of small filled-in boxes) prompts forward activity in CDZs of levels 1 and 2 (bold arrows and filled-in boxes). In panel c , forward activity activates specific CDRs, and in panel d , retroactivation from CDRs prompts activity in early somatosensory, auditory, motor, and other visual cortices (bold arrows, filled-in boxes). Retroactivation generates displays in “image space” as well as movement (selective set of small filled-in boxes).

     
    In this architecture, knowledge retrieval would be based on relatively simultaneous, attended activity in many early cortical regions, engendered over several reiterations of such reactivation cycles. Those separate activities would be the basis of reconstructed representations. The level at which knowledge is retrieved would depend on the scope of multiregional activation. In turn, this would depend on the level of CDZ that is activated. 7
The Model at Work
     
    What evidence is there that the convergence-divergence model fits reality? Recently, my colleague Kaspar Meyer and I reviewed a large number of studies in the areas of perception, imagery, and mirror processing and considered the results from the perspective of the convergence-divergence model. 8 Many of the results we reviewed constitute interesting tests of the model. Here is a case in point.
    In a conversation with another person, we hear the speaker’s voice and see the speaker’s lips move at the same time. The CDZ model predicts that, as a certain lip movement repeatedly occurs along with its specific sound counterpart, the two neural events, in the early visual and auditory cortices, respectively, become associated in a shared CDZ. In the future, when we are confronted with only one part of that scene—for example, as we watch a specific lip movement in a muted video clip—the activity pattern induced in the early visual cortices will trigger the shared CDZ, and the CDZ will retroactivate, in the early auditory cortices, the representation of the sound that originally accompanied the lip movement.
    In keeping with the CDZ framework, reading lips in the