Is your brain a precise digital computer or a bubbling cauldron of chemical signals?

Ideas & Philosophy · Published 29 September 2026 · Updated 24 October 2026 Swipe more like this →

In short: In her 1994 Christmas Lectures, Dr. Susan Greenfield explored the mysterious mechanics of the human brain. By examining how neurons communicate through electrical impulses and chemical messengers, she challenged the idea of the brain as a simple machine, revealing instead a complex, shifting landscape that defines our very consciousness.

In her third lecture of the 1994 series 'Journey to the Centres of the Brain,' delivered at the Royal Institution on December 22nd, Dr. Susan Greenfield investigated the fundamental operations of the human mind. She posed a provocative question: does the brain function like a rigid computer, or is it better understood as a dynamic, bubbling cauldron of chemical activity? To answer this, she traced the journey of information from the retina, where physical visual data is converted into nerve signals, through to the brain's internal processing centers.

The mechanism of this communication relies on the neuron, the brain's basic building block. When a neuron must transmit a signal, it generates an 'action potential'—a rapid electrical event lasting only one to two milliseconds. This process involves the redistribution of sodium and potassium ions across the neuron's membrane, creating a sharp change in potential difference. Once this electrical signal reaches the end of the neuron, it triggers the release of chemical messengers known as transmitters. These chemicals diffuse to the next cell, binding to target proteins to open ion channels and convert the message back into an electrical signal.

This intricate dance between electricity and chemistry is the foundation of our thoughts, emotions, and prejudices. Because this process relies on specific chemical interactions, it is highly susceptible to external influence; a wide variety of drugs can interfere with these messengers, dramatically altering how we think and feel. Despite our deep understanding of how individual neurons and specific brain regions function, the ultimate mystery remains: how do these disparate parts work together to generate a cohesive, individual consciousness? While we have mapped much of the brain's architecture, the synthesis of these signals into a singular sense of self remains a tantalizing puzzle that continues to define the limits of modern neuroscience.

Greenfield, born in 1950, emphasizes that our brains are, in essence, ourselves. Every hope and fear is grounded in a molecular scenario occurring within the silent organ between our ears. While we have made significant progress in understanding the electrical and chemical processes that drive our cognition, the transition from these molecular events to the subjective experience of being human is a bridge that science has yet to fully cross.

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