Re: Guest Post - Scienceguest Fridaypost

1

Somebody is going to do a study of where on the cortex people store the information that there's a specific location on your cortex in which stuff is stored and the MRI is going to blow-up and kill everybody.


Posted by: Moby Hick | Link to this comment | 10-18-13 7:49 AM
horizontal rule
2

So pretty soon we will be able to use lasers to zap out the part of the brain that holds memories of old relationships, and then if we run into that person we will fall in love again, as if for the first time?


Posted by: Natilo Paennim | Link to this comment | 10-18-13 7:55 AM
horizontal rule
3

and that has a characteristic physical relationship to the place where you represent a toaster (it's kind of above it)

I hope it's fairly stable, because if the Eiffel Tower fell on top of the toaster, the toaster would be toast.

Also, where do I store the image of that happening?


Posted by: chris y | Link to this comment | 10-18-13 7:56 AM
horizontal rule
4

2: only if you have had a relationship with a toaster.


Posted by: ajay | Link to this comment | 10-18-13 8:00 AM
horizontal rule
5

There need to be a region 34 which stores the porn of all the other images stored in the cortex.


Posted by: Barry Freed | Link to this comment | 10-18-13 8:01 AM
horizontal rule
6

Also, where do I store the image of that happening?

That's a much more complicated question, as you might imagine. And it's worth nothing that these areas are really for identifying what you're looking at, so if somebody shows you a picture of a toaster, this is the area of your brain that lets you figure out what it is. What happens then (do you toast something? Do you topple the eiffel tower onto it?) involves many, many more brain areas. What's cool about this study, I think (and the linked blog post talks about it) is that the way objects are mapped in the brain gives you clues as to what is important about them. So the ways that you can interact with a toaster are fundamentally different than the ways you can interact with the eiffel tower, but on some important level they're similar to the ways you can manipulate (say) a basketball. Whereas, for animals, the way you interact with a cat is not terribly different from the way you interact with a horse on some important level. And the way you interact with a horse is wholly different than the way you interact with anything along the toaster-tower axis.


Posted by: IRFT | Link to this comment | 10-18-13 8:27 AM
horizontal rule
7

2: I saw that movie. It was pretty good. Kirsten Dunst dances around in her underwear.


Posted by: rob helpy-chalk | Link to this comment | 10-18-13 8:27 AM
horizontal rule
8

Whereas, for animals, the way you interact with a cat is not terribly different from the way you interact with a horse on some important level.

While I know what you mean, and it sounds perfectly reasonable, this gives rise to all sorts of ill-advised looking images.

And the way you interact with a horse is wholly different than the way you interact with anything along the toaster-tower axis.

Same here -- while this is also perfectly reasonable, I now want to list ways I interact with horses exactly like I interact with things on the toaster-tower axis. (Well, I sit on them. Or have.)


Posted by: LizardBreath | Link to this comment | 10-18-13 8:36 AM
horizontal rule
9

Not that I sit on toasters. But if you draw a line from a toaster to the Eiffel Tower, it would include at least some things that I would sit on.


Posted by: LizardBreath | Link to this comment | 10-18-13 8:37 AM
horizontal rule
10

I wonder what happens with objects intended to blur the lines. Does C-3PO register as people or an inanimate object? What about R2D2? What about a toaster with cat ears glued to it?


Posted by: LizardBreath | Link to this comment | 10-18-13 8:43 AM
horizontal rule
11

Robin Thicke?


Posted by: heebie-geebie | Link to this comment | 10-18-13 8:44 AM
horizontal rule
12

10: They get famous, at least if they have the most famous man in Canada for a father.


Posted by: Moby Hick | Link to this comment | 10-18-13 8:44 AM
horizontal rule
13

7: I don't remember any lasers in the critically acclaimed Bring it On.


Posted by: Annelid Gustator | Link to this comment | 10-18-13 8:44 AM
horizontal rule
14

D'oh.


Posted by: Moby Hick | Link to this comment | 10-18-13 8:44 AM
horizontal rule
15

I wonder what would happen if they did that experiment on my stepdaughter. Does her brain see the toaster as an animate object? What about her stuffed animals?


Posted by: peep | Link to this comment | 10-18-13 8:45 AM
horizontal rule
16

It's becoming pretty clear to me from 8-10, especially 9, that a map of LB's brain would probably be startlingly different from a map of most other brains, and might very well be one of those maps that includes the homelands of the Arimaspes and the Cynocephali and the kingdom of Prester John.


Posted by: ajay | Link to this comment | 10-18-13 8:46 AM
horizontal rule
17

Does her brain see the toaster as an animate object? What about her stuffed animals?

Look that was just one study--odds are that, done well, any MRI of your daughter's stuffed animals would show no activity at all w/r/t toasters.


Posted by: Annelid Gustator | Link to this comment | 10-18-13 8:48 AM
horizontal rule
18

Actually, I think you'd want Oudemia and Smearcase, both well-known lamp-pitiers, in the MRI.

I may be prone to wondering whether it would really be wise to interact with a horse that had jumped on top of my refrigerator in the same way I'd deal with a cat that did the same thing, but that's an entirely separate issue.


Posted by: LizardBreath | Link to this comment | 10-18-13 8:49 AM
horizontal rule
19

So the ways that you can interact with a toaster... on some important level they're similar to the ways you can manipulate (say) a basketball.

And this has turned into an athletically themed Pop-Tarts commercial.


Posted by: LizardBreath | Link to this comment | 10-18-13 8:52 AM
horizontal rule
20

But if you draw a line from a toaster to the Eiffel Tower, it would include at least some things that I would sit on.

Assuming you occasionally sit on the ground, I suppose that's a pretty safe bet. But, facetiousness aside, I'm not sure what would lie on a conceptual line between the two, considered for example functionally or aesthetically, nor am I at all confident that I'd expect a chair to form part of the set.

This is one of the things that intrigues me about this finding. It seems to suggest that the categories applied are fairly fixed, but I don't see why they should be. What if you come from a culture that doesn't eat toast, or has never heard of Paris?


Posted by: chris y | Link to this comment | 10-18-13 8:53 AM
horizontal rule
21

I'm not sure what would lie on a conceptual line between the two

toaster → French toast → Eiffel Tower


Posted by: MAE | Link to this comment | 10-18-13 8:55 AM
horizontal rule
22

There need to be a region 34 which stores the porn of all the other images stored in the cortex.

Region 34 is located in the back of the left frontal lobe, in a directory titled "not porn".


Posted by: Spike | Link to this comment | 10-18-13 8:58 AM
horizontal rule
23

As to whether French toast falls into the category of things that you sit on, Rule 34 applies.


Posted by: MAE | Link to this comment | 10-18-13 8:58 AM
horizontal rule
24

Now my mind is full of kitties climbing the Eiffel Tower.


Posted by: Flippanter | Link to this comment | 10-18-13 8:59 AM
horizontal rule
25

But, facetiousness aside, I'm not sure what would lie on a conceptual line between the two,

The toaster end of the line is the hard bit. That is, if you hand me the Eiffel Tower, and tell me to make something like it, but closer to a toaster, the obvious move is to make it smaller. And at some point you end up with things like jungle gyms and metal railings, which are definitely in the class of things that I would sit on if I found myself near them. But while a jungle gym is both clearly sort of like the Eiffel Tower, and more like a toaster than the Eiffel Tower is, it's hard for me to picture how to get much conceptually closer to a toaster from there without either making some leaps, or creating things that would have no reason to exist other than to provide intermediate forms between the two.


Posted by: LizardBreath | Link to this comment | 10-18-13 8:59 AM
horizontal rule
26

7 Kirsten Dunst dances around in her underwear.

I didn't even remember that she was in the movie.

I guess I've forgotten most of the movie, except that I saw it on the day I graduated from college and it was kind of a semi-date with a woman who made me miserable for a while. I was pretty stupid then.


Posted by: essear | Link to this comment | 10-18-13 9:01 AM
horizontal rule
27

10 asks good questions. Unfogged grant application time!


Posted by: essear | Link to this comment | 10-18-13 9:02 AM
horizontal rule
28

What about a toaster with cat ears glued to it?

Highly saleable on ThinkGeek and at anime cons, I should think.

I get 20%.


Posted by: Flippanter | Link to this comment | 10-18-13 9:04 AM
horizontal rule
29

Where does the Death Star fit into this categorization scheme?


Posted by: AcademicLurker | Link to this comment | 10-18-13 9:04 AM
horizontal rule
30

things like jungle gyms and metal railings

It would be interesting if these things lie somehow around the boundary of the two brain regions.

Is there any chance that one object could be mapped to more than one region depending on its distance from the viewer?


Posted by: essear | Link to this comment | 10-18-13 9:04 AM
horizontal rule
31

Also, do dead animals land in the same region as live animals? What about, like, wall-mounted buffalo heads?


Posted by: essear | Link to this comment | 10-18-13 9:05 AM
horizontal rule
32

Is this like on that one episode of House where they read the patient's mind and then it turns out she had a brain worm?


Posted by: Todd | Link to this comment | 10-18-13 9:06 AM
horizontal rule
33

25. Please make a video of the process you describe and post it to youtube. Including leaping towards toasters and creating things that have no reason to exist.


Posted by: chris y | Link to this comment | 10-18-13 9:08 AM
horizontal rule
34

8. last: In fact, when writing that I thought of your oft-expressed desire to pet a lion like a kitty.

20.last: right, that's what's interesting. It isn't a priori clear that real world size should be a useful way to organize things -- a glowing hot coal is small, but you definitely don't want to be picking it up, for instance. But it turns out that real world size is how things are organized, so then you have to start thinking about why that would be.

30.1: As far as I know it's specifically size, not anything about affordances or manipulability or anything like that.

30.2: Probably not; the author of the paper cited in the blog post has done previous work showing that retinal size doesn't have any impact on where along this map objects get represented.


Posted by: IRFT | Link to this comment | 10-18-13 9:17 AM
horizontal rule
35

Incidentally, if you'd like to look at the actual object images that the researchers used, they're posted here.

Stuffed animals (or something like a roomba) are an interesting case. As far as I know they haven't tested those, in part because this paper showing that these maps exist is so new. Now that you know they're there, you can start looking at edge cases and potential oddballs.


Posted by: IRFT | Link to this comment | 10-18-13 9:21 AM
horizontal rule
36

One argument in favor of stuffed animals getting filed in the "animate" areas is that the fusiform face area (which is right in the middle of the animacy band that they found) shows activation for cartoon faces as well as real faces.


Posted by: IRFT | Link to this comment | 10-18-13 9:23 AM
horizontal rule
37

"It's Raining Florence Tenderson"


Posted by: nosflow | Link to this comment | 10-18-13 9:25 AM
horizontal rule
38

Now that you know they're there, you can start looking at edge cases and potential oddballs.

And start testing lamp-pitiers and people who work for Pixar generally to see if they have a less robust distinction between the animate and the inanimate than the rest of us.


Posted by: LizardBreath | Link to this comment | 10-18-13 9:25 AM
horizontal rule
39

The pessimist by principle, connecting the brain-place where he stores Edward Teller to the brain-place he stores Bernays with a shortcut to Snowden, is not all that excited by brain mapping. We won't own this, anymore than we own the Internets.

Peasants are owned by stuff like this.


Posted by: bob mcmanus | Link to this comment | 10-18-13 9:34 AM
horizontal rule
40

Stuffed animals (or something like a roomba) are an interesting case.

This could get complicated quite fast: is Hobbes processed the same way by Calvin and his father? One sees him as an object and the other as something more. Hoe is this represented? Is it represented?


Posted by: chris y | Link to this comment | 10-18-13 9:34 AM
horizontal rule
41

18/19 cracked me up (or, rather, had me stifling my laugh because I didn't want to have to explain what was funny to a co-worker).


Posted by: NickS | Link to this comment | 10-18-13 9:36 AM
horizontal rule
42

And, if we put you in an MRI, we could read out those maps to the millimeter.

You guys should get a better MRI. That's not very good resolution for an MRI. Or, if it is, we're writing papers on whole bunches of noise.


Posted by: Moby Hick | Link to this comment | 10-18-13 9:37 AM
horizontal rule
43

What I would find fascinating is whether it is a continuum -- Hobbes and C-3PO can hang out together right on the line, with Darth Vader close to them on the animate side and R2D2 on the inanimate side -- or if it's two separate buckets and your brain has to pick one. And if the latter, what precisely are the criteria?


Posted by: LizardBreath | Link to this comment | 10-18-13 9:38 AM
horizontal rule
44

I didn't even remember that she was in the movie

Really? Her in her underwear and the reveal about her character in the end were the only two things I did remember about the movie.


Posted by: rob helpy-chalk | Link to this comment | 10-18-13 9:42 AM
horizontal rule
45

42: Not an expert, but as I understand it, fMRI is more like PET in terms of resolution.


Posted by: ydnew | Link to this comment | 10-18-13 9:43 AM
horizontal rule
46

So I guess this means that "Things that, at a distance, resemble flies" is not a basic category the brain uses?


Posted by: rob helpy-chalk | Link to this comment | 10-18-13 9:44 AM
horizontal rule
47

Hobbes and C-3PO

Nasty, burnished, and short.


Posted by: Moby Hick | Link to this comment | 10-18-13 9:45 AM
horizontal rule
48

46: Only the cat brain. Which divides all objects into "things that, at a distance, resemble mice" and "other".


Posted by: Cryptic Ned | Link to this comment | 10-18-13 9:45 AM
horizontal rule
49

Okay, I checked into this a little bit more for you guys. It sounds like Hobbes and C-3PO would both get filed as "animate", because they have faces, and our brains tend to put anything with the visual properties of a face into that bucket... of files. I can also report that these representations are probably due to visual properties of the object, rather than conceptual properties. Some of the same authors did some (possibly unpublished) work where they familiarized subjects with objects made of legos; one group had objects made with normal legos, and the other group had objects made with giant legos, to see if the experience of real-world size would change how the objects were represented, even if they appeared identical when shown to the subjects in the scanner. They found no effect, which they took to mean that the visual properties of the objects are really what's driving where they get represented.


Posted by: IRFT | Link to this comment | 10-18-13 9:46 AM
horizontal rule
50

42: It isn't very good resolution for structural MRI, but for functional MRI it's extremely good -- actually probably about twice as good as the resolution they really worked with. (Sorry to be inexact.)


Posted by: IRFT | Link to this comment | 10-18-13 9:48 AM
horizontal rule
51

I didn't know there was that much of difference.


Posted by: Moby Hick | Link to this comment | 10-18-13 9:50 AM
horizontal rule
52

So pretty soon we will be able to use lasers to zap out the part of the brain that holds memories of old relationships, and then if we run into that person we will fall in love again, as if for the first time?

We already kinda sorta can do this. In mice. And for the emotional affect of memories, not the memories themselves. Potentially it has applications in treating PTSD and the like.

I guess I've forgotten most of the movie, except that I saw it on the day I graduated from college and it was kind of a semi-date with a woman who made me miserable for a while.

If this isn't supposed to be super meta, it should be.


Posted by: Ginger Yellow | Link to this comment | 10-18-13 9:51 AM
horizontal rule
53

I can also report that these representations are probably due to visual properties of the object, rather than conceptual properties

Making R2D2 squarely inanimate, probably, despite having an appealing personality. And Tom Hanks' volleyball-friend Wilson animate.


Posted by: LizardBreath | Link to this comment | 10-18-13 9:53 AM
horizontal rule
54

What movie is it where Kirsten Dunst dances around in her underwear? I have a friend who wants to know.


Posted by: Spike | Link to this comment | 10-18-13 9:54 AM
horizontal rule
55

54: Eternal Sunshine of the Spotless Mind.


Posted by: nosflow | Link to this comment | 10-18-13 9:54 AM
horizontal rule
56

54: Jumanji, you sick bastard.


Posted by: Moby Hick | Link to this comment | 10-18-13 9:55 AM
horizontal rule
57

Thanks, I will tell my friend that. He is from Canada.


Posted by: Spike | Link to this comment | 10-18-13 9:55 AM
horizontal rule
58

52.last: I went to see that movie with married friends who were at an extremely low ebb in their relationship, and sort of at the point of deciding whether to give up or to start over again from scratch with each other. It would be fair to say that the experience of watching the movie was both meta and really, really intense for both of them.


Posted by: Sifu Tweety | Link to this comment | 10-18-13 9:55 AM
horizontal rule
59

51: IRFT will probably answer, but acquisition times for fMRI are short (I skimmed the original paper, but I don't have a sense of normal here). Structural MRI frequently uses contrast agents and you can average multiple scans in systems were there's not a lot of motion (like brains).


Posted by: ydnew | Link to this comment | 10-18-13 9:59 AM
horizontal rule
60

That makes sense. There's a direct trade-off between acquisition time and resolution.


Posted by: Moby Hick | Link to this comment | 10-18-13 10:01 AM
horizontal rule
61

Folks should be making a note to think about seeing this movie when it comes around. You don't even want to know what regions of the brain are involved.


Posted by: CharleyCarp | Link to this comment | 10-18-13 10:02 AM
horizontal rule
62

Right. Bet there'd be lots of money in developing a contrast agent for fMRI, too.


Posted by: ydnew | Link to this comment | 10-18-13 10:03 AM
horizontal rule
63

Does gadolinium not go through the brain's "I'm so fucking special I get my own blood" barrier?


Posted by: Moby Hick | Link to this comment | 10-18-13 10:04 AM
horizontal rule
64

Once an organ develops consciousness, it gets just too smug for its own good.


Posted by: Moby Hick | Link to this comment | 10-18-13 10:05 AM
horizontal rule
65

I checked the methods for you two, and this paper used a 2 second temporal resolution for the functional acquisition and a 3mm voxel, on a 4T scanner. I assume the voxels were relatively large because they were acquiring a relatively large chunk of the brain on each frame. I believe that in studies that are looking at smaller regions, people are able to get 2mm voxels with a 2 second TR on a 3T scanner.


Posted by: IRFT | Link to this comment | 10-18-13 10:05 AM
horizontal rule
66

63 and 64 now seem petty.


Posted by: Moby Hick | Link to this comment | 10-18-13 10:06 AM
horizontal rule
67

Especially since we only have a 3T.


Posted by: Moby Hick | Link to this comment | 10-18-13 10:08 AM
horizontal rule
68

I once mocked a someone with a 1.5T scanner until I met a guy with a 7T scanner.


Posted by: Moby Hick | Link to this comment | 10-18-13 10:14 AM
horizontal rule
69

63: It does, but fMRI is basically detecting oxygen levels as a proxy for blood flow to determine areas of activity. I imagine that gadolinium would basically mess with your ability to see change in signal over time (because it would diffuse everywhere blood goes and wash out slowly). You might be able to get an initial image of brain activity, but you wouldn't be able to do repeated scans with good signal to noise.

65: Yeah, I did read that, but I didn't bother to look up how short 2 sec was relative to structural MRI.


Posted by: ydnew | Link to this comment | 10-18-13 10:18 AM
horizontal rule
70

68: There's always someone with a bigger scanner. I'm sure it's more in what you do with it.


Posted by: ydnew | Link to this comment | 10-18-13 10:18 AM
horizontal rule
71

If there's something bigger than a 7T scanner, there can't be more than a handful of them in the world.


Posted by: Moby Hick | Link to this comment | 10-18-13 10:20 AM
horizontal rule
72

Uh, ladeez?


Posted by: Moby Hick | Link to this comment | 10-18-13 10:22 AM
horizontal rule
73

69.last: As far as I know, it's hard to do a good structural scan in less than ten minutes. That might have changed.

It does, but fMRI is basically detecting oxygen levels as a proxy for blood flow to determine areas of activity.

As you know, Bob, it's much worse than that; it's detecting oxygen levels as a proxy for blood flow which is a proxy for astrocyte activity which is a proxy for neurotransmitter levels in synaptic gaps which is a proxy for neural activity. That it works at all is really pretty astounding, and requires a fair bit of after-the-fact correction to get the timing and magnitudes to accurately reflect response to the stimulus.


Posted by: IRFT | Link to this comment | 10-18-13 10:22 AM
horizontal rule
74

Aren't 7T scanners not actually that much better for some reason? I feel like somebody told me that once.


Posted by: Sifu Tweety | Link to this comment | 10-18-13 10:22 AM
horizontal rule
75

They probably aren't much better for ordinary diagnostic purposes.


Posted by: Moby Hick | Link to this comment | 10-18-13 10:23 AM
horizontal rule
76

Apparently there are 9.4T scanners, at least.


Posted by: Sifu Tweety | Link to this comment | 10-18-13 10:24 AM
horizontal rule
77

Not that I have the slightest idea about how to diagnose anything.


Posted by: Moby Hick | Link to this comment | 10-18-13 10:25 AM
horizontal rule
78

It only takes 17T to levitate a mouse? Science project time.


Posted by: Moby Hick | Link to this comment | 10-18-13 10:26 AM
horizontal rule
79

There's no way they had that justification for that experiment ahead of time. "Hey guys, let's levitate a mouse for hours!" "Why?" "Cuz, uh, I dunno, space?"


Posted by: Sifu Tweety | Link to this comment | 10-18-13 10:33 AM
horizontal rule
80

I believe she also dances around in her underwear in Crazy/Beautiful. Science!


Posted by: Robert Halford | Link to this comment | 10-18-13 10:33 AM
horizontal rule
81
"[ the mouse ] tried to grab on to something. I guess it wasn't used to floating," says Liu. "It bumped on the cage and started spinning. It obviously didn't like it that much."

I GUESS IT WASN'T USED TO FLOATING


Posted by: Sifu Tweety | Link to this comment | 10-18-13 10:34 AM
horizontal rule
82

The part of my brain that says things about ethics and animal cruelty can barely be heard over the part of my brain saying, "Science rules!"


Posted by: Moby Hick | Link to this comment | 10-18-13 10:36 AM
horizontal rule
83

Or even the part that says, "Let's try it with a small turtle."


Posted by: Moby Hick | Link to this comment | 10-18-13 10:40 AM
horizontal rule
84

What's all the way down now, stupid turtle!


Posted by: Sifu Tweety | Link to this comment | 10-18-13 10:41 AM
horizontal rule
85

74: Signal to noise increases roughly proportional to field strength (waves hands at math), but contrast doesn't necessarily (because you have one kind of tissue next to another), so in terms of clinical use, there probably isn't a big advantage. Also, I assume that for scanning people in structural MRI, there's a certain desired resolution below which you don't get improved info (eg how much narrower than a small blood vessel do you need to be). In general, though, if you want to take images with a shorter acquisition time, higher field is better, so it might matter more for capturing high res images quickly.


Posted by: ydnew | Link to this comment | 10-18-13 10:44 AM
horizontal rule
86

I was thinking (for functional stuff) it was maybe something about a limitation of the head coils, but I dunno.


Posted by: Sifu Tweety | Link to this comment | 10-18-13 10:46 AM
horizontal rule
87

WE CAN HAZ MOAR BIGGER MAGNETS? has been the theme of a lot of my discussions lately.


Posted by: essear | Link to this comment | 10-18-13 10:47 AM
horizontal rule
88

there's a certain desired resolution below which you don't get improved info (eg how much narrower than a small blood vessel do you need to be)

It's not so much that you don't want to get more resolution, it's that you quickly reach the point where noise from other sources makes greater resolution impossible. Especially for weight-bearing joints.


Posted by: Moby Hick | Link to this comment | 10-18-13 10:49 AM
horizontal rule
89

Oh, and high field magnets aren't unusual in other areas (see protein NMR, where a 500 MHz/11.8T magnet is low-end and 1 GHz is state of the art). They just require a lot more space/care/liquid He and create a lot more interference (bad for pacemakers).


Posted by: ydnew | Link to this comment | 10-18-13 10:49 AM
horizontal rule
90

fMRI is basically detecting oxygen levels

Wait, how does this work? I thought it was detecting hydrogen.


Posted by: essear | Link to this comment | 10-18-13 10:52 AM
horizontal rule
91

I think I just short-circuited myself, and also I wish I hadn't skipped breakfast.


Posted by: Jesus McQueen | Link to this comment | 10-18-13 10:55 AM
horizontal rule
92

90: apparently (thanks, Wikipedia!) it's actually measuring the magnetic susceptibility of oxyhemoglobin vs. deoxyhemoglobin.


Posted by: Sifu Tweety | Link to this comment | 10-18-13 10:56 AM
horizontal rule
93

Now I want to find a spare few hours to read about how fMRI works. But I have to go catch a flight.


Posted by: essear | Link to this comment | 10-18-13 10:59 AM
horizontal rule
94

Sometimes when commenting here I feel like a parody of myself.


Posted by: essear | Link to this comment | 10-18-13 11:01 AM
horizontal rule
95

Tell me about it.


Posted by: Sifu Tweety | Link to this comment | 10-18-13 11:01 AM
horizontal rule
96

Taking a flight does involve being scanned.


Posted by: Moby Hick | Link to this comment | 10-18-13 11:02 AM
horizontal rule
97

Designing high field magnets is really hard. I have a bout of magnet design coming up and I'm not looking forward to it. My boss thinks it's really straightforward but I've done it before and it sucks. Convincing him that water cooling is called for is going to be hard.


Posted by: togolosh | Link to this comment | 10-18-13 11:03 AM
horizontal rule
98

This seems to be the answer:

Hemoglobin without bound oxygen molecules, deoxyhemoglobin, is paramagnetic because of the high spin state (S = 2) of the heme iron. In contrast, oxygen-bound hemoglobin, oxyhemoglobin, has low spin (S = 0) and is diamagnetic


Posted by: Sifu Tweety | Link to this comment | 10-18-13 11:05 AM
horizontal rule
99

I have a bout of magnet design coming up and I'm not looking forward to it.

Keep a bucket handy just in case.


Posted by: Sifu Tweety | Link to this comment | 10-18-13 11:05 AM
horizontal rule
100

97: Liquid helium or go home.


Posted by: Moby Hick | Link to this comment | 10-18-13 11:09 AM
horizontal rule
101

Now I really want essear to explain what proton relaxation means.


Posted by: Sifu Tweety | Link to this comment | 10-18-13 11:15 AM
horizontal rule
102

Oh, hey. While we're sounding like parodies of ourselves, I'm curious as to what IRFL meant by 'informed by our evolutionary history' in the original post. Is there any sort of link to similar brain regions in related organisms (I suppose there's no way to access actual human ancestors)? What's the evolutionary history aspect of it?


Posted by: LizardBreath | Link to this comment | 10-18-13 11:15 AM
horizontal rule
103
This article needs attention from an expert in Spectroscopy.

Wikipedia is getting deep with its article-problem flagging.


Posted by: Sifu Tweety | Link to this comment | 10-18-13 11:17 AM
horizontal rule
104

93,98: I can't get the full thing, but if you do a PubMed search for "bold fmri review", there's an article titled The physics of functional magnetic resonance imaging (fMRI) in Rep Prog Phys Sept 4 2013 epub date that might be a good summary. 98 gets it right on the para/diamagnetic properties of Fe/hemoglobin. Sorry, I was shorthanding earlier. MRI can read quite a few nuclei, not just 1H. Some groups at Johns Hopkins do stuff looking at 19F.

100: Except for that whole shortage thingy.


Posted by: ydnew | Link to this comment | 10-18-13 11:20 AM
horizontal rule
105

101: Only essear?


Posted by: ydnew | Link to this comment | 10-18-13 11:24 AM
horizontal rule
106

102: Well, it's sort of second order, really, but the linked blog post discusses it a bit; once you've found that this division exists consistently in the brain, you have to start thinking about what functional role having things divided that way plays, which is really asking an evolutionary question.

As to the question of whether this appears in other animals, I really don't know. Monkeys definitely have face and body areas in something like the same topographic layout as humans so, and there's some evidence that they have homologs of at least some of the human object areas, so it might be the case that they have this same organization.

One question is if it would be harder to find homologies in animals that don't have the ability to manipulate objects. Some people hypothesize (I don't have a cite, unfortunately) that rats, while they can be trained to recognize objects, don't really do it naturally, and are instead focused more on the affordances of surfaces (can they be climbed) and whether they're food (animacy); you would expect that their neural layout would be very different, but I don't know that anybody has done that work.


Posted by: IRFT | Link to this comment | 10-18-13 11:27 AM
horizontal rule
107

105: oh, no, not at all. He just seemed like a promising candidate. Lay it on me!


Posted by: Sifu Tweety | Link to this comment | 10-18-13 11:27 AM
horizontal rule
108

In nuclear magnetic resonance spectroscopy and magnetic resonance imaging (MRI) the term "relaxation" describes several processes by which nuclear magnetization prepared in a non-equilibrium state returns to the equilibrium distribution. In other words, relaxation describes how fast spins "forget" the direction in which they are oriented. The rates of this spin relaxation can be measured in both spectroscopy and imaging applications.


Posted by: Robert Halford | Link to this comment | 10-18-13 11:41 AM
horizontal rule
109

104: this one?


Posted by: Sifu Tweety | Link to this comment | 10-18-13 11:47 AM
horizontal rule
110

108: Plagiarism!


Posted by: peep | Link to this comment | 10-18-13 11:56 AM
horizontal rule
111

106: I'm importing pop-evolutionary psychology related pissiness to this, which is why I'm noting the self-parody. And I'm not actually griping at this research at all. But if that's what you're talking about, characterizing it as 'informed by our evolutionary heritage' seems precisely ass-backwards, or at least premature -- it sounds to me like the location of a consistent physically identifiable structure with a functional role allows the coherent posing of evolution-related hypotheses that can be tested in future research, rather than itself being informed by our evolutionary heritage.

Which is really really interesting, and sounds like science on a completely different level than the sort of pop-EP I gripe about: "this well-defined thing physically exists, so now let's figure out how it evolved" is head and shoulders different from "I have weak evidence that something may exist, and speculation about how it could have been evolutionarily advantageous, which proves that it does exist." I'm just quibbling about your wording.


Posted by: LizardBreath | Link to this comment | 10-18-13 12:03 PM
horizontal rule
112

I'm just quibbling about your wording.

Reasonably. I do think that the line of research into animacy as a category has been informed by evolutionary hypotheses, but it's just as correct to say that this research informs evolutionary hypothesizing, and that construction might be more apposite.


Posted by: IRFT | Link to this comment | 10-18-13 12:11 PM
horizontal rule
113

I believe she also dances around in her underwear in Crazy/Beautiful.

She really is wonderful.


Posted by: rob helpy-chalk | Link to this comment | 10-18-13 12:11 PM
horizontal rule
114

107: Here's the basic explanation. Not sure how simple or complicated I should be. For Google-fu, the concept is usually explained if you look up NMR spectroscopy. For example, this lecture is pretty good. There are two explanations about how MRI / NMR work. There's one that's more quantum physics and one that only invokes presence or absence of a magnetic field.

So, basically, the way NMR or MRI work to generate a signal is that they apply an external magnetic field to molecules. This causes nuclei with nonzero spin states (1H, 13C, 19F for example) to change from their previously randomly oriented nuclear spins to aligned spins, mostly with the field, some against. (Quantum physics explanation here.) The nuclei aligned against the field are higher energy; the ones aligned with the field are lower in energy. Absorption of energy to go from low to high gives the signal for the nucleus. The transition from high energy to low energy spin state is termed relaxation. The environment of the nucleus gives different characteristic signals, which allows interpretation of the data. (Magnetic field theory here.) The magnetic field theory says that the signal doesn't come from the transitions between two spin states, it comes from the energy emitted when the nuclei aligned in the magnetic field relax to a random pattern like they started. The end result is the same: a characteristic signal relying on local environment of the nucleus.

For example, MRI looks at the protons in water, which have a characteristic signal different from all other protons in proteins or other biomolecules, so you generate an image basically from the signal of water. The more water you have (for MRI), the stronger the signal (this is why MRI is good for soft tissue vs Xray or CT). It's not limited to looking at water, though. If, for example, you had a drug with a 19F on it, you might be able to do an MRI to see the biodistribution of that drug. If you had a protein with a characteristic signal (and you were super-lucky about concentration being high enough and low noise from other biomolecules), you could look at a specific protein.

109: Yeah, our subscription ends in 2011, so no promises about whether it's a good overview or cherry-picked topics of interest to the author.


Posted by: ydnew | Link to this comment | 10-18-13 12:20 PM
horizontal rule
115

Bachelorette was a very good turn for her. Also features another Lizzy Caplan-Adam Scott romance, Party Down fans.


Posted by: k-sky | Link to this comment | 10-18-13 12:22 PM
horizontal rule
116

115 to 113 and to fans of inconsistent italicization.


Posted by: k-sky | Link to this comment | 10-18-13 12:23 PM
horizontal rule
117

I used to grade exams for extra $$ in grad school. One exam asked students how MRI works because the prof had a doctor appt where the doc explained "it makes all your cells spin - but don't worry; it won't hurt." The students wrote beautiful stuff like "MRI chops you into slices and then puts you back together to form a 3D image."


Posted by: ydnew | Link to this comment | 10-18-13 12:24 PM
horizontal rule
118

114.last: it seems to be freely available at the link I posted? Or is that an institutional artifact?


Posted by: Sifu Tweety | Link to this comment | 10-18-13 12:24 PM
horizontal rule
119

118: Huh, yeah, it works from the journal's page too but not via any of my normal links (out of PubMed or via our ejournal library link). Thanks. It is in fact a nice review, and the explanation of relaxation is on p 4.


Posted by: ydnew | Link to this comment | 10-18-13 12:34 PM
horizontal rule