Self Comes to Mind

absence of any sound induces activity in the auditory cortices, and the evoked activity patterns overlap with those elicited during the perception of spoken words. 9 The auditory map of the sound becomes an integral part of the representation of the lip movement. The CDZ framework explains how one can hear sound, in the mind’s eye, upon receiving the appropriate visual stimulus, or vice versa.
    Should anyone regard the brain’s feat of synchronizing visuals and sound as a trivial achievement, just think of the discomfort and irritation one feels when the quality of a film projection fails and the sound track and visual image go out of sync. Or worse yet, when one has to watch a great Italian film badly dubbed in unsynced English. A variety of other perceptual studies involving other sensory modalities (smell, touch) and even neuropsychological studies in nonhuman primates yield results that are satisfactorily explained by the CDZ model. 10
    Another interesting set of data comes from studies of mental imagery. The process of imagination, as the term suggests, consists of the recall of images and their subsequent manipulation—cutting, enlarging, reordering, and so forth. When we use our imagination, does imagery take place in the form of “pictures” (visual, auditory, and so forth), or does it rely on mental descriptions resembling those of language? 11 The CDZ framework supports the picture account. It proposes that comparable regions are activated when objects or events are perceived and when they are recalled from memory. The images constructed during perception are re- constructed during the process of imagery. They are approximations rather than replicas, attempts at getting back at past reality and thus not quite as vivid or accurate.
    A large number of studies indicates unequivocally that imagery tasks in modalities such as visual and auditory usually evoke brain activity patterns that overlap to a considerable extent with the patterns observed during actual perception, 12 while the results from lesion studies also provide compelling evidence for the CDZ model and the pictorial account of imagination. Focal brain damage often causes simultaneous deficits in perception and imagery. An example is the inability to both perceive and imagine colors caused by damage to the occipitotemporal region. Patients with focal damage to this region see their visual world in black and white, literally in shades of gray. The patients are unable to “imagine” color in their minds. They know perfectly well that blood is red, and yet they cannot picture red in their mind’s eye, any more that they can see red when they look at a red-colored chip.
    Evidence from both functional imaging and lesion studies suggests that recall of objects and events relies, at least in part, on activity near the points where sensory signals enter the cortex, as well as near motor output sites. It is certainly no coincidence that these are the sites engaged in the original perception of objects and events.
    Mirror neuron research also provides evidence that a convergence-divergence architecture is a satisfactory means to explain certain complex behaviors and mental operations. The key finding in mirror neuron research ( Chapter 4 ) is that the mere observation of an action leads to activity in motor-related areas. 13 The CDZ model is ideal for explaining this observation. Consider what happens when we act. An action does not consist merely of a sequence of movements generated by the brain’s motor regions. The action encompasses simultaneous sensory representations that arise in the somatosensory, visual, and auditory cortices. The CDZ model suggests that the repeated co-occurrence of the varied sensorimotor maps that describe a specific action leads to repeated convergent signals toward a particular CDZ. At a later occasion, when the same action is perceived, say visually, the activity generated in visual cortices activates the pertinent CDZ. Subsequently, the CDZ uses divergent back projections toward early sensory cortices to reactivate the related associations of the action in modalities such as somatosensory and auditory. The CDZ can also signal toward motor cortices and generate a mirror movement. From our perspective, mirror neurons are CDZ neurons involved in movement. 14
    According to the CDZ model, mirror neurons alone would not enable observers to grasp the meaning of an action. CDZs do not hold the meaning of objects and events