Where in the brain does consciousness reside? Scientists think they might know

In the mysterious world of neuroscience, researchers have long grappled with a baffling disorder. Called unilateral neglect, it befalls over a quarter of all stroke victims, damaging their consciousness. This syndrome leads individuals to lose conscious awareness of half of their visual field. 

For example, after a stroke affecting the right half of the brain, a person might only eat what’s on the right side of their plate, or see only the right half of a photograph, oblivious to the left half of their environment.

Intriguingly, despite their conscious disregard for one half of their surroundings, these stroke victims still exhibit emotional reactions to the entire scene. It appears that their brains are processing the whole picture, yet they remain consciously aware of only half of their world.

Unilateral neglect illuminates an enduring question in brain science: what separates the act of perceiving something from being consciously aware of that perception? 

For instance, you might not consciously register passing a shoe store while scrolling through Instagram, but you suddenly start searching for shoe sales online. It’s clear that your brain is recording things that don’t reach your conscious awareness.

Compelling new insights

On this subject, a new study led by neuroscientists from the Hebrew University of Jerusalem and the University of California, Berkeley provides some compelling insights. 

The experts claim to have identified the brain region responsible for holding sustained visual images during the brief moments we perceive them. The findings were recently published in the scientific journal Cell Reports.

“Consciousness, and in particular, visual experience, is the most fundamental thing that everyone feels from the moment they open their eyes when they wake up in the morning to the moment they go to sleep,” stated Gal Vishne, a graduate student at Hebrew University and lead author of the paper. “Our study is about your everyday experience.”

While these findings don’t yet fully explain the disconnect between perception and conscious awareness, they could have practical implications for future medical treatments. 

For instance, doctors might be able to discern, based on brain activity, whether a coma patient is still aware of the outside world and potentially able to improve. Unraveling the mysteries of consciousness could also pave the way for treatments for other disorders.

Focus of the study

Study senior author Leon Deouell is a Hebrew University professor of psychology and member of the Edmond and Lily Safra Center for Brain Research. He drew inspiration for his work from stroke patients suffering from unilateral neglect. 

“That actually triggered my whole interest in the question of conscious awareness,” said Professor Deouell. “How is it that you can have the information, but still not acknowledge it as something that you’re subjectively experiencing, not act upon it, not move your eyes to it, not grab it?” 

The study focused on understanding the link between brain activity and our conscious awareness. The researchers conducted tests on 10 patients undergoing brain surgery for epilepsy, measuring their brain activity while showing them different images for various durations.

The traditional methods for recording human neural activity, such as functional MRI (fMRI) or electroencephalography (EEG), can only provide detailed data on where or when the brain activity is occurring, not both. By utilizing electrodes implanted inside the skull, the experts overcame this limitation.

What the researchers learned 

Through the use of machine learning to analyze the collected data, the researchers discovered that the brain retains information about perceptions for much longer than previously thought. 

Unlike some earlier studies, they found that the prefrontal and parietal cortexes at the front of the brain only become active when something new is perceived, with information disappearing entirely within half a second.

However, the experts also found that the occipitotemporal area of the visual cortex at the back of the brain remains active, albeit at a lower level, for a significant period as a person views an image. This finding suggests a neural basis for stable perception over time.

Theories of consciousness 

The implications of these findings for theories of consciousness remain open to interpretation. Some researchers suggest that conscious awareness might arise when the prefrontal cortex accesses the sustained activity in the visual cortex. Others, like Deouell, believe that consciousness arises from connections among many areas of the brain.

The study’s results have been affirmed by the Cogitate Consortium, a group that held an event in New York City to debate two leading theories of consciousness. 

With over 20 current theories of consciousness, Deouell cautions that the multitude of theories indicates our lack of understanding.

However, it’s believed that this study, along with ongoing research funded by the Templeton Foundation, could eventually lead to a true, testable theory of consciousness.

Future research 

While both theories tested in the study had some accurate predictions, none of the current theories completely explain consciousness, Vishne noted. 

“With so much still unknown about the neural basis of consciousness, we believe that more data should be collected before a new phoenix can rise out of the ashes of the previous theories.”

Looking to the future, Deouell and his co-author, Robert Knight, a UC Berkeley professor of psychology, plan to explore the electrical activity associated with consciousness in other regions of the brain, such as the areas that deal with memory and emotions. 

As researchers continue to piece together the puzzle of consciousness, it’s clear that there are many more exciting discoveries on the horizon.

More about human consciousness

Understanding human consciousness is one of the great unsolved mysteries in science and philosophy. The broad consensus among researchers is that consciousness is the state of being aware or perceptive of one’s surroundings, thoughts, feelings, and experiences. 

However, the exact nature, origin, and mechanisms of consciousness are the subject of much debate and research.

Here are some key points to understand about consciousness:

Levels of consciousness

Consciousness isn’t binary (either on or off); it has various levels. These range from full alertness and wakefulness to different stages of sleep and unconsciousness. Some altered states of consciousness can be achieved through meditation, hypnosis, or the use of certain substances.

Consciousness and the brain

Consciousness is believed to arise from complex and synchronized activity among several areas of the brain, in what’s known as the global workspace theory. This theory proposes that different sensory stimuli compete for attention in the brain, and the “winning” stimuli enter our conscious awareness.

Subjective experience

Consciousness is often associated with subjective experiences or qualia, which refer to individual perceptions of the world, such as how we uniquely experience the color red or the taste of an apple.

Self-awareness

A key aspect of human consciousness is self-awareness or self-consciousness – the ability to reflect on our own thoughts and emotions. This is a characteristic that sets humans and some animals apart from other species.

Stream of consciousness

This term describes how our thoughts, perceptions, and feelings seem to flow from one moment to the next, creating a continuous narrative or “stream” that reflects our experience of the world.

Consciousness and cognition

Consciousness is intertwined with other aspects of cognition, such as memory, attention, and decision-making. For instance, we often become conscious of things that we pay attention to, and our conscious experiences shape our memories.

Theories of consciousness

There are numerous theories about the nature and origins of consciousness, ranging from dualism (the belief that mind and body are distinct entities) to physicalism (the view that consciousness is a physical phenomenon). Some leading theories in neuroscience include the Integrated Information Theory, the Global Workspace Theory, and the Orchestrated Objective Reduction theory, among others.

Neuroscience and consciousness

Studies using neuroimaging technologies like fMRI and EEG have shed light on the brain areas and networks involved in conscious awareness. This includes the prefrontal cortex, the posterior cortical areas, and the thalamus.

Disorders of consciousness

Certain conditions, such as vegetative states, coma, and brain death, are characterized by different levels of impaired consciousness. Understanding these conditions can help shed light on the neural mechanisms underlying conscious awareness.

Artificial consciousness

The field of artificial intelligence has raised questions about whether machines could ever achieve consciousness. Some researchers argue that complex computational systems could, in theory, develop a form of consciousness, while others maintain that consciousness is uniquely human and biological.

While we have made significant strides in understanding consciousness, it remains a largely mysterious phenomenon. The so-called “hard problem” of consciousness, as posed by philosopher David Chalmers, refers to the question of why and how physical processes in the brain give rise to subjective experiences. 

This question remains unanswered. Researchers from diverse fields such as cognitive science, neuroscience, philosophy, and even quantum physics continuing to explore this fascinating subject.

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