neurobiology
sporte | June 19, 2008Right or wrong, the word "dopamine" always conjures up images in my head of rats pushing levers over and over again, working desperately hard to send shots of dopamine into their tiny little rodent brains.
Dopamine, like many other neurotransmitters (chemicals that send signals in the brain), works by binding to proteins on the surface of brain cells and sending a signal to the cell. There are five different subtypes of receptors for dopamine (D1-D5) with somewhat different activities (1) and drugs that bind to these receptors are known to have potent effects on brain activity and behavior (…
sporte | June 18, 2008In a recent post, I wrote about an article that I read in Science magazine on the genetics of learning.
One of things about the article that surprised me quite a bit was a mistake the authors made in placing the polymorphism in the wrong gene. I wrote about that yesterday. The other thing that surprised me was something that I found at the NCBI.
The article that I wrote about definitely made a mistake and I don't understand why it wasn't caught by the reviewers. I found it pretty quickly by searching OMIM and I was only trying to find information about dopamine, not verify results.…
sporte | June 17, 2008In its simplest sense, we imagine that learning occurs through a series of positive and negative rewards. Some actions lead to pleasure, others to pain, and it seems reasonable to expect that people will repeat the actions with pleasurable results and avoid those that ended in pain. Yet, we all know people who aren't deterred by the idea of punishment. We all know people who never seem to learn.
Could there be a physical reason, hidden in their genes?
In December 2007, Science published a study by Klein et. al. (1) where they asked if a specific genotype at a location called "DRD2-TAQ-IA"…
pharyngula | June 2, 2008
We're all familiar with Pavlov's conditioning experiments with dogs. Dogs were treated to an unconditioned stimulus — something to which they would normally respond with a specific behavior, in this case, meat juice which would cause them to drool. Then they were simultaneously exposed to the unconditioned stimulus and a new stimulus, the conditioned stimulus, that they would learn to associate with the tasty, drool-worthy stimulus — a bell. Afterwards, ringing a bell alone would cause the dogs to make the drooling response. The ability to make such an association is a measure of the…
pharyngula | May 24, 2008
We mammals have been beaten again. Shrimp have more sophisticated eyes than we do, with the ability to see things we can't, and I'm feeling a bit envious.
There are a couple of general properties of light that can be captured and measured with a light detector. One is the amplitude of the light wave, which we see as differences in the intensity of light. This is the most basic measurement of a photoreceptor, sensing the raw amount of energy being transmitted. Another property is wavelength, which we perceive as the color of light. Many mammals are incapable of detecting the wavelength,…
pharyngula | May 15, 2008
By now, everyone must be familiar with the inside out organization of the cephalopod eye relative to ours: they have photoreceptors that face towards the light, while we have photoreceptors that are facing away from the light. There are other important differences, though, some of which came out in a recent Nature podcast with Adam Rutherford (which you can listen to here), which was prompted by a recent publication on the structure of squid rhodopsin.
Superficially, squid eyes resemble ours. Both are simple camera eyes with a lens that projects an image onto a retina, but the major details…
pharyngula | April 14, 2008
I'm busy preparing my lecture for genetics this morning, in which I'm going to be talking about some chromosomal disorders … and I noticed that this summary of Fragile-X syndrome that was on the old site hadn't made it over here yet. A lot of the science stuff here actually gets used in my lectures, so they represent a kind of scattered online notes, so I figured I'd better put this one where I can find it.
I haven't even finished grading the last of the developmental biology papers, and already my brain is swiveling towards the genetics literature, as I get in the right frame of mind to…
pharyngula | April 14, 2008Jay Hosler has a new book out, Optical Allusions(amzn/b&n/abe/pwll). If you're familiar with his other books, Clan Apis(amzn/b&n/abe/pwll) and The Sandwalk Adventures(amzn/b&n/abe/pwll), you know what to expect: a comic book that takes its science seriously. Hosler has a fabulous knack for building serious content into a light and humorous medium, just the kind of approach we need to get wider distribution of science into the culture.
This one has a strange premise. Wrinkles the Wonder Brain is an animated, naked brain working for the Graeae Sisters, and he loses the one eye they…
pharyngula | February 3, 2008Many of you have already seen the gorgeous video below: it's a spectacularly beautiful animation of the activity in a cell.
I like it, and it's a useful illustration, but … there's something fundamental that it gets completely wrong. So today I'm not going to praise it, I'm going to criticize it. It's a substantial criticism, too, one that means I wouldn't show this video in my classes without spending more time explaining the error than it takes to show it.
Here's the central problem: molecules don't behave that way. What is portrayed is wonderfully precise movement; it looks like the…
grrlscientist | December 17, 2007tags: Encephalon, blog carnivals
The 38th edition of Encephalon is now ready for you to read, so stampede on over there for some brainy goodness!
mark_antimony | December 15, 2007A friend of mine, who's name won't be mentioned, blacked out in class the other day. Since then, he's been on a seizure drug. The drug is giving a very weird side effect. It must be affecting his auditory cortex, because he is hearing all audio roughly a half-octave lower than what it really is. In fact, he's using a sound editing program to raise his entire music library up the ~half-octave to compensate. The name of the drug is Tegretol. In the midst of headaches over finals, I'll see if I can find any interesting papers on it.
grrlscientist | December 14, 2007tags: brain blogging, blog carnivals
The 23rd edition of the Brain Blogging carnival is now available for you to enjoy. And hey, they included one of my pieces!
pharyngula | December 14, 2007
On the one hand, this is a strange tale of mutant, bisexual, necrophiliac flies, and you've got to love it for the titillating nature of the experiments. But on the other, much more interesting hand, it's a story about drilling down deeply into the causes of a complex behavior, and tracing it to a single gene product — and it also reveals much about the way the chemicals sloshing about in the brain can modulate responses to stimuli. Work by Grosjean and others on a simple Drosophila mutant, genderblind, which causes flies to be indiscriminate about gender in their courtship, opens up a…
bright_lights | December 8, 2007Wow, it's been a little while since I last blogged. I've been busy trying to stain the eyes of my zebra fish, but still with little luck. My goal is to dye the retinas and their resulting optic nerves and neural pathways of developing zebrafish. After staining the retinas and optic nerve, I was going to keep a group under constant intense lighting conditions, another group under a regular 12 hour dark and 12 hour light cycle, while raising yet another group in complete darkness for 6 days after fertilization. I would then test their visual processing skills by rotating a stimulus around their…
grrlscientist | December 3, 2007tags: encephalon, blog carnivals
The 37th edition of Encephalon is now available for your reading pleasure. The editor included a submission from me, so of course, I am happy!
pharyngula | December 3, 2007Two big specialty science carnivals are up today: Circus of the Spineless #27
and
Encephalon #37. Take your pick, invertebrates or nervous systems…or read them both.
mark_antimony | November 21, 2007Some observations on working with zebrafish:
Their vision isn't as reliable as I thought. They would try like there's no tomorrow to swim through the Plexiglas wall when there's a hold only a few inches over. If I want to continue my experiments without having an aneurysm, I'll have to make a few changes.
1 - The walls will have to be marked up opaque so that the fish don't keep trying to swim through them.
2 - Since they have trouble navigating the single chamber, I'll have to use plastic sheets to funnel them toward the door.
3 - I have a new set of tests to run. Is it the food that…
katie glasrud | November 19, 2007For this week's in-class "NeuroSlam" I spoke about a paper on mirror-touch synesthesia-- a condition in which an individual reports feeling an actual tactile sensation in response to seeing someone else touched. For example, this synesthete would feel as if someone touched their arm if they saw someone touching another's arm. Inspired by an fMRI of a mirror-touch synesthete that showed hyperactivity of mirror-touch network neurons (mirror neurons we all have in the somatosensory cortex, premotor cortex, and parts of the temporal lobe that fire in response to touch and viewing touch),…
harderkid13 | November 18, 2007As other members of my class have posted before me, we are giving presentations on synesthesia. I will be presenting possible mechanisms of grapheme-color synesthesia. Grapheme-color syesthesia is where a person sees numbers or letters as specific colors. One possible mechanism is local crossactivation. In the thalamus is the lateral geniculate nucleus (LGC). The LGC is a sensory relay nucleus. It has six layers, and the fourth layer (V4) is specifically involved in color analysis. It also happens to be next to the visual word form area (VWF). The VWF is responsible for processing strings of…
harderkid13 | November 6, 2007While reading the book Time, Love, Memory I ran across the phrase, time-blind. It was used in the context of saying that without clock genes, genes that define our circadian rythm, we would be time-blind. Is this possible, are there people who have no concept of the passage of time?