Every day we learn something new; facts, actions, routes, people, recipes, stories, etc.. For example, I am currently learning to play the guitar. But that’s a slow process. After watching one YouTube video, why can't I just replay the song right away?
Our brains are made up of neurons that together form a network (see brain basics). The connections in a network could be compared to roads. If you want to learn something new, a new road must be built in your brain. When you first do or learn something, you have to make your way through a dense forest, but the more often you take the same route, the more passable the path becomes. And over time, with recurrent practice of the skill you want to learn, the forest path can turn into a highway. The synapses between neurons strengthen, this is called long-term potentiation. Vice versa it works the same way, by not using the highway anymore (for example, by not playing guitar for a long time), the highway will overgrow and become a forest path again (aka the synapses between neurons weaken and you forget the skill). These changes in the brain are called neuroplasticity.
There are several ways the brain does "road construction". The brain can simply create new neurons (neurogenesis), but in adults this happens rarely and only in specific areas (in the hippocampus and olfactory bulb). Much more common is that the postsynaptic neurons create more receptors as a reaction to the increase of released neurotransmitters caused by recurrent practice. This allows the postsynaptic neurons to pick up more neurotransmitters released by the presynaptic neurons. The connection between pre- and postsynaptic neurons therefore strengthens. The neurons can also create new dendrites, creating whole new synapses. In this way, the pathways of the brain network can change.
Neuroplasticity requires a lot of repetition and consistency. This is why you cannot succeed in imitating a song flawlessly after watching one youtube video (except in very exceptional cases) and why it takes years of intensive training to become very good at something. If you want to learn something new, it is especially important to practice a lot, so that the forest path in your brain becomes a highway. Practice makes perfect!
Author: Pauline van Gils
An "electronic Ear" - cochlear implants
Many people benefit from technological development. Being able to use a phone or personal computer makes your life a lot easier. Although it sometimes seems some people are not able to function without their device, as if it has become a part of their body, other people actually rely on devices to take over bodily or sensory functions. One such example is a cochlear implant (CI). This is a medical device that is used to provide the brain with input; more specifically it can restore some access to sound to people with severe to profound hearing loss. In this article, I will explain how a CI works and some of the benefits and challenges that come with this technology.
From pressure changes to electricity
In order to understand how a CI works, it is important to know a bit more about the auditory system and what sound actually is. Physically, sound is pressure changes in the air (or another medium) caused by an object's movements or vibrations. Usually, we can perceive this sound since the ear can transfer these pressure changes into electrical signals, and subsequently meaningful sounds and speech. The auditory signal takes the following path for this: first, the pinna picks up the sound, which then travels through the ear canal unit it arrives at the ear drum. The eardrum is set into vibration by the air pressure changes from the sound. This, you could say, causes a chain reaction: the vibrating of the eardrum causes the three smallest bones in your body, the ossicles (hammer, anvil and stirrup) to vibrate in succession, which amplify the vibration and transmit it to the oval window. This oval window is part of the cochlea, a snail-like structure filled with liquid, that consequently vibrates too. Within the cochlear lie various structures: the basilar membrane, organ of Corti and tectorial membrane, which are all set into motion. Most importantly, the hair cells start to move, which transduce the environmental stimulus waves into electrical signals. In these hair cells, the movement (bending of the hair cells) triggers a sequence of chemical reactions that lead to action potentials. Interestingly enough, these hair cells do not vibrate in a random fashion. Both their pattern of vibration and intensity convey properties of the sound signal. The pattern or place of the vibration within the cochlea conveys the pitch of the sound; this is called tonotopy. These vibrations trigger electrical signals, action potentials, which are then sent through the auditory nerve to the brainstem and from there are transmitted to higher-order structures of the brain, such as the auditory cortex.
Technology to the rescue
However, some parts of this auditory pathway might not function properly. For every step up to the brainstem there is a device that can be used to restore hearing: from a hearing aid that amplifies incoming sound to bone-conduction devices, a cochlear implant and an auditory brainstem implant. Of these devices the CI is, after the conventional hearing aid, the most widely used. CIs can help people with severe to profound hearing loss to receive a sensation of sound by directly stimulating the auditory nerve fibers in the inner ear. In terms of technology, it consists of an external microphone that picks up the sound, a speech processor that processes the sound, a transmitter that sends the signal to the implanted receiver (coil), and an electrode array that is placed inside the cochlea. That sounds amazing, right? A device that lets almost and completely deaf people hear again. And not only that, but indirectly it also leads to less depression, social isolation, unemployment, and more independence.
Do not forget the brain
Although a CI might lead to great results, it is not “plug and play”. The sound that is produced by a CI is less nuanced than natural hearing because it is processed by a little computer. The sound can be described as sounding similar to a robot voice. It, therefore, takes some time to get used to before speech can be understood from this distorted signal. This shows that a CI really is a BCI (Brian Computer Interface), it is not only important to develop a good device, but it interacts with the brain which in turn has to adjust to the device and vice versa. Luckily there are professionals, called audiologists, that fit (tune) the device to the CI user's needs and guide them during rehabilitation. There are many different settings, from the way that sound (and background noise) is processed, to the way that the auditory nerve is stimulated. But researchers are also trying to understand how the brain actually deals with the signal and how effortful listening with a CI is. Because even though someone might understand perfectly with a CI, it might be that they still need to put a lot of effort into achieving this.
If you are interested to learn more about this topic
For Dutch-speaking people, in the podcast “Met Hertz & Ziel – de rol van cochleaire implantaten” three Flemish audiologists discuss cochlear implants. They not only describe, for example, how a CI works, but they also discuss how CIs changed the lives of some of the users, why they cannot predict how well someone will perform with a CI, how audiologists fit the device when someone is not able to communicate how well they perceive sounds, or what drives the decision to get or not get a CI from both a clinical and user perspective. https://open.spotify.com/episode/135M0GXTfEAIdY06gxFRed
Quite a strange idea: Every night we lie down waiting to go into some sort of unconscious state, trusting that we will wake up about 8 hours later. This is what we call sleep. We sleep 1/3th of our lives, that is on average 26 years! But how do we get into such a sleep state? And what good does it actually do?
It used to be thought that the brain simply "turns off" during sleep, but this is not true. A whole lot of
things happen. When it gets dark, the pineal gland, a gland in the center of the brain that looks like a very small pinecone, activates. This produces melatonin, a substance that makes you sleepy. Light causes inhibition of the pineal gland, then melatonin production stops. This is why we feel tired at night and (hopefully) not during the day.
The brainstem (including the pons, medulla, and midbrain) and the hypothalamus produce GABA, an inhibitory neurotransmitter. This neurotransmitter causes other neurons to fire less frequently and therefore puts the brain in a calmer state. With an electroencephalogram (EEG), we can measure this change in brain activity.
During sleep we go through different stages. We first enter non-REM sleep. On the EEG, the frequency of brain activity slowly decreases and the amplitude increases. This means that neurons are firing synchronously in a slower rhythm. And that's how we enter deep sleep. The thalamus, the gatekeeper of the brain, no longer lets signals through to the cortex, isolating you from the external world. Then brain activity accelerates again as we enter REM sleep. Interestingly, during REM sleep the EEG shows the same activity as when you are awake. This is because we are dreaming. The thalamus then sets the gate ajar allowing signals to go to the cortex. These signals fuel the content of our dreams. The brainstem sends inhibitory signals to the muscles so that we do not actually execute the movements in our dreams. Our whole body is paralyzed during REM sleep, except for the eyes that do move during dreaming. That explains the term "rapid-eye movement" sleep. This cycle from non-REM to REM sleep lasts ±90 minutes and repeats itself about 5 times in one night.
There are books filled with explanations about the mechanisms behind sleep, but this, in a nutshell, is how it works. That leaves the question of why we actually sleep. In fact, evolutionarily speaking, sleep seems like a waste of time. You would think that an organism would be better occupied gathering food or finding a mate, rather than sleeping 1/3rd of the day. There are several theories about the usefulness of sleep. One explanation is that it is a kind of eco-mode of the body to save energy, since we burn 10% fewer calories during sleep. Also, our body recovers during sleep. After all, sleep strengthens the immune system and growth hormones are released. In addition, during sleep the brain is "cleaned" of waste products accumulated during the day. Changes also take place between connections in the brain. This is called neuroplasticity. Among other things, this allows us to store information in memory more efficiently. The saying “let me sleep on that” therefore makes a lot of sense! In short, sleep has many different functions and is important for our health. In fact, sleep is vital.
Author: Pauline van Gils Illustrations: Pauline van Gils
Brain basics: Fear in the brain
We are all afraid from time to time. Some cannot stand horror films, others are afraid of spiders, and yet others get weak in the knees from high altitudes. But why do we experience fear in the first place? And how does that work in the brain?
Experiencing some degree of fear is very useful. In the past, it ensured that our ancestors did not get too close to a deep cliff or an angry bear. Therefore they had a better chance of survival and thus passing on their genes to the next generation. So, a certain degree of fear was evolutionarily very beneficial. This answers the question why we experience fear. But how does fear actually arise?
Information from the environment always passes the thalamus (the brain's gatekeeper, as explained in the Brain Basics article). When this is threatening information, the thalamus transmits it directly to the amygdala. The amygdala, also known as the “fearcenter” of the brain, is a small almond-shaped cluster of neurons in both medial temporal lobes. When we perceive a fear stimulus (something scary), the amygdala becomes active. It then sends a signal to the hypothalamus, an area that makes sure the body is in balance. The hypothalamus triggers a "fight, flight, or freeze" response in the body via the stress hormones cortisol and adrenaline. Your heart starts beating faster in preparation to run. Your pupils enlarge so you can see better. Even your pain sensation may temporarily diminish during a fear response. When the fear stimulus is gone, your body returns to its original state.
This fear-invoking event is stored in the hippocampus, an area responsible for memories. To make sure we don't forget this fearful event, the amygdala puts a kind of stamp on the memory with "DON'T FORGET, IMPORTANT!". The more intense the experience, the bigger the stamp, and the better we remember it. This is why we often remember scary events from the past (losing your mother in town as a child), while we quickly forget mundane emotionless events (what you had for breakfast last week). This is useful. By remembering the unpleasant experience you can, hopefully, avoid similar situations from happening in the future.
The interaction between the amygdala and the hippocampus also goes the other way around. For example, you may be very startled by something at first, such as a barking dog. The amygdala then immediately jumps into action. Once the information is also processed by the hippocampus and the frontal cortex, they have the ability to suppress the activation of the amygdala. For example, when you realize the barking came from your neighbour's sweet dog. The hippocampus does this with positive memories (e.g. every time you pet the dog), and the frontal cortex throws logic into the fray (e.g. that the dog is behind a fence and is therefore harmless). Because of these two brain areas, you realize that the initial fear reaction was unjustified, and there is nothing to be afraid of.
To sum up: Although the amygdala is known as the "fear-center" of the brain, this is oversimplified. Fear is caused by a complex interaction between a fast pathway via the amygdala, which triggers the initial fear response, and a slow pathway via the hippocampus and frontal cortex, which analyses the situation with more nuance. The collaboration between the amygdala and the hippocampus causes us to remember scary things better. So, if sometimes you are still plagued by a memory of when you were stuck in the toilet stall as a child, know that your brain is not holding on to this memory to harass you, but to help you not make the same mistake again.
Author: Pauline van Gils Illustrations: Pauline van Gils
Brain Basics
At Brainmatters we are fascinated by the brain. But if you were to see a brain lying on a table, it wouldn't look all that impressive. It’s a 1.5 kilo slimy pudding. It’s hard to imagine that this pudding is responsible for all our thoughts and actions. How is that possible?
What you can't see with the naked eye is that the pudding consists, among other things, of 86 billion neurons. These are specialized cells that are interconnected. They can communicate with each other using electrical and chemical signals. The different communication patterns of the neurons allow us to think, move, see, hear, feel, remember, and so on. But there are costs associated with this supercomputer in our head. It consumes least ⅕ of all the body's energy. That is quite a lot when you consider that the brain only takes up 2% of our total body weight.
What you can see when you look at the brain is that the brain consists of two parts. A left hemisphere and a right hemisphere. The left hemisphere is responsible for the right part of our body and vice versa. So if the left side of the brain gets damaged, you might not be able to properly move your right arm anymore. The two halves can communicate with each other through a "bridge" that connects them, the corpus callosum.
What is also immediately noticeable about the brain are the grooves and ridges. This outer part of the brain is called the cerebrum. From an evolutionary point of view, this is the newest part of our brain. It consists of different lobes, each with its own function. The reason for the ridges and grooves is simply to fit the brain in your skull. You can compare it to a piece of paper that you crumple up. A wad of paper also takes up less space than a wrinkle-free sheet.
What we cannot see, are all the parts of the brain that lie under the cerebrum. A very important structure that lies in the middle of the brain is the thalamus. This is the gatekeeper of the brain. It stops many irrelevant stimuli that are picked up by our senses. And that is a good thing! If the thalamus didn't do this, we would be completely overwhelmed by all the impressions around us. The thalamus basically decides which sensory stimuli (except hearing) are processed by the rest of our brain.
What we also cannot see with the naked eye is that these neurons in the brain form networks. Just like highways connecting cities together. A network is a cluster of neurons that work together to perform a certain function. One of the most important networks is the limbic system. This network is responsible for emotions. In this system different parts of the brain work together (among others the amygdala, the hippocampus, and the hypothalamus) to generate several emotions. There are many other networks besides the limbic system, such as a network that enables us to move and stop moving, the language network, the attention network, the memory network and so on. We do not yet exactly know how all these networks work. But science is working on it.
Finally, from the outside, you can see that there is a small lobe at the back below that large cerebrum. That is the cerebellum. The cerebellum is mainly involved in movement. It finetunes our movements and makes sure our movements are always up to date with our surroundings. This is especially useful when things around us are also moving, like when you are trying to catch a ball.
This was a very global overview of how the brain works. But how it all works exactly, we do not know yet. It is a fascinating, ongoing, and perhaps never-ending quest to find out how this incredibly complicated organ works. Hopefully you tag along to find out more about this pudding-like organ.
Author: Pauline van Gils Illustrations: Pauline van Gils
A first encounter with the brain
Here at brainmatters.nl, we love the brain and we hope to get you just as excited about this mysterious organ inside our heads. If you don't know much about the brain, this is a good place to start. Let's start at the beginning: How did the brain originate?
As with anything that develops, the growth of the brain begins with the most important parts. Namely, the parts that make sure we stay alive. As a fetus grows into a baby in 9 months, so does the brain. The brain initially develops from a neuronal tube, which after a few weeks grows into three different parts at its end. These are very conveniently called the hindbrain, midbrain and forebrain. The rest of that tube later becomes the spine, while the hind, mid and forebrain continue to develop.
After all, what does a baby need to stay alive? A heartbeat and breathing. That's not a mere luxury. The areas that control these functions develop first. That development happens as follows: The hindbrain develops in the myelencephalon (or medulla) and the metencephalon, which in turn develops in the cerebellum and the pons. Together, the pons, medulla and midbrain form the brainstem. And it is precisely this brainstem that regulates the heartbeat and breathing of the future baby.
Well, now that the brain is up to the most essential tasks, it can continue to develop. Now it's the forebrain's turn. This develops into the telencephalon and diencephalon. The diencephalon turns into the thalamus, the structure that is particularly important for communication between brain parts and the hypothalamus, the structure that controls needs such as hunger, thirst, fight or flight and fatigue and sleep, among others. The telencephalon also develops from the forebrain. From this later develops the limbic system, responsible for emotions, and the basal ganglia, responsible for regulating movement. So now, very simply put, we have a fetus that is alive (has a heartbeat and breathing), has needs (sleep, hunger, thirst, etc.), and can respond to them (with emotions or movement).
Now there is a large part of the brain that we have not yet discussed, namely the cortex. The cortex is what most people know as the brain, that squiggly structure on the outside of the brain. It also originated in the telencephalon and is divided into four parts called lobes: The frontal lobe, temporal lobe, parietal lobe and occipital lobe. Each part has specific functions associated with it, but it is important to note that most of the actions people perform involve multiple parts. The occipital lobe is used primarily for seeing, the temporal lobe for hearing, and the parietal lobe for sensing and spatial awareness. These parts ensure that our future human can perceive things around them.
The only thing missing is a kind of control system that ensures that we do not act like unguided projectiles reacting to every need (for example, that we do not go peeing in the street, or eat the entire birthday cake at a party). That's what we have the frontal lobe for. This is the most complex lobe and you could say that it distinguishes us from monkeys. This is because this lobe is involved in driving goal-directed behaviour including self-control, speech and memory. At birth, however, this lobe is not yet fully developed (this can also be seen in the behaviour of babies and children). The frontal lobe continues to develop until sometime in adolescence. Only then is the brain fully developed, which is exactly why you can only drive a car and drink alcohol when you are older.
This was a brief introduction to the brain, but there is much more to learn. So did you find this article interesting? And would you like to learn more about the different parts of the brain and the ways research is done? Then read our Brain Basics articles.
Author: Loes Beckers Illustrations: Pauline van Gils
Reference: Breedlove, S. M., and Watson, N. v (2013). Biological psychology: An introduction to behavioral, cognitive, and clinical neuroscience, 7th ed. Sunderland, MA, US: Sinauer Associates.
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