Imagine looking at two pictures of a house. To most people, the difference between them is clear. However, for a patient named P.S., who suffered a stroke affecting the right side of her brain, both images appeared identical. This stroke left her unaware of everything on her left side. Yet, when asked which house she preferred to live in, P.S. consistently chose the one that wasn’t on fire. This suggests that her brain was still processing information from her entire field of vision, even though she wasn’t consciously aware of it. If a ball was thrown at her from the left, she might instinctively duck without knowing why.
P.S.’s condition, known as hemispatial neglect, highlights a fascinating distinction between how the brain processes information and our conscious experience of that processing. This conscious experience is what we refer to as consciousness. It encompasses our awareness of the external world and our internal selves, including our thoughts and emotions. But where does this consciousness originate? For centuries, scientists, theologians, and philosophers have debated this question without reaching a consensus.
One recent theory suggests that consciousness is the brain’s imperfect representation of its own activity. To grasp this theory, it’s helpful to understand how the brain processes sensory information. The brain constructs models based on sensory input—simplified, continuously updating descriptions of objects and events. These models form the basis of our knowledge, capturing just enough detail for the brain to determine appropriate responses.
For example, the visual system has a model that interprets white light as brightness without color. In reality, white light contains all the wavelengths corresponding to the colors we can see. Our perception is simplified but sufficient for functioning. Similarly, the brain’s model of the body tracks the configuration of our limbs but not individual cells, as that level of detail isn’t necessary for planning movement. Without this model, we would struggle to move safely.
The brain also constructs models of itself. It can focus attention on specific objects and events, shifting focus as needed. This ability is crucial for assessing threats, completing tasks, and functioning effectively. To control focus, the brain creates a model of its own attention. With 86 billion neurons interacting, this model can’t be perfectly self-descriptive, but it doesn’t need to be.
Our sense of having a subjective experience may stem from one of the brain’s models—a simplified description of focused information processing. Scientists are exploring how the brain creates this self-model. MRI studies are promising for identifying the networks involved. These studies compare neural activation patterns when a person is and isn’t conscious of a sensory stimulus, like an image. Results show that visual processing areas activate regardless of awareness, but an additional network activates only when conscious of the image. Patients with hemispatial neglect, like P.S., often have damage to a specific part of this network. More extensive damage can lead to a vegetative state, with no signs of consciousness.
Such evidence brings us closer to understanding how consciousness is embedded in the brain, but much remains to be discovered. The specific computations of neurons in consciousness-related networks are beyond our current technological capabilities. As we explore consciousness scientifically, we open new avenues for understanding human identity.
Review the case of P.S. and other similar cases of hemispatial neglect. Analyze how these cases contribute to our understanding of consciousness. Discuss in small groups how these insights might influence future research or clinical practices.
Using materials like clay or digital modeling software, create a model of the brain highlighting areas involved in consciousness. Label the regions and networks discussed in the article, such as those involved in sensory processing and attention. Present your model to the class, explaining the significance of each area.
Engage in a debate about the different theories of consciousness. Divide into teams, with each team representing a different theory, including the one mentioned in the article. Prepare arguments and counterarguments, and present them in a structured debate format. Reflect on the strengths and weaknesses of each theory.
Imagine a scenario where you experience hemispatial neglect. Write a short essay describing your daily life, focusing on how your perception and interactions would change. Consider how your understanding of consciousness might evolve through this experience.
Simulate a research study using MRI data to explore consciousness. Work in groups to design a study that investigates neural activation patterns related to conscious awareness. Present your study design, including hypotheses, methods, and potential implications, to the class.
Here are two images of a house. There’s one obvious difference, but to the patient, P.S., they looked completely identical. P.S. had suffered a stroke that damaged the right side of her brain, leaving her unaware of everything on her left side. However, when researchers asked her which house she would prefer to live in, she consistently chose the house that wasn’t burning. P.S.’s brain was still processing information from her entire field of vision. She could see both images and tell the difference between them; she just wasn’t aware of it. If someone threw a ball at her left side, she might duck, but she wouldn’t have any awareness of the ball or any idea why she ducked.
P.S.’s condition, known as hemispatial neglect, reveals an important distinction between the brain’s processing of information and our experience of that processing. That experience is what we refer to as consciousness. We are conscious of both the external world and our internal selves—we are aware of an image in much the same way we are aware of ourselves looking at an image, or our inner thoughts and emotions. But where does consciousness come from? Scientists, theologians, and philosophers have been trying to answer this question for centuries—without reaching any consensus.
One recent theory is that consciousness is the brain’s imperfect picture of its own activity. To understand this theory, it helps to have a clear idea of one important way the brain processes information from our senses. Based on sensory input, it builds models, which are continuously updating, simplified descriptions of objects and events in the world. Everything we know is based on these models. They never capture every detail of the things they describe, just enough for the brain to determine appropriate responses.
For instance, one model built deep into the visual system codes white light as brightness without color. In reality, white light includes wavelengths that correspond to all the different colors we can see. Our perception of white light is oversimplified, but good enough for us to function. Likewise, the brain’s model of the physical body keeps track of the configuration of our limbs, but not of individual cells or even muscles, because that level of information isn’t needed to plan movement. If it didn’t have the model keeping track of the body’s size, shape, and how it is moving at any moment, we would quickly injure ourselves.
The brain also needs models of itself. For example, the brain has the ability to pay attention to specific objects and events. It also controls that focus, shifting it from one thing to another, both internal and external, according to our needs. Without the ability to direct our focus, we wouldn’t be able to assess threats, finish a meal, or function at all. To control focus effectively, the brain has to construct a model of its own attention. With 86 billion neurons constantly interacting with each other, there’s no way the brain’s model of its own information processing can be perfectly self-descriptive. But like the model of the body or our conception of white light, it doesn’t have to be.
Our certainty that we have a subjective experience may come from one of the brain’s models, a simplified description of what it means to process information in a focused and deep manner. Scientists have begun trying to figure out how the brain creates that self-model. MRI studies are a promising avenue for pinpointing the networks involved. These studies compare patterns of neural activation when someone is and isn’t conscious of a sensory stimulus, like an image. The results show that the areas needed for visual processing are activated whether or not the participant is aware of the image, but an additional network lights up only when they are conscious of seeing the image. Patients with hemispatial neglect, like P.S., typically have damage to one particular part of this network. More extensive damage to the network can sometimes lead to a vegetative state, with no sign of consciousness.
Evidence like this brings us closer to understanding how consciousness is built into the brain, but there’s still much more to learn. For instance, the way neurons in the networks related to consciousness compute specific pieces of information is outside the scope of our current technology. As we approach questions of consciousness with science, we’ll open new lines of inquiry into human identity.
Consciousness – The state of being aware of and able to think about one’s own existence, thoughts, and surroundings. – In his lecture, the professor discussed how consciousness is a central topic in both psychology and philosophy, exploring how we become aware of our own thoughts and feelings.
Brain – The organ in the head of humans and other animals that is responsible for thought, memory, emotion, and sensory processing. – Neuroscientists study the brain to understand how different areas contribute to cognitive functions and behavior.
Awareness – The ability to directly know and perceive, to feel, or to be cognizant of events. – Developing self-awareness is crucial for personal growth and understanding one’s impact on others.
Experience – The knowledge or skill acquired by a person through involvement in or exposure to events. – Philosophers often debate whether experience is the primary source of knowledge or if innate ideas also play a role.
Theory – A system of ideas intended to explain something, based on general principles independent of the thing to be explained. – Freud’s theory of psychoanalysis revolutionized the way we understand the unconscious mind and its influence on behavior.
Model – A simplified representation or framework used to explain complex phenomena or processes. – The cognitive model of depression suggests that negative thought patterns contribute to the development and maintenance of depressive symptoms.
Perception – The process by which individuals organize and interpret sensory information to give meaning to their environment. – Gestalt psychology focuses on how perception is not just about sensory input but also about the mind’s ability to organize patterns.
Attention – The cognitive process of selectively concentrating on one aspect of the environment while ignoring other things. – Studies on attention reveal how multitasking can impair performance and lead to cognitive overload.
Identity – The qualities, beliefs, personality, and expressions that make a person or group different from others. – Erikson’s stages of psychosocial development highlight the importance of identity formation during adolescence.
Neglect – A condition in which a person fails to attend to stimuli on one side of space, often due to brain damage. – Patients with hemispatial neglect may ignore objects or even their own limbs on the affected side of their body.
