Part 4

Making memories For the brain to learn things and to remember experiences, it needs to make memories. The hippocampus in the brain is important for creating memories– but there isn't just one type of memory. Remember when... I remember that! Episodic memory creates records of experiences, or "episodes". It's a multi-step process that involves a memory forming, being stored, then being recalled. The hippocampus is vital for all of this. 1 At the party Experiencing or learning something activates a number of neurons in different areas of the cerebral cortex and the hippocampus as the event happens. 2 A memory forms The spiking of these neurons together strengthens their connections. A memory is stored when the connections between the hippocampus and cerebral cortex get stronger. 3 Can you remember? Just a small reminder of the event, perhaps what you ate, makes the hippocampus switch those same neurons back on again. Then you remember the whole thing. OTHER TYPES OF MEMORY The brain uses different systems to learn new skills or temporarily hold information. Procedural memory Learning new skills, or "procedures", like playing the piano, is a different type of memory that doesn't involve the hippocampus. Instead, it requires synapses changing strength in the cerebellum and elsewhere. Working memory Holding information in the mind for a short time, such as when you're doing sums, involves neurons in the cerebral cortex spiking all the time that you're retaining the information.

Emotions Emotions are your feelings about what's happening to you or the world around you. Emotions affect your body and behaviour, and how others respond to you. You show emotions through facial expressions. These tell others how you're feeling, so they can understand you. Four emotions Scientists now think there are only four basic emotions: happiness, fear, sadness, and anger. All the many different feelings you have are a mix of these four basic reactions. Emotional response Emotions cause your body and behaviour to change– but it works the other way round, too. Your physical state can make you feel a certain way. Take anger, for example: Bodily responses Fast heartbeat Deep breaths Blood goes to muscles ready for action Emotion Anger Behavioural responses Focus on problem Shouting Frowning Where does fear come from? The amygdala in the centre of the brain generates a feeling of fear. The hypothalamus controls your body's response to it, while the frontal lobe shapes how fear affects your behaviour.

Thinking and intelligence Thinking is the most complex thing a brain does. It involves combining new sensory information with previously stored memories, working out what it all means, then deciding what to do. Remember the worms on page 25? Their simple brains collect sensory information, then automatically respond to it. Sometimes humans do this, but often we stop and think. Rules vs. creativity Sometimes intelligence requires working out the right answer from known rules– like in maths. Other times, the best solution is creating something completely new, like when you write a story or paint a picture. Thinking ahead Intelligence is about solving problems using your imagination. First you must decide what your aim is, then imagine different actions you could take, and finally choose the best option for a happy result. Here's an example: Oh no! Imagine walking along and seeing a friend drop their scarf when it's cold. You can imagine the different outcomes. Thinking it through Without the scarf, your friend might get cold. You can also imagine their emotions– they might be sad to have lost it. Finding a solution If you pick up the scarf and return it to your friend, the problem is solved! They are happy and warm, and you are happy to have helped. CONSCIOUSNESS Consciousness is the personal experience of being alive. You aren't conscious when you sleep. The brain's workings create consciousness, but why exactly we feel it is still a great mystery!

Sleeping and dreaming Every night you do something very mysterious– you sleep and dream. Scientists don't fully understand why these processes happen, but we do know that they help to keep the brain healthy. Light and deep sleep During the night you move through different types of sleep, which have different jobs. In deep sleep you are very difficult to wake. REM sleep is much lighter, and dreams mainly happen then. REM stands for "rapid eye movement". When you dream, your closed eyes dart about. Daily rhythms Over each day's 24-hour cycle, your brain and body's activities change to match the time. When it gets dark, the brain tells the body it is time to sleep. Sorting memories Scientists think that dreams help mix the new memories you made in the day with memories already stored in your brain. Deep sleep might also help change new memories into long-term ones. Cleaning the brain When a brain is busy in the day, rubbish builds up– including old neurotransmitters and other chemical waste. During deep sleep, the brain washes away this material.

The ageing brain The brain changes throughout life– it gets better at some things and worse at others. Living a healthy life can help keep the brain in good condition. Older and wiser As you get older, you gain more memories and knowledge. Some brain processes keep improving during adulthood, such as certain maths skills and thinking about complex problems. Brain drain From around 30 years old, human brains start to shrink gradually. Both episodic and working memory get slightly worse with age. Other thought processes also become slower. Brain illness Some brain diseases are more common in old age. Alzheimer's disease causes neurons to die and areas of the brain to shrink. This can lead to confusion and forgetfulness. Cerebral cortex This is where language and thoughts are made and where information is processed. Hippocampus This area is essential for the brain to make new memories. Ventricles These spaces in the brain get bigger as neurons shrink and die. Hippocampus Lots of shrinkage here can cause memory loss and forgetfulness. Cerebral cortex Thinking can become confused as this area shrinks. HEALTHY BODY, HEALTHY BRAIN Exercising regularly and eating healthy food helps the brain to age better. It's also important to use your brain a lot– thinking hard and educating yourself may help to protect the brain from illness.

Our different brains A person's DNA and their life experiences shape how their brain works. Knowing the differences that can occur in individuals' brains is helpful for understanding the challenges some people face. Dyslexia Many people have dyslexia, which can make reading and making sense of words difficult. For people with dyslexia, connecting written words with the sounds of words can be tricky. Autism Individuals can have very different experiences of autism. People with autism often find communication difficult. They may also dislike loud noises and bright lights, and find busy places confusing. MENTAL HEALTH We can all feel sad and upset from time to time. However, some people feel like this all the time, and this could be a sign that their mental health needs looking after. The reasons can be hard to explain but, just like physical problems, the feelings can be treated and made better. ADHD Attention deficit hyperactivity disorder (ADHD) can make it difficult for people to concentrate or to stay still. People with ADHD are often very active and quickly switch from one task to another. How to help If you are struggling with a problem, talk to a person you trust. If you see someone else who needs help, ask how they are and always remember to be kind and try to understand their feelings.