Monday, 24 September 2012

Why you can't tickle yourself

Kids often ask me, "Why can't I tickle myself?" It's an excellent question, and not only kids want to know the answer. Grown-ups wonder about this one, too.

The anti-self-tickling culprit is a part of the brain called the cerebellum. The cerebellum is involved in muscle memory. If you've ever played a musical piece without thinking about it, you can thank your cerebellum. It also monitors and corrects ongoing muscle movements.

Imagine that your friend throws a ball and you want to catch it. You stretch out your hand. Now your cerebellum takes over. It takes information from your eyes (Where's the ball? How fast is it going?) and your arm (Where's my hand?) and does split-second calculations so that you can predict where the ball is going to go and move your hand to get it. Your cerebellum is a physics whiz. "Calculate the trajectory of the ball" would take a few minutes in a written physics exam. Your cerebellum can do it in microseconds.

What if you miss the ball? Your cerebellum's next job is to figure out what you did wrong and fix it, so that you don't make the same mistake again. This is why the cerebellum is so important for muscle learning.

Here's the point: Your cerebellum always knows where your body is, and what it's doing. It never turns off. It never takes a break. It's your muscular micro-manager, and it's really, really good at its job.

So what does this have to do with tickling? Let's look at what happens when someone else tickles you, and when you try and tickle yourself.

When someone else tickles you:
Actually most spiders, including this little cutie, rarely bite humans.
It's unexpected. Your cerebellum doesn't know it's coming.You respond with surprise, giggling, sometimes even a queasy feeling. Lots of people don't like it, even though they laugh. Scientists think that the tickle response is "adaptive", which means its something we picked up through evolution because it helps us survive. If a giant, hairy, poisonous spider crawls on you with its eight giant, hairy legs, you're going to be surprised, and squeal, and brush it off. You might get queasy, and you'll probably feel twitchy and jumpy after. But the key point is: you brushed the spider off. Now it can't bite you and kill you. That you have a similar response to tickling fingers as to tickling spiders is a side-effect. If the tickle response keeps you alive, your body doesn't care if it also gives your sister a chance to drive you crazy.

When you try to tickle yourself:
You can't tickle yourself, even when you close your eyes and don't look. That's because it's expected. No hairy poisonous spiders or annoying sisters here. How does your body know it's not a spider, even when you close your eyes? Because of your cerebellum, of course! It knows what you're trying to do! Remember that it knows exactly where every muscle is, always, and that includes your fingers. And it can tell the difference between expected sensations (self-tickling) and unexpected sensations (hairy spiders). It ignores expected sensations, because they aren't a threat. So when you start trying to tickle yourself, it says, "nice try, but I know that's you. You're not scaring me! I'm not scared! I won't jump or squeal!" And it's right. It won't. Or rather, you won't. Your cerebellum puts the brakes on the tickle response, effectively telling the rest of your brain to ignore it. And since you can't fool your cerebellum, you can't tickle yourself.

Monday, 17 September 2012

BRAIN MYTH-BUSTING: Dogs can't see color

My dog, Oscar
One popular brain myth is that dogs can only see in black and white. It's not true. Dogs can see color - they just can't see as many colors as we can. Or, I should say, as most of us can.

In your eye you have special cells called rods and cones. When you see things, you're looking at light bouncing off of objects. The job of the rods and cones is to detect that light, and send the information to your brain.

Rods
Rods are very sensitive to light, but can't see color. They're what you use at night.

Cones
Cones only work in bright light, but they can see different colors. Since this post is about color vision (and whether dogs have it), I'll talk about cones for the rest of the post.


How color vision works:

Visible light is a spectrum made up of all the colors
White light is a spectrum made up of all the colors. You can check this out for yourself by shining light through a prism. When that light hits an object, the object absorbs some of the colors, and reflects others. What you see is the reflected light, or the reflected colors.

You have three types of cones, each specialized for different colors: red, green, and blue. Red light activates the red cones. Purple light activates the red and blue cones. This is kind of like how mixing primary colors when painting creates new colors. The only difference is that in paint, the primary colors are red, yellow, and blue; but in light, the primary colors are red, green, and blue. Every color you see comes from the three cones being activated in different amounts, with the amount depending on the color. The cones talk to the brain. The brain calculates the different levels that the different cone types are activated, comes up with a result, and perceives it as color.


Color blindness:

Some people only have two types of cones instead of three. These people are colorblind. The most common kind is red-green colorblind, where someone is missing either the red cones or the green cones, and has difficulty telling the difference between red and green. More rarely, people will lack blue cones, and have difficulty telling the difference between blue and yellow. Colorblindness is hereditary, and more likely to affect boys than girls.
 

Rainbow - Normal color vision

Rainbow - Red-green colorblind
Rainbow - Blue-yellow colorblind












How dogs see:

From psychologytoday.com
If dogs could only see black and white, then they should only have rods. But it turns out that dogs have cones. They have two types of cones, instead of three. Sound familiar?

Dogs are red-green colorblind. We know this because 1) they have two cones types, and 2) when given vision tests, (with lots of yummy treats for motivation!) they can distinguish colors like red-green color blind people can. This means they can see colors, but they can't tell the difference between red and green.

Myth busted!

Monday, 10 September 2012

How to become a neuroscientist

NOTE: Thanks to so many kids, more than I can count, for this post idea.

So you think you want to be a neuroscientist? Great! But maybe you aren't so sure how to get there. Here's your how-to guide, from someone who's made it through to the end.

First, there's one thing you need above all else. If you have this one thing, it's going to be a lot easier.

YOU MUST LOVE THE BRAIN.

I'm serious. That's the most important thing. There's some rough sections on the path to neuroscience-dom, but if you love the brain, you'll make it through.

Now the step-by-step:


ELEMENTARY SCHOOL (up to 5th grade):

Have fun and enjoy the world. Maybe do a science fair. Congrats, your work here is done.


MIDDLE SCHOOL (6th-8th grade):

Life's starting to get a little weird. Social rules are more difficult to comprehend. Maybe you're getting teased for being a science geek. It's okay. Stick it out.

Your grades don't have to be fabulous, but don't fail anything. It's okay if you get a few C's. I did. But I got A's in all my science classes. This was partly because I was smart, but mostly because I loved science. The point is, middle school's stressful enough without adding more stress over a C or two. But you should still apply yourself, especially in those science classes.

For the awkward kids, a side note: I remember middle school as the worst time in my whole life. The worst. Today, I'm over-the-moon happy with my life, with a great job and wonderful friends. So stick it out. IT GETS BETTER.


HIGH SCHOOL (9th-12th grade):

This is where colleges start paying attention, so you need to pay attention to those grades. Again, a C or two won't kill you, but don't fail anything. You need to get into college (Canadians: by "college" I mean "university"), one that has a neuroscience research program. So apply yourself.

Extracurricular activities are good. Colleges love extracurriculars.

Write a decent college essay. I'm serious. Nothing will make you look less intelligent or teachable than bad grammar. (Assuming you're a native English speaker. You get a pass on the "perfect grammar" rule if you're ESL, but you do have to be understandable.)

I graduated high school with a 3.6-3.8 GPA (I don't actually remember). I was a member of zero honors societies. I took 4 AP courses and passed 4 AP tests. I picked up a C or two along the way, but I got A's in all science classes. My SAT score was a 1450 (back when SATs were out of 1600). I ended up going to University of California, Davis on a partial merit scholarship.

My point is that you don't have to be perfect, but you do have to be good enough to get into a research university. I got Cs, but I had a clear ability for science. The key is: never lose sight of that love for science.


COLLEGE / UNIVERSITY:

The key here, the absolute most important thing you can do, is GET RESEARCH EXPERIENCE. That's why I told you to pick a school with a research program. Yes, grades are important. Get good grades.You don't have to major in science (though it helps). What you need to do is RESEARCH.

You need to do this because when you hit graduate school, all you'll be doing is laboratory research. Grad school supervisors look for enthusiastic people with good research backgrounds and good letters of recommendation. How do you get a good letter of recommendation? Why, work in someone's lab, of course! Then they'll know you well, and can write a glowing letter about how much you love neuroscience and what a hard worker you are.

This is also important because you need to find out now whether you even like being in a lab. Because if you don't like lab work, don't try for a Ph.D.

I spent two years working in a food microbiology lab and one year working in a neuroscience lab. While working in the neuro lab, I did my own research project and wrote it up as an undergraduate honors thesis. I highly recommend this. It's pretty much a requirement if you want to be competitive.


GRAD SCHOOL:

Congrats! You made it to the Ph.D. Now enjoy spending the next 6 years in indentured servitude.

Grad school is hard. At some point, probably in your third year, you're going to want to quit. You'll end up sleeping in the lab on multiple occasions. Your romantic life will quite possibly be in shambles. You will be broke and living off oatmeal and ramen noodles. But that's okay. Why? Because you have the most important quality that someone needs to become a neuroscientist. YOU LOVE IT. When you get new data, your heart pounds and you get giddy and you want to show the whole world. You gush to everyone you meet about how awesomtastic the brain is. And it's because you love it that you'll make it through this final trial.

Once you're done, you get the Ph.D. Congratulations! You're a doctor! You made it! Now you just need to find a job...


THE TAKE-HOME MESSAGE:

I once asked my Ph.D. supervisor which was more important in a potential student: intelligence, or enthusiasm. He said "enthusiasm." He told me that given the choice between a genius student with a lazy attitude, and a less smart student who was excited to work in the lab and learn about the brain, he'd take the less smart student, any day. Yes, smarts are important to being a scientist. You do need to be smart. But enthusiasm is more important. Without it, you'll never make it through grad school. So I'm going to repeat the first point, because it's just that critical...

YOU MUST LOVE THE BRAIN.

Monday, 3 September 2012

Why cannibalism is bad

Um...because it's gross??

Well, yes. Unless you happen to be a zombie or a tadpole, cannibalism probably isn't something you'd ever consider doing. (Yes, tadpoles are cannibalistic. I've seen it. It's a little creepy.) But some people are cannibals. They don't kill people in order to eat them. There's no murder going on here. They eat parts of their already dead relatives, in order to absorb their spirit and power, and return their life force to the community. It's a form of mourning. But this custom has one very big, very deadly downside. Cannibalism is an excellent way to give yourself a brain disease.

A tadpole (well, technically a froglet) of the South African clawed toad. Cute, right? Sure, until you realize that their favorite snack is each other! From caudata.org.

Let's go back about 50 years. There was a tribe of people living in Papua New Guinea. They called themselves the Fore. And they had a problem. People were coming down with a terrible wasting sickness. They had difficulty moving, headaches, tremors, and difficulty speaking. They eventually lost the ability to coordinate their movements, and became unable to speak or respond to their surroundings. Everyone who had the disease died. The people called it kuru, which meant "shiver", after the uncoordinated, jerky muscle movements.

A doctor named Michael Alpers and an anthropologist named Shirley Lindenbaum visited the Fore, and they recognized the disease. It looked like a form of a very rare neurodegenerative disease called Creutzfeldt-Jakob Disease (CJD). ("Neurodegenerative" diseases are diseases where neurons die.) CJD is sometimes inherited, and sometimes people develop it randomly for unknown reasons. There's a third way it can be spread: by eating infected brains.

That's how it was spreading in the Fore. Most likely someone, sometime in the past, randomly developed the disease. When that person died, their relatives ate the brain, which to them was a sign of respect. Over the years, those relatives died. Their brains were eaten, and the disease spread. Since the time from infection to the first appearance of symptoms (known as the incubation period) is between 5 and 20 years, but can get as high as 50 years, not everyone who ate the brains died from kuru. No one connected cannibalism with the disease.

CJD and kuru are part of a family of diseases called the transmissible spongiform encephalopathies (pronounced en-sef-uh-lop-uh-thee). That's a mouthful, so I'm going to shorten it to TSEs. But that name essentially means, "diseases which make the brain look like a sponge". TSEs kill neurons, causing holes in the brain and creating the spongy appearance. They are caused by prions, which are infectious proteins. There is no cure.

You're probably already familiar with at least one prion disease. In the 1990s, a bunch of people in Britian got sick after eating beef. They had a terrible neurodegenerative disease, with symptoms a lot like kuru and CJD. After they died, their brains looked like sponges. Have you guessed the disease yet? The clue is the word "beef." This disease is called bovine spongiform encephalopathy. Also known as....MAD COW DISEASE.

Healthy brain tissue from a cow. From the FDA.

Brain tissue from a cow with mad cow disease. Note all the holes that make it look spongy. From the FDA.

In humans, TSEs usually exist as single, isolated, cases, not as epidemics. The mad cow disease epidemic happened because cow food came with added bits of cow, including cow brains. That's right...people were feeding cows to cows. It was cow cannibalism. So the prions from one or two sick cows quickly spread to lots of cows. Those cows were made into hamburgers, but the burgers were contaminated with the brains and spines of the cows. People who ate the contaminated burgers became infected with the prions, and got sick with mad cow disease.

Once we figured out what was going on, cow cannibalism became illegal. People are no longer allowed to feed cows to cows. There are also strict rules in place to prevent any brain tissue from getting into burgers. Thanks to these rules, there hasn't been another outbreak. But the British outbreak isn't over. Since the incubation period is so long - up to 50 years - it's likely that more people will develop symptoms over the next few decades.

Mad cow disease is EXTREMELY RARE!! Every time a cow is discovered with the disease, there's a world-wide media panic attack. Calm down everyone! It's not that bad! Yes, what happened in Great Britain was terrible, but we learned from it. There's lots of measures in place to prevent prions from getting in to food. The chances of new human cases are extremely small. So you can keep eating beef if you want. Just don't eat the brains.

Oh, and just in case you're wondering, the Fore people still live in Papua New Guinea, and they no longer eat each other's brains.