Stanislas Dehaene (2014): Consciousness and the Brain: Deciphering how the brain codes our thoughts (Viking, New York)
(also available through LibGen)
Dehaene is a leading neuroscientist on consciousness, and an extremely smart guy. His analysis of consciousness is based on massive amounts of experimental and observational evidence together with a coherent theory (the global neuronal workspace). He does away with all the vagueness, obscurity, wild speculation, and philosophical nonsense that is usually associated with the concept of consciousness. Instead, he focuses on the direct connections between measurable neural processes and subjective, conscious experiences, in order to tease out exactly what distinguishes conscious from subconscious cognitive processes, and how the former can emerge from the latter.
He moreover offers a clear and convincing explanation of why consciousness evolved as a control layer on top of earlier subconscious processing. His main idea is that subconscious processes proceed in parallel in a lot of specialized modules while constantly changing the state of activation of the brain. Consciousness selects the most important of these subconscious perceptions and conceptions and puts it in a temporary buffer, the "working memory" or "global workspace", where it can be examined, combined with other conceptions from different origins, and thus sequentially processed in a controlled manner. The contents of the global workspace are then broadcasted to all other brain regions, so that the focus of consciousness can direct the activity of otherwise independent, automatically proceeding subconscious modules.
The emergence of a conscious thought in the global workspace happens through a phase transition which Dehaene calls "ignition", in which a wide area of the cortex suddenly becomes activated and synchronized in its firing. It is is based on a positive feedback of activated neurons activating more neurons, until they form a coherent, self-sustaining pattern that corresponds to a particular thought. This pattern simultaneously suppresses the activation of all other neurons not related to the conscious thought. Thus, thoughts compete for access to the global workspace, according to a "winner takes all" dynamics that only allows a single thought to be in focus at a time.
That explains the sequential processing characterizing consciousness, but not yet the capacity of working memory, which can sustain roughly 4 items for eventual combination (e.g. when you make a mental calculation involving several numbers). (A possible explanation is that working memory is broader than global workspace, keeping items that are no longer in focus weakly activated so that they can easily reenter the workspace when needed). Perhaps Dehaene will explain this in the chapters I have not read yet...
If you read only one book or article on consciousness, this should be it. Forget about zombies, the "hard problem" and other philosophical thought experiments that have no relation to the real world. This is scientific research the way it should be done: based on concrete evidence, with lots of practical implications, yet grounded in deep, elegant and general theoretical modelling.
Moreover, Dehaene has the talent to write a book that goes into quite a bit of technical and theoretical detail, yet is easy and fun to read. Highly recommended!
Here's the book's blurb:
A breathtaking look at the new science that can track consciousness deep in the brain
How does our brain generate a conscious thought? And why does so much of our knowledge remain unconscious? Thanks to clever psychological and brain-imaging experiments, scientists are closer to cracking this mystery than ever before.
In this lively book, Stanislas Dehaene describes the pioneering work his lab and the labs of other cognitive neuroscientists worldwide have accomplished in defining, testing, and explaining the brain events behind a conscious state. We can now pin down the neurons that fire when a person reports becoming aware of a piece of information and understand the crucial role unconscious computations play in how we make decisions. The emerging theory enables a test of consciousness in animals, babies, and those with severe brain injuries.
A joyous exploration of the mind and its thrilling complexities, Consciousness and the Brain will excite anyone interested in cutting-edge science and technology and the vast philosophical, personal, and ethical implications of finally quantifying consciousness.
Evolution, Complexity and Cognition group
Free University of Brussels