Category: Neurotech History

What if doctors could see the brain without using ionizing radiation? Magnetic resonance imaging (MRI) answered that question by using powerful magnets and radio waves to produce exceptionally detailed images of soft tissue. MRI rapidly became one of medicine’s most important diagnostic tools. Today’s structural and functional brain imaging depends on the technologies pioneered through MRI.

Until the early 1970s, physicians could rarely see inside the living brain without surgery. Computed tomography (CT) changed that by combining X-rays with computer reconstruction to create detailed cross-sectional images of the brain. For the first time, strokes, tumours, and bleeding could be identified quickly and non-invasively. Modern medical imaging began with CT and transformed neurological diagnosis.

Until the 1960s, scientists could study the brain’s electrical activity, but connecting a single neuron to a deliberate movement remained difficult. Edward Evarts changed this using implanted microelectrodes.

Evarts recorded individual neurons in the motor cortex of awake monkeys as they pulled a lever. He discovered that some neurons changed their firing with the timing and force of movement.

For the first time, researchers could listen to a single brain cell while an animal acted, linking neural activity directly to behaviour. The experiments involved invasive surgery, restraint, and trained primates—methods that also raise enduring ethical questions about the use of animals in neuroscience.

Why do we remember some experiences for a lifetime while others disappear?

Canadian psychologist Donald Hebb proposed that learning occurs when neurons repeatedly become active together, strengthening their connections. His famous idea is often summarized as, “Cells that fire together, wire together.”

Although later refined, Hebb’s theory became one of the foundations of modern neuroscience.

Today’s understanding of learning, neuroplasticity, and many artificial neural networks traces its intellectual roots to Hebb’s insight.

How does a nerve cell produce an electrical signal? By the mid-twentieth century, scientists knew neurons were electrical, but no one understood the mechanism.

Working with the giant axon of the squid, Alan Hodgkin and Andrew Huxley measured the flow of ions across the neuronal membrane. Their mathematical model showed how sodium and potassium ions generate the action potential—the electrical impulse that carries information through the nervous system.

Their work remains one of the greatest achievements in neuroscience.

Modern neurotechnology, from neural simulations to brain-computer interfaces, is built on the principles they uncovered.

Imagine remaining awake while a surgeon gently stimulates different parts of your brain with a tiny electrode.

During epilepsy surgery, Canadian neurosurgeon Wilder Penfield asked awake patients to describe what they experienced as he stimulated the cerebral cortex. Different locations produced different sensations, movements, and occasionally vivid memories, allowing him to map the functional organization of the human brain.

Penfield’s work transformed neurosurgery and deepened our understanding of the cortex. Functional brain mapping remains fundamental to neurosurgery, neurostimulation, and modern neurotechnology.

Until the 1920s, no one had successfully recorded the brain’s electrical activity from outside the skull.

German psychiatrist Hans Berger developed the electroencephalogram (EEG), demonstrating that tiny electrical signals from the brain could be measured non-invasively from the scalp.

EEG opened a completely new window into brain function and quickly became an essential clinical and research tool.

Modern hospital EEG systems and consumer brain-sensing devices trace their origins to Berger’s pioneering work.

Scientists knew neurons communicated, but how one cell influenced another remained unclear.

Charles Sherrington introduced the term ‘synapse’ to describe the tiny junction where one neuron communicates with the next. His work explained how billions of individual cells form coordinated networks.

The concept of the synapse became central to understanding learning, memory, and neurological disease.

Today’s neuroscience and many neurotechnologies are built on understanding and influencing synaptic communication.

By the late nineteenth century, many scientists believed the brain formed one continuous network.

Using Golgi’s staining technique, Santiago Ramón y Cajal carefully examined nervous tissue and concluded that the brain is built from individual neurons separated by tiny gaps. He proposed the neuron doctrine, one of the foundational principles of neuroscience.

His work transformed our understanding of how information flows through the nervous system.

Every modern model of neural circuits and brain function builds on Cajal’s insight.

Looking through a microscope, the brain once appeared as an indistinct mass of tangled tissue. Scientists could see cells, but not how individual neurons were organized or connected.

In 1873, Italian physician and scientist Camillo Golgi transformed neuroscience by developing the Black Reaction (la reazione nera), a silver chromate staining technique that randomly stained only a small number of neurons. Because just a few cells were coloured while their neighbours remained transparent, each stained neuron could be seen in its entirety—its cell body, branching dendrites, and long axon. For the first time, researchers could appreciate the extraordinary complexity and diversity of individual neurons.

One laboratory technique opened an entirely new window into the brain’s architecture, laying the foundation for modern neuroscience.

Golgi’s method also enabled Santiago Ramón y Cajal to demonstrate that the brain is composed of individual neurons rather than a continuous network, establishing the neuron doctrine that underpins modern neuroscience.