One of my patients had been the epitome of middle-aged success: a businessman from south London who ran a thriving textiles firm.

Then he developed a brain tumour, had an operation to remove it – and everything changed.

He proceeded to fire staff on a whim, and squandered money chasing deals he could never hope to close. He signed an enormous contract with a materials supplier, despite having neither the staff nor storage space to handle the fabric when it was delivered to his factory. Material worth a fortune rotted outside his company headquarters.

Then there was my female patient in her late 60s who’d also had a brain tumour removed. She was sat bolt upright, apparently concentrating on the memory test I’d given her, when I suddenly felt her hand sliding up my thigh to my crotch.

I handled it as best I could, gently removing her hand and saying, ‘Please concentrate on the test.’ ‘Oh, I had no idea what I was doing!’ she said, before sliding her hand back up my leg minutes later.

These patients had suffered damage to a vital area of the brain – their frontal lobe, which can be found just behind your forehead. It takes up about 30 per cent of the brain’s volume and controls much of our behaviour.

It’s the home of our executive function – those mental skills we use to manage our impulses, juggle tasks in pursuit of a goal, and hold information in our minds from moment to moment (known as ‘working memory’).

As more than one patient has shown me, damage to the frontal lobe can impair judgment, causing people to say things that are uncharacteristically rude or inappropriate. It can also affect their ability to complete tasks that used to be simple for them – like my formerly proficient businessman suddenly struggling to manage his finances.

Dr Adrian Owen has been a neuroscientist for more than 35 years and spent much of his working life at the University of Cambridge, before moving to Canada in 2010 to work at the Centre for Brain and Mind at Western University

A neuroscientist for more than 35 years, I’ve spent much of my working life at the University of Cambridge, before moving to Canada in 2010 to become professor of cognitive neuroscience and imaging at the Centre for Brain and Mind at Western University.

Over my career, I’ve been lucky enough to be part of a neuroscientific revolution which has allowed us to make detailed maps of the brain with fMRI (functional magnetic resonance imaging) scanners. Thanks to research I was involved in, we now know which areas of the brain become active – or light up on the scan – when, for example, you plan something, solve a problem or imagine your future.

In 2006, my lab made a landmark discovery that changed how we think about the vegetative state. When we asked a patient believed to be entirely unaware to imagine playing tennis, her brain responded exactly as a healthy person’s would, showing she was conscious and able to follow what we were saying.

A few years later we went further, showing that patients like her could even answer questions and communicate with the outside world using nothing but their thoughts. Since then, my lab has completed dozens of studies on executive function, scanning the brains of thousands of people, some with brain injuries and many without.

And thanks to our digital cognitive assessment platform Creyos – which allows other researchers and clinicians to access the short, gamelike tasks we’ve developed to assess memory, attention, reasoning and self-control – we’ve tested the brains of almost 20 million volunteers.

Through this testing, again and again I’ve seen how our executive function drives every conscious decision we make – determining the shape of our lives, defining our successes and failures.

We scientists have increasingly learnt how failures of executive function are apparent in those recovering from strokes, cardiac arrests and brain injuries.

But perhaps most fascinating are the emerging links between deteriorating executive function and Alzheimer’s disease.

Although most people associate Alzheimer’s with long-term impaired memory, there’s increasing evidence that executive function is also affected. Impairments in working memory, for instance, have been reported in the earliest stages of the disease.

Indeed, research published in the journal Alzheimer’s & Dementia in 2016 found that cognitive deficits entirely unrelated to long-term memory – such as trouble planning ahead or juggling several things at once – can emerge as many as 14 years before a formal Alzheimer’s diagnosis.

Spotting the earliest signs of dementia is hugely important. More than 100 anti-Alzheimer’s drugs are currently in clinical trials worldwide, and many of the results suggest early intervention is going to be most effective when trying to slow the disease’s progression.

If spotting deteriorating executive function – the kind of slip that looks like struggling to stay on top of bills, or losing the thread halfway through a task – could give you as much as a 14-year head start on an official diagnosis, well, the implications are obvious.

And, remarkably, there is evidence that teaching people in the early stages of the disease a few simple mental strategies can measurably improve their working memory. Even more amazing is the fact that such working-memory training in mild Alzheimer’s disease can, at least temporarily, put the brakes on the downward spiral of cognitive deterioration.

One study published in the British Journal of Psychiatry in 2017 recruited 30 patients with mild Alzheimer’s disease and presented them all with increasingly long sequences of numbers, which they would have to repeat back after a short delay.

Some of the patients were then trained in a method known as ‘chunking’, where you break digits into smaller, more manageable chunks and develop a system to spot patterns. The others spent exactly the same amount of time on a similar number task, but without the chunking method.

After 18 half-hour sessions over eight weeks, remarkably, the trained group improved significantly in their ability to remember sequences that had some sort of structure or pattern to them. No such effect was observed in the other group.

The untrained patients also dropped almost two points on the Mini Mental State Examination, a widely used measure of cognitive performance, which is also a tool for diagnosing dementia.

In contrast, the trained patients’ performance remained the same as at the beginning of the trial.

Another way to slow cognitive deterioration in early Alzheimer’s is the ‘memory palace’ technique, which taps into our spatial navigation abilities – our brain’s built-in GPS, if you will.

Spatial navigation relies on an area in the brain known as the hippocampus, which is also responsible for forming and storing recent memories. So, whether you’re physically tracing your steps back to where you parked the car or mentally rehearsing the route you’re going to take to your favourite restaurant across town, your brain is creating, updating and using mental maps to guide you.

To do this, so-called ‘place cells’ in the hippocampus effectively create a mental map of the environment. Each place cell is tuned to a particular location, so as we move through a space such as a room, different place cells fire in a sequence reflecting the path and layout of that room.

Users of the ‘memory palace’ technique utilise their natural spatial navigation abilities to mentally associate the information they want to remember with familiar locations, such as the interior of a house.

By mentally navigating this familiar environment, individuals can recall information in a specific order. I was most impressed by the ‘memory palace’ technique when I appeared at Latitude Festival in 2009 to give a talk on drugs and the brain.

It was 45 minutes long, full of unpronounceable words, and I‘d agonised over it. Immediately after I delivered it, the next person to speak was memory maestro Richard Bowdler, who proceeded to repeat my talk in about eight minutes – not far off word for word – having heard it just this once.

To achieve this, while I was talking, he started his mental journey within the festival tent, in the corner where there was a fridge. When I mentioned the word ‘hippocampus’ he visualised a hippopotamus sitting on top of the fridge, before moving on to the next location – he explained that the wackier the mental links he made, the better.

Another way to give your memory a hand in early Alzheimer’s – and, indeed, in general – is to turn facts into a story.

To hold on to a short list of errands, you might link them into one absurd little scene: you post a letter, the postbox bursts into flames, and the fire is put out by the milkman you still owe money to.

The stranger the story, the harder it is to forget. My lab’s studies with MRI have proven that these sorts of methods can reduce the mental load by anchoring new information to stronger neural pathways, effectively providing ‘memory crutches’.

As with my female patient with the wandering hands, the loss of inhibitory control – or willpower – is another failure of executive function. This is also seen in dementia patients.

Willpower is considered one of our most important executive functions because it’s key to almost every decision we make.

A test I have used with great effect to examine someone’s inhibitory control is known as Double Trouble.

I display the word ‘red’ in a red-coloured font and ask the subject to say the colour of the font. This, they easily manage. But when the word ‘red’ is written in blue type, and they have to say the colour of the font, it becomes much harder.

This is because our brains are wired to automatically read words, and so to not do so requires effort – or what we in neuroscience call inhibition.

Recently, my lab found testing one’s inhibitory control can predict the onset of dementia with startling accuracy.

In 2023, using the digital cognitive tests available through Creyos, we developed an algorithm designed to identify people with dementia-like cognitive impairment based solely on their performance on two cognitive tests, one of which was Double Trouble.

Remarkably, this was able to accurately spot patients who had dementia more than 80 per cent of the time.

It suggests early failures of inhibitory control in the general population may predict the onset of dementia further down the line. If so – and larger studies will be needed to confirm it – this could be a game-changer in the race to detect, prevent and treat Alzheimer’s disease. But there’s a flip side to this.

Drugs which have been recently approved for conditions like Alzheimer’s come with a considerable cost and potential unwanted side-effects.

Some studies have shown coffee, in moderation – up to three or four cups a day – can improve aspects of executive function, such as planning and task-switching. But perhaps the easiest trick of all is to simply pick up a pen, push everything else out of your head and write a list

Treating a patient for Alzheimer’s could have disastrous results if they are simply showing the natural signs of cognitive wear and tear. So correctly predicting who will not go on to have Alzheimer’s disease is just as important as predicting who will.

If Double Trouble could play any role in that, it would be a huge step forward. Unlike blood tests, genetic screening or expensive brain scans, a simple five-minute online test of executive function costs almost nothing and can easily be administered to huge numbers.

Alzheimer’s charities and campaigners have often asked us to imagine a future where there is a cure for this terrible disease.

While that still seems far off, my work points to something nearer: a future in which, even after Alzheimer’s takes hold, memory loss can be slowed and the mind kept steadier for longer, with simple mental strategies and training.

Why hunger is bad for your brain

Even outside of Alzheimer’s, failures of executive function happen to us all – many elderly adults get lost, confused, blurt out whatever comes to mind, or tell the same story again and again. Even the young can sometimes be inexplicably beset by ‘brain fog’ – a kind of confused muddle.

The memory strategies I’ve described (see above) can help us to hold on to specific things more reliably, from a shopping list to a set of directions. But there are lifestyle changes which can be made, too.

Regular physical exercise, particularly aerobic activity (such as running or cycling), has been shown to enhance frontal lobe function and improve planning ability, even in older adults.

Exercise enhances blood flow to the brain, which may encourage the growth of new brain cells, and boost the release of brain-derived neurotrophic factor – a sort of fertiliser for your neurons. The impact is short term, but is still evident.

Sleep is another non-negotiable. Sleep deprivation disrupts activity in the dorsolateral prefrontal cortex – the very region that’s critical for planning. Keeping to a consistent sleep schedule (even on weekends) is one of the most powerful ways to preserve your mental stamina.

Many studies have shown that sleep-deprived people are not only more reactive but less able to interpret facial expressions accurately, sometimes mistaking neutral or even friendly expressions as threatening. This ‘emotional dysregulation’ can lead to conflicts, anxiety and a distorted view of social situations.

When we’re stressed, anxious or feeling low, our ability to switch between different tasks suffers.

These emotional states demand cognitive resources, leaving fewer available for juggling multiple streams of information. Even mild stress can cause a rapid and dramatic loss of prefrontal cognitive abilities.

Stress management through mindfulness, moderate exercise or just taking regular breaks can help. This is not a luxury – it’s brain maintenance.

Hunger is also bad for your frontal lobes, particularly your ability to regulate your emotions. Indeed, ‘hanger’ is real, rooted in the immense energy requirements of the human brain.

The brain voraciously consumes energy, accounting for about 20 per cent of our total energy use, and it’s critically dependent on glucose to deliver those essential calories. One theory about ‘hanger’ is that the brain responds by reserving its stock of glucose for essential functions like seeing and moving, while less critical functions (like behaving within socially acceptable norms) get temporarily shut down.

What you eat can also affect your executive function. In one 2016 study, 25 adults drank grape juice every day for 12 weeks, and improvements in attention, working memory and planning were noted – there were also improvements in the participants’ behaviour when driving, suggesting the benefits of drinking grape juice translate into real-world differences.

A more recent study in 2023 at King’s College London found some aspects of executive function were better in blueberry eaters than in participants who were fed a placebo. Both grapes and blueberries are rich in flavonoids, a natural compound found in fruits and other plants.

Some studies have suggested flavonoids can reduce inflammation, protecting brain cells from damage –while animal studies have shown flavonoids can block beta-amyloid plaque build-up in the brain. These protein clumps that form between nerve cells are a hallmark of Alzheimer’s.

Some studies have shown coffee, in moderation – up to three or four cups a day – can improve aspects of executive function, such as planning and task-switching.

It also increases the levels of several brain chemicals including dopamine and acetylcholine, which may affect mood, energy levels and executive function.

However, perhaps the easiest trick of all is to simply pick up a pen, push everything else out of your head and write a list. As well as helping memory, writing also helps the executive function of planning.

Adapted from Think Before You Think by Dr Adrian Owen (Guardian Faber Publishing, £20) to be published August 13. © Dr Adrian Owen. To order a copy for £18 (offer valid to 11/08/26; UK P&P free on orders over £25) go to www.mailshop.co.uk/books or call 020 3176 2937.