This is an excellent review of consciousness from the neurobiological point of view. Consciousness has been an interesting topic for study not only for neurobiologists but also for philosophers and physicists. Although consciousness is a highly debated topic because of its close interaction with matter in space and time, it is certainly least understood subject as it is at the borderline of physics, philosophy and neurobiology. Some quantum physicists argue that it is a universal field like space, time or energy, but consciousness does not figure in equations or any mathematical calculations. Secondly consciousness is found only in living beings and not in inanimate objects: Particularly animals that have brain and central nervous system. The book is summarized as follows:
Three working assumptions are made as methodological platform; 1) the physics assumption; conventional physical processes are required to explain consciousness or the conscious experience, 2) the evolutionary assumption; consciousness is evolved by natural selection in the animal systems, and 3) qualia assumption; the subjective, qualitative aspects of consciousness, being private, cannot be communicated directly through a scientific theory. The authors do not attempt to explain many forms of perception, imagery, thought, emo¬tion, mood, attention, will, or self-consciousness. Instead, they concentrate on certain fundamental properties of consciousness that are shared by every conscious states, such as the unity of a conscious state experienced as a whole and cannot be subdivided into independent components, and the infor¬mativeness, i.e., where a conscious state is selected from a repertoire of billions of possible conscious states, each with different behavioral consequences within a fraction of a second. The basic assumption in all this is that consciousness is a process that is private, selective, and continually changing. It is strictly a process, and not belonging to a particular section of brain. This means that consciousness is associated with biological structures that produce dynamic processes. Thus both morphology and consciousness are the products of evolutionary selection (natural selection). This assumption about the evolutionary origin of consciousness avoids fruitless efforts to relate consciousness to computer logic or the effect of quantum gravity on neurons or a pure quantum physical process while diminishing the role of brain.
Neural substrates of consciousness involve large populations of neurons and no single area of brain is responsible for conscious experience. As the task to be learned is practiced and its performance becomes more and more mechanical then the learning task fades from the memory and the regions for this task becomes smaller. Conscious experience is associated with changes of activity patterns occurring simultaneously in many regions of brain (i.e., activation and inactivation of a population of neurons). It is not how many neurons are active but it is the distribution of groups of neurons that can engage in strong and rapid re-entrant interactions. Further more, the activity patterns of rapidly interacting groups must be constantly changing and sufficiently differentiated from each other: This is called Dynamic Core Hypothesis. Consciousness is an extraordinarily differentiated. At any given time, we experience a particular conscious state selected out of billions of possible states, each of which can lead to different behavioral consequences. The occurrence of a particular conscious state is therefore highly informative in the specific sense that information is the reduction of uncertainty among a number of alternatives. If this is the case the neural processes underlying the conscious experience must also be highly differentiated and informative.
Memory is a central brain mechanism that leads to consciousness. Memory does not store inscription or information in any format. In higher organisms it is an act of creation for every act of perception, and every act of memory is an act of imagination. The primary consciousness has the ability to construct an integrated mental scene in the present that does not require language or true sense of self. The integrated neural scene depends on both perceptual categorization of incoming sensor stimuli (the present) and its interaction with categorical memories (the past). The neural mechanisms distinguish primary consciousness and higher order consciousness. Primary consciousness is found in human as well as some higher order animals, but these lack language, analytical skill, and limited symbolic (semantic) capabilities. Still they are capable of constructing a mental scene. The higher-order consciousness found in humans has semantic capability and linguistic capability in most advanced form which provides a sense of self and the ability to construct past and future. The author' main contention is that the consciousness arose from evolutionary innovations in the morphology of the brain and body. The mind arises from the body and its development. Much of the discussion by the authors are theoretical in nature and needs extensive experimental evidences to support this theory.