Consciousness and the Brain: Deciphering How the Brain Codes Our Thoughts is a 2014 book by Stanislas Dehaene. It summarizes research on the neuroscience of consciousness, particularly from recent decades.
Book outline
Introduction: The Stuff of Thought
Dehaene reviews historical intuitions that consciousness must be separate from matter. He explains how consciousness was not even mentioned in neuroscientific circles until the late 1980s, when a revolution in consciousness research began. Dehaene believes that "access consciousness" (being aware of and able to report on information) is the right definition to start with for scientific investigation. While some philosophers insist that access consciousness differs from "phenomenal consciousness" (e.g., the way qualia feel), Dehaene considers the access/phenomenal distinction "highly misleading" and feels it "leads down a slippery slope to dualism" (p. 10).
Ch. 1: Consciousness Enters the Lab
Dehaene distinguishes conscious access from related but not identical ideas: "attention, wakefulness, vigilance, self-consciousness, and metacognition" (p. 25).
He introduces the project of measuring neural correlates of consciousness using paradigms like minimal contrasts of images, masking (subliminal stimuli), binocular rivalry, and attentional blink. The attentional blink relates to the psychological refractory period, inattentional blindness, and change blindness. Olaf Blanke's studies on out-of-body experiences explore an example where conscious experience changes while external stimuli stay the same.
In Ch. 4, Dehaene notes that correlates of consciousness are actually insufficient, because many things can correlate with conscious perception, including even brain states prior to presentation of a stimulus. Dehaene is most interested in neural signatures of consciousness that represent the consciousness brain processing itself. (p. 142)
Ch. 2: Fathoming Unconscious Depths
Dehaene reviews unconscious brain processing of various forms: subliminal perception, Édouard Claparède's pinprick experiment, blindsight, hemispatial neglect, subliminal priming, unconscious binding (including across sensory modalities, as in the McGurk effect), etc. Dehaene discusses a debate over whether meaning can be processed unconsciously and concludes based on his own research that it can be. An N400 meaning-based wave occurs for unexpected words even when masked or not attended to. Unconscious processing is not just bottom-up but can be enhanced when top-down attention is directed toward a target, even if the target never becomes conscious. Brains can even do some mathematical operations unconsciously, and sitting on a problem to let the unconscious mind work out an answer has proved helpful in several experiments.
Ch. 3: What Is Consciousness Good For? While some view consciousness as an epiphenomenon of brains, Dehaene sees it as playing functional roles, such as Collapsing many lower-level probability assessments into one conscious perception sampled from the Bayesian posterior distribution, allowing us to make a single decision, in a similar way as the FBI summarizes much low-level data into a single brief for the president of the United States. Convergence on a single interpretation of local receptive-field data does not occur under anesthesia. Creating lasting thoughts that can remain in working memory for use at a later time. Daniel Dennett compares this with an echo chamber. In contrast, unconscious information decays away exponentially within about a second. Reasoning through multi-step strategies and performing serial computations, such as the steps in figuring out that 12 x 13 = 156 in your head. Consciousness seems "to collect the information from various processors, synthesize it, and then broadcast the result -- a conscious symbol -- to other, arbitrarily selected processors" (p. 105). This resembles a production system in artificial intelligence. Sharing the contents of our minds with others, via language and non-verbal signals. Brains can make confidence assessments in their opinions, which helps with combining judgments optimally.