I had somewhat fragmented knowledge of recent advances in the search for neural correlates of consciousness (NCC). I needed a book that could put everything in order: what kind of experimental paradigms are used, what brain regions are investigated, and what gaps in knowledge can be clearly identified. I found the book just right. The Neurology of Consciousness, edited by S. Laureys, O. Gosseries, and G. Tononi. 

This book is a very large piece, containing 25 chapters written by top scholars on various topics, such as anatomical basis of consciousness, states of consciousness, disorders of consciousness, and consciousness vs. cognitive processes. From the multitude of topics covered in the book, I would like to mention here several things that I found interesting.

Researchers seem to converge on the idea that consciousness and attention are two different processes. Some experimental manipulations involve both, but some may involve only attention (but not consciousness), and yet others involve primarily consciousness (but limited or no attention). For example, the detection of stimuli with further reporting requires both attention and consciousness. When, during someone’s talk, your colleague asks you to repeat what the speaker has said, you will answer if you have been consciously attending the talk. However, we may be conscious of more than we attend. For example, we are able to detect the gender of a face somewhere on the periphery of our visual field while attending to another object. Therefore, the evidence points in the direction of dissociation between attention and consciousness, as well as dissociation in thier neural underpinnings.

Out-of-body experience is compelling evidence that consciousness could remain while there is, so to speak, no body feeling. Clinical cases of out-of-body experience usually involve some kind of trauma, anesthesia, seizures, or substances. It is by no means a normal case of existence, though it is a very peculiar one. Additionally, it has been found that electrical stimulation of temporal-parietal junction on the right side of the brain give rise to out-of-body experience. Moreover, similar states are reported by experts in transcendental meditation. Notably, people who had out-of-body experience would describe that they (or their conscious self) are still localized somewhere behind the eyes, suggesting an absence of experience of having a body while still having an experience of being. 

Many studies rely on participant’s reports, meaning that after showing a picture, the participant should respond with a button press if she sees the picture. This generates additional activity, not only related to the button press but also to the act of introspection. In reality, a large portion of our experiences are unreflective. We go about our lives without constantly thinking how we do that. Therefore, probably frontal cortex, that is believed to be the center of our rational, executive, and decision-making abilities, lights up in consciousness tasks only because of the need for introspection to generate the report. Perhaps the frontal cortex is not a key part of consciousness, and perhaps those who don’t have frontal lobes are nonetheless conscious.

Some other interesting findings:

• with increasing anesthesia, high-amplitude alpha rhythm emerges in frontal cortex (under normal conditions, it is absent there);

• we switch between attending to our inner world and our outer world regularly and spontaneously every 20 seconds or so;

• it is particularly challenging to diagnose patients with disorders of consciousness (locked-in syndrome, minimally conscious state, vegetative state), and some of them are misdiagnosed;

• professional athletes perform worse when they focus on the skill when compared with when their attention is divided.

I enjoyed the book. It hits all the possible angles from which consciousness can be investigated with the current methods in neuroscience. The information is abundant and there are references for papers for those who would like to dig deeper. However, preexisting knowledge of brain anatomy and neurophysiology is implied. 

Yet, one piece of information is lacking. The book omit the discussion of different neurosciency theories of consciousness, creating the impression that only one theory exists. Other theories are mentioned in between the lines, and one of them is secretly attacked. It would be nice of the authors chose to stay transparent and name theories explicitly.

Another thing that I found eerie was the cover. On the cover, the book has a brain, which is made from human bodies. But why?…

Favorite quote:

”consciousness - in the sense of having an experience - does not require sensorimotor loops involving the body and the world, does not require language, introspection, or reflection, can do without spatial frames of reference and perhaps even without a sense of the body and the self, and does not reduce to attention or memory”

June, 2024