Monday, 29 October 2012

Selective attention

Today's post starts with a video. This video will take you through an activity. It takes about 90 seconds, and all the instructions and credits are on-screen. Have fun!










I didn't see it the first time I took the test. Now I can't not see it. When I visit kids' classrooms, I show this video every time I have an internet connection. In a class of 30, one or two kids will notice it. Maybe.

This video demonstrates a phenomenon called selective attention. Selective attention happens when we pay so much attention to one thing, that we miss other things going on around us. It's better known as the "cocktail party effect", because it describes how people at a party can focus on a single conversation, even though the room around them is filled with loud music, loads of voices, laughing kids, and who knows what else.

Let's pretend that you have a set of neurons that response to people in white shirts passing basketballs. Maybe you do and maybe you don't, but you definitely have neurons that respond to white, and neurons that respond to moving images, and neurons that respond to people. Let's put all those together to get a group of neurons that respond to people in white shirts passing moving basketballs.

If you're walking by a basketball court and you see someone in white passing a ball, those neurons will fire. (By "fire", I mean, send information in the form of action potentials.) But they won't fire much, because you're not very interested in that - you're more interested in the gorilla doing a jig on the sidelines. But let's say someone asks you to pay attention to the basketball player. "It is very, VERY important that you watch that basketball player," says the mysterious somebody. "The fate of the world depends on it." So you shift your attention to the basketball player. The neurons which respond to white-wearing-basketball-passers suddenly go berserk. They fire loads. And neurons that are firing loads are usually neurons that have something important to say, so you notice, and pay lots of attention to the basketball game.

But heavy firing of some neurons isn't the only thing going on. All your other groups of neurons - those that fire when you see trees, or barking dogs, or gorillas - they aren't firing as much. To the brain, they aren't as important. Your frontal lobe filters them out. It does this though inhibition.

The frontal lobe (in red) is responsible for directing attention, and for inhibiting information that isn't important. (picture from Wikimedia Commons)
Inhibition is a type of electrical activity in the brain. When a neuron is "inhibited", it slows down or stops sending electrical signals. In order to inhibit a neuron, a different neuron has to release inhibitory neurotransmitters. (Neurotransmitters are the chemicals neurons use to talk to each other.) When a neuron receives inhibitory neurotransmitters, it shuts down. The information it has can't go any further. If the brain doesn't want you to pay attention to something, like a gorilla, it inhibits the neurons that "see" and "hear" that gorilla. The information stops. It can't access the higher processing centers - the ones involved in consciousness and awareness. So even if there's a gorilla doing a dance on the basketball court, you don't notice.

The take-home message is this: Our brains are set up to magnify important information and ignore anything that isn't important. What this means is, we don't notice most of what's going on around us. Just think about how much you're missing!

Monday, 22 October 2012

BRAIN MYTH-BUSTING: Nice pheromones. Wanna date?

Romantic love is a huge part of life. Adults and teens think about it a lot. Most kids have had their first crush by middle school. But even with 7 billion people in the world, finding "the one" is surprisingly difficult.

A big industry has sprouted up, promising to sell you products guaranteed to make finding the love of your life as easy as making toast. One such product is perfume spiked with pheromones. Squirt on a few pheromones, and the next thing you know, you'll be standing at an altar in a white dress while a handsome tuxedoed gentleman puts a ring on your finger. Supposedly, pheromones bypass all the logic and control centers of the brain and go straight to the areas that control love and attraction. They're a real life love potion! As soon as you smell them, you fall madly in love with someone. That guy/girl is so amazing! You don't know why! There's just something fabulous about him/her! You want to marry him/her now! Or so pheromone perfume ads promise us. And then they charge more money for that perfume, because the pheromones make it super special.

But what are pheromones? And do they work?


What are pheromones?
Pheromones are chemicals that animals release in order to communicate with other animals. They're chemical "words." Pheromones are used by insects, amphibians, reptiles, and some mammals like rats and rabbits. Pheromones can signal alarm or the presence of food. There are pheromones that mothers use to let their babies know it's time to nurse. Pheromones can also signal the desire to mate, which is what I'm talking about in today's post.
These bug nymphs release a pheromone which causes them to aggregate, or group together. From Wikipedia.

Whether humans release pheromones is controversial. We just aren't sure. There's some evidence that we do, but it's not very convincing. My money's on "no." Even if we do release pheromones, we still have to be able to sense them. There's no point in wearing pheromone perfume if your crush can't sense pheromones. So...


How do animals sense pheromones?
Even though pheromones show up in perfumes, they aren't scents. They're similar, but not the same. They aren't picked up by the nose, and the brain doesn't process them the same way. Animals that sense pheromones have a vomeronasal organ (VNO). If pheromones are words, then VNOs are ears.

In order for humans to sense pheromones, we would have to have a VNO. We don't. Well, that's not quite true. Unborn fetuses have a VNO. Then it degrades. By the time you're born, it's gone. In animals, neurons in the VNO talk to an area of the brain called the accessory olfactory bulb. Humans don't have an accessory olfactory bulb. So we lack both the organ that senses pheromones, and the brain area that processes them. In other words, we are physically unable to sense or respond to pheromones. 

The vomeronasal organ connects to the accessory olfactory bulbs. The yellow outline at the top is the snake's brain. From neuro.fsu.edu

Despite lots of effort, there has never been a scientific study showing that humans can sense pheromones or that pheromones change the way we act and behave. So it doesn't matter if we release them, or how many perfumes we wear. It's like yelling at a fully deaf person and expecting them to respond. It just won't work.

LIES!! And what do you mean by "smelling gland"? You don't smell with glands. Glands release things like sweat or adrenaline. This picture is nonsense. It's from one of those websites that tries to steal your money with worthless pheromone perfumes. Just because someone posts a sciency-looking picture, it doesn't mean they know the first thing about science. Don't fall for the scam!

Pheromones don't work. At least, not in humans.

In other words, if you want to get someone to like you, don't wear pheromone perfume. It's not a love potion. You're wasting your money. Instead, how about you try talking to your crush?

Monday, 15 October 2012

BRAIN MYTH-BUSTING: We have five senses

Since elementary school, we're all taught that we have 5 senses: smell, touch, taste, sight, and sound. Pop culture has a term: "the sixth sense". Fictional characters with a sixth sense can usually do some cool supernatural thing, like reading thoughts or seeing dead people (as in the appropriately titled movie, The Sixth Sense). But guess what? We all have sixth senses. And seventh senses. And eighth senses. Some neuroscientists estimate we have up to twenty senses. And none of them are supernatural.

Here are some of the more over-looked senses:

Proprioception:
This is the sense of body position. It's how you know you're sitting or standing, even without looking. It's why you can scratch your bum without looking at your hand or your bum.

Equilibrium:
This is your sense of balance. The vestibular apparatus, which senses balance, is located inside your ear.

Acceleration:
The vestibular apparatus also senses how your body is moving. Are you speeding up? Slowing down? Spinning in circles? The ability to know this is one of your senses. (Next time you feel dizzy, blame your vestibular apparatus.)

The inner ear. The brown loops are the semi-circular canals, and they are part of the vestibular apparatus. I talk a lot more about the vestibular apparatus in my post on carsickness. (picture from wikipedia)

Nociception:
This is the sense of pain. It is not the same as touch! Some of these senses seem like they could count as "touch", but they aren't the same. This is because different neurons do the sensing, and the sense is processed in different areas of the brain. A good example is pain which, in brain-terms, is completely different from touch.

Temperature:
The ability to sense hot or cold is also different from touch.

Hunger:
Yep, that counts as a sense.

Thirst:
Well, if hunger does, thirst must.

The need to go to the bathroom:
Also separate from touch.

How much carbon dioxide is in your blood:
Why do you think it hurts so much to hold your breath? You can sense when your body needs more oxygen. Usually this runs on auto-pilot. Your brain monitors carbon dioxide levels and controls the lungs so you breathe regularly without thinking about it. But if you hold your breath, you'll start to feel it pretty quickly.

Chronoception:
You can sense the passage of time. Your body cycles through a natural 24-hour rhythm, called the circadian rhythm. This is controlled by an area of the brain called the superchiasmatic nucleus. You can also sense time on shorter or longer scales, even if you aren't consciously aware of it.

There are even more senses that I haven't listed here. Can you think of some? Think of all the things your body goes through on a given day. Think of the steps you take to take care of your body, and why you feel like you should take those steps.


Animal senses:
 
There's even more senses out there! Animals have lots of cool senses that humans don't have. Here are some examples:

Magnetoception:
Birds can sense magnetic fields. It's how they migrate.

Pheromones:
Pheromones are chemicals that animals use to communicate with each other. It's like smell, but different. Some people think humans can sense pheromones. I disagree, and the science backs me up. Next week's post is devoted to debunking the humans-sense-pheromones myth.

Bats use echolocation to find tasty bugs
Echolocation:
Dolphins and bats can tell where things are based on reflected sound. They make a sound, which bounces off an object, and they sense the bounced sound and can tell, from that, where something is.

Electric fields:
Some fish, including sharks, can sense electric fields around them. Some fish even make electric fields, which they use to communicate with each other.


Plant senses:

Plants have senses too!
Mustard plants can sense gravity.

Gravity:
Plants can sense gravity. This is how they grow upright.

Light:
Some plants can sense and turn towards light. This is important, since plants need light to live.

Monday, 8 October 2012

Caffeine

Caffeine is everywhere. Coffee. Tea. Soda. Chocolate. Those crazy energy drinks that undergraduate computer science students chug like water. I don't know many kids who like coffee, but I know lots of kids who like soda and chocolate.

Check out what happens to spiders when they're on caffeine:

The web on the left was made by a spider who'd never had caffeine. The web on the right was made by a caffeinated spider.

But what is caffeine? It's a chemical in chocolate and soda, yes. But what does it do to your brain? Because as soon as you feel that jolt, something's happening in your brain. Caffeine is what neuroscientists call a "stimulant". This means that it wakes you up. How?

Your brain needs energy to work. It gets this energy from a chemical called adenosine triphosphate, or ATP. Your neurons make ATP from the food you eat. When your neurons need energy, they break a molecule of ATP. This is kind of like snapping a twig. When you snap a twig, you hear a noise and feel a jolt. The noise and jolt are both types energy that are released by snapping the twig. When your neurons break ATP, there is energy released. But instead of being wasted in a snapping sound, your neurons harness that energy and use it to do all the work that neurons do.

Adenosine triphosphate (ATP). ATP is made from adenosine (which is adenine and ribose - the blue and pink) and three phosphate groups (the yellow circles). Breaking off the phosphate groups produces energy, which the neurons need to work. Adenosine is left over.
What's left over from the breaking of ATP is a molecule called adenosine. As you use more and more energy, the adenosine in your brain builds up. Your brain senses this big increase in adenosine. It knows that if adenosine levels are high, it means you've been working hard for a long time. Which means it's time to sleep! So it makes you feel tired, and the next thing you know, you're in dreamland.

This is where caffeine comes in. It stops neurons from sensing adenosine. If neurons can't sense adenosine, they don't know you're supposed to be tired. So you stay awake, typing blog posts until late in the night even though you have work at 8 am. Oh, wait....that's just me. But the point is, caffeine wakes you up by making your neurons insensitive to adenosine. It doesn't give you energy. It stops your brain from noticing that you're out of energy.

Caffeine has other effects, too. It increases the activity of certain neurotransmitters. Neurotransmitters are the chemicals that neurons use to talk to each other. Glutamate is a neurotransmitter important for learning and memory. Dopamine is a neurotransmitter that gives you feelings of pleasure and reward. Caffeine increases neurotransmission of both glutamate and dopamine. The result? First, you get really good at studying. Second, you feel happy. And both those things make you want more caffeine. Because of the dopamine effect in particular, caffeine is addictive.

Caffeine has some annoying side effects outside of the brain, like increasing heart rate and giving some people upset stomachs. Plus, if you're addicted to caffeine and stop drinking it, you become head-achy and cranky and no fun to be around. So it's a good idea to limit the amount of caffeine you eat or drink, especially if you're a kid. Kids are more sensitive to the effects of caffeine - including the bad effects - than adults. But if someone tells you that caffeine stunts your growth, you can go ahead and tell them that's a myth.

Caffeinated soda (pop, soft drink, whatever you call it) works by tricking your brain into thinking you have energy to burn.

Monday, 1 October 2012

Santiago Ramón y Cajal


Santiago Ramon y Cajal. From wikipedia.
If you want to get a neuroscientist excited, try mentioning Santiago Ramón y Cajal (Cajal is pronounced ca-HALL).

Santiago Ramón y Cajal is the father of modern neuroscience. He was fantastic for two very big reasons:


1. He came up with the neuron doctrine.
The neuron doctrine is the idea that the brain is made up of millions of distinct units called neurons. It also says that neurons are cells. But the really important part is that neurons are not continuous - in other words, every neuron is separate from every other neuron.

While Cajal was coming up with the neuron doctrine, another scientist named Camillo Golgi had a different idea. He thought the brain was one continuous mesh, with no gaps or breaks. Cajal disagreed. He said the brain wasn't continuous. He thought there had to be breaks between the neurons. These breaks would allow for the neurons to communicate, and for neural signals to be modified or changed if necessary. Cajal was right. The breaks are what we now call synapses.

Classic synapses communicate using chemical messages called neurotransmitters. But there are some electrical synapses, called gap junctions. These are kind of like the continuous mesh that Golgi thought up. They're rare, but it's a little vindication for Golgi. Just a little. The neuron doctrine is still right ~99%+ of the time.

Both Cajal and Golgi got the Nobel Prize in Physiology or Medicine in 1906. This despite the two of them hating each other. They were both convinced the other was wrong and a fool. Apparently it caused quite the kerfluffle. 


2. His drawings are GORGEOUS.
Cajal made beautiful drawing of the nervous system, in a time when microscopes were pretty basic. Here's some examples:
Purkinje neurons in the cerebellum. The cerebellum is involved in muscle movement and muscle memory.

The hippocampus, which is a brain area important for learning and memory.


The retina, which is the layer of neurons at the back of the eye.

Santiago Ramón y Cajal is so important to science history that he has his very own asteroid. In 2005, a man named Juan Lacruz discovered an asteroid and named it 117413 Ramonycajal. I couldn't find a picture of that asteroid, so here's a different one, just for fun.

Beware the asteroids of neuroscience!