What Is Consciousness? The Brain, the Mind, and the Mystery Science Still Cannot Solve

By Dr. Rachel Mills

There is something strange about consciousness.You can measure a heartbeat. You can record electrical activity in the brain. You can watch blood flow change when a person sees a face, remembers a childhood event, or feels pain.

But there is one thing science still cannot place neatly on a scanner.The experience itself. The redness of a sunset. The feeling of embarrassment. The taste of coffee in the morning. The sudden memory of someone you have not seen for years. The quiet sense that, behind all of these events, there is a person experiencing them.

That is the mystery of consciousness. And despite decades of increasingly sophisticated neuroscience, scientists still do not have a universally accepted explanation for how physical activity inside the brain becomes subjective experience.

This is not because we know little about the brain. Quite the opposite. The human brain contains about 86 billion neurons, connected through an enormous network of synapses and other cellular interactions. The scale alone is extraordinary.

Yet consciousness may not be hiding in the sheer number of neurons. The deeper question is what those neurons are doing together.

The brain is not a television screen

One of the oldest intuitions about consciousness is that the brain somehow creates an internal picture of reality, like a tiny screen on which the world is displayed. Modern neuroscience does not support such a simple picture.

Instead, perception emerges from distributed neural processing. Different brain systems process information about colour, movement, shape, sound, memory, attention and bodily state. What we experience as a single coherent world is associated with the coordinated activity of many interacting systems. This is one reason consciousness is so difficult to study. There is no single structure that can simply be labelled “the consciousness centre.”

Research into the neural correlates of consciousness has identified networks and processes associated with conscious states, while clinical neuroscience has shown that changes in brain activity can profoundly alter awareness. But identifying neural activity that accompanies consciousness is not the same as explaining why that activity produces experience in the first place.

That distinction is crucial. A brain scan can tell us that something is happening. It does not automatically tell us why there is something it feels like to be that brain.

Theories of consciousness have multiplied

Scientists have developed several major theories to explain how consciousness might arise. One influential approach is Global Neuronal Workspace Theory, or GNWT. In simplified terms, it proposes that information becomes consciously accessible when it is broadly distributed or “broadcast” across interconnected brain systems, allowing it to influence multiple cognitive processes.

Another is Integrated Information Theory, or IIT. It approaches consciousness from the idea that a conscious system must possess a particular form of integrated information, with the structure of the system itself playing a central role.

Other frameworks emphasize recurrent processing, higher-order representations, predictive processing, memory, or interactions across different levels of the brain.

The important point is that these are theories, not established facts.

A 2024 review in Neuron argued that different theories may sometimes be addressing different levels or aspects of consciousness and could potentially contain compatible elements rather than being completely irreconcilable competitors.

That is an important scientific distinction. The field is not simply choosing between one proven explanation and several failed alternatives. Researchers are still trying to determine which observations truly distinguish the theories.

Then came one of the biggest tests

In 2025, researchers attempted something unusually ambitious. Instead of allowing competing theories of consciousness to accumulate evidence largely within their own research communities, an international consortium designed an adversarial collaboration to test two prominent frameworks directly: IIT and GNWT.

The experiment involved 256 human participants and combined three different measurement techniques: functional MRI, magnetoencephalography and intracranial EEG.

The researchers also preregistered the competing predictions. The result was not a clean victory for either side. Instead, the experiment found evidence consistent with some predictions of both theories while substantially challenging important claims made by each. IIT faced challenges to its prediction concerning sustained synchronization in posterior cortex, while GNWT was challenged by the observed lack of some predicted prefrontal “ignition” patterns.

This is precisely what good science can look like. The experiment did not produce a dramatic answer to the question “What is consciousness?” It produced something more useful. It showed where existing explanations appear to work, where they struggle, and which assumptions need to be reconsidered.

Consciousness may not have a single location

The 2025 findings also reinforce a broader idea emerging from contemporary consciousness research: experience may depend on interactions between multiple neural processes rather than on one isolated anatomical location. That does not mean that every part of the brain contributes equally.

Different regions and networks appear to play different roles, and research continues to investigate how posterior cortical regions, frontal areas, thalamic systems and large-scale networks contribute to conscious states. But the search for a single “seat of consciousness” may ultimately be the wrong question. Perhaps consciousness is less like an organ and more like a process.

Consider music.

A song does not exist inside one instrument. A violin contributes something different from a drum, a piano or a human voice. Yet the music emerges from their coordinated relationship. The analogy is imperfect, but it captures something important: a complex phenomenon can depend on interactions between components without being reducible to one component.

The strange relationship between perception and reality

There is another reason consciousness is so fascinating. The world we consciously experience is not a direct copy of the physical environment.The brain receives signals from the senses, processes them through multiple neural pathways, combines them with previous information and generates an ongoing representation of what is happening.

That means conscious perception is already an interpretation. This does not mean that reality is imaginary. It means that our access to reality is mediated by the nervous system. The implications are profound. If the brain constructs our conscious experience from neural signals, memories, expectations and sensory information, then the world we experience is always partly a product of biological processing.

Our perception of colour is one example. The physical world contains electromagnetic radiation with different wavelengths. The experience of colour, however, is generated by the nervous system responding to those signals.

The same physical environment can therefore produce radically different experiences in different nervous systems.

That question is explored in greater depth in How the Brain Constructs Reality — The Astonishing Science Behind Conscious Perception, where we look at the neuroscience behind perception and the brain’s construction of experienced reality.

What happens when consciousness disappears?

Perhaps one of the most revealing ways to study consciousness is to examine what happens when it changes. Sleep, anaesthesia, coma and disorders of consciousness provide natural experiments of a kind.

When consciousness changes, measurable changes occur in brain dynamics. Researchers have developed increasingly sophisticated methods using EEG, fMRI, electrophysiology and other techniques to investigate whether a person who appears unresponsive may still retain signs of awareness.

This has important medical consequences.

A patient who cannot communicate is not necessarily a patient without consciousness. A systematic review of disorders of consciousness has highlighted the limitations of relying solely on behaviour and the potential value of combining neuroimaging, metabolic measurements, electrophysiology and stimulation techniques to identify covert signs of awareness.

In other words, consciousness is not merely a philosophical puzzle. It can become a clinical question with enormous consequences for patients and families.

And then technology enters the picture

Once scientists begin to understand which patterns of brain activity accompany conscious experience, another question becomes almost unavoidable.

Could technology reproduce them? This is where consciousness research begins to overlap with artificial intelligence, brain-computer interfaces and the idea of mind uploading. Today, brain-computer interfaces can already translate certain forms of neural activity into computer commands. But this is fundamentally different from transferring a mind.

A system that decodes a neural signal associated with movement does not contain the person’s memories, personality, emotions or subjective experience. The gap between reading information from a brain and reproducing a conscious person is enormous.

Our article Brain-Computer Interfaces: When the Brain Starts Talking to the Machine explores the real technology that currently exists at this boundary between neural activity and machines.

That distinction becomes particularly important when discussing the future. We can imagine a machine that perfectly reproduces certain brain functions. But would that machine be conscious? And if it were conscious, would its experience be anything like ours? Science does not currently know.

The hardest question may be the simplest one

Imagine that, one day, scientists understand every neuron involved in a particular conscious experience. They understand the electrical signals. They understand the synapses. They understand the chemical messengers. They understand the networks. They can reproduce the relevant activity in a sufficiently advanced computational system. Would that system experience something?

Or would it merely behave as though it did? This is where neuroscience reaches the boundary of philosophy. Science can investigate measurable differences between conscious and unconscious states. It can identify neural patterns, test predictions and build increasingly sophisticated models.

But subjective experience presents a special problem. You can observe another person’s brain. You cannot directly experience their experience. You know what pain feels like because you have experienced pain yourself. You can measure another person’s neural responses to pain, ask them to describe it and compare their reports with brain activity.

But the first-person experience remains private. That is one reason consciousness has remained such a persistent philosophical problem even as neuroscience has become dramatically more powerful.

Are we closer to an answer?

In one sense, yes.

The scientific study of consciousness is far more empirical than it was several decades ago. Researchers can manipulate conscious perception, measure neural dynamics with increasingly precise tools, study altered states and test competing theoretical predictions.

The field is no longer limited to asking abstract philosophical questions.

But greater measurement has not automatically produced a final explanation.

A 2026 review of contemporary consciousness research still describes the field as lacking a comprehensive account of the neural basis of conscious experience, while comparing several major theories and emphasizing unresolved disagreements.

That may sound disappointing. It is actually a sign of scientific maturity.

A field becomes stronger when it can distinguish between what it knows, what it suspects and what it simply does not yet understand. And consciousness remains firmly in that third category.

Perhaps the mystery is the point

There is a temptation to believe that every mystery becomes less mysterious as technology improves.

Sometimes it does. But consciousness may be different. Every new discovery gives us a more detailed picture of the machinery inside the brain. Yet the central question remains strangely intact: Why does all of this processing feel like something from the inside? Why is there an experience of being you?

Why is there a point of view?

Why is there a mind watching the world?

We may eventually discover that consciousness emerges from principles that can be described completely in physical and computational terms. We may discover that several current theories capture different pieces of the same phenomenon. Or we may find that the question itself needs to be reformulated. For now, the most scientifically honest answer is also the most fascinating one.

We know enormously more about the brain than we did a century ago.But we still do not know exactly how a collection of living cells becomes a conscious self. And somewhere inside that gap between neural activity and subjective experience lies one of the greatest unanswered questions in science.