Good morning friend,

How have you been? Are you ready for Halloween? Do you have your costume ready? Pumpkin bucket of candy ready to go? 🎃

Here’s what I have for you today:

• One big thing. Your brain’s still under construction. The question is—are you building reserves or running them down? 🏗️🧠

• You have to check this out. How much do you remember about the radio in the 1970s?

Get another cup of coffee. All set? Ok, let’s jump in? ☕🦘

1️⃣ ONE BIG THING

Building a brain that ages well.

Think of your brain like a city.

Every year, some roads crack or close. Construction zones appear. A few bridges wear down. But if the city has built enough alternate routes—side streets, bypasses, crosswalks—traffic still flows. Damage to some routes doesn’t shut the city down.

As I outlined in last week’s letter, cognitive reserve is all about redundancy.

It’s the brain’s ability to reroute signals when some paths fail. Like a city’s roads, you can invest in this long before you need it.

Last week, I talked about the Nun Study — a rare window into how some people die with advanced Alzheimer’s yet never show its symptoms. Their secret wasn’t luck or genetics. It was a lifetime of expanding mental infrastructure through education, purpose, and connection.

The nuns gave their brains more ways to get where they needed to go.

This week, I want to unpack the kinds of midlife activities that can expand your neural networks (and why these specific things work).

You have likely heard the classic ideas: do some puzzles and eat leafy greens.

Or maybe you’ve seen those awkward Prevagen commercials: “I’m a motivational speaker and I’ve been taking Prevagen for three years.”

• If you’re curious, research on Prevagen and similar supplements—sold as food, not drugs—concluded, “We found little or no scientific evidence available to support the use of any of these substances to ameliorate memory loss or other cognitive symptoms.”

With cognitive reserve, what truly matters is actively building new neural networks—essentially laying down fresh roads, tracks, and sidewalks within your mind.

To truly trigger growth, you need to engage in activities that wake the brain up, sustain its attention, and stretch it across uncharted terrain.

Neuroscience shows there are three especially powerful ways to do that:

• Novelty — exposing your brain to something new and unpredictable.

• Meaning — pursuing activities that matter deeply to you.

• Social connection — engaging with others, especially in more complex social settings.

These are not separate concepts, but interlocking forces that create a feedback loop for mental resilience in midlife.

• Novelty flips the brain’s learning switch on.

• Meaning keeps the circuits active long enough to change.

• Connection binds those changes together, giving them context and life.

Together, they build your brain’s resilience system, adding layers of redundancy that keep it flexible and strong.

Novelty: Your brain’s wake-up call.

Novelty is the brain’s favorite teacher.

When you do something new — try , learn a skill, explore an unfamiliar city — your brain doesn’t just take in new information. It physically changes.

However, not all experiences achieve this. You won’t build new neural connections driving down the same roads you’ve always taken.

The first spark comes from surprise—when your internal models clash with reality, a prediction error. “Brains shift only when something is unpredicted,” explains David Eagleman in Livewired.

As you’ve gotten older, however, fewer things surprise you. This is a good thing. It means you’ve had success figuring out the world you live in.

“Neural networks lock themselves more deeply into place not because of fading function, but instead because they have had success in figuring things out… What we lose in modifiability, we gain in expertise,” Eagleman says.

Think back to the last time you started a new job (or worked for a new client). Some things are as expected, but some things are new. You navigate a new commute, make sense of new social hierarchies, and learn new IT or similar systems.

Where things are novel, where they differ from your expectations and experience, your brain will take note and prepare to alter its architecture (to physically change).

If all reports at your new job are delivered as live presentations to the whole office (and your last job only used written reports), your brain will build new neural capacity as you do more and more live presentations.

This expansion and alteration of neural pathways happens with molecules called neuromodulators. These fellas are cool. While neurotransmitters work at the level of the individual synapse (the connection between neurons), neuromodulators work across brain regions.

Some of the neuromodulators are very famous, such as dopamine and serotonin, and spend their summers along the Amalfi Coast.

But when it comes to the manual labor of building new neural networks, the task at hand as we build up cognitive reserves, we must turn to our friend acetylcholine.

Acetylcholine lays the groundwork for change. It turns on plasticity.

When you experience something novel (or meaningful, as you will see in the next section), it broadcasts a message to relevant brain regions saying, this is important—pay attention and get better at detecting this.

Sadly, acetylcholine can’t get things done on its own. Once it signals to a brain region, “pay attention,” it needs its famous friend dopamine to extend that announcement to, “pay attention, this is good, we need this.”

Together, these two flip the brain from its energy-saving “autopilot” mode into a high-alert learning state.

That’s why novelty feels so alive. It’s not just psychological; it’s biochemical. The brain is literally pouring fuel into the process of wiring new connections.

Once you understand this, you see why some activities build cognitive reserve and others don’t.

It’s not the activity, but whether your brain still finds it novel. The first few crossword puzzles build new links. Once you’re skilled, the brain becomes efficient. Repetition helps productivity but limits growth.

Novelty wakes the brain up. It keeps the learning gates open and the wiring adaptable. And as you’ll see next, what keeps those new circuits alive isn’t just doing new things, it’s caring deeply about them.

Meaning and caring: The brain’s save button.

If novelty flips the brain’s learning switch, meaning decides whether the lights stay on.

You know the difference between forcing yourself to memorize something dull and diving into a subject you love. The first fades; the second sticks. The reason isn’t willpower or talent, but chemistry.

In the last section, you learned that novelty (contrasts between what you expected and what you experienced in the world) triggers the release of acetylcholine and dopamine, preparing your brain to physically adapt to new conditions and build new neural capacity.

If surprise is an external stimulant for change, meaning is the internal equivalent. Let’s use some language examples to make this clearer.

Imagine taking a cruise around the world, and the boat breaks down in Tallinn, Estonia (which, by all accounts, is a fabulous place). You are there for four days, trying your best to buy coffee and beer in Estonian (Palun üks õlu.). This is a novel situation, unless you’re Carmen Kass. Wait—Is Carmen really subscribed to my newsletter? Hi Carmen!

Hearing Estonian is novel, but if you’ll never return to Tallinn, learning isn’t meaningful. You might remember õlut for a few days, but your brain’s language center won’t shift.

However, if I get stuck in Tallinn for four days, only to discover that Carmen Kass reads my newsletter and wants to meet me, my desire to learn Estonian may magically surge.

This is where dopamine really does its best work. Acetylcholine primes the pump (this is important, pay attention), while dopamine encodes that this new thing is rewarding—this matters, save this.

That’s why meaning and purpose are such powerful amplifiers of learning and neural development.

For building cognitive reserve, this matters a lot. Novelty opens the door for new connections, but meaning cements them in place. The combination of challenge and caring keeps the brain expanding.

Purposeful activities — those that engage emotions, curiosity, or a sense of contribution — lead to broader, more integrated neural networks. These are the connections that can help the brain reroute around damage later in life.

In this sense, meaning is more than philosophical—it's mechanical. It directs where the brain spends its plasticity budget. This same circuitry infuses life with purpose and naturally draws us toward others.

This brings us to the final—and most powerful—builder of cognitive reserve: social connection.

Social connection: The brain’s full-body workout.

If novelty sparks growth and meaning locks it in, social interaction is where everything comes alive.

Talking may seem ordinary, but to the brain, it’s complex. Every conversation utilizes memory, language, empathy, timing, and self-regulation—multiple brain regions firing simultaneously. You read expressions, interpret tone, predict reactions, weigh words, and adjust on the fly.

Neuroscientists call this whole-brain engagement. The prefrontal cortex makes decisions, the temporal lobes process language and emotion, the limbic system manages feelings and rewards, and mirror neurons help us intuit others’ feelings. In one exchange, your brain generates feedback loops that integrate thought, feeling, and prediction in real-time.

This is why social connection protects cognition so effectively. Findings from the Harvard Study of Adult Development, which I discussed in my letter, The Shared Happy Pill, show that strong relationships are the best predictor of health and cognitive vitality in later life. The reason is that social engagement keeps numerous systems active simultaneously. It’s exercise for the circuitry that makes you human.

Social experiences combine learning and reward chemistry, acetylcholine for novelty, dopamine for engagement, and sometimes oxytocin for trust and bonding. Conversation often involves novelty — unexpected turns, new ideas — which activates acetylcholine. Add the emotional resonance of human connection, and you get dopamine and oxytocin, reinforcing the sense of meaning and belonging. These are the same chemicals that sustain learning, mood, and resilience.

In short, social life doesn’t just feel good; it builds your brain. Each interaction strengthens multiple routes across the neural map, creating redundancy and flexibility. And because social exchanges are unpredictable, they continually challenge the brain to adapt. Even small talk at the coffee shop is a light mental workout; deep, emotionally charged conversations are more like endurance training.

This is the final layer in the resilience system: novelty opens the learning gates, meaning keeps them open, and connection weaves the changes together across the whole brain. Together they form a loop. Curiosity drives engagement, caring deepens attention, and interaction keeps the system flexible.

Bringing it all together.

Your brain isn’t fixed; it’s a living network, constantly under construction.

Every time you do something new, care about what you’re doing, or connect with others, you’re adding new beams to that structure, quiet renovations that keep it flexible and strong.

This week, we’ve examined how these three types of experiences contribute to building cognitive reserves.

Next week, I’ll get into how to add these into your life — the specific habits and practices that can build up your cognitive reserve. 

Thanks for reading today, my friend.

Have a great week.

Kevin

P.S. If you like this newsletter and want to support it, forward it to a friend with an invitation to subscribe right here: news.secondactcreator.com/subscribe.

P.P.S. If you’d like to continue reading, here are two recommendations:

1. Editing Life to Boost Happiness: Learn how to stretch joy, shrink pain, and slow down time by arranging your experiences differently.

2. Time is the Same, in a Relative Way: The speed of life is relative. Learn why memory and novelty matter, and how you can shape time to enhance satisfaction.