What happens to your brain as you age

このノートは, The Economist > What happens to your brain as you ageのスクリプトです

Script

Your brain is one of your most important organs, home to billions of neurons, it’s your body’s mission control. As you go through life, your body changes radically. Inside your head, your most complex organ is constantly transforming too, beginning work before you’re born and continuing even after you’ve been declared dead.

This is the life cycle of your brain.

Your brain starts to form about two weeks after conception. On one side of the developing embryo, the cells thicken to form what is called the neural plate. Around week 4, this folds over onto itself forming a tude which ultimately creates the nerveous system. Every minutes, from the time the neural tube closes, your brain is growing hundreds of nerve cells called neurons.

At birth, your brain contains about 100,000,000,000 neurons, more than an adult. This gives the baby the best chance of developing a healthy brain. The excess neurons are shed before you become an adult.

But what you don’t have is a lot of synapses, the point of contact where electronic signals are passed between neurons, which in turn change the behavior of the neurons. Some neurons become insulated by a fatty substance myelin. These neurons, known as White matter, are able to transmit information faster between brain areas, allowing more complex processes to take place.

When you’re born, the average number of synapses per neuron is 2,500. But that increases to approximately 15,000 per neuron over the first few years of your life, as your neurons mature and create new synapses.

The speed at which they form synapses could be one reason children find it easier to learn things like languages or musical instruments. It’s also why children’s experience in this phase can have lasting effects on their development.

From age three until about ten, your brain starts to remove connections it no longer needs. Neuroscientists used to think all synapses work at a constant and fixed level, but now they understand synapses can be stregthened and weakened depending on how they are used. This is known as neuroplasticity. It’s essentially your brain’s way of making sure it’s more effecient with experience and absorbs new information.

By the time you become a teenager, your brain has stopped growing but it continues to develop. The insulation of the nuerons which begins at birth continues over many years. It starts at the back of the brain and moves forward. So different parts of your brain develop at different rates. Area associated with reward, like the ventral striatum, develop faster than the Prefrontal cortex, which is linked to self-control and rationality. Teens also experience major changes in their Limbic system, the part of the brain that controls emotions. All this might explain why teenagers experience more mood swings than adults. Neuroscientists believe the difference in development between the emotion-driven part of the brain and the rational part may also be the reason teenagers are more likely to take risks or experience addiction compared with adults.

Puberty also brings with it increased activity in the Ventromedial prefrontal cortex, the part of the brain that relates to self-evaluation. This change can improve teenagers understanding of social interactions and their ability to form friendships. But it might also make them more susceptible to social anxiety.

Post puberty, the brain continues to develop. Brain tissue in the Prefrontal cortex increases connections, joining the emotional and motor centres. Your brain reaches full-development by your 30s and white matter reaches the highest volume at about 40. But it’s not all downhill from there. As you age, plasticity allows your brain to keep changing and adapting.

Research has shown older adults more likely to use both sides of the brain for short-term memory, rather than just the left brain hemisphere. Middle-aged brains have also learned to minimize the negative. Scientist has found the amygdala, the part of the brain which deals with emotion, lights up when younger people look at both positive and negative images, but for the older adults it reacts much less when shown negative images. This might be because as you age, you become more resilient. Decades of experience in dealing with difficult situations activates neural pathways which can be used when you experience a similar situation.

For those who go through menopause, changes to the amount of estrogen affect brain energy consumption, producing symptons like hot flushes and mood swings. The volume of white matter also falls and doesn’t recover. but despite this, those who are post menopausal have higher structural connectivity between some brain regions than those who don’t go through menopause, meaning that the connections in those regions may become more efficient. The point at which your brain begins to slow down depends on your genes, but on the whole studies show that the slowing process begins in your 30s or 40s, before accelerating in your 60s and 70s.

AS you move into later life, your cerebral cortex, which is the outer layer of the brain, thins. This is particularly noticeable in the frontal lobe and the Hippocampus, which are important for memory, emotions and navigation. Your white matter shrinks and the brain generates fewer chemical messengers such as dopamine and serotonin, which leads to slower cognitive processing.

Until very recently, neuroscientists didn’t know what happens to your brain when you die. But by chance, doctors were recording brains waves of a patient when he died of a heart attack. They found a change in a specific band of brain-waves involved in high cognitive functions, such as concentraing, dreaming and memory retrieval, suggesting that just befor you die, your brain may recall important life events, which may explain why those who have near-death experiences reports seeing their lives flash before them and your brain doesn’t stop working even when you are dead.

Some stidies have found that brain activity may continue for several minutes even after your heart has stopped.

Related Topics

Artists ‘have structurally different brains’ from BBC 17 April 2014

Researchers peered into the brains of 21 art students and compared them to 23 non-artists using a scanning method called voxel-based morphometry. They found that the people who are better at drawing really seem to have more developed structures in regions of the brain that control for fine motor performance and what we call procedural memory.

Those better at drawing had increased grey and white matter in the cerebellum(小脳) and also in the supplementary motor area - both areas that are involved with fine motor control and performance of routine actions. Grey matter is largely composed of nerve cells, while white matter is responsible for communication between the grey matter regions.

But still it is unclear what aspect of artistic talent was innate or learnt.

Are artistic brains different? - 6 Minute English

They are wondering why artistic ability comes more naturally to some people than others. They have interviews with experts for their opinions.

Dr Rebecca Chamberlain says:

“Artist seems to be processing the visual world in a different wat to non-artists. The artists takes a more global approach to looking, so they make bigger saccades, bigger eye movements, and firter fixations onm the image.”

Words and phrases

Neuron

A neuron is a specialized cell that is the basic building block of the nervous system, which includes the brain, spinal cord, and peripheral nerves. Neurons are responsible for transmitting information in the form of electrical signals within the nervous system. They play a crucial role in various cognitive functions, sensory perception, motor control, and the regulation of bodily functions.

Conception

Examples

• the moment of conception
• A child is born about 40 weeks after conception takes place

fold

Examples

• He folded the map up and put it in his pocket.
• First, fold the paper in half.
• The bed can be folded away during the day
• The table folds up when not in use.

shed(verb)

Example

• The factory is sheding a large number of jobs
• Museums have been trying hard to shed stuffy image
• Luke shed his cloths onto the floor

Idioms

• Recent research has shed new light on the causes of the disease.

insulated

• HOme owners are being encourraged to insulate their homes to save energy

excess(adjective)

• Excess food is stored as fat
• Driving with excess alcohol in the blood is a serious offence

emotion

“emotion” is generally uncountable, but when you are talking about specific instances or types of emotions, you can use countable nouns.

Example

• She experienced a range of emotions during the movie.
• The painting conveys a sense of emotion
• He lost control of his emotions
• They expressed mixed emotions at the news

self-evaluation

Self-evaluation plays a crucial role in shaping and developing one’s personality.

susceptible

• He’s highly susceptible to flattery
• Some of these plants are more susceptible to forst damage than others
• She was both charming and susceptible

References

• The Economist > What happens to your brain as you age
• BBC > Artists ‘have structurally different brains’