Damasio took on the interaction between emotions and reason, consicousness, and now, with this book, feelings. These are not unimportant, trivial or simple problems for a neurologist to tackle. They are among the greatest mysteries left in science. Now, do not take this to mean I think I agree wholly with Damasio, or that he has solved these puzzles completely. No. But he has made progress, and he has advanced some really intersting hypothesis. Damasio therefore is rightly considered one of the foremost theorethical neuroscienctists, and although seems sometimes to dismiss much of the literature and consider only evidence coming out of his lab, his ability to so easily transform his theories into highly readable popular accounts is scary.
Damasios main concern in this book is to present an neurobiological account of feelings. Now the first move he makes is to distinguish them from the related phenomenon of emotions. These are not to be confused, even when they are highly related. Felling, to Damasio, comes only after the emotion, and is very different from it. Emotions are complexes of chemical and neural patterns that drive the organism by automatical alterations of the state of the body, towards evolutionarily set places of well-being. Fellings are the perceptions of changes in, or the states of the body, and the modes of thinking that these ensue. To Damasio then, the feeling of fear would consist of the infromation provided by the body proper as well as of the way the cognitive mechanism functions because of the changes that are taking place. Since Damasio considers body regulating, homeostatic, and body sensing so important for feelings, he mantains the neurobiological underpinnings of feelings must be structures related to these functions. And he has evidence to support this claim. Imaging experiments show activity in the brain stem, hypothalamus,cingulate cortices and insula correlated with feelings. These structures have in common precicely their activity in regulating or obtaining information of the body. For theoretical reasons, Damasio holds the insula to be the main player here.
With these thoughts in mind, Damasio lists what he thinks are the necessary and sufficient conditions to have a feeling. THese are a nervous system with a body, a way for that nervous system to map and transform body states in neural maps, and then create out of these mental patterns or images, consicousness, a way for the nervous system to change the state of the body. Dmasio then also discusees the probable functions of feelings, its evolutionary origins, and possible reasons why feelings feel the way they do. The first of these questions he anwers in his first book, Descartes error. The second, because emotions were there as were the neural patterns that mapped body state changes, as well because feelings promoted survival by their function. The third, why feelings feel the way they do, Damasio answers speculatively but very interestingly. The life process, its design in multicellular organisms, the way the life process is altered by changes in the body and thr innate reactions of the body,thenature of the nural medium where these structures are mapped, explain together why feeling feel the way thet do. Damasio also discusses how mental images might arise, speculates about the origins of a mental level of neurobiological phenomena, and discusses mind-body philosophical issues. Also, in between these issues, Damasio devotes roughly a third of the book to his interest on the life and philosophy of Spinoza, who Damasio reads as to have anticipated some of Damasios ideas on the body and the mind.
There remain some problems with Damasios account of course. For example, he seems to say a system that has the necessary and sufficient conditions for feelings but is not alive would not feel. His inclusion of consciousness as a necessary condition makes sense, but also obscures his explanation. Is consciousness itself explained? probably not in Damasios terms, but certainly not in the terms probably most relevant for feelings: qualia. What would life add to a system to make it feel,but qualia, that is, the essence (content?) of a feeling? But why would life bring qualia?if life is a physical process too, so qualia should be a physical process too, and therefore a physical system could have it too. But not necesarily an alive physical system. Damasio also never specifies what takes place between a neural pattern and a mental image for the latter to arise out of the former. This is the qualia problem again. So Damasio does not explain qualia? so what? nobody else has. But it is a reality that feelings will not be explained without a proper account of qualia. There is also the issue of predictions and testability. Will damage to the inusla cause loss of feeling? will a brain in a vat feel? Damasio also gives little space to neurochemistry, and it is obvious that it is a very important part of the making of feelings. How do serotonin, dopamine, acetycholine, and other neuromodulators affect feelings? directly, by changing neurons? Chemicals can alter feelings in predictable ways, so does the insula have special receptors, and if so what are their functions? If feelings require consicousness, and as some mantain, consicousness requires language, does feeling require language? how about the memories of feelings. Do memories of feelings activate the insula too, and if not, can feelings arise then out of association cortex (for memories of feelings bring a little of those feelings into the mind)? These questions are some philosophical and some empirical, but they all have somthing to say about feelings, and Damasio gives us no answers.
The book is a great acomplishment, and anybody interested with the hard problems of neuroscience, consciousness, emotions, the self, will want to read this book. Damasios views are predictable given his other two books, but they are original and very interesting. Few other neuroscientists are as thought provoking, or write as clearly as Damasio does.