1GIGA-Consciousness, Coma Science Group, University of Liège, Liège, Belgium.
2Centre du Cerveau2, University Hospital of Liège, Liège, Belgium. 
3Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona 08036, Spain.
4Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098XH Amsterdam, Netherlands.
5Institute for Bioengineering of Catalonia (IBEC), Barcelona Institute of Science and Technology, Barcelona 08028, Spain.
6Biomedical Research Networking Center in Bioengineering, Biomaterials, and Nanomedicine (CIBER-BBN), Madrid 28029, Spain.
7Present address: Teamit Institute, Barcelona.
8Department of Anesthesia and Intensive Care Medicine, Liege University Hospital, Liege, Belgium.
9Anesthesia and Perioperative Neuroscience Laboratory, GIGA-Consciousness Thematic Unit, University of Liege, Liege, Belgium.
10Inria, CEA, Université Paris-Saclay, Paris, France.
11Department of Anatomy and Neuroscience, School of Medicine, Universidad Autónoma de Madrid, Madrid 28029, Spain.
12Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain.
13Computational Neuroscience Group, Center for Brain and Cognition, Universitat Pompeu Fabra, Barcelona, Spain.
14Joint International Research Unit on Consciousness, CERVO Brain Research Centre, U Laval, Canada.
15International Consciousness Science Institute, Hangzhou Normal University, Hangzhou, China.

Abstract

Experimental and clinical studies of consciousness identify brain states (i.e., transient, relevant features of the brain associated with the state of consciousness) in a non-systematic manner and largely independent from the research into the induction of state changes. In this narrative review with a focus on patients with a disorder of consciousness (DoC), we synthesize advances on the identification of brain states associated with consciousness in animal models and physiological (sleep), pharmacological (anesthesia) and pathological (DoC) states of altered consciousness in human. We show that in reduced consciousness the frequencies in which the brain operates are slowed down and that the pattern of functional communication in the brain is sparser, less efficient, and less complex. The results also highlight damaged resting state networks, in particular the default mode network, decreased connectivity in long-range connections and in the thalamocortical loops. Next, we show that therapeutic approaches to treat DoC, through pharmacology (e.g., amantadine, zolpidem), and (non-)invasive brain stimulation (e.g., transcranial current stimulation, deep brain stimulation) have shown some effectiveness to promote consciousness recovery. It seems that these deteriorated features of conscious brain states may improve in response to these neuromodulation approaches, yet, targeting often remains non-specific and does not always lead to (behavioral) improvements. Furthermore, in silico model-based approaches allow the development of personalized assessment of the effect of treatment on brain-wide dynamics. Although still in infancy, the fields of brain state identification and neuromodulation of brain states in relation to consciousness are showing fascinating developments that, when united, might propel the development of new and better targeted techniques for DoC. For example, brain states could be identified in a predictive setting, and the theoretical and empirical testing (i.e., in animals, under anesthesia and patients with a DoC) of neuromodulation techniques to promote consciousness could be investigated. This review further helps to identify where challenges and opportunities lay for the maturation of brain state research in the context of states of consciousness. Finally, it aids in recognizing possibilities and obstacles for the clinical translation of these diagnostic techniques and neuromodulation treatment options across both the multi-modal and multi-species approaches outlined throughout the review.

The Full Paper

This review is currently being submitted. A recent version of the manuscript can be found here: https://zenodo.org/record/8377867.

The Live Figures

The review "Brain state identification and neuromodulation to promote recovery of consciousness" is accompanied by data and figures that readers can interact with for increased understanding of the core concepts described in the text. These Live Figures are hosted here on EBRAINS, and this pages is the common entry point to find them.