LMAYQ: Scales

The word "scale" can mean many things, and The Internet can't yet use context to tell the difference. So for this issue of Let Me Answer Your Questions, here are questions about scales that The Internet thinks The Cellular Scale can answer. As always these are real true search terms, and all the posts in the LMAYQ series can be found here. 

A Question of Scale (source)

1. "Can you give a rat scales?"

 I have never thought to ask this question, but it is an interesting one. If you can grow weird things on mice, like ears, then why not scales? Well here's the thing, the 'ear mouse' is growing skin like it normally does, the skin is just growing over an ear-shaped mold. It would actually be harder to make a rat grow scales. If it is possible, it would take some mastery in genetic manipulation...

Bee-Rat, the ultimate achievement in genetic manipulation (source)

Some sniffing around on wikipedia taught me that scales have evolved several times (fish, reptiles, arthropods, etc). It might be possible to make a rat (or mouse) grow scales by isolating the scale gene from these other animals and inserting it into the rat genome. However, since rats already grow fur, teeth, and nails, which are related to scales, it might be possible to manipulate those features already in the rat to become more scale-like.

But to answer your question, no. I am pretty sure we can't give a rat scales yet.


2. "Does the giant squid have scales?"

Another interesting question. The quick answer is no, giant squid and colossal squid (like their normal squid counterparts) have smooth skin that does not contain scales. This isn't too surprising because squid aren't fish, they are cephalopods (like octopus and cuttlefish). Cephalopods sometimes have shells, but not scales. 

Zoomed in view of Squid Skin (source)

Instead of protective scales, cephalopods use pigment in their skin to camouflage themselves or confuse predators.

Blue Octopus, Eilat Israel (I took this picture)

This octopus turning blue sure confused me.


3. "How to turn your cell phone into a scale."

There are a couple of ways that you might think a cell phone could be used as a scale. One is by the touch screen sensor. However, most smart phones now have capacitive touch screens which respond to the electric change your finger induces on the screen. That means that the amount of pressure applied doesn't matter. So you couldn't use a smart phone as a scale in that way.

Another way is through the accelerometer. Smart phones also have accelerometers, which you could possibly use to measure the force of something moving. But this wouldn't tell you the mass of the object unless you already knew the acceleration. (force = mass * acceleration). 

But really the only way that seems to actually work (albeit slowly and with questionable accuracy) is using the 'tilt sensor' of the smart phone.

But really you just as well make your own if you are weighing out small amounts of something.

Most importantly it's helpful to know what some typical objects around the house weigh, so you can use them to calibrate a phone or homemade scale.  Here are some useful weights:

1. US penny 2.5g
2. US nickel 5 g
3. 1ml water 1g
4. Euro 7.5g
5. British pound 9.5 g



4. "What is the scale on the cellular level?" 

Finally a relevant question! Most cells are measured in microns, with a blood cell being about 6-8 microns in diameter.

blood (source)

Neurons on the other hand can have somas (cell bodies) ranging from tiny (5 micron diameter) to large (50 micron diameter). But even for neurons with small somas, the dendritic or axonal arbors can be gigantic. 

Some neurons in the aplysia (snail) can get up to 1mm (1,000 microns) in diameter. Which is ridiculously huge for a neuron. For perspective, C. Elegans, a nematode frequently used for neuroscience research, is about 1mm in length. The whole animal! Including its 302 neurons! 

© TheCellularScale

A new look at light

You might know that your retina senses light primarily through its rods and cones which are sensory cells specialized in converting photons into electrical signals.


Pisa at Sunset (I took this picture)


What you might not know is that there is a third light-sensitive cell in the mammalian eye. These cells are retinal ganglion cells (RGCs), but not all RGCs are directly sensitive to light.

But what you really probably don't know is that these RGCs sense light using the same protein that allows a toad's (Xenopus Laevis) skin to sense light (melanopsin). 


"It's true, I tell ya!"

These cells (the non-rod, non-cone light sensors) react to light directly, but they aren't exactly good at it. Their sensitivity is lower than the rods and cones, and they don't seem to transmit shape or color information.  So what is their purpose? Why have a secondary set of cells that sense light in a poor and unfocused way when you already have highly specialized rods and cones? 

To make it even more confusing, the rods and cones actually connect to these cells, adding their light-sensing information to theirs. 

weird, right? In a recent review paper, Pickard and Sollars (2012) explain that these cells likely play a role in controlling the sleep-wake cycle (circadian rhythm). Rats and mice with strongly degenerated rods and cones still set their circadian clock by the light cycle they are exposed to.  These cells send strong projections to the hypothalamus which controls everything sleep-wake cycle.


In addition, these cells or at least the melanopsin gene, may play a role in Seasonal Affective Disorder (SAD) by modulating the light-dependent cycles of the suprachiasmatic nucleus (a part of the hypothalamus).



SAD (source)

Their vague ability to sense 'brightness' makes these cells nicely suited to regulating the body's response to daily and seasonal changes in light. But whether these cells need to be light-sensitive to perform these functions or whether their sensitivity to light is just an evolutionary remnant is unclear. 



© TheCellularScale



 Pickard GE, & Sollars PJ (2012). Intrinsically photosensitive retinal ganglion cells. Reviews of physiology, biochemistry and pharmacology, 162, 59-90 PMID: 22160822



Beer Yeast and Zoloft

Beer Sampler (I took this picture)

Yeast is an amazing organism that converts sugar into ethanol, or in other words barley into beer. It is used to ferment beer and is then usually filtered out.  (The leftmost beer sample in the picture above is an unfiltered beer and is cloudy because of the yeast still floating in it). 

Aside from providing proof that god loves us and wants us to be happy, yeast also provides a fascinating model in which scientists can study specific cellular processes. Because it is a simple eukaryote and can be easily cultured and easily mutated, yeast has long been used to test the effects of genetic manipulation on eukaryotic intracellular workings.

(source)

However, it's not often thought that yeast would be a good model for studying processes specific to the brain. But a recent paper published in PLoS One uses yeast to test the cellular actions of anti-depressants.  Specifically, they apply Zoloft to yeast cells.

Zoloft (like Prozac and other highly prescribed anti-depressants) works as a selective serotonin reuptake inhibitor (SSRI), inhibiting the uptake of serotonin after it has been released into the synapse, functionally allowing more serotonin to remain in the synaptic cleft. 

But Yeast don't have serotonin receptors and they don't have synapses. So what on earth could Zoloft do in these cells?

("Zoloft Does Everything" from Hipstercards.com)

Well here's a possibility: maybe Zoloft doesn't just alleviate depression by inhibiting the re-uptake of serotonin.  Maybe it does something else too. And if you are looking for non-serotonergic actions of Zoloft, yeast becomes the perfect organism to experiment on.

One reason to think there might be other (non-serotonergic) effects is that Zoloft takes a while to start 'working'.  That is, when Zoloft is taken, the enhancement of serotonin is almost immediate, but the actual effect on depressive symptoms can take weeks to appear.

So the question is: Are there effects of Zoloft which take a while to appear and do not specifically involve serotonin? 


Well, yes, there are.  Zoloft actually accumulates in the membrane of yeast cells, often killing them.  Which... doesn't sound promising. But Chen et al., 2012 shows that this membrane accumulation doesn't always kill the yeast cell and that in some select situations the membrane accumulation could have a protective effect by triggering cell-repair activities.  At "sub-lethal" doses, Zoloft can partially rescue stunted growth in certain yeast mutants.


This work seems to support the neurotrophic hypothesis of depression which says that neurons die depression, and that anti-depressants actually "reduce neuronal atrophy"
Does this paper show that Zoloft prevents neuronal death? No, not at all. It is investigating yeast, and shows that Zoloft could in some situations trigger cell repair.  But it doesn't say that Zoloft acts this way in neurons.


Obviously a lot more work needs to be done to really understand the actions of Zoloft and other anti-depressants. This study in yeast is a first step, but the findings need to be extended actual neurons before the trophic mechanism of Zoloft becomes anywhere close to as convincing as the SSRI mechanism. 

© TheCellularScale

Chen J, Korostyshevsky D, Lee S, & Perlstein EO (2012). Accumulation of an antidepressant in vesiculogenic membranes of yeast cells triggers autophagy. PloS one, 7 (4) PMID: 22529904

Science + Art at Artomatic

As much as I may complain about misrepresentations of literature in science or misrepresentation of science in entertainment, I love artwork inspired by science. Which is why I was delighted by the many science and art connections to be seen at Artomatic this year. 

(A very cellular scale) "Portrait of a Human" by Artologica

The work I was most excited to see was from Artologica. Michele Banks makes gorgeous water color paintings of neurons and microbes. I love how she brings out the natural beauty of bacteria. It reminds me how beautiful and sufficient the natural world is.

Another fantastic exhibit was by Sarah Noble, a research scientist at NASA and artist.

"Our Earth" Sarah Noble

She has some amazing portraits of planets and abstract rockets, but I really love her 'earth from space' series. Especially "our earth" shown above.  I love the stark whites, the hint of blue on the earth, and the feeling of loneliness it evokes. It reminds me of the scene in Ursula LeGuin's The Left Hand of Darkness, where two characters are traveling alone on a glacier which extends as far as the eye can see.

The 30 Computers Project uses discarded computer parts to make large 3D models of viruses and molecules and other exciting science things!

Adeno cd virus

You can go HERE to see how they made this large sculpture. 

Another favorite was Erika Rubel's Had Matter kitchen bugs: 

Kitchen Spatula Bug

These insects made with salvaged vintage kitchen utensils remind me of the little steampunk robots in Girl Genius. The only thing that could make them cooler is if they were controlled by rat neurons. 

Another delightful exhibit was from Duncan Guthery, quite possibly the coolest 11 year old ever.
He makes lego mosaics of familiar characters, like this streetfighter:

pixels made with legos

Also on exhibit were the Beatle's Yellow Submarine and a big Totoro. Not exactly science related, but turning legos into pixels is pretty cool.

And finally, the great Peep Diorama Contest submissions were all on display.  Although the "OccuPeepDC" diorama won the contest, my favorite was the peep CERN lab. 

Peep CERN lab

close up of marshmallow Peep CERN lab

There was so much more at Artomatic than I can possibly cover here. I was there for 4 hours or so and still only managed to see 3 of the 11 floors full to bursting of art exhibits. I am sure I missed some amazing science-related art. If you were there or are a science-related artist, please comment or email to let me know about your work. 


© TheCellularScale 
(I took all of the pictures here except "our earth" which I got from Sarah Noble's website)

Unveiling the New Look of The Cellular Scale

Shirt Art embroidered this brain neuroscience shirt for me! (I took this picture)

I am delighted to present the new header for The Cellular Scale.  Thank you to Shirt Art Inc. for designing this beautiful banner. 

Shirt Art is a small, family run business and they do seriously great work.  If you ever need conference shirts, lab shirts, or even embroidered lab coats, they can take care of you.

They can use all sorts of specialty inks.  So if you want a set of shirts for your lab with a gfp-style glow in the dark pyramidal neuron on it, they can do it. If you want a shirt with a brain on it  that says "neuroscience"...done! They made me one (see above), and you could contact them to order one yourself if you want.  They can even do high-resolution color blending, so if you've always wanted some brainbow shirts, they could do that too. 

I think this would make a good shirt

So for all your science apparel needs, go to www.shirtartinc.com

3 months of blogging

I love reading other blog posts about ridiculous scientific (and unscientific) claims.  They are usually entertaining and always informative.  (3 notable examples: Neuroskeptic, Respectful Insolence, Neurocritic)

Originally when I started this blog (waaaay back in January 2012), I thought I would do something similar, find outrageous claims in the press or the scientific literature and explain what was wrong with them.  The "Cellular Scale" was supposed to imply the weighing of these claims and judging them on their scientific worth. This name would have been delightfully clever if I had actually stuck to this original plan. 

I suppose there are 3 reasons why this didn't happen:

1. I didn't immediately find many outrageous claims specific to neurons (most of the claims are a little 'zoomed out' from the cellular scale and involve whole human brain areas), so I only managed to produce one (not very) skeptical post. 

2. I got sidetracked by all  the   -   totally  -  cool   -   things  -  that  -  cells  -  do.

3. Mass Effect 3 came out, so I had to play it and blog about it....twice.


I am pretty happy with how the blog is going so far because I have:

A. Stuck to cellular-level neuroscience for the most part.  Even though my 3 most  -  popular  -  posts are not about cells at all.

B. Posted something about twice a week.

C. Not run out of ideas. I was worried about this at first, but now every time I hear something interesting I think 'I could blog about that' and actually have a list of ideas that is growing faster that I am posting.

Over the next 3 months I want to:

i. Get back to my original plan and clear up some misconceptions people might have about cells.

ii. Get more comfortable on Twitter. Right now it is like being at a party eavesdropping on a super-interesting conversation between people I don't know.

iii. Post more pictures of my dog. 

CellularDog

Thanks for reading!
TheCellularScale

© TheCellularScale

Reasons for Reason Rally

Reason Rally: a reason to stand in the rain
(I took these pictures)

On March 24th, 2012 there was a Reason Rally in Washington DC.  The idea was to celebrate reason, science, and the atheist community. Despite the rain, free thinkers from all over the country participated in numbers to rival Glen Beck's rally the year before last.  There were plenty of clever signs (my favorite: "let's have a moment of science"). Some people dressed like Jesus.

Jesuses

Or Jesus riding a dinosaur:

not quite Mario and Yoshi

 Or wore flying Spaghetti monster hats:

noodles for your noodle

While entertaining, these signs and costumes were not the main point of the Reason Rally.
Here are some of the main messages from the first half of the rally.

1. Separation of church and state (Jessica Ahlquist, Taslima Nasreen)
This is by far the most important message of the atheist movement right now.  With Rick Santorum publicly saying that JFK's statement "church and state should be completely separate" made him want to vomit, the threat of theocracy has become all to real. 

Jessica Ahlquist, a highschooler who won a lawsuit to have the prayer banner removed from her school spoke early in the day about the way non-atheists in her school treated her and how a congressman even called her 'evil little thing'.  It is unfortunate that lawsuits like hers are needed to preserve the freedom of religion. 

Taslima Nasreen, an exile from Bangladesh, really drove home the dangers that can come from not maintaining a separation of church and state illustrated through Islam.  She explains that you can be arrested for simply saying that you do not believe in god in her home country; and that the religious leadership of her country allows policies that oppress women as 'slaves, objects, and baby-making machines' It is easy for even religious Americans to see that the Islamic theocracies are not compatible with equal rights, freedom, or democracy. It is frustrating when people don't see that a christian theocracy would be equally oppressive. 

2. Atheism is not a religion (Bill Maher, Tim Minchin)
Another important point is that atheism is not just one of several religious choices. 

"Atheism is a religion the way abstinence is a sexual position" Bill Maher

Atheism and the following of 'reason' involves a fundamentally different way of thinking than a religion.  That is, skeptics and atheists use evidence and science to form their beliefs and are willing to change those beliefs if new evidence appears.  Religion on the other hand is based on believing something without (and often in spite of ) evidence. As Tim Minchin says in his poem "Storm":
"Science adjusts is views based on what's observed.
Faith is the denial of observation so that belief can be preserved."

Watch the whole poem with animation accompaniment here:


3. Skeptics are not Cynics (Michael Shermer, The Amazing Randi)
The heading says it all.  Being skeptical does not mean you are cynical and see the bad side of things.  Skepticism is simply not believing something until you have a reason to.  You can be an optimistic skeptic, hoping for the best, hoping a new treatment will work, but not believing that it works until you see evidence.  I would argue that scientists are almost all (and should be) optimistic skeptics.  Scientists wouldn't do their experiments if they didn't expect something out of them. 

Similarly, skeptics are not unhappy, and scientists are not incapable of awe. As illustrated in my favorite xkcd comic of all time, scientists see deep beauty in the world as it is. 

The natural world is astounding and awe-inspiring, why gild the lily or perfume the violet with the supernatural (summary of Tim Minchin).  You don't need to think that god created it to see the beauty in a flower, the wonder of a neuron, or the delicacy of the fly proboscis.

(source) (I did not take this picture)

 I had to leave the rally early, so I don't know how the second half shook out, leave a comment if you have something to add. 

© TheCellularScale

How animals, Shrek, and Yoda stimulate your neurons.

Is CellularDog thinking 'yum'? or 'aww'? (I took this picture)
(and, yes, sometimes I wear ugly Christmas pants)

Recent studies have found that specific cells in the human brain respond to specific things.  And I don't just mean those vision neurons that respond to lines or circles that you learned about in psychology 101.  There are neurons in your brain that selectively respond to concepts (like celebrities, faces, and animals).  Let's talk about animal cells...(that is human cells that respond to pictures of animals.)

Studies recording from cells in the human brain can be conducted on patients who need electrodes implanted for other reasons (such as epilepsy monitoring). Testing neuronal responses in 41 such patients, Mormann et al., (2011) found that certain cells in the right amygdala responded to pictures of animals (They also showed pictures of people and places, but these neurons only responded to the animal pictures). 

Mormann et al., 2011 Supplemental Figure 2a

Here are some of the pictures that they showed the patients.  The blue dashes below each picture represents each time a particular neuron fired.  As you can see this particular neuron fires a lot when a picture of an animal is shown, but is not so excited by buildings or Brad Pitt. 

While there were cells that responded to all animals presented, some cells only responded to certain animals, like this one, which prefers mice and rabbits, and doesn't respond to rhino, tiger or eagle. 

Mormann et al., (2011) supplemental figure 2b

They also tested pictures of two 'ambiguously animalistic' characters: Shrek and Yoda. Many cells in the right amygdala that responded to animals also responded to pictures of Shrek and Yoda, so they classified them as animals...

animal, mineral, or vegetable?

A side note on scientific practice:

Is this correct scientific practice to classify something because it fits in with the rest of your data?

No way, Jose.
They should have done all their statistics without those two 'ambiguous' pictures because their classification was based on the very result they were investigating.
(To be fair, they apparently did test everything whithout shrek and yoda and it "did not alter any of the reported findings")

but, here's another way to look at it:



some pseudo-data

I want to do a study to test whether people like red or blue objects.  So I line up a bunch of red and blue objects on a table and have people come pick out five of their favorite.  I record what fraction of the favorite items is red and what fraction is blue.  But just for fun I throw in some purple objects.  Then I look at all my data and see that there were more favorite objects that were blue than red, and I see that the people who picked a lot of blue objects also picked a lot of purple objects. So I decide to classify the purple objects as 'blue' because the same people who picked blue picked purple.
The finding that blue is preferred over red is not altered, because people preferred blue already (see pseudo-data), but it's better to report the findings without the a posteriori classification of purple as blue. 

So yeah, no. Don't do that.

Ok back to the study, which despite this 'Yoda and Shrek are animals a posteriori' thing, is still pretty awesome. 

The Big Question: What does it mean that these cells respond only to pictures of animals?

In the supplementary discussion, the authors point out that the amygdala neurons fire 300-400 ms after the picture is presented.  They say that this timing is almost certainly after the identification of the picture would have taken place.  That mean that these neurons are probably not the ones telling you 'this is a tiger', or 'this is a spider', but instead might encode a response to knowing that it is a tiger or a spider. 

Are these neurons coding for that "awww" feeling that you get when you look at cute things? The authors say 'probably not' because the spider is not really an 'awww' inducing image. (Though given that yoda and shrek stimulate these neurons, would pictures of babies, stuffed animals, or other abstractions stimulate them as well?)

Are these neurons coding for a fear response? This is the amygdala after all. But again the authors say 'probably not'. 

"Previous studies have implicated the human amygdala in fear- and threat-related processing. The animal images that elicited neuronal responses in the amygdala contained both aversive and cute animals, and we found no relationship between amygdala responses and either the valence or arousal of the animal stimuli."

In the end, they really don't have a satisfying explanation for what the amygdala, and even more interestingly only the right hemisphere's amygdala responds selectively to animals. 

"A plausible evolutionary explanation is that the phylogenetic importance of animals, which could represent either predators or prey, has resulted in neural adaptations for the dedicated processing of these biologically salient stimuli."

So basically they say, maybe neurons in the amygdala tell you 'this is animal-like, so pay attention' because of 'the evolutionary salience of animals'.  This might be true, but it's a pretty thin and un-meaningful explanation. 

It will be difficult to conduct more detailed experiments because these are human subjects with electrodes implanted in specific places for epilepsy monitoring.  That means, you are not going to be able to test what cells are synapsing onto these animal cells or where these cells send their signals.  But even with these limitations, interesting advances can be made by testing a wider variety of pictures to the subjects, to see how specific these cells can actually be.  (What if the animal is small and in the corner of a picture, where do babies or children fit in,  etc) 


© TheCellularScale

Mormann F, Dubois J, Kornblith S, Milosavljevic M, Cerf M, Ison M, Tsuchiya N, Kraskov A, Quiroga RQ, Adolphs R, Fried I, & Koch C (2011). A category-specific response to animals in the right human amygdala. Nature neuroscience, 14 (10), 1247-9 PMID: 21874014

Know thyself, Cell: Neuronal self-recognition

A neuron's shape is important for its function, but how does it get its shape in the first place? As we've discussed before, dendrites grow out of the cell body (soma) and follow a somewhat pre-described pattern.  A Purkinje cell always has a general corral-like shape, but each individual neuron is shaped a little differently.  (Just like an oak tree looks different from a pine tree, while at the same time no two oak trees are exactly the same.) 

branching tree at sunset, San Diego: taken by me

And just as trees branch and grow based on where the sunlight is coming from, dendrites can branch and grow depending on external factors.  Of course dendrites don't care about sunlight, but they do want to efficiently 'cover space' to receive lots of incoming signals. 

So how do they do it?

Some neurons have dendrites that repulse eachother. As in, if two dendrites are rooted to the same soma, those two dendrites will avoid eachother.  This is one way that the dendrite can 'cover space' very efficiently, it will branch and grow until it sees 'itself' and then it will stop and grow in a different direction. 


(source) The Leech: yuck.

In 1998, Wang and Macagno published a fascinating study using the mechanosensory neurons in the leech. These particular neurons show 'self-avoidance' (the dendrites of the same neuron do not overlap), but they don't show 'class-avoidance' (Dendrites from the same class of neurons do overlap).
Wang and Macagno wanted to test what exactly was so self-repulsive about these dendrites. 

There are two ways the cell could recognize itself:

1. Through the use of external signals (such as a chemical marker on the surface of the dendrites that sibling dendrites can detect)
2. Through the use of internal signals (such as the voltage activity transmitted within the cell)

To find out what method the dendrites are using to recognize themselves, Wang and Macagno used a laser to separate a small section of dendrite from the rest of the neuron.  Would the other dendrites still avoid this severed dendrite, or would they suddenly see it as a stranger and start to overlap with it?


Wang and Macagno, 1998 Figure 4

The attached dendrites start to treat the severed dendrite as a stranger, growing into its area and overlapping with it.  Figure 4 from Wang and Macagno shows the intact cell (A), the location of the cut (star in B), and the regrowth of both the severed dendrite and the still attached dendrite (arrow in D).

The authors offer several possible explanations for why a severed dendrite would appear to be a stranger to the rest of the dendrites, but all are speculative.  Maybe the electrical signal prevents gap junctions from forming. Maybe there are channels (such as NMDA receptors) that repulse each other when they are both active at the same time.  Maybe there is some cytoplasmic molecule that diffuses between the dendrites and prevents overlap (though the authors admit this mechanism sound too slow to do the job.)  The authors even find a problem with the electrical signal hypothesis in that:

"In some systems the blockade of electrical activity does not affect morphogenesis."

Since no one has tested a blockade of electrical activity on these neurons, the mechanism underlying the self-repulsive nature of these dendrites is still a mystery.
© TheCellularScale


Wang H, & Macagno ER (1998). A detached branch stops being recognized as self by other branches of a neuron. Journal of neurobiology, 35 (1), 53-64 PMID: 9552166

Neurons tuned like the strings of a harp

The auditory brainstem of the boring-old-chicken is actually home to some fascinating neurons.

Key West rooster, taken by me.

The Nucleus Laminaris (NL) is a group of coincidence-detecting neurons which receive indirect input from both ears and is located in the bird auditory brainstem.

NL neurons show a peculiar dendrite pattern.  These bipolar neurons fall into the particular category of football shaped cells which have dendrites coming out the top and bottom of their cell body. The cell body (soma) of these neurons are about the same size, but depending on where they are in the NL, the cells have either short, medium or long dendrites. 

The ones near the midline have a bunch of short stubby little dendrites.

Figure 2B from Smith and Rubel, 1979

If they are a little further out from the midline, they have longer dendrites.

Figure 3B from Smith and Rubel, 1979

and finally if they are furthest from the middle, they have fewer and much longer dendrites.

Figure 10A Smith and Rubel 1979

all together this makes a gradient from short to long dendrites.  

From Figure6 Smith and Rubel 1979

The big question here is "Why?"

What is the purpose of having stubby or extended dendrites like this?  Well, even in 1979 when Smith and Rubel reconstructed these neurons, they knew that these neurons had a special answer to the "form and function" question.


The amazing thing about these neurons is that they are 'tuned' to respond maximally to specific frequencies (sound waves).  And just like strings on an instrument, the cells with shorter dendrites respond to higher frequencies and the cells with longer dendrites respond to lower frequencies. 

Why is this? Dendrites don't actually vibrate like strings, but there must be some reason for a cell with short dendrites to respond to higher frquencies and a cell with long dendrites to respond to low frequencies. 

The answer lies in what the Nucleus Laminaris actually does. In the next post we'll venture into the wilds of computational neuroscience and explore the reason behind this strange connection between dendrite shape and cell function. 

© TheCellularScale

Smith DJ, & Rubel EW (1979). Organization and development of brain stem auditory nuclei of the chicken: dendritic gradients in nucleus laminaris. The Journal of comparative neurology, 186 (2), 213-39 PMID: 447882