From brain to mind
A road from the discovery of nerve cells to the question of what consciousness is. As knowledge of how the brain works grew, the question of what the mind is took new forms; most of these questions are still open.
This page delivers no verdict; it presents claims and evidence with their sources. No theory in science is absolute.
Stop 11888Psychology and mindIdea / theory / claim
The neuron doctrine
Cajal argued that the nervous system is made of separate cells, while Golgi saw a continuous network. The two received the Nobel Prize in the same year.
Claims, evidence and sources →Stop 21952Psychology and mindEvent / publication / experiment
The electrical model of the nerve impulse (Hodgkin–Huxley)
Hodgkin and Huxley described with equations how the nerve signal arises from the movement of ions across the membrane.
Claims, evidence and sources →Stop 3November 1899Psychology and mindIdea / theory / claim
Psychoanalysis
Freud proposed that much of the mind works outside awareness; how far his theory can be tested has been debated ever since.
Claims, evidence and sources →Stop 41990Psychology and mindTechnology / invention
Functional magnetic resonance imaging (fMRI)
fMRI made it possible to watch the working human brain without surgery; the method's statistical limits also emerged over time.
Claims, evidence and sources →Stop 52018Psychology and mindQuestion
Are new neurons born in the adult human brain?
Whether new neurons form in the adult brain remained open, with studies published in the same years reaching opposite results.
Claims, evidence and sources →Stop 6Psychology and mindQuestion
Consciousness (open question)
How brain processes become subjective experience stands as one of the hardest questions in science and philosophy.
Claims, evidence and sources →Stop 71988Psychology and mindIdea / theory / claim
Global (neuronal) workspace theory
On one theory, consciousness is information being broadcast to a wide network in the brain.
Claims, evidence and sources →Stop 82004Psychology and mindIdea / theory / claim
Integrated information theory (IIT)
On another theory, consciousness is the amount of integrated information in a system. The two theories were pitted against each other in a joint experiment in 2025, and neither confirmed all its predictions.
Claims, evidence and sources →Stop 9PhilosophyQuestion
Free will
Experiments showing that decisions are prepared in the brain before awareness added a new dimension to the free-will debate; what the experiments mean is itself disputed.
Claims, evidence and sources →
Other journeys
- The story of the atom · 7 stops
- From the night sky to the beginning of the universe · 11 stops
- The journey of medicine · 8 stops
- From counting to artificial intelligence · 11 stops
- Reason and revelation: a debate in Islamic thought · 9 stops
- Views on the origin of living things · 11 stops