A review of “The Brain” by David Eagleman

Eagleman is an assistant professor of neuroscience at Baylor College of Medicine in Houston. A wonderful presenter, he created and wrote the fascinating six-part television series “The Brain” which was first aired on PBS in the United States in 2015 and subsequently shown (and reshown) on BBC in Britain (which is how I saw it). This book, issued to accompany the series, covers exactly the same ground in six chapters and, as you read it, you can hear Eagleman’s fluent and mellow tones.

What is the brain? Eagleman explains that an adult brain weighs three pounds (1.4 kilograms) and has the same number of cells as a child’s brain (in fact, a child of two has double the number of synapses of an adult prior to a process of neural “pruning”). He tells us that the typical brain has about 86 billion neurons and each neuron makes about 10,000 connections sending tens or hundreds of electrical pulses to thousands of other neurons every second. Consequently Eagleman estimates that the number of connections in the brain is around quadrillion (that is 1,000 billion). Twenty per cent of the calories we consume are used to power the brain which uses about the energy of a 60-watt light bulb. Since the brain has no pain receptors, a patient can be awake during brain surgery.

If there is one clear message from the series and the book, it is that the brain exhibits remarkable plasticity. People talk of the brain as hard-wired, but it is the opposite of that. So, over a period of weeks, participants in one study could cope with prism goggles that flip the left and right sides of vision. Eagleman describes some remarkable cases of people recovering from injury or operation and concludes: “The brain is fundamentally unlike the hardware in our digital computers. Instead, it’s ‘liveware’.” This plasticity has enabled the use of the cochlear implant to restore hearing or the retinal implant to restore sight and is behind the notion of sensory substitution where blind people can ‘see’ through pressure or sound.

Eagleman underlines that there is no objective reality out there, waiting to be accessed by all of us all of the time. Instead, even people with a full range of the five senses are only experiencing a version of the world created by the brain which is both very limited and very personal. Take the sense of sight. Visible light constitutes only a tiny fraction of the electromagnetic spectrum. Furthermore the brain constructs visual images based in large part of what it expects to see from previous viewing, so that “at any moment, what we experience as seeing relies less on the light streaming into our eyes, and more on what’s already inside our heads”. If the present is a variable ‘reality’, then the past is even more problematic: “Our past is not a faithful record. Instead it’s a reconstruction, and sometimes it can border on mythology.”

Neuroscientists are especially fascinated by people with special mental deficiences or proficiences caused by genetics or accidents and Eagleman quotes some amazing cases.

A young girl called Cameron Mott suffered so seriously from violent seizures as a result of a rare form of epilepsy that would eventually lead to her death, so a team of neurosurgeons removed an entire half of her brain and, except for some weakness on one side of her body, she encountered no problems because the remaining half of her brain dynamically rewired to take over the missing functions. Ten year old Austin Naber holds a world record for a sport known as cup stacking which involves transforming a stacked column of cups into a new symmetrical display in a matter of a few seconds while not actually thinking about it. Eagleman is especially interested in people who experience what is called synesthesia which is a condition in which senses are blended, so that for instance people taste words or see sounds as colours.

And we are only just beginning to understand how the brain works and why sometimes it does not (such as the growing problem of dementia). In the final chapter, Eagleman considers how we could augment our senses and extend our bodies and even speculates about whether we could one day free the brain from the body and upload our consciousness to a different platform or place. Mind-boggling stuff.


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