Are You Paying Attention?

An Inquiring Mind by Ginny Smith

Ever found yourself mid-conversation with a colleague who’s telling a long and boring story and realised you haven’t got a clue what they have been saying for the last few minutes?

Well you may have fallen foul of a brain chemical called acetylcholine. Acetylcholine is involved in alertness, attention and motivation, something that may be lacking when listening to anecdotes about Gary’s new lawnmower! At a more fundamental level, acetylcholine helps you switch your focus between external stimuli (such as your work colleague) and internal (like what you are going to have for dinner). This is incredibly important, not just for learning new information, but for storing and retrieving it as well.

Circuits in your brain can be divided into two types: those that provide information about the external world, and those that process that information internally. Often the same neuron will receive input from both external and internal circuits, so it has to ‘decide’ which is more important at any point in time. This is where acetylcholine comes in. When levels of this chemical are high, it boosts your response to external input and suppresses internal feedback. This puts you in the perfect state to learn new things, as you are focused on taking in new information. After a while, however, acetylcholine levels drop, and your attention starts to drift. During slow-wave sleep (the deepest phase of sleep, when brain waves sync up and slow down) and when you are awake but resting, acetylcholine levels are lower in a region of the brain called the hippocampus. This area has long been known to be vital for memory formation, and longer-term storage. Less acetylcholine here means your internal circuits they become dominant. This allows memories formed during focused wakefulness to be stored as long-term memories.

Acetylcholine also helps with memory recall. When trying to retrieve a stored memory, your brain activates other concepts relating to that fact. For example, I have been trying to teach myself Spanish recently, but have found that the French I learnt as a child (and which I thought I had forgotten entirely) is holding me back. Quite regularly, when I try to retrieve a Spanish word, the French one comes to mind, so I end up with sentences like ‘Hola, je m’appelle Ginny’. While frustrating, this makes a lot of sense once you know how the brain stores memories. We don’t store information exactly as it is; rather we extract the gist from it. So rather than remembering every word in this post, your brain will (hopefully) process the information it contains and produce a nice, concise, take-away message for you.

Not an actual brain scan

But this is where problems can start. My brain has stored a link between the phrase ‘my name is’ and ‘je m’appelle’. Now, I am trying to learn ‘me llamo’, but every time I go to store that, my brain could also activate the old, French trace. Because of the way memories work, the more a trace is activated, the more efficient it becomes, as the connections between the neurons strengthen. So my repetition of ‘my name is’= ‘me llamo’ might be enhancing the Spanish trace, but it is also strengthening the French one. So how can I ever hope to be able to speak Spanish without peppering my conversation with French words? Acetylcholine to the rescue! When brain levels of this chemical are high, attention is focused on the external world, and internal pathways become weaker. This means I can activate the ‘my name is’= ‘me llamo’ memory trace, strengthening it without reinforcing the French version as well.

We know a lot of this because of experiments using drugs that change the levels of acetylcholine in the brain. One widely studied drug is scopolamine, which is used to treat motion sickness. Scopolamine blocks acetylcholine receptors, meaning the brain no longer responds to the chemical when it is released, tricking the brain into thinking levels are low. When people are given this drug straight after learning a list, they are able to recall the words without any problems. But if an injection is given before the learning session, their recall suffers. Unable to detect the acetylcholine their brains are producing, the subjects get stuck in internal mode, happily consolidating old memories but finding it hard to form new ones.

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Interestingly, these drugs aren’t a new discovery, made by researchers working in neuroscience – quite the opposite. Jimson weed is a plant in the nightshade family (which also includes potatoes, tomatoes and tobacco) which was used as an ancient medicine and to anaesthetise people during surgery. Its hallucinogenic properties have also led to its use during religious rituals and recreationally for centuries. Its active ingredients include scopolamine, and this is thought to be responsible for the severe amnesia that users experience.[1]

Datura stramonium, known by the common names thorn apple and Jimson Weed

In fact, some scientists believe that scopolamine is to blame for the hallucinogenic effects as well. With the brain unable to detect acetylcholine, this may cause a dramatic shift to focus on internal perceptions. This prioritisation of consolidation and recall of memory rather than storage could mean that the drug user starts to ‘experience’ their memories, believing them to be real and current. Effects are usually temporary, although memories of the time when the drug was in a person’s system rarely return, fitting with the idea they weren’t stored in the first place. Sadly, the plant can be fatal, in doses not much higher than needed to produce the hallucinogenic experiences.

Luckily, without drugs, our levels of acetylcholine don’t tend to drop enough to cause hallucinations, but they do fluctuate throughout the day. This is linked to how awake and alert you feel, and how good you are at taking in new information. So the next time you find yourself daydreaming rather than paying attention to whatever it is you are doing, you’ll understand a bit more about what’s going on in your brain. It hasn’t switched off- far from it, it is probably busy storing and updating memories, thanks to changes in the levels of acetylcholine.


You might’ve noticed less blogs on The Cosmic Shambles Network from myself of late, but there’s a good reason. Over the last 2 years or so I have been working on my first solo book. And now, it is (very nearly) time to release it into the world. To say I’m nervous is a bit of an understatement, but I’m excited too. While it wasn’t exactly easy, I loved writing it. Over the next few weeks, I’m going to share some of my favourite stories from the book with you.

I have always been curious, wanting to understand why and how the things around me work (hence the name of this blog!), but it wasn’t until university that I discovered my fascination with brain science and whether it could answer perhaps the most fundamental question of all, why do we behave the way we do?

As I learned more, I began to realise that while the cells that make up our brains are important for this, it is the chemicals that bathe them, and allow them to communicate, that paint the complex details which colour every aspect of our daily lives. At the same time, I saw these chemicals begin to pop up in the media, with headlines like ‘serotonin is the happiness chemical ’ or ‘ dopamine is addictive ’. But these articles were rife with oversimplification, and missed so much of the important nuance as to render the statements pointless.

So I decided the time was right for a book on the complex and intricate workings of our brains, and the molecules that control it. A book that explores that complexity and celebrates it, while keeping things comprehensible and cutting through the scientific jargon to investigate the underlying concepts. Each chapter in the book covers a different area of life, and examines the roles our brain chemicals take in controlling everything from hunger to decision making, from learning and memory to pain. While the book may not be able to provide all the answers to how and why our brains do what they do (in many cases we just don’t know them yet), I hope that it sparks your curiosity, arms you against those trying to sell them ‘solutions’ based of over-simplified or junk science, and encourages you to want to find out more about their incredible brain. It’s called Overloaded : How Every Aspect of Your Life Is Influenced by Your Brain Chemicals and you can pre-order it now before it’s release on April 1st.

Ginny will also be on Book Shambles with Robin and Josie chatting about the book next week and look out for an in conversation event with Ginny and Helen Czerski on Shambles soon.

[1] Which makes me wonder whether Jimson weed actually anaesthetised patients, or whether they just couldn’t remember afterwards the excruciating pain they felt during surgery.

Ginny Smith is a science presenter and writer. A Natural Sciences and Psychology graduate of Cambridge, Ginny performs science shows all over the world and presents a wide range of science content for the likes of the Cosmic Shambles Network and the Naked Scientists. She is the co-author of three DK Publishing books looking at science, food and the human body. Her frist solo book, Overloaded is out in April 2021. She is @GinnySmithSci on Twitter.

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