Archive for the 'Neuroscience' category

SCIENCE 101: Cranial Nerves IV and VI, the Trochlear Nerve and Abducens Nerve

Today we continue ONWARD with the series on the Cranial Nerves. But we're doing something a little different. Because last time we covered the Oculomotor Nerve, which innervates FOUR of the SIX muscles which control the eye, today we're going to round out the eye (heh, round, eye, heh) and do the other TWO. But we're going to have to go out of order. The order of the Cranial Nerves (with convenient mnemonic!) goes like this:

Oh: Olfactory
Oh: Optic
Oh: Oculomotor
To: Trochlear
Touch: Trigeminal
And: Abducens
Feel: Facial
Virginia's: Vestibulocochlear
Gucci: Glossopharyngeal
Vest: Vagus
Ah:Accessory
Heaven: Hypoglossal

We've been through the Oh, Oh, Oh (cranial nerves I, II, and III), but the two cranial nerves that control motor movements of the rest of the eye are NOT IV and V. Instead, they are IV and VI, the Trochlear Nerve and the Abducens. And we're going to cover them together, because each one is a motor nerve that moves exactly one muscle, and each one sends signals out from exactly one nucleus. Nice and relatively simple.

So here we go. And we'll start out seeing where they peek out from the brain:

You can see the trochlear nerve poking out, all thin, just to either side of the top of that rounded trapezoid that is the basal pons, while the abducens comes out of the bottom of the basal pons.

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SCIENCE 101: Cranial Nerve III, the Oculomotor Nerve

May 23 2011 Published by under Basic Science Posts, Neuroanatomy, Neuroscience

In the last few posts we've covered the first two cranial nerves, the Olfactory and the Optic nerves (remember our mnemonic: Oh, Oh, Oh, To Touch And Feel Virginia's Gucci Vest, Ah Heaven). Both of these cranial nerves carry sensory information IN to the brain for processing, and don't really control motion. For nerves like the olfactory, you wouldn't expect much motion (can't really move our nose around very well), but for the visual system, eye movements are extremely important, allowing you to focus the eye on the things that are most important in the visual field. Being able to do this accurately and at speed is extremely for complete processing of our visual field.

So today is for the third "Oh", the oculomotor nerve. Move those eyeballs!

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SCIENCE 101: Cranial Nerve II: The Optic Nerve, Part 2.

May 18 2011 Published by under Basic Science Posts, Neuroanatomy, Neuroscience

Last time we talked about the very basic anatomy of the eye. It was a lot of material. It's too much. For you, I will sum up.

Light and images come through the cornea and hit the lens. The lens flips the image backward. The light continues to the back of the eye, often to your area of best focus called the fovea, where it filters through the layers of cells to hit your rods and cones. The rods and cones send signals to bipolar cells, which send signals to ganglion cells. The axons of the ganglion cells mass up at the back of eye and head off as your OPTIC NERVE!

Got it? Good. 🙂 If you want more, please head over to Monday's post!

So, an image comes in. It will get flipped BACKWARD. It will hit the first cells LAST (the rods and cones are actually buried beneath several other layers). From here, we will go along to the back of the brain, and on the way the information will get flipped upside down. And then our brain processes it, and everything's all right.

So, the image has come through. We're past the lens, and everything is backward.

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SCIENCE 101: Cranial Nerve II: The Optic Nerve, part 1, aka, the EYE

...or rather, the visual system. Cause you can't really talk about the optic nerve unless you talk about the rest of the eye along with it.

We humans rely pretty heavily on vision as a species. At least, being able to see is a lot more important to our daily lives than, say, being able to smell. But the visual system is, in many ways, surprisingly simple. In many OTHER ways, it's confusing as all get out. I will do my best. 🙂

So, I'm going to start with this: an image is going to come in. It will get flipped BACKWARD. It will hit the first cells LAST. It will then go along to the back of the brain, and on the way it will get flipped upside down. And then our brain processes it, and everything's all right. It's opposite day, my friends!!!

Got it? Good.

Let's go!

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SCIENCE 101: Introduction to the Cranial Nerves

I've been waiting for a while to take on another multi-part project (ok, I needed to recover from EB first), and now I think it is TIME. Time for a series SO LARGE that it's going to take me probably more than three weeks, or even four to finish (with breaks for Friday Weird Science, hey, I know what you're really here for). This is going to be INTENSE.

Today I would like to introduce you to the CRANIAL NERVES. When many people think of nerves, they tend to think of white, ropey kind of things which go down your hand. You know, like this:

The nerves that we tend to think of are bundles of neurons which extend from the central nervous system to provide impulses to, and receives sensory information from, various areas of our body. Most people think that these nerves extend exclusively from the spinal cord, and that all the impulses that you need travel up and down via the spinal cord. And these nerves certainly exist and you couldn't do a whole lot without them. But what a lot of people don't know is that a large portion of your body is innervated DIRECT from your brain, with nerves that we call the cranial nerves (because they emerge from, you know, the cranium). There are twelve of these cranial nerves, and over the next several weeks, you all will be getting a crash course in neuroanatomy as I go through them in detail, where they come from, where they go, what they are generally responsible for, and what happens when they are not working properly.

You can see the twelve cranial nerves listed in the photo above. Numbered 1-12, grad students in neuroscience and medical students in anatomy have to remember them all, as well as their characteristics (luckily for you, there will be no quiz at the end of this lesson!). To help in these we've contrived various mnemonics over the years. My favorites (the ones that aren't horribly dirty) are below.

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Magazines, Media, and Teen Body Image

Apr 25 2011 Published by under Neuroscience, Uncategorized

There's no question that the opinions of society play a very large role in how we perceive ourselves, particularly in terms of physical attractiveness. For example, in our society (Western/USian), women are judged heavily on their body weight. Men get flak for not being muscular enough (though not half as much as women). We all get a lot of pressure to conform to a certain body type. And we get it through many different types of media: TV, the internet, books, radio, magazines. But how much of a role does each type of media really play? Are there some types of, say, magazines, that are worse than others?

We've got a study for that.

Renee Botta. "For Your Health? The Relationship Between Magazine Reading and Adolescents’ Body Image and Eating Disturbances" Sex Roles, 2003.

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If Stress is Getting you Down, you can blame your BDNF

People react to stress in different ways. Some people seem to thrive under a constant deluge of deadlines, and galvanize to action in the face of life stress. In others, stress can be a trigger for psychiatric disorders such as depression, leaving them feeling helpless and causing difficulties in their everyday lives. But each person is different. So...WHAT is the difference? What makes one person respond well to stress and another shut down?

The answer, in part, may be brain derived neurotrophic factor (BDNF), one of the hot buzz-proteins being thrown around neuroscience circles these days. It's important in depression, in drug addiction, and now, possibly, in stress resistance.

So how do you look at the effects of BDNF on stress? Well, stress some rats. We'll start with a simple Advanced Calculus quiz...

Taliaz, et al. "Resilience to Chronic Stress Is Mediated by Hippocampal Brain-Derived Neurotrophic Factor" J. Neuroscience, 2011.

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Cell phones: coming for your brain cells since...well, maybe not.

Feb 23 2011 Published by under Behavioral Neuro, Neuroscience

After however long Sci has been in the blogsphere, I think I've become inured to the near constant babble of breathless science reporting.  Oral contraceptives CHANGE YOUR BRAIN!!  You are yourself...ON HORMONES.  Cell phones cause brain cancer!  TIDAL WAVES of hormones. TSUNAMIS of brain activity!  A veritable STORM SURGE  of wave metaphors have invaded our science reporting, folks.  But then I think, meh, you know, it's just another report from someone who just read an already breathlessly written press release, it'll all work itself out, and I just can't get worked up anymore...I need another latte...

And then I see this kind of thing:

Power-talkers with cell phones glued to their ears may be getting more than conversation.

(Source)

Do cell phones cause cancer?

We'd all like to know, but unfortunately there's no clear answer — yet.

(Source)

And then it's coupled with things like "brain metabolism", "brain activity", and my current favorite (emphasis mine):

higher rates of glucose metabolism in the brain can mean a number of things. Yes, tumor cells may gobble up more glucose to fuel their relentless growth, but healthy brain cells need constant replenishment too, to keep up the intricate network of messages and connections that help us think, eat, move and stay alive.

(Source)

Yeah, it COULD be your greedy TUMOR CELLS gobbling up your BRAIN ENERGY!!!  Or it could be something else!

I feel comforted now. You?

Luckily, most of the reporting was really pretty even handed, but I don't think it's for lack of trying.  Rather it's because...well...the study had very little to report.

But just in case...

 

Volkow et al. "Effects of Cell Phone Radiofrequency Signal Exposure on Brain Glucose Metabolism" JAMA, 2011.

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The cerebellum and premenstrual dysphoric disorder

Feb 21 2011 Published by under Behavioral Neuro, Neuroscience, Uncategorized

Today's post is actually a TANDEM post. I'm sharing posting on this piece today with the brilliant and totally cool Kate Clancy of Context and Variation. So once you've finished here, head over THERE for her half of the take on this paper.

Kate showed me this paper, and I was immediately interested by the title and by the concept. And then she showed me the media coverage.

Is it that time of the month? These are the words no man should ever utter. How about this for a diplomatic alternative: "Are your GABA receptors playing up?"

You may be spot on. It seems that these brain cells are to blame for some women's monthly mood swings.

Heh. You watch out. Those GABA receptor...brain cells...are about to make your mood swing. I generally expect better from New Scientist, but it was pretty clear that this was based on the press release, and if so (I don't have the press release), the press release seems more than a little misleading. My "orly" cells are pinging.

On the other hand, I would like to note that I LOVE that New Scientist includes journal references to what papers they are talking about at the bottom of their articles. SEE?!?! It's not so hard!!!

It's time to look at this paper.

Rapkin et al. "Neuroimaging Evidence of Cerebellar Involvement in Premenstrual Dysphoric Disorder" Biological Psychiatry, 2011.

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The power of learning a second language: look to the caudate

Feb 16 2011 Published by under Behavioral Neuro, Neuroscience, Uncategorized

Sci's terrible at languages. TERRIBLE. In my time, I've successfully mastered English, and attempted to master four other languages (five if you count a brief foray into Elvish when I was 15, but that doesn't really count) in my time. I have failed at ALL of them. Every once in a while I would achieve some semblance of competency, but there's no doubt that either I didn't start early enough, didn't try hard enough (two semesters of immersion definitely weren't enough), or there's only one language for this geek.

But what about people who DO learn more than one language? For those who learn as adults, it's often an extremely hard won skill. For those who learn from early childhood to mid adolescence, it's often a little easier. But no matter when it happens, it's an impressive skill. Those learning a second language will master additional tens of THOUSANDS of words along with the ones from their first language.

Two languages, but you've only got one brain. And that brain only have one major language circuit. Right now, scientists think that people who are bilingual use processing in their major language circuit to monitor and to control their FIRST language, so it doesn't butt in on their second (or third, or fourth). We know that some people are better at learning a second language than others. But what makes them different? Is it a different in your anatomy (which could depend on several factors, including genes, environment, development, etc), or is it just training? And then, can training influence your anatomy?

Tan et al. "Activity levels in the left hemisphere caudate–fusiform circuit predict how well a second
language will be learned" PNAS, 2011.

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