Dehaene researches cognitive neuroscience. This book describes the experimental research he has done on human consciousness.
In computer AI research and philosophy, it is commonly stated that we do not understand how human consciousness can arise from computation. Dehaene argues that we do have evidence from brain studies that provide (or are starting to provide) answers to the question.
Dehaene provides a definition of consciousness, or more exactly a definition of one aspect of consciousness that his research focuses on.
The book focuses mainly on visual processing. Using fMRI, EEG, and MEG the brain’s internal processing of visual images can be monitored. The experiments use visual illusions, subliminal images, and masking techniques to examine when the brain becomes conscious of the visual images.
What is evident in the experiments is that the low-level image processing detects the stimulus but only under certain (threshold) conditions does the person become aware of the image. When the person perceives the image, there is a sort-of phase transition in the brain where the whole brain seems to light up.
A fascinating book. Highly recommended.