I have superpowers? Snap.

May 11, 2011 2:10 PM

"Even beyond the philosophical wonder of passively sampling our outside environment in a shared, meaningful fashion is the ridiculous sensitivity of our senses."

Included in the article is a video of this superstar, a blind boy who can skateboard using echolocation.

Here is the Ted talk Bradley Voytek gave in 2010 about folks with a variety of brain issues. (He's a bit slow to get going but hey, he was still working on his PhD.) About 8:17 is some graphic brain surgery - with the patient awake.

He is also on the board of the Zombie Research Society.

posted by Glinn (27 comments total)

I wonder what is going on at 2:11, where we see a close up of the kid's eyes while he is playing on a gameboy. Reminds me of deaf percussionist Evelyn Glennie and the documentary Touch the Sound, where they show her having a conversation on a telephone.

Also, puppy at 1:29.
posted by ianhattwick at 2:28 PM on May 11, 2011

Whoops - had the wrong clip copied - here are the 2:11 and 1:29 clips.
posted by ianhattwick at 2:33 PM on May 11, 2011

Never saw "Touch the Sound". That is really cool.
posted by Glinn at 2:38 PM on May 11, 2011

Do you need more senses than what you already have? Wanna detect magnetic fields?

Also:Body Hacking!

I'm waiting until they figure out how to piggyback magnetic field information to the optic nerve so I can see the fields as a slight distortion, kind of like birds do, but at least have an on-off switch. I don't want to walk by some large electric motor and then have the world look like some acid flashback scene (at least not all the time). Is anyone working on this yet?
posted by chambers at 2:49 PM on May 11, 2011 [1 favorite]

Fun fact 1: outer hair cells in the cochlea have the ability to actively vibrate at specific frequencies so that constructive interference occurs with incoming sound waves, thus providing selective amplification.

Fun fact 2: the processing of visual information (for example, the enhancement of lines and edges) begins with neurons located in your retina.

Fun fact 3: unlike the other four tastes (salty, sour, sweet, and umami), which are detected by one or two types of receptor each, bitterness is detected by over sixty different types of receptor.

Fun fact 4: one controversial theory of smell posits that olfactory receptors work by detecting how odorant molecules vibrate when they bind the receptor, rather than how they fit the receptor in the traditional lock-in-key sense.

Fun fact 5: capsaicin, a chemical found in chili peppers, results in a "hot" sensation because it activates thermoreceptors that normally respond to heat. Likewise, menthol seems "cool" because it activates thermoreceptors that normally respond to cold.
posted by dephlogisticated at 3:33 PM on May 11, 2011 [8 favorites]

This seems as good a time as any to ask a question that's been bugging me about how we hear sound, which is basically this: it seems that our hearing is very specifically oriented towards pitch, so we'll tend to experience a periodic sound wave at a certain frequency as a single conceptual entity, and a periodic sound wave at a different frequency as another. Given that it takes a certain non-zero amount of time to deduce a frequency given some sound input, what is the brain doing in the time span before it can figure that out? I know that it's not literally calculating what the frequency is or anything like that, but it seems evident that there is some mechanism in the brain that can represent frequency as a sensation, and I'm not sure what that process is or how it deals with the incomplete information at the onset of a signal.
posted by invitapriore at 4:17 PM on May 11, 2011

invitapriore: pitch distinguishing starts in the ear, and mechnaically. You don't even receive the raw data, the pitch is inferred from which hairs are twitching.
posted by idiopath at 4:37 PM on May 11, 2011

A little background on fun fact 4

Luca Turin is the bull in that china shop, but there are other theories at large.

(Of course I saw the damn gorilla.)
posted by IndigoJones at 4:40 PM on May 11, 2011

mechanically even - the cochlear cilia act like tuning forks, responding to specific small frequency ranges each.
posted by idiopath at 4:41 PM on May 11, 2011

So uh... yeah. Weird to hear from a friend that my post and talk made it to the blue. Been a lurker here for a loooooonnnnnnggggggg time. (Seriously. Like, since the days when the most riveting internets for me were the things ParisParamus was saying on here about politics.)

First of all, to clarify about the Zombie Research Society thing... it's such a FUN way to talk about neuroscience stuff. Plus I got to meet the original zombie brain guy (Steven Schlozman) and George Romero! (!!!)

The reason I wrote the blog post is because I'm so damned fascinated by the effects of brain lesions both in terms of what they can tell us about the brain, and what they make us consider about consciousness, cognition, and perception. It's what I did my PhD work on.

I'm also a huge fan of neuroscience history (because it's so weirrrrd), and I love digging up old experiments and writing about them.

I kind of took some flak over on reddit for not being 100% super accurate in my post, but nothing in the post is untrue. It's all been peer-reviewed and pretty well replicated. I just don't treat my blog like I do peer-review, so I don't feel like I have to explain everything. The blog is a way for me to sort through ideas. I definitely buy into the whole "if you can't explain it simply, you don't really understand it" idea.

Also I wrote it after a Portal 2 binge. So if you don't like the post, blame Valve. :D

Anyway, I'm totally excited to be on the blue. If you've got any brain-y questions, let me know. I'd be happy to talk.
posted by bradleyvoytek at 4:58 PM on May 11, 2011 [18 favorites]

mechanically even - the cochlear cilia act like tuning forks, responding to specific small frequency ranges each.

Excellent, thank you. What an elegant solution!
posted by invitapriore at 5:00 PM on May 11, 2011

Actually, wait; so do you mean to say that our sense of pitch is quantized, or is there some sort of interpolation mechanism where two hairs vibrating will result in a pitch sensation somewhere in the middle?
posted by invitapriore at 5:02 PM on May 11, 2011

So pitch is actually really weird... because pitch isn't necessarily a property of the sound pressure waveform but rather our perception of it. So pitch isn't just frequency.

In the video I linked to in the post, you can see a toy model of how sound vibrates the basilar membrane in the cochlea. Low energy sounds vibrate one end while high energy sounds vibrate the other. Where the basilar membrane moves determines which hair cells fire action potentials. These hair cells then project to many subcortical nuclei that then determine timing between sounds and location in space.

The auditory pathway projects into the neocortex (outer part of the mammalian brain) in a tonotopic fashion, meaning the frequency information is actually encoded partly by where in the auditory cortex the neurons are activated.

There's been some amazing work by Michael Merzenich using this fact to examine neuroplasticity.

If you really want the fine details of pitch processing, I'd suggest you start with the research by Frederic Theunissen at Berkeley.
posted by bradleyvoytek at 5:24 PM on May 11, 2011 [2 favorites]

the latter, actually a whole range are excited, and they are interpolated to find a "center", that may not be precisely at any of them (thus louder sounds will appear subjectively to have wider bandwidth). If you read about how they do perceptual encoding for mp3 etc. much of it is about hacking the limitations of the ear ("this other sound will seem identical due to the way the ear works, and requires only 60% as much data to store").
posted by idiopath at 5:25 PM on May 11, 2011 [1 favorite]

Oh my god, this is the best thing ever. Thanks bradley and idiopath!
posted by invitapriore at 5:32 PM on May 11, 2011

Another weird thing about pitch, it is dependent on both the frequency of the sound, and the change in frequency. In other words, its context. A cool example of this is the Shepard Tone, forever descending (or ascending) like an auditory analog of Escher's Staircase.
Long story short, most perceptual processes (my field) are a combination of what we call "bottom-up" processes, going from the raw energy into conscious perception, and "top-down" processes, in which our expectations and assumptions create the perceptual world that we experience.
posted by cogpsychprof at 5:56 PM on May 11, 2011 [2 favorites]

This is awesomeawesome! Thanks so much for delurking, bradleyvoytek.
posted by Glinn at 6:10 PM on May 11, 2011

Also, is this the dean from Community?! o_O
posted by bradleyvoytek at 6:11 PM on May 11, 2011

Oh, and also, Bradley Voytek, your blog is awesome. I was looking for the little RSS subscribe button, and couldn't find it. How's that for perceptual super powers?
(yes, I eventually found it)
posted by cogpsychprof at 6:19 PM on May 11, 2011

Apparently, Ben Underwood (the skating echolocator) died at 16 years old in 2009 from the same cancer that took his vision.
posted by ErWenn at 6:56 PM on May 11, 2011

cogpsychprof: Another weird thing about pitch, it is dependent on both the frequency of the sound, and the change in frequency.

As a visual perception guy, I would put that in different terms. The sensation of motion is not completely determined by change in position. This is different from saying that perception of position is dependent on motion.
posted by a snickering nuthatch at 6:46 AM on May 12, 2011

So pitch is actually really weird... because pitch isn't necessarily a property of the sound pressure waveform but rather our perception of it. So pitch isn't just frequency.

QFT. A bell can emit some set of frequencies F and be perceived to have a same pitch as a sine wave with a frequency not in F! So you might have a bell that emits 350Hz and 450Hz, with a perceived pitch the same* as a sine wave at 100Hz!

*But is it really "the same"? Or is it just substantially similar, in a way that we perceive the pitches of notes separated by octaves to be substantially similar?
posted by a snickering nuthatch at 6:59 AM on May 12, 2011

Thanks, cogpsychprof! :D Maybe the RSS button is too big? That's pretty amusing.

And Jpfed, I could easily see myself having gone down the auditory research route because it's such a cool system to study plasticity, perception, etc.
posted by bradleyvoytek at 9:58 AM on May 12, 2011

Jpfed: "might have a bell that emits 350Hz and 450Hz, with a perceived pitch the same* as a sine wave at 100Hz!"

That is a very small set of frequencies for a bell, but yeah, as you are probably aware, if the strongest resonant modes of the object are spaced at 100 hz from one another, the brain hears a 100hz fundamental, even if it does not produce 100hz. This is also a component (along with the moving) of the Shepard Tone effect (my favorite example - Ligeti did it on a piano without electronics).
posted by idiopath at 10:37 AM on May 12, 2011

Isn't that 100Hz business just beats? (I.e. if you mix two pure frequencies f1 and f2, the resultant will also contain f1+f2 and f1-f2.)

What I find amazing is the octave. Some people cannot distinguish between f and 2f.
posted by phliar at 4:12 PM on May 12, 2011

phliar: "What I find amazing is the octave. Some people cannot distinguish between f and 2f."

By almost the same logic you mention: a tone with a fundamental of frequency f and some semblance of a proper overtone series will almost always be periodic at 1/2 f and 2 f.
posted by idiopath at 4:43 PM on May 12, 2011

Isn't that 100Hz business just beats? (I.e. if you mix two pure frequencies f1 and f2, the resultant will also contain f1+f2 and f1-f2.)

No, beats are different from partials. Beats are a multiplicative change in amplitude (the overall volume envelope of the sound is multiplied by the difference frequency; that variation is called beating); partials are additive (the moment-to-moment fluctuation of pressure/velocity in one wave is superimposed on, or "rides on top of", another).

Here's how they're related. Here's a signal expressed in terms of partials:

sin(2*pi*f1*t) + sin(2*pi*f2*t)

and here is that same signal expressed in terms of beats:

sin(pi*t*(f1-f2)*t) * sin(pi*(f1+f2)*t)

I'm glossing over phase here, but whatever. Notice how the "partials" expression adds two sine waves and the "beats" expression multiplies two sine waves.

Scientists have known for a long time that our inner ear decomposes signals into something very much like a set of partials. So from the perspective of our ear listening to our example signal, f1 and f2 have a particular role to play in our perception of the sound. Now, it very well may be that beats are also used in pitch perception. I don't know. But f1+f2 and f1-f2, if they have a role to play, are going to figure into our perceptual arithmetic in a completely different way, because they're a fundamentally different aspect of the signal than f1 and f2 are.

As a side note, distortion (like an electric guitar's effects pedal) actually does add sum and difference frequencies into their output as partials. Distortion can take a clean sound without many partials and make it sound much richer by giving it all sorts of integer combinations of the original frequencies.
posted by a snickering nuthatch at 8:26 PM on May 12, 2011