Tuesday, March 26, 2013

musical memories

Y’all- rarely do I blow my own mind. But tonight, I did just that.

I was typing the word “accept” and had to momentarily consider whether it or its homonym “except” was appropriate. The thought train took me to “accept is a verb” and “except is a …. what is it?…. ah yes, preposition.”

And then, I spontaneously busted out in a song that I have not heard nor sang in sixteen years. You see, my third grade language teacher made us memorize all of the prepositions by putting them to the tune of Yankee Doodle. Catchy little song. I aced my English test on prepositions and have not thought about that song since.

Yet sixteen years later, I am able to perfectly rattle off those forty-six arbitrary words in perfect alphabetical order. That song was in my brain all this time. Untapped, unused, but unchanged. How can this be?

Remember our chat about neurons? Well, their little fingers are called dendrites. These dendrites are what reach out and make connections to other neurons. The number of dendrites per cell is plastic- meaning your neurons can grow or lose dendrites- and therefore connections- according to how much the present ones are used (do a Sodoku puzzle tonight! Grow some dendrites!). These connections are what constitute your memories. Fire one chain of them off, boom: your fifth birthday party. Fire a different combination of connections off: that Halloween you lost your wallet and walked home in the rain, maybe sort of inebriated, dressed as Chewbacca. Your recollection of your life’s experiences is a complex network of chemo-electric signals. That’s insane, right?

A study in the mid-90’s looked at memory and music. And boy, are they correlated. Text recall was significantly better when set to the tune of a song than when simply spoken. However, it was significantly worse when just one verse was sung or when plural melodies were introduced in a single song (Wallace 1994). From this, we can conclude that it’s not just rhythm that enhances our dendritic connections- it’s actual music. Be it a stupid yet catchy tune (“Call Me Maybe,” I’m looking at you and your stupid lyrics), or soul-moving sounds like Mozart’s Requiem.

It’s can be unsettling that memories of things like your first kiss or precious time with loved ones that have since died are nothing more than very specific paths of action potentials traveling from neuron to neuron in that hunk of meat we call a brain. But the fact that they are solidified by music makes it easier to stomach- at least for me. “Party in the USA” takes me right back to margaritas in my college apartment, laughing with my girlfriends so hard I couldn’t breathe. “Leave” by JoJo puts me right back in my sister’s Jetta, making late-night summer trips into Bossier City to get soft serve ice cream from the McDonald’s drive-through. I can put on Rachmoninov’s second concerto, about halfway through the first movement, and be transported back to my father’s strong hands on the steering wheel as he drove me home from my first year in college- and actually feeling the sense of content safety I felt then.

And that, to me, is simply beautiful- dendrites and action potentials included.

Wallace, Wanda T. Memory for music: Effect of melody on recall of text. Journal of Experimental Psychology: Learning, Memory, and Cognition, Vol. 20 (6). Nov. 1994, 1471-1485

Tuesday, March 19, 2013

walker texas ranger tears

As I sat and ate my grilled cheese sandwich on my lunch break not long ago, Walker Texas Ranger played on the TV. Walker’s girlfriend, Alex, has survived being kidnapped and almost killed, and is now lying in a hospital bed while he lovingly comforts her in all his ginger glory. He tells her how much she means to him, and then pulls a ring out of his pocket. And there it is… “Alex, will you marry me?”  It pans to the highlights of their relationship. In typical cheesy 90’s slow-mo style, Alex and Walker stroll through fields hand in hand, laugh together, cry together, and share loving looks into each other’s eyes as their perfectly teased Texas hair blows in the breeze.

And suddenly, I am bawling.

The credits begin to roll and I brush my tears off of my grilled cheese and wipe my eyes. Something isn’t right- I should be laughing hysterically, not crying hysterically. I look at my calendar on my phone and then it makes sense.

Let me tell you folks, hormones are very real. They don’t only control your mood- they control things like sleep, friskiness, stress response, fight or flight response, puberty, hunger, parenting, and in-utero develepment. Pretty much every process or event your body undergoes is driven by hormones in one way or another

But how do they work? Having to direct things from slow-paced things like ovulation to fast-acting processes like adrenaline rushes, how do they make things happen? Where do they come from? Where do they go? How do they get there?

Hormones are little molecules that are manufactured by your body. They can come from individual cells, organs, or more frequently from glands (think thyroid, testes, ovaries, adrenal, etc.). Different glands manufacture different hormones.

Major glands  (wikicommons)
To name a few: Testes and ovaries manufacture sexy hormones that influence puberty, ovulation, parenting, menopause, and male machoism. Your adrenal glands sit on top of your kidneys and produces adrenaline- key in stress response, fight or flight, and cell metabolism. Your thyroid gland in your neck manufactures a variety of hormones, mainly affecting metabolism. The big daddy gland- the pituitary- is buried at the base of your brain and is perhaps our most primitive gland. It regulates just about everything from sleep to sex drive. The pineal gland, also of primitive origin, plays a role in light detection and internal calendar regulation.

From their respective glands, hormones are released into the bloodstream in order to travel to their target tissues. Let’s take adrenaline, for example. Say you’re walking down a dark alley and all the sudden a man steps out in front of you with a knife and says “give me your money!” Time for fight or flight response. Your brain immediately sends signals down to your adrenal glands, which then flood your whole body with adrenaline. But you only need certain tissues to respond, right? Your cardiac muscles need to quicken, your pupils need to widen, your blood vessels need to dilate so you can haul ass. Well, nature has it so that only these target tissues have receptors to recognize these hormones. So while your pinky toe is getting the same dose of adrenaline, it don’t give a $h*t. But the cells of your heart and blood vessels certainly do- and respond to help you get out of this hairy situation. This is how the whole hormone system can be so refined- receptors only exist where their hormones are meant to act.

The guy with a knife is still standing in front of you. You kick him in the balls and run. You make it safely away and stop to catch your breath. That jittery feeling that makes you ready to punch somebody in the face is the adrenaline coursing through your body. Within the next few minutes, you’ll start to feel more normal. This is because the adrenaline is being cycled out of your cells and metabolized to the point of no longer being hormones.

The system is pretty much the same for slow-release events like ovulation and puberty. Your pituitary regulates your internal calendar, activating the right tissues at the right time.

When you break it down like this, it all sounds so scientific and straightforward. But when you’re sitting next to a lady with a baby on an airplane and are desperately hoping she’ll ask you to hold it, or crying at Walker Texas Ranger, it doesn’t feel so scientific or straightforward. Makes you wonder how much of the human experience is just molecules binding to receptors. But then again, maybe that makes it that much more extraordinary.

Monday, March 18, 2013

have you SEEN a dik-dik?

A recent and actual G-chat transcript, between my sister and me.

Alix: Have you SEEN a Dik-dik?

Me: No. What is a Dik-dik?

Alix: A tiny tiny antelope.
             They are monogamous.
They can run 26 mph.
Can you imagine if a Dik-dik ran past you at 26 mph?

It would be amazing.

I wish lap giraffes were real.

Okay got to go. Love you bye.

Of course, I immediately Wikipedia’ed Dik-dik, and was faced with the cutest ungulate I’ve ever seen.

OH MY GOD. (wikicommons)
They are little antelopes that live in Africa. They eat small plants and shrubs, throw it back up, chew it some more, and eat it again. This would be gross, but they’re so tiny that it’s more funny than it is gross.

What really caught my eye in the Wikipedia article was the blurb referring to their monogamy. It reads:

“Monogamy in dik-diks may be an evolutionary response to predation; surrounded by predators, it is dangerous to explore, looking for new partners.”

Monogamy exists all throughout the animal kingdom. Selective pressures vary in each instance of it, but it is safe to make the sweeping statement that monogamy usually evolves as a means to protect highly vulnerable young. Take us, for example. The survival rate of babies (before the present-day civilization) must have been waaaaay higher if Dad stuck around to protect mom and child from saber-toothed tigers and to help provide food. On the other end of the spectrum, consider a housefly. Baby houseflies are ready to buzz off and start life as soon as they hatch. Mom and dad aren’t even around- they’re already off having irresponsible sex with new partners. Monogamy wouldn’t make sense for them.

Dik-dik being sassy. (pbase.com)

Never before had I seen monogamy explained as a response to predatory danger for the parents. No way this could be true, I thought to myself. I researched further, and lo and behold: a whole paper has been published on Dik-dik monogamy. And they found something pretty interesting.

It had been previously assumed that Dik-diks were facultatively monogamous. Facultative monogamy is monogamy that is the result of restrictions on resources. In other words, male Dik-diks could only defend enough territory to accommodate one female, and that’s why they only mated one female. If more resources were available, then the male Dik-diks could afford to pimp two or more females.

Researchers found evidence to the contrary of this model. Male Dik-diks routinely defend territory (and therefore resources) to accommodate several females! Why do they date just one lady, then?

Obviously, because they have the capacity to love. (Alix, you stop reading here. Life will be better if you do.)

No, that’s not true. Rather, it’s because the males are jealous little suckers and don’t want any other guys picking up their girlfriends. It’s formally called mate guarding- and is an evolved behavior that increases the likelihood that their genetic material is passed on to the next generation. If Dik-diks had the equivalent to “The Maury Show,” the audience would be sorely disappointed that Dik-diks rarely question the paternity of their fawns. Daddy Dik-diks keep close enough eyes on their ladies that they’re not too worried about it.

This being said, monogamy rarely occurs in nature without extra-pair copulation, aka “getting some on the side.” In Dik-diks, only males will engage in extra-pair copulation. Mated females are noted to rarely, almost never, engage in extra-pair copulation (go figure).

So, several components contribute to Dik-dik monogamy. It is safer for the tiny, herbivorous animals to stick to their territory instead of going down to the local drinking hole to try to meet new Dik-diks. Also, mated pairs spending almost all of their time together increases paternal fidelity. And even though males have the capacity to mate more females, they don’t- the lingering urge to mate guard has been passed down from earlier times when perhaps the Dik-dik male could only defend territory for one female.

My initial balking reaction to the explanation of Dik-dik monogamy was short-sited. It wouldn’t make sense for the natural world to be as diverse and multifarious if evolution followed a blueprint. Regardless of how many notes I took or outlines I made about monogamy as an evolved reproductive strategy while I was in college, I don’t know diddly squat.

When asking questions about the evolution of life, always remember to keep an open mind. If researchers hadn’t kept open minds about Dik-dik monogamy, we’d still be without the knowledge that males mate one female, even though they can mate more. And I prefer to live in a world where Dik-diks stick by each other's sides in a non-obligatory capacity. Don’t you?

Here's the paper:

Female dispersion and the evolution of monogamy in the dik-dik. Brotherton, PNM, and Manser, MB. Animal Behavior, 1997. Volume 54 (6), 1413-1424.

Friday, March 8, 2013

put your science panties on (part 2)

 Last time, we covered the first part of the journey a neural signal takes on the way to becoming muscular movement.  We started at the brain and made it all the way down the nerve highway to a muscle. And it is here at the neuromuscular junction that you have been waiting with bated breath for the tale to continue.

When an action potential makes it to the end of the nerve road, it must make something happen in your muscles. The electro-chemical energy of the action potential must be somehow translated into kinetic energy. While your muscles are capable of creating large-scale movements like swinging a golf club, the tiny movements of the molecular structures of your muscles is where this kinetic energy is translated. So let’s get up close and personal with muscle structure.

Your muscles are like bundles of cords within bundles of cords- kind of like Russian nesting dolls- bound together by connective tissue. When you get down to the cellular unit, a single muscle cell is called a muscle fiber. A single fiber is made of smaller units called myofibrils. It is in these myofibrils that the basic contractile units of muscles are found. This basic contractile unit is called a sarcomere. Sarcomeres are made up of long proteins that slide past each other to make the muscle contract. These two stringy proteins are actin and myosin.

A relaxed sarcomere
Myosin filaments have these little bulbs hanging off called “myosin heads.” The myosin heads like to link up with the actin filaments. Through a process involving some supplementary energy molecules (holla, ATP!), the myosin heads creep along the actin filaments, bringing them closer together. Think of a little army guys (myosin heads) climbing along a rope (actin). This is muscle contraction on the tiniest level.

Contracted sarcomere

So, imagine that a whole bunch of sarcomeres are crammed into a muscle fiber. And a whole bunch of fibers are crammed into a single muscle. You’ve got tons of sarcomeres, working simultaneously, causing a whole chunk of muscle to squeeze in on itself.

Well that’s all well and good. But how is it that we’re so coordinated? I wouldn’t call Beyonce’s performance in the video for Single Lady “chunks of muscle squeezing themselves.” I mean, one muscle group is capable of a wide variety of motion, so there must be more nuance to it than  “chunks of muscle squeezing in on themselves,” right?

Right. This is where we go back to part 1- the innervation of the muscle. The complex maze of nerve fibers feeding muscle is responsible for the precise control we have over our movement. Your brain can selectively fire the pathways that feed just part or parts of a muscle. These different combinations are what make a smile different from a frown, from an inquisitive facial expression, from an embarrassed expression, from an amused expression. All use the same muscle groups, but each stimulates them in a different pattern.

The complex neural to motor pathway, to me, is one of the most intricately wired processes in all of Vertebrata, but always funnels down to one of the most basic: the little sarcomere.