Self Comes to Mind

their unique relation to the body (see Chapter 4 ). Feelings are spontaneously felt images. All other images are felt because they are accompanied by the particular images we call feelings.
    These important brain-stem nuclei do not produce mere virtual maps of the body; they produce felt body states. And if pain and pleasure feel like something, these are the structures we first have to thank, along with the motor structures with which they incessantly loop back to the body, namely, those of the periaqueductal gray nuclei.
The Beginnings of Mind
     
    To illustrate what I mean when I talk about the beginnings of mind, I need to discuss, however briefly, three sources of evidence. One comes from patients whose insular cortices have been damaged. Another comes from children born without a cerebral cortex. The third has to do with the functions of the brain stem in general and the functions of the superior colliculi in particular.
FEELING PAIN AND PLEASURE AFTER
INSULAR DESTRUCTION
    In the chapter on emotions ( Chapter 5 ) we shall see that the insular cortices are unequivocally involved in the processing of a large range of feelings, from those that follow emotions to those that signify pleasure or pain, known as bodily feelings for short. Unfortunately, the powerful evidence relating feelings to the insula has been taken to mean that the substrate of all feelings is to be found only at the cortical level; the insular cortices thus pose as the rough equivalent of the early visual and auditory cortices. But just as the destruction of visual and auditory cortices does not abolish vision and hearing, the complete destruction of the insular cortices, from front to back, in both left and right cerebral hemispheres, does not result in a complete abolition of feeling. On the contrary, feelings of pain and pleasure remain after damage to both insular cortices caused by herpes simplex encephalitis. Along with my colleagues Hanna Damasio and Daniel Tranel, I have repeatedly observed that these patients respond with pleasure or pain to a variety of stimuli and continue feeling emotions, which they unequivocally report. Patients report discomfort with temperature extremes; they are displeased by boring tasks and are annoyed when their requests are refused. The social reactivity that depends on the presence of emotional feelings is not compromised. Attachment is maintained even to persons who cannot be recognized as loved ones and friends because, as part of the herpetic syndrome, concomitant damage to the anterior sector of the temporal lobes severely compromises autobiographical memory. Moreover, experimental manipulation of stimuli leads to demonstrable changes in the experience of feelings. 7
    It is reasonable to propose that in the absence of both insular cortices, the feelings of pain and pleasure arise in two brain-stem nuclei I mentioned earlier (the tractus solitarius and the parabrachial), both of which are suitable recipients of signals from the body’s interior. In normal individuals, these two nuclei send their signals on to the insular cortex via dedicated nuclei of the thalamus ( Chapter 4 ). In brief, whereas the brain-stem nuclei would ensure a basic level of feelings, the insular cortices would provide a more differentiated version of those feelings and, most important, would be able to relate the feelings to other aspects of cognition based on activity elsewhere in the brain. 8
    The circumstantial evidence in favor of this idea is telling. The nucleus tractus solitarius and the parabrachial nucleus receive a full complement of signals describing the state of the internal milieu in the entire body. Nothing escapes them. There are signals from the spinal cord and trigeminal nucleus, and even signals from “naked” brain regions such as the nearby area postrema, that are devoid of the protective blood-brain barrier and whose neurons respond directly to molecules traveling in the bloodstream. The signals compose a comprehensive picture of the internal milieu and viscera, and that picture happens to be the prime component of our feeling states. These nuclei are richly connected to one another and are just as richly interconnected with the periaqueductal gray (PAG), which is located in their vicinity. The PAG is a complex set of nuclei, with multiple subunits, and is the originator of a large range of emotional responses related to defense, aggression, and coping with pain. Laughter and crying, expressions of disgust