The Spike
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The Spike

The Spike: An Epic Journey Through the Brain in 2.1 Seconds

My new book about your life in spikes

Credit: Princeton University Press

Your life is lived in spikes. Your brain uses electricity to communicate, its neurons talking to each other by sending tiny pulses of voltage down a gossamer thin cable. We neuroscientists call those pulses “spikes”. And as spikes are how neurons communicate, they are how you do anything: talk, eat, and run; see, plan, and decide.

It is the spikes pouring forth from the end of motor neurons that make your muscles contract just so, into a broad grin, eyes wrinkling; into an outstretched arm, grasping that steaming mug; into the thumb swiping up and up, scrolling and scrolling and scrolling your feeds.

It is the spikes pouring from your retina that brought the grin-inducing skit, the half-forgotten coffee, the smeary phone screen into your purview. And it is the spikes pouring across cortex that do much of what makes you human, of reading, listening to, and understanding words.

Of the 86 billion neurons in the adult human brain, about 17 billion of those are found in the cortex. Each of those sends at most one spike per second, on average. The United Nations tells us the expected lifespan of a human on this planet is about 70 years. That’s more than two billion seconds, each of which contains about 17 billion spikes in your cortex. All told, your lifespan is about 34 billion billion cortical spikes.

In my new book, THE SPIKE, I tell you the story of just two of those seconds. Of a simple act: you spot that last cookie in the office, and think — no one will mind if I take that, right?

The story of a spike’s journey from the eye that receives the light bouncing from the vista before you of desktop, box, cookie, and coworkers, through the seeing parts of cortex turning patterns of light and shade into the edges, curves, crumbs and colours of the cookie, on to cortical areas for perceiving, deciding, and remembering, plunging into the depths of the motor system, and out, out through the spine and on to the muscles, finally moving your hand to what your eye can see. A journey from seeing to deciding to moving, from eye to hand.

THE SPIKE is the story of everywhere the spike was sent, and of everything it saw on the way — the twinkling galaxy of neurons, the deep darkness of the cortex, the loneliest neuron. Of splitting into a thousand clones. Of spontaneous birth and instant death. An epic journey, all in but a moment of time.

Yet a journey replayed two billion times over, in your life in spikes.

The mewl you emitted on your appearance in the world. Your first wobbly, uncertain steps. The pain when Susan’s wildly swinging arm knocked out your wobbly tooth in primary school. Recognising that cluster of trees in the distance, and the relief of knowing you’ll now find your way across the damp, foggy hills back to the welcome warmth of the car. Plucking up the courage to ask for a date, and blurting it all out in a rush. The flush of embarrassment. The quiet euphoria of a yes. Deciding you just have to do something about the clash between the purple sofa and the lime green curtains. Remembering the smell of your mum’s bread and dad’s roast chicken. Cradling your baby. Reading this sentence. And this one.

All spikes.

From the magnificent to the mundane, everything you’ve done is in those 34 billion billion spikes that have streamed across your cortex. If I were to write the story of your life with one word for every spike, your biography would be longer than the combined length of all novels in English ever published.

You’ll forgive me if I attempted something more tractable: Instead I wrote the biography of the spike, of everything we know about your brain’s own language.

Credit: Princeton University Press

The Spike: An Epic Journey Through the Brain in 2.1 Seconds is published by Princeton University Press, and will be launched worldwide on March 9th 2021 as a hardback, e-book, and audiobook.

Some places to buy:
US: Barnes & Noble | Powell’s | Amazon
UK: Hive | Foyles | Waterstones | Amazon
Canada: BAM | Indigo | Amazon

Can’t find it where you are? Order direct from the publishers, with shipping worldwide

Listen to a sample from the audiobook

More praise for THE SPIKE:

“This book is truly wonderful. Mark Humphries takes us on a magical, demystifying tour of the brain, letting us tag along on a neural signal’s journey from eyeball to hand — as when you see a mosquito and swat it. Rollicking but deftly organized, The Spike is cast in everyday, easygoing language yet backed by tight science and state-of-the-art insights. This book’s fresh approach will charm novices as well as old neurobiological hands.” — Patricia S. Churchland, author of Conscience: The Origins of Moral Intuition

“The Spike is a fun yet deeply informative account of the electrical journey that information takes as it passes into our eyes and through our mind, and ultimately leads us to act. Drawing on the latest neuroscientific discoveries and theories, Humphries tells a compelling story of how minute changes in electrical signals in the brain give rise to our thoughts and actions.” — Russell A. Poldrack, author of Hard to Break: Why Our Brains Make Habits Stick

“The Spike gives a brilliant overview of our current understanding of brain function, from perception to action, based on our knowledge of systems neuroscience. Conveying ideas and concepts with impressive clarity, Humphries covers an astonishing amount of scientific literature. A joy to read.” — Matthias Hennig, University of Edinburgh

Want to know more about the brain? Follow us at The Spike on Medium

Twitter: @markdhumphries



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Mark Humphries

Mark Humphries


Theorist & neuroscientist. Writing at the intersection of neurons, data science, and AI. Author of “The Spike: An Epic Journey Through the Brain in 2.1 Seconds”