Self Comes to Mind

themselves; they reconstruct meaning via time-locked multiregional retroactivation into varied early cortices. Since mirror neurons are likely to be CDZs, the meaning of an action cannot be subsumed by mirror neurons only. A reconstruction of varied sensory maps previously associated with the action needs to be carried out under the control of the CDZs in which a linkage to those original maps has been recorded. 15
The How and Where of Perception and Recall
     
    The perception or recall of most objects and events depends on activity in varied image-making regions of the brain and often involves parts of the brain related to movement as well. This highly dispersed pattern of activity occurs within the image space . It is this activity, rather than the activity to be found in neurons at the front end of the processing chains, that allows us to perceive explicit images of objects and events. From a functional as well as an anatomical standpoint, the activity at the end of the processing chains occurs within dispositional space . The dispositional space is made up of CDZs and CDRs, in association cortices, which are not image-making cortices. The dispositional space guides the image-making but is not involved in displaying images itself.
    In this sense, the dispositional space contains “grandmother cells,” defined liberally as neurons whose activity correlates with the presence of a specific object, but not as neurons whose activity permits, in and of themselves, explicit mental images of objects and events. Neurons in anterior medial temporal cortices can indeed respond to unique objects, in perception or recall, with high specificity, suggesting that they receive convergent signals. 16 But the mere activation of those neurons, without the retroactivation that would follow from it, would not allow us to recognize our grandmother or remember her. To recognize or remember our grandmother, we must reinstate a substantial part of the collection of explicit maps that, in their entirety, represent her meaning. Like mirror neurons, so-called grandmother neurons are CDZs. They enable the time-locked multiregional retroactivation of explicit maps in early sensorimotor cortices.

     
Figure 6.3: The image space (mapped) and the dispositional space (nonmapped) in the cerebral cortex. The image space is depicted in the shaded areas of the four A panels, along with the primary motor cortex.
The dispositional space is depicted in the four B panels, again marked by shading.
The separate components of the image space resemble islands in the ocean of dispositional space shown in the four bottom panels.
    In conclusion, the CDZ framework posits two somewhat separate “brain spaces.” One space constructs explicit maps of objects and events during perception and reconstructs them during recall. In both percept and recall, there is a manifest correspondence between the properties of the object and the map. The other space holds dispositions rather than maps, that is, implicit formulas for how to reconstruct maps in the image space.
    The explicit image space is constituted by the aggregate of early sensorimotor cortices. When I talk about “workspace” in relation to the sites where images are assembled, I think of such a space, as a playground for the puppetry we behold in the conscious mind. The implicit, dispositional space is constituted by the aggregate of association cortices. This is the space where many unwitting puppet masters pull the invisible puppet strings.
    The two spaces point to different ages in brain evolution, one in which dispositions sufficed to guide adequate behavior and another in which maps gave rise to images and to an upgrade of the quality of behavior. Today they are seamlessly integrated.

PART III
Being Conscious
     

7
Consciousness Observed
     
Defining Consciousness
     
    Open a standard dictionary in search of a definition of consciousness , and you are likely to find some variation of the following: “consciousness is a state of awareness of self and surroundings.” Substitute knowledge for awareness , and own existence for self , and the result is a statement that does capture some essential aspects of consciousness as I see it: consciousness is a state of mind in which there is knowledge of one’s own existence and of the existence of surroundings . Consciousness is a state of mind— if there is no mind there is no consciousness; consciousness is a particular state of mind, enriched by a sense