naturally selected

April 1, 2009

Dislike at first sight

Filed under: science — benkallman @ 3:28 pm

First impressions matter, as the saying goes. They matter enough for researchers to dedicate their researching to figuring out how they’re formed in the brain. To this end, a team of psychologists and neuroscientists at NYU have correlated activity in two ares of the brain with first-time social evaluation.

The team set up a paradigm in which subjects, abed inside an MRI machine, were shown pictures of a face (all were male, to control for gender biases). After a few seconds, they were shown either three negative sentences or three positive sentences, all describing the “face’s” personal character (i.e. “He did a mean thing” or “He helped a little old lady cross the street”). After a few-second interval, they were given the other three sentences (positive if the first three were negative, or vice versa). At the end, the subjects were asked to rate their impression of the face on a scale of 1 (don’t like) to 8 (really like).

(Oh, by the by, please keep in mind that throughout this whole procedure, the researchers were imaging the subjects’ brains with the MRI.)

So after all the evaluations were done, the researchers went on to correlate brain activity with individual impressions of the face. (This, as it were, is the point of any MRI study.) If the subject gave the face a positive score, then the team looked at the brain activity during the presentation of the positive sentences (the “evaluation-relevant” information). Conversely, if the subject said they didn’t like the face, the brain activity during the presentation of the negative sentences was used. In both cases, the sentences opposite the subjects’ evaluations were the “evaluation-irrelevant” information.

With these statistical parameters in hand, the team could isolate which areas of the brain were being called upon when the subjects were forming their impression of the face. The difference in brain activity between presentation of the evaluation-relevant and evaluation-irrelevant sentences should theoretically isolate which areas are specifically utilized to, well, evaluate!

And so it was. Two areas in particular–the amygdala and the posterior cingulate cortex (PCC)–were more highly activated during presentation of information used to make first impressions than when the irrelevant information was presented. Also interesting is the fact that the strength of the activity was tied to how positive or negative the impression was. The stronger the impression (in either direction), the more active the amygdala/PCC.

The amygdala and PCC aren’t the only areas used to form impressions, but they’re undoubtedly important, and they’ve been shown to play critical roles in the general areas of learning, emotion, and arousal (as in motivation, not sexy stuff). A study like this one is instructive, but it’s not going to lay out exactly how impressions are formed on a neural-circuit-based level. There’s no A-to-B here, but rather an A-affects-B-to-a-certain-extent. But being able to point to two areas and say: “These are critical” is neveretheless pretty astounding.

March 24, 2009

The old switcharoo

Filed under: science — benkallman @ 4:02 pm

The extent to which the brain can reorganize itself never ceases to amaze me. All that bunk they taught you in high school about how the adult brain is immutable, how the number of brain cells is fixed at birth, etc. is, well, bunk. New neurons are born all the time, in particular in two areas of the brain, the subventricular zone (SVZ) and the subgranular zone (SGZ) of the dentate gyrus. The new neurons from the SVZ replace olfactory receptor neurons in your nose, which die after a few weeks. Without them, you wouldn’t be able to smell. And the neurons from the SGZ migrate to the hippocampus, where memories are formed. Without them, you wouldn’t be able to remember.

But beyond the birth of new neurons, the brain has the remarkable abililty to reorganize what it’s already got. This is called neuroplasticity, and is one of the “hot” areas of neuroscience. Immature brains are known to be very plastic. That plasticity is what allows babies to learn to speak and toddlers to learn to read.

However, there’s less evidence for large-scale neuroplasticity after maturity. After amputation of a limb, for instance, the sensory areas of the brain reorganize themselves, but this reorganization is fairly local and within only one modality (i.e. sense). Basically all the cells that were dedicated to the amputated limb rededicate themselves to other limbs.

Now there’s a really interesting study being published next week in PNAS which demonstrates cross-modal (i.e. cross-sense) neuroplasticity. The group, from Virginia Commonwealth University, experimentally deafended adult ferrets (sorry, PETA), and then checked out the areas of the brain dedicated to hearing to see what happened.

The result was pretty amazing. Basically the entire auditory area of the brain was converted to process somatosensory (tactile) information. Stimulating different parts of the ferrets’ bodies activated cells that were once only activated by sound! In the end, 84 percent of cells in the auditory cortex responded to somatosensory stimulation. Pretty cool, but the authors make a good point at the end of the paper. Just because the cells have been converted to process tactile information doesn’t mean the ferrets can use that information functionally or perceptually. But it’s still interesting to think that no brain goes to waste, even after injury. Shit is precious!

The science of relaxation

Filed under: Uncategorized — benkallman @ 1:56 pm

All you need is coffee

Filed under: science — benkallman @ 1:44 pm

Via Bagel, a post from an apparently defunct “zine” called Litmus that takes a scientific approach to coffee. Some interesting factoids:

The aroma of roasted coffee is thought to result from a combination of about 25 volatile organic compounds, the ‘aroma compounds’, found at a total concentration of only 1g/kg of coffee and ranging in individual concentration from the lower part per million range down to as little as parts per trillion.

Only 25 compounds! That’s, like, nothing, compared to apples (356) or grapes (466).

Also, the difference between Arabica and Robusta beans is apparently gene-deep:

Another way in which C. arabica and C. canephora are different is in their ploidy, the number of copies of the genome present in each cell. C. canephora has the usual two copies (diploid) of its genome, common to all other species in the genus Coffea, but C. arabica is allotetraploid, it has two pairs of genome copies to a total of four copies of its genome. It is thought that C. arabica may have originated from a spontaneous cross between two diploid species, followed by a duplication of the two genomes.

Sometimes I forget that coffee comes from a plant. Or, in the immortal words of Tracy Jordan: “Sorry, I was just thinking about how weird it is that we eat birds.”

Totally not science-related WHAT?

Filed under: Uncategorized — benkallman @ 2:22 am

Flavor Flav is 50 years old.

March 23, 2009

Arachnophobia and Octomom

Filed under: science — benkallman @ 11:35 pm

To anyone who still reads this rag, I apologize for the week that’s passed since my last post. It’s been kind of busy at work, and I was drunk all weekend, so, truly, it was out of my hands!

Onward and upward. I’ve been on a David Attenborough kick recently, having illegally downloaded the several episodes of Life of Mammals that I hadn’t seen. It’s an awesome series. Not on par with Planet Earth, but totally captivating nonetheless.

An aside: Someone asked me this weekend what my dream job was — as in, barring any financial, educational, reality-based obstacles, what I’d want to do for a living. I lamely said “travel writer,” but immediately afterwards realized I’d actually want to be David Attenborough. To just go around the world and watch animals in their natural habitats and get paid for it? Oh mama! Plus, I’d have British citizenship and knighthood.

Anyway, last night I got the first disc of Attenborough’s more recent series, Life in the Undergrowth. It’s about insects and worms, mostly, so I was kind of skeptical. But the success of the series is in making superficially boring things like bees’ search for nectar and the spinning of spiders’ webs legitimately entertaining.

One part of the episode concerned the mating and reproductive habits of the wolf spider. Male wolf spiders have these fuzzy organs called palps on their two front legs. As part of their courtship ritual meant to attract lady spiders, they move them in circles in complex but stereotypical ways. It’s kind of hypnotizing, actually. I couldn’t find a video of the courtship scene online, but I was able to find the one showing what happens after successful fertilization. The female wolf spider spins this crazy egg sac out of papery silk and carries her eggs on her back for the duration. And even after they hatch, the spiderlings cling to their mother’s back until they’re ready to head out on their own.

Arachnid mothers are better than some human mothers I know. Of course, not mine. I’m thinking…her.

March 17, 2009

Green links (for St. Patrick’s Day?)

Filed under: science — benkallman @ 1:41 pm

A couple of environmental tidbits:

  • A well-researched, timely and sharply written article by Leslie Kaufman in The New York Times about the spreading trend of municipally subsidized solar panels.
  • A moderately scary post at The New Republic‘s Vine Blog about the growing consensus among climatologists that by 2100 sea levels will rise one meter if current emissions levels are sustained. Even scarier is that most of the cities on the East Coast of the U.S. will likely see an additional rise of eight inches, which the post explains is a result of fast-moving ocean currents that have kept the sea level in the Northeast relatively low. Once those currents slow down (as they inevitably will), the sea level in New York, say, will rise at a faster rate than elsewhere.
  • And lastly, a short piece in The Economist about a new type of battery that is able to recharge much more quickly than a normal lithium-ion battery. There are obviously lots of potential applications, but the one the article singles out is plug-in cars, whose batteries, up until now, took ages to charge and even then did not last very long. The electricity used to charge a plug-in car costs the equivalent of 94 cents a gallon, so a fast-charge battery could make it easier (read: cheaper) to mass produce and market plug-ins to even the most skeptical SUV owners.
  • March 12, 2009

    Beauty and the brain

    Filed under: science — benkallman @ 7:24 pm

    There’s been a spate of research lately that’s begun to confirm what most non-scientists already kind of new, namely that men and women approach the world in different ways. Even when controlling for culture, age, race or class, differences between men and women exist and, to a large extent, are the result of differences in the way their brains are wired.

    Into the mix comes a new report, published this week in PNAS, suggesting that men and women see and evaluate beauty in very different ways. A group of Spanish researchers showed 10 male and 10 female subjects various pictures, some of renowned works of art and some of decrepit urban streets. At the same time they measured brain activity via an extremely sensitive technique called magnetoencephalography (MEG), which measures the minute magnetic fields given off by brain cells every time they fire (on a scale of milliseconds).

    Overall, most activity in both men and women was localized to the parietal lobe, which is basically equivalent to the top of the brain. This makes sense, as the parietal lobe is known to be where high-level processing of visual input takes places. What’s interesting is the lateralization of activity between men and women (i.e. the difference in activity between the left and right hemispheres).

    Pop psychology tells us that “right-brained” people are intuitive and holistic while “left-brained” people are more logical and analytical. From a totally non-feminist, anecdotal perspective, one would assume that women (the perhaps more “holistic” sex) would show more activation on the right and men (the more “logical” sex) would show more activation on the left.

    But, as so often happens in science, the opposite was true. Activity in women was found on both sides of the brain, whereas men showed much more activity in the right hemisphere than on the left. The authors spend a lot of time thinking about why this is true, but here’s a good summary:

    Men tend to solve navigation tasks by using orientation-based strategies involving distance concepts and cardinal directions, whereas women tend to base their activities on remembering the location of landmarks and relative directions, such as “left from,” or “to the right of.”

    I suppose that’s true, but what’s even more intriguing is these differences could have possibly evolved. The authors mention a theory, called the hunter-gatherer hypothesis, that attempts to explain sex differences in brain activity as a result of the gender-based task specializations that early human society was likely founded on. Hunters (i.e. men) needed to be able to position themselves using landmarks that may or may not have been visible, and whose sizes and shapes changed based on perspective. They had to be able to identify a landmark from a kilometer way or from a few meters away and more importnatly tell it was the same landmark. This probably required a lot of flexibility in terms of processing spatial information.

    On the other hand, gatherers (i.e. women) had to be able to remember and later recognize specific characteristics of a food. They had to be able to tell what was edible and what was dangerous, and also to remember the specific location of a bush or a tree. Like hunting, this surely required some on-the-go processing, but successful gathering relies heavily on direct recall as well.

    It’s interesting to think what other sex-based differences the hunter-gatherer dichotomy has left behind. Besides looking at art, do men and women read differently? Do math differently? The possibilities…

    Did not know

    Filed under: Uncategorized — benkallman @ 3:04 am

    I’m really not a cat person, probably due to my crippling codependency issues. (Dogs are better for the socially awkward.) Anyway, I’m also not a Cat Fancy subscriber, so I missed this interesting feline fact when it was finally substantiated four years ago. Apparently it’s been anecdotally known for millenia that felines of all sizes, from house cat to lion, are completely indifferent to sweets. This makes cats stand out from most other mammals, who will gobble up sugar if given the chance. Until 2005, no one was really sure why cats were uninterested by saccharine goodness. Lots of possibilities were thrown around: no sweet taste buds, messed up brain circuitry and the like. All wrong. Turns out that all felines possess a naturally occurring deletion of a gene, T1r2, that encodes the sweet taste receptor.

    Without the ability to taste sweetness, humans and most other mammals would suffer, since a large part of our and their diet is based on fruits and vegetables, which are often identified by their sweetness factor. Cats on the other hand rely primarily on meat to make up the bulk of their diet. Since meats are essentially sugarless, not being able to detect sweetness isn’t such a big deal for them. So basically, no cavities for Simba.

    March 11, 2009

    Jacques Henri Lartigue, with commentary

    Filed under: Uncategorized — benkallman @ 8:38 pm

    The ocean looks like proscuitto.

    When were tires elliptical?

    Yes to corn.

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