Consciousness is the state of being aware and able to think about one's own existence, emotions, thoughts, and relationship to the environment.
For centuries, efforts to understand consciousness have fueled debate among philosophers, who investigate questions like, "What makes us, us?" and "Do we have free will?" While we know that consciousness is inextricably linked to the brain, a comprehensive understanding of this connection remains an open scientific question.
What is consciousness?
Consciousness encompasses our awareness of self and our relationship to the world around us. It is what allows us to enjoy the experience of tasting a slice of pizza, to recognize the smell of ocean air, to indulge in curiosity about our own thoughts, and to daydream about our plans for the future. These experiences, known as qualia, highlight the distinctly individual nature of consciousness. To some, consciousness is the ability to think about thinking—detached from unconscious mental functions.
Consciousness and Anatomy
How consciousness arises from the brain is a puzzle that fascinates scientists and philosophers alike. To explore the connection between the biological brain and the intangible conscious mind, researchers start with the brain's anatomy. The human brain contains approximately 86 billion neurons, or nerve cells, that transmit information throughout the body and communicate with one another through synapses. This complex network of neurons and synapses processes information that ultimately influences our emotions, thoughts, and behaviors.
One predominant approach to understanding how humans become conscious is called the neural correlates of consciousness (NCC). This concept, made popular by former Caltech professor Christof Koch, describes how different parts of the brain work together to give rise to consciousness. It suggests that specific neural processes and activities in the brain are connected to specific aspects of the conscious experience. For instance, when scientists take images of brain activity using fMRI, they can observe how different areas of the brain "light up," or activate, depending on the thoughts or emotions an individual is experiencing. If a person is shown a picture of a face for example, the fusiform face area (FFA) in the temporal lobe of the brain shows increased activity. However, if the person is shown a picture of a house, the parahippocampal place area (PPA) in the brain shows increased activity instead. This suggests that these patterns of activity among nerve cells in the brain are deeply related to our subjective conscious experiences.
The connection between consciousness and the physical brain also becomes apparent when brain function is impaired through injury or neurodegenerative conditions such as Alzheimer's or Parkinson's diseases. In the case of Alzheimer's, for example, abnormal deposits of proteins build up in the brain and lead to progressive damage and death of neurons, particularly in regions involved in memory and cognition, such as the hippocampus and cerebral cortex. As a result, individuals with Alzheimer's often experience a gradual decline in cognitive function, memory loss, and changes in their conscious experiences, such as difficulty in recognizing familiar people or places, disorientation, and altered perceptions of reality.
Additional Perspective
Cognitive neuroscience, the study of the brain as it relates to things like memory, language, and other mental processes, provides additional perspective on consciousness by examining how the brain handles information. While the NCC approach focuses on identifying specific brain areas and networks associated with conscious experiences overall, cognitive neuroscience looks at cognitive functions, such as attention, perception, and problem-solving, and how these processes are integrated in the brain.
Cognitive neuroscientists use tools like brain imaging to map which areas of the brain are active during cognitive tasks, and they aim to understand the biological roots of consciousness. This perspective can inform how brain activity, structure, and cognitive processes contribute to our inner experiences and sense of conscious awareness.
The Hard Problem
Despite advances in our understanding of the brain, explaining how consciousness is derived remains an open question in science and philosophy. It is even referred to as the "hard problem" of consciousness, a term coined by philosopher David Chalmers.
"Why should there be a certain way to experience being a human when we are conscious that vanishes in a coma or dreamless sleep and is entirely absent in inanimate objects like chairs or jackets?" says Ralph Adolphs, Bren Professor of Psychology, Neuroscience, and Biology. "This contrast underscores a deep mystery."
Chalmers also identified the "easy problem" of consciousness: understanding brain functions like perception, attention, and memory. Neuroscientists and psychologists have made significant progress in these areas, revealing much about how neural circuits and information processing work. However, these explanations do not address what it is like to be that brain, leaving the hard problem unresolved.
The Mind–Body Problem
This question ties into a long-standing philosophical debate known as the mind–body problem, which considers the relationship between the mental and the physical. Dualism, one view within this debate, suggests that consciousness arises from nonphysical substances or properties, such as the soul or the mind, rather than solely from brain activity. In contrast, materialist or physicalist views argue that consciousness is a product of the brain and can be fully explained by physical processes.
"Consider this example: Philosopher Gottfried Leibniz asked us to imagine miniaturizing ourselves and walking into someone's brain. Despite seeing all the molecules, neurons, and electrical potentials, we would not have any clue that there is conscious experience in that brain," Adolphs says. "Similarly, if intelligent aliens were to visit Earth and observe humans and animals from a distance, would they ever stumble upon the idea that any of these are conscious? No, how could they?"
Neuroscientists and philosophers alike continue to work toward a more comprehensive understanding of how the brain gives rise to our subjective experiences. This work calls for an interdisciplinary approach spanning the fields of neuroscience, psychology, philosophy, and computer science, with each contributing unique observations and perspectives to this complex question.
