The Man Who Tasted Words is a deep dive into the world of our senses — one that explores the way they shape our reality and what happens when something malfunctions or functions differently.

Despite the complicated science permeating the narrative and the plethora of medical explanations, the book is also part memoir. And because of the way the author, Dr. Guy Leschziner, treats his patients — and how he presents the ways their conditions affect their lives and those of the people around them — it is also a very humane, heartfelt book.

We rely on vision, hearing, taste, smell, and touch to not only perceive the reality around us but also to help us navigate it by constantly processing stimuli, predicting what will happen based on previous experiences, and filling the gaps of everything we miss as we construct it. However, that truth, the "reality" we see, taste, hear, touch, and smell, isn't actually there; our brains, with the help of our nervous system continuously build it for us. But sometimes our brains or nervous system have a glitch, and that has affects reality. The Man Who Tasted Words carefully looks at — and tries to explain — some of the most bizarre glitches.

"What we believe to be a precise representation of the world around us is nothing more than an illusion, layer upon layer of processing of sensory information, and the interpretation of that information according to our expectations," states Leschziner. When one of those senses doesn't work correctly, that illusion morphs in ways that significantly impact the lives of those whose nervous systems or brain work differently. Paul, for example, is a man who feels no pain. While this sounds like a great "flaw" to have, Leschziner shows it's the opposite. Pain helps humans learn "to avoid sharp or hot objects." It teaches that certain things in our environment are potentially harmful, tells us when we've had an injury and makes us protect it, and even lets us know there's an infection in our body so we can go to the doctor. Without pain, none of that happens.

And Paul, whose inability to feel pain is due to an extremely rare genetic condition called congenital insensitivity to pain, is only one of the many people Leschziner focuses on in this book. There's also Nina, whose life has been plagued by accidents that have turned her vision problems into a nightmare. She suffers from Charles Bonnet syndrome — "the brain's desire to see, even in the absence of vision" — which causes bizarre hallucinations that include Lilliputians and, in her case, cartoon characters. She's one of three cases in the book in which not having vision doesn't equal not being able to see. Other outstanding people with horrific stories include Joanne, whose parosmia meant had to live with the "all-pervasive, all-consuming" stench of decay every day;" Dawn, a young mother who developed tumors that strangled and damaged her optic nerve; and Irene, a sommelier who worked at Michelin-starred restaurants for several years before she lost her sense of taste and learned to rely on her sense of smell to do her job.

Each case allows Leschziner to explain more about how our senses, brains, and nervous systems work, and the science is fascinating. For example, the passages dealing with deafferentation theory — the idea that "removal of inputs from an area of the brain leads to decreased inhibition of that area of cortex, causing hyperexcitability" and forcing neurons to forge new communication pathways — and Riddoch phenomenon, which is when completely blind people can "see" moving objects, are incredible interesting and make for truly engaging reading.

Despite all the science, this is a book about people, and that includes Leschziner. He writes eloquently about his family's migration and roots, his feelings and concerns while dealing with patients, and his early career as a doctor. He is also very honest about everything science doesn't know about the brain and the nervous system, the way doctors learn to accept their own mortality, and even the impact of the Covid-19 pandemic on the profession:

"This pandemic compels us to accept that there are forces beyond our control, that chance has a role. Our health, our vitality, can turn on the spin of a coin, a cough of a passer-by, a hand on a shopping trolley. We live with the knowledge that modern medicine is fallible, imperfect, and does not have all the answers."

We walk around feeling like we know what reality is, but the message at the core of this book is that all sensory information we receive is intrinsically ambiguous. And that's only one of three main problems with the senses. As Leschziner states, the first problem is that "the quantity of information that we are constantly bombarded with is simply too vast for our limited nervous systems to be able to process. The second issue is that "we are essentially living in the past" because the entire process of nerve cells communicating and interpreting stimuli takes time, so there is "an inherent delay in our perception of the world."

If we have all our senses intact, we see, taste, hear, touch, and smell every day and probably think little about the complex systems that make it all possible and the many things science still ignores about those processes. This book changes that and forces readers to question the "reality" they have created, and that makes it the kind of book that has a lasting impact.

Gabino Iglesias is an author, book reviewer and professor living in Austin, Texas. Find him on Twitter at @Gabino_Iglesias.

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