Part V
When science reaches the edge of consciousness
Modern neuroscience can now observe many things that were once completely out of sight. Brain scans record changes in neural activity while someone looks at another person’s face, recalls an old memory, listens to music, enters deep meditation or moves into an unusual state of consciousness. EEG can also track changes in electrical activity across waking, sleep, dreaming, anaesthesia and the effects of psychedelic substances.
The amount of data keeps growing, yet one problem remains: how does electrochemical activity in brain tissue become the feeling of “I am here”?
A neuron can fire. Neural networks can increase or decrease their activity, coordinate with one another or change the way they connect. Science can measure many of the changes that accompany an experience, but what red actually looks like, how sadness is felt in a piece of music, or why pain feels painful still belongs to the person having the experience.
In 1995, Australian philosopher and cognitive scientist David Chalmers called this the hard problem of consciousness. The term separates subjective experience from functional questions such as how the brain receives signals, processes information, controls behaviour or distinguishes between stimuli.
Neuroscience has described many of the brain changes that accompany different states of consciousness.
Meditation, sleep, anaesthesia and psychedelic substances can all alter conscious experience alongside measurable changes in brain activity. During some of these states, the sense of self may weaken, the boundary between self and surroundings may become less distinct, time can feel unusual, or a powerful sense of unity may appear. Some people describe such experiences as unusually clear, expansive and extremely difficult to express in ordinary language.
Instruments can record changes in the nervous system during these moments, while the content of the experience still has to come from the person living through it.
- You can look at a brain scan of someone in pain, but you do not directly feel their pain.
- You can record the brain activity of someone who is dreaming, but you still have to wait until they wake up to hear what happened in the dream.
- A scanner can detect neural changes when someone reports a sense of unity, but it cannot tell us what that experience felt like from the inside.
Consciousness therefore comes with two kinds of data. An outside observer can measure neural activity, while the inner experience is directly accessible only to the person having it.
The debate around consciousness also runs into another issue: does the brain produce consciousness, or is it the condition through which consciousness becomes expressed?
Most modern neuroscience begins from the strong dependence of conscious experience on the nervous system. Brain injury can alter personality, memory or awareness. Anaesthesia can interrupt conscious experience for a period of time. Sleep, drugs, electrical stimulation and many other biological changes can also directly affect what a person perceives and feels.
A different philosophical tradition, often described through filter theory or transmission theory, treats the brain more like a filter or receiver. In this view, consciousness may not be produced entirely within the brain; the brain might instead limit, shape or transmit it into human experience. William James, Henri Bergson and later writers discussed different versions of this idea.
So far, the brain-as-receiver model has no experimental evidence that establishes it as a scientific explanation. It remains primarily a philosophical hypothesis.
We know that damage to particular brain regions can alter memory, which networks tend to become active when people think about themselves, and how sleep, anaesthesia or drugs can change consciousness. We also know that the brain can build whole worlds in dreams, link bodily states with emotion, respond to other people and adjust to the surrounding environment.
What still lacks a widely accepted explanation is why all of these processes are accompanied by subjective experience at all. Answering that may require several fields to work together beyond neuroscience as it currently stands, or even force us to rethink how the problem itself is framed.
At present, we are left with a piece of tissue whose activity can be weighed, scanned and measured, while its subjective experience remains only partly explained. A part of the universe has become capable of looking at the sky, remembering, dreaming, loving, fearing and observing itself. In this series, “Sanctuary of the universe” is a name for that strange condition: matter living through experience while also trying to understand where that experience comes from.
The End.
References
- Chalmers, D. J. (1995) — Facing up to the problem of consciousness
- Koch, C., Massimini, M., Boly, M. et al. (2016) — Neural correlates of consciousness: progress and problems
- Franks, N. P. (2008) — General anaesthesia: from molecular targets to neuronal pathways of sleep and arousal
- Stoliker/Razi et al. — Neural mechanisms and psychology of psychedelic ego dissolution
- Abellaneda-Pérez et al. (2024) — Neuromodulation and meditation: A review and synthesis...
- Brain-as-filter / transmission theory của William James