Taxi Drivers?

Should We Have Been Taxi Drivers?

A (not-so-mini) Miami Chronicle…. By A Salinas

I meet weekly with a small group of friends—all in our seventies, classmates from high school, and contemporaries. We share entertaining activities and some concerns too. Recently, one of us confessed to being insomniac, and it turned out he wasn’t the only one. Everyone knows the basic prescription for insomnia: if you nap, keep it short and early; avoid heavy dinners (watch that extra “drink”); stay away from bright screens before bed; sleep in a cool, dark room; keep a consistent schedule; and for the snorers, wear a CPAP mask.

But the fear lies elsewhere—namely, in the risk of developing dementia. Because insomnia contributes…

Does the kind of work we did during our productive years play a role in prevention? I recently discovered that London taxi drivers seem to be protected against Alzheimer’s…

Would it have been better to be taxi drivers instead of lawyers, economists, engineers, businessmen, or doctors? I’ve had highly prestigious colleagues who ended their days in severe dementia. Would it have been better to be a cabbie than a surgeon?

We still don’t know exactly what causes Alzheimer’s. There are a few medications that help, but their results are generally poor. So the best treatment is—not getting sick in the first place!

Can it be prevented? A new clue recently appeared from an astonishing source…

We know there are genetic and environmental risks that cause the progressive buildup and deposition of misfolded proteins (amyloid substances) in the brain, which the body can’t easily break down or eliminate. These form plaques in the cortex—but especially in the hippocampus. What’s that, you ask? I’m getting there…

The brain looks like a cyclist’s helmet with a pair of earmuffs. It’s divided into two halves or hemispheres (right and left) by a long central groove. At the bottom of that groove lies the corpus callosum, a kind of bridge that keeps the two sides connected. The cortex has a large surface area and must fold over itself many times to fit inside the skull. Those folds (or fissures) give it that brain-like appearance. There’s also not much room inside that helmet for the structures that bring in sensory signals from the body.

Deep in the brain, toward the center, around ear level, there’s a curved tongue-like structure on each side—about 5 cm long, 5 mm thick, and 5–8 mm wide—curled onto itself. Anatomists in the 6th century thought it looked like a seahorse, hence the Latin name hippocampus. (The same creature that the Chinese now consume dried for €2500 per kilo, pushing the species toward extinction…)

Henry Molaison: The Man Without Memory

For Henry Molaison, time stopped in 1953…

He hit his head in a bicycle accident at age 9, in Hartford, Connecticut, in 1935. Possibly as a result of that trauma (a theory never confirmed), he began experiencing frequent, debilitating epileptic seizures at age 16, despite receiving appropriate medical care. At 27, he was referred to Dr. William Scoville, a neurosurgeon at the local hospital, to explore a surgical option.

Scoville, guided by old-fashioned EEGs (this was before MRIs), located the epileptic focus in the temporal lobe, somewhere in the brain’s middle—“around ear level”—but couldn’t pinpoint which side. By then, some medial temporal lobe resections (on one side only) had already been performed to treat epilepsy with some success and minimal side effects. This time, Scoville proposed a bilateral medial temporal lobectomy.

On September 1, 1953, Scoville performed one of the first bilateral medial temporal lobectomies on Henry Molaison—removing a thumb-sized portion from each side, including both hippocampi…

The surgery was successful in stopping Henry’s seizures. But it came with an unexpected complication: he lost the ability to form new long-term memories (anterograde amnesia), though he retained his intelligence and remote memory. He remembered almost everything from before the surgery. But if he met someone new, by the time they said goodbye a few minutes later, he had already forgotten them.

He was left like Leonard Shelby, the protagonist of Christopher Nolan’s brilliant film Memento (2000), which won multiple awards and is on Amazon Prime. The disturbing screenplay shows a former insurance investigator who, after a brain injury and permanent damage to both hippocampi, tries to solve his wife’s murder—forgetting every step of his investigation. He tries to preserve the clues, not in his lost memory, but by taking Polaroids…

This surgical outcome surprised Scoville, who two years later sent Henry to Montreal for evaluation by expert neuropsychologists. In retrospect, it revealed the hippocampus’s crucial role in memory and helped us understand the complex learning process, which wasn’t well understood at the time. Henry lived to 82 and donated his brain for further study. His memory remained frozen back in 1953…

So how does it all work?

The brain receives sensory stimuli from the body (what we see, hear, smell, feel, etc.) and sends that information to the hippocampus, which decides whether it’s worth remembering. If so, it processes it as short-term memory and then sends it back to different areas of the cortex to be stored long-term. And all of this happens while we sleep! During sleep, the hippocampus “replays” our experiences to build lasting memories.

It also generates spatial memory, thanks to neurons that detect where we are, helping us recall places and build a mental map to orient ourselves. That memory—like all others—is first stored temporarily in the hippocampus and, during sleep, sent to the brain for long-term storage.

Fun fact:

The hippocampus is the only place in the brain where new neurons can be generated throughout life. So even in adulthood, we can boost our memory with physical exercise and mental challenges. However, it’s also vulnerable—to stress, and especially to Alzheimer’s, where it’s the first structure to deteriorate. Hence the early symptoms: recent memory loss and spatial disorientation. People go out alone and get lost, unable to find their way home…

And what about taxi drivers?

In a landmark study published in 2000, MRIs were done on 16 healthy, right-handed, male London taxi drivers (from a city with no grid, hard to navigate), and compared with 50 right-handed, healthy men from the general public. The taxi drivers had noticeably larger hippocampi, and the longer they’d been driving, the bigger their hippocampi were. Intensive and prolonged spatial navigation (driving from place to place) can change the structure of the human brain, particularly enlarging the hippocampus.

In a study published last year on Alzheimer’s mortality among taxi and ambulance drivers in the United States, researchers reviewed the occupations listed on death certificates for 9 million people who died between January 1, 2020, and December 31, 2022. The incidence of Alzheimer’s was significantly lower—four times lower—among taxi drivers compared to the general population. It was even lower for ambulance drivers.

Other types of drivers—bus drivers, commercial pilots, and ship captains—showed the same risk of dying from Alzheimer’s as the general population. Why? Perhaps because those jobs follow predefined routes, which don’t require much hippocampal effort. So if you thought driving for Uber would help prevent dementia, think again…

“Life without work is worth nothing, but work without purpose is worthless too.” —Seneca

No honest work is undignified. All are necessary. But I don’t think we need to quit our professions and become taxi drivers. Ambulance drivers instead of doctors? No, no, no! Maybe we could help prevent Alzheimer’s by driving without GPS and getting intentionally lost now and then…

I recently read that the shingles vaccine and tech use seem to help prevent dementia. And that tooth loss and gum disease are linked to hippocampal shrinkage. Go figure!

We all want to reach the end in good shape.

“Old age is not a time of waiting, but a stage of life that demands reinvention.” —Simone de Beauvoir

Besides having good genes, we must move, eat well, socialize, relax—and sleep well! And just in case, get vaccinated and floss your teeth…

I know a 93-year-old rabbi who’s in great shape. He’s an avid reader and, as far as I know, active on four social media platforms—YouTube, Twitter, Instagram, and Facebook.

My father-in-law is 91 and also doing great. He goes to synagogue every morning and does a crossword almost daily…

Alberto Salinas,

writer (and retired surgeon)

Miami, May 4, 2025

For my friend “A”, the insomniac…

P.S. To get a license to drive one of London’s classic black cabs, candidates must pass a rigorous process known as “The Knowledge.” It takes 3 to 5 years (I studied Medicine in 6), and requires memorizing 25,000 streets and routes to nearly every point of interest—hospitals, hotels, police stations, restaurants, theaters, and more. Many of these drivers don’t rely on GPS…