A historical review of consciousness and its disorders.
Handbook of clinical neurology – January 01, 2025
Source: PubMed
Summary
Awareness and wakefulness are vital components of consciousness, with profound implications for understanding brain function. In examining disorders like delirium and coma, it’s revealed that some patients previously deemed "vegetative" may retain cognitive abilities; fMRI studies show up to 15% of these individuals exhibit brain activity linked to awareness. Advances in technology have illuminated the complex interactions among brain regions, emphasizing that behavioral responses alone cannot gauge consciousness levels. This evolving knowledge challenges our perceptions and treatment approaches for those affected by consciousness disorders.
Abstract
Concepts of consciousness and its disorders begin with the realization that both reside in the brain. Then came the realization that consciousness had various components, with two principal aspects, wakefulness and awareness. Awareness has multiple interconnected components, ranging from perception to abstract thought. These require selection of certain stimuli and processing as well as judgment and motivation, colored by emotion, before a consciously directed action is produced. The brain processes information and can influence behavior at levels below conscious awareness. Deeper insights into underlying neuronal functions and the complex interactions of various brain regions that support conscious experience have been made possible by scientific and technologic advancements. Our understanding of regional and global brain functions has been influenced by studies of various diseases and disorders, ranging from "brain death" to delirium. We now recognize that we cannot solely rely on behavioral responses to determine the conscious level, as some "unresponsive-wakeful," previously termed "vegetative," patients retain cognitive capacity, revealed by fMRI and electrophysiologic advances. There is still much to learn, especially as to how full awareness and the awareness of awareness arise from the brain and how to best assess and manage patients with various disorders of consciousness.