YOUR MYSTERIOUS BRAIN
BBC Focus - Science & Technology|November 2021
Science has mapped the surface of Mars and translated the code for life. By comparison, we know next to nothing about what’s between our ears. Over the next few pages, we ask leading scientists to answer some of the most important questions about our brains…

Do we really have free will?

DR LISA FELDMAN BARRETT

Lisa is a professor of psychology at Northeastern University. Her latest book is Seven And A Half Lessons About The Brain (£14.99, Picador).

The question of free will is still hotly debated. On the one hand, we clearly experience ourselves as able to make choices and freely act on them. If you fancy some crisps, you can choose to walk into a shop, buy a packet and eat them. Or you can choose to eat a pastry, a salad, or nothing at all. This certainly feels like free will.

On the other hand, neuroscience evidence clearly shows that the brain usually initiates our actions before we’re aware of them. Here’s what I mean. Your brain’s primary task is to regulate the systems of your body to keep you alive and well. But there’s a snag: your brain spends its days locked in a dark, silent box (your skull) with no direct access to what’s going on inside your body or outside in the world. It receives ongoing information about the state of your body and the world – ‘sense data’– from the sensory surfaces of your body (your retina in your eyes, your cochlea in your ears, and so on). These sense data are outcomes of events in the world and inside your body. But your brain does not have access to the events or their causes. It only receives the outcomes. A loud bang, for example, might be thunder, a gunshot, or a drum, and each possible cause means different actions for your brain to launch.

How does your brain figure out the causes of sense data, so that it prepares the best actions? Without direct access to those causes, your brain has to guess. And so, in every moment, your brain remembers past experiences that are similar to your present circumstances, to guess what might happen in the next moment, so it can prepare your body’s next action. Guessing (and potentially correcting mistakes) is more efficient than reacting from scratch. These predictions, are, in effect, your brain changing the firing of its own neurons to prepare your body to act, a second or so before the movements actually occur. This predictive process happens completely outside your awareness, but it is continuous throughout your life, and a growing number of scientists are now pretty sure that it’s a primary driver of your actions.

From this perspective, your brain’s decision to eat a packet of crisps was launched as a plan for action before your brain made itself (you) aware of this plan. So this action, like most of your actions, was guided by predictions that were under the automatic control of your memory and your current surroundings. This description of your brain’s inner workings certainly seems to suggest an absence of free will.

And so we arrive at the point where the free will debate has lingered for a long time. We won’t settle the debate here, but I’ll highlight one puzzle piece that is often ignored. Your brain predicts (in large part) by reassembling your past experiences that are similar to the present moment. That means every new experience you cultivate for yourself – every new thing you read, every new person you talk to, every new thing you learn – is an opportunity to change what your brain will predict in the future, and which actions you may take. In other words, your brain (meaning you) can nudge its future predictions in various directions, right now, by investing in new experiences. You are continually cultivating your past as a means of controlling your future. This may be a form of free will, but it’s extended over time and therefore different from how we usually think about free will in the moment. If you practise a skill, whether it’s riding a bicycle, or talking to someone who believes things that you abhor, you hone your brain’s predictions until that skill becomes automatic and likely to be repeated.

With practice and a little investment of energy, you can make some automatic behaviours more likely than others and have more control over your future actions. Perhaps not as much control as you might want, but more than you might think.

Do genetics affect mental health?

DR DEAN BURNETT

Dean is a neuroscientist and author. His latest book is Psycho-Logical (£9.99, Guardian Faber).

When it comes to things that protect or harm our mental health, the role of our genes is often an afterthought. After all, mental health disorders and issues are products of our minds and brains, whereas our genes are microscopic elements of our DNA. It may seem a bit of a reach to assume that the two are connected.

This is wrong, though. Scientific research has revealed that many mental health disorders have a significant genetic component, which undoubtedly shapes our understanding and treatment of them.

If you step back and look at it logically, it makes perfect sense that our genes would influence our mental health. After all, as intangible as they may be in so many ways, our minds, consciousness, thoughts and emotions are all products of activity in the brain, of the countless complex signals being sent and received by billions of brain cells, also known as neurons. And these signals depend on intricately complicated brain cells working as they should. The good functioning of cells is reliant upon the molecules that make them up. And these molecules, particularly proteins, are determined by our genes.

This means that if there’s a flaw or issue with the code in a specific gene, the molecules it produces won’t be quite the right shape. And for proteins in particular, their shape is a crucial aspect of their ability to interact with other molecules in the appropriate way, which is what they’re for. This means that any cell which has these flawed proteins will be less able to function properly. And if these cells are neurons, then the processes that lead to the formation of our minds can be affected, sometimes in ways that are disruptive, or at least unhelpful.

So, although it’s via several steps, it’s easy to see that our genes can play a role in our mental health. This isn’t to say that they’re the sole factor determining our mental health. It’s not the case that some people have a specific ‘depression gene’ or ‘anxiety mutation’, and that those with these genetic traits develop the eponymous disorder, and those without them never will. In truth, the brain is far too complex for that, particularly when it comes to the parts that result in our mind. There are so many components at work, so many systems combining to give rise to consciousness, and so much redundancy and adaptability in your typical brain, that a single atypical gene automatically producing a (complex and versatile) disorder is extremely unlikely, just like how a single poorly installed circuit in an electricity grid doesn’t inevitably lead to blackout.

However, genetic factors can increase the risk of mental health issues, or make us more vulnerable to developing them, by reducing the brain’s ability to deal with or compensate for traumas and other disruptions. This is presumably why many mental health problems are seemingly hereditary, and why some mental health conditions seem to have similar genetic attributes.

Overall, it’s fair to say that genes play a significant role in our mental health. But so do many other things. And that’s where it gets confusing.

Brain food

Fill your plate with these to keep your grey matter healthy

Can you improve your brain with food?

KIMBERLEY WILSON

Kimberley is a chartered psychologist, author and visiting lecturer, with a degree in nutrition. Her first book, How To Build A Healthy Brain (£16.99, Yellow Kite), is available now.

Your brain is hungry. In fact, it is the hungriest organ in your body. Despite making up only around 2 per cent of your overall body weight, your brain consumes about 20 per cent of your body’s total energy requirement. But it is a mistake to think that it’s only energy that the brain needs to function well; a full complement of micronutrients in sufficient quantities are essential for a healthy brain.

Evidence is growing that deficiencies in these nutrients contribute to poor brain and mental health. Moreover, there is not a single point in the lifespan, from conception to old age, where nutrition doesn’t play an important role in brain structure and mental health. For example, we know that it is important for women trying to conceive to take folic acid (a B vitamin) to prevent neural tube defects conditions such as spina bifida. Of course, it’s not just folic acid that the developing brain needs. The essential omega-3 fatty acids form the structural building blocks of brain cell membranes. One of these fats, DHA, makes up between 10 and 20 per cent of the brain’s total fatty acid content. DHA promotes healthy neuronal morphology and cell signalling, allowing brain cells to communicate efficiently. During pregnancy, accumulation of DHA in the brain and retina is necessary for proper brain development and visual function.

The body is unable to synthesise adequate amounts of DHA, so it must come from the diet. Fortunately, it is abundant in seafood and oily fish such as sardines, mackerel, salmon and trout, and one 140g serving of mackerel supplies enough omega-3 for a week. Consequently, greater maternal seafood consumption during pregnancy is associated with improved brain development and cognitive function in children, including better scores on assessments of verbal intelligence and fine motor control. Lower blood levels of omega-3 in children are connected to poorer behaviour, worse verbal learning and poorer reading skills.

In adults, higher blood levels of DHA are associated with reduced risk of dementia, which is the leading cause of death in the UK. Mild cognitive impairment (MCI) is the agerelated decline in cognitive function that can be a precursor to Alzheimer’s disease, the dominant form of dementia. A randomised controlled trial of elderly individuals with MCI found that supplementation with B vitamins combined with high blood levels of omega-3s resulted in a 40 per cent slower rate of neuronal atrophy.

The protective effect of omega-3 intake on neurodegeneration is good news, but the bad news is that fish consumption in the UK is below recommended levels. Fewer than 5 per cent of UK children are consuming adequate amounts of oily fish.

Polyphenols are another class of nutrient with profound beneficial effects on brain function. Polyphenol-rich foods include tea, coffee, dark chocolate, berries, herbs, spices and wine. In placebo-controlled trials, polyphenol-rich foods increased brain blood flow and enhanced performance on tests of attention, memory and processing speed.

There is even good evidence that improved nutrition can support emotional wellbeing. A landmark Australian study showed that increasing fresh fruits, veg, wholegrains and oily fish in the diet reduced depression severity.

But what about foods to avoid? There seems to be no good news about sugar-sweetened beverages. In healthy young men these drinks rapidly increase markers of inflammation. In animal studies they seem to impair hippocampal function, which has negative effects on learning and memory. Human studies have shown that the typical Western diet can have negative effects on the brain within a week. So we should try to think of sweets, refined cereals, fried food, fast food, processed meats and sugary drinks as ‘extras’ or ‘fun foods’ and limit their consumption.

In conclusion, your brain is hungry and not only can you feed it, for the sake of children’s brain development and adult mental health, it is imperative that you do.

What is brain fog?

DR CHRISTIAN JARRETT

Christian is a neuroscientist and deputy editor of Psyche magazine. His latest book is Be Who You Want (£14.99, Robinson).

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