Friday, February 24, 2012

Post Lecture Recap

Wednesday night, I headed to the beautiful Bell House in the Gowanus section of Brooklyn for the monthly Secret Science Club lecture by NYU Neuroscientist David Carmel. Dr Carmel's field is the role of the brain in visual perception, and his lecture was accompanied by many displays illustrating the topics he addressed. Before the lecture, attendees were supplied with small slips of paper displaying the classic blind spot demonstration, and "glasses" with a red and a green gel, much like classic 3-D glasses (not to be confused with X-Ray Spex).

Humans tend to recognize patterns, and often impose aninterpretation on objects which isn't supported by further observation.

The "blind spot" phenomenon was explained- the optic nerve connects to the retina in a region that lacks the cells that "receive" incoming light. The blind spot test allows one to "locate" one's blind spot, but an unusual thing occurs- the brain "fills in" the missing details, in the test, one perceives a blank white space in the white background, if one were to draw a line on the paper through the two test images, one would perceive a continuation of the line where the "missing" image should be.

After a brief discussion of "metacognition", basically one's abilitity to know what one knows, and the ability of one to recall images briefly flashed on a screen, Dr Carmel presented a bunch of bistable images, which are basically unchanging stimuli which can be perceived in various ways. A classic bistable image is the Necker Cube. Dr Carmel also displayed the ambiguous duck/rabbit (sounds like an ingredient in a McGravitasian recipe), the vase/face image and the young woman/old crone image. Notably, one cannot perceive both images simultaneously.

The most mind-blowing part of the lecture was a demonstration of the selective attention test, which must be seen to be believed. Sadly, I fall within the 50% or so percent of the population which gets blindsided by the test. It's truly humbling. The sequel is not quite so bad.

Dr Carmel then went on to demonstrate binocular rivalry, instructing the audience to use the two-toned "glasses" to "separate" the two images in this composite- as one looked at the image with glasses, one would alternate between seeing the face and the building. I am ashamed to admit that I asked a n00b question, about the ability of color blind persons to perceive the two images, forgetting that they would experience the binocular rivalry, with the two images appearing gray. I sure hope a colour vision specialist doesn't read this, because I really didn't drink enough Ommegang to justify the lapse.

Dr Carmel went on to discuss the portions of the brain involved in perception, focusing on the use of transcranial magnetic stimulation to monitor brain activity. Here's a nice, brief overview of TMS... Dr Carmel showed a video of himself receiving TMS, and having one of his hands moving without his volition (a waggish bastard in the audience asked him if TMS had been weaponized for use in crowd suppression... not yet, at any rate). While the primary visual cortex is located at the rear of the brain, there are other portions of the brain which are involved in perception. Dr Carmel studied the role of the right parietal lobe in perception of and found that TMS affected the duration of "dominance" in binocular rivalry. At the same time, one of his colleagues found that TMS decreased the duration of "dominance". They were able to reconcile these seemingly contradictory findings by ascertaining that they had been stimulating slightly different regions of the parietal lobe. One portion of the parietal lobe plays a role in maintaining an interpretation of visual stimuli, while another plays a role in changing our perception of something based on changes in the perceived stimuli.

The lecture ended with a summation- we perceive the world with our brains. Perception is a balancing act- we make choices as to how we interpret the visual stimuli we receive. All told, it was yet another brilliant lecture, and the accompanying video presentations really knocked it out of the park- I'm still a little freaked out about the selective attention test.

Sorry about the delay, folks, but I had to chase down links to a lot of the images which were featured in the lecture (and ya know, I almost forgot one of the best examples of bistable imagery.

17 comments:

Another Kiwi said...

Ooh fuck! I had an idea for a poem about perception and how it would be if we could tap into everyone's perception of where we were. For instance 4 people at an intersection and you can see the sum of their views. I hadn't made the brain connection, just thought about the visual bit.
Therefore the world each of lived in would be the sum total of the people around. I'm not sure that our brains could cope with it. Sadly this poem is not being forthcoming however this is another piece in the puzzle, maybe.
Great post, old chum!

Big Bad Bald Bastard said...

Sadly this poem is not being forthcoming however this is another piece in the puzzle, maybe.

You need all nine muses to perceive an inspirational message!

Great post, old chum!

It didn't do the lecture justice, though! So, when are you going to get your butt to New York to lecture on microbiology while knocking back a few IPA's?

wiley said...

I first read about the selective attention test in a book called "Deep Survival". Along those lines, in flight simulations, a lot of perfectly good pilots did not see another jet moving across the runway and so landed as if the jet weren't there. It really explains a lot of accidents that don't, when described, appear to be anything but gross negligence or drug use.

We fill in a lot of data and filter a lot out when we look at the world, especially when it's a very familiar world. Our brains are a wonder.

Big Bad Bald Bastard said...

We fill in a lot of data and filter a lot out when we look at the world, especially when it's a very familiar world. Our brains are a wonder.

Wiley, that first "selective attention test" video still has me embarassed, and I first saw it on Wednesday.

wiley said...

It's nothing to be embarrassed about. It's not like you designed our brains. Most people who focused on the count missed the gorilla. I was already familiar with the concept and didn't bother counting. I just waited for the gorilla to see what the suit looked like, for the same reason I don't play chess.

I can take a lot of tedium if it's MY JOB, otherwise I would rather hit myself with a hammer, even in the interest of science. Though I am currently doing some pretty tedious greenhouse work, there will be a great payoff for me if I don't screw it up.

I can't say if I would have noticed the gorilla or not had I never heard of the test and actually taken the challenge. I do, however, pick up on change, which is what made me such a good scope-dope.

Once things become overly familiar to me, they become invisible to me enough for me to trip over them, which is why I have to rearrange my furnishings from time to time.

Laura said...

I didn't see the Gorilla either. I called Tony over, told him to take the test and after he said the # and then mentioned seeing the Gorilla.

This is all quite interesting. I've never given any of it much thought but still, appreciate learning more about it! Sounds like a great night. :)

((HUgs))
Laura

zombie rotten mcdonald said...

I didn't see a blog.

Maybe I am doing this wrong.

Substance McGravitas said...

I have an "If I don't expect it to be there it isn't there" problem, so if you mildly rearrange objects they might vanish. The last, most embarrassing incident of this kind happened at work when I complained that a keyboard was missing. It wasn't in its little slide-away tray under the desk, and after I bitched and moaned it was pointed out that the keyboard was on top of the desk right before my eyes.

zombie rotten mcdonald said...

I just go steal someone else's keyboard.

This stack of keyboards on my workstation have nothing to do with me officer.

zombie rotten mcdonald said...

Heh. I noticed the 'rilla. Of course, I gave up on counting the passes, because, fck the man, you know?

Smut Clyde said...

The entire concept of "selective attention" is foreign to mOH LOOK A SQUIRREL.

I have an "If I don't expect it to be there it isn't there" problem, so if you mildly rearrange objects they might vanish.

Technically this is known as "male blindness". Especially if SOMEONE shifts those objects to the WRONG SHELF in the 'fridge.

Smut Clyde said...

Also relevant.

Substance McGravitas said...

The fridge is entirely different. No using the fridge drawers please: it's like you've disintegrated the food.

zencomix said...

You might find this interesting, where does seeing take place?

vacuumslayer said...

Holy shit, it took me soooooo long to see the crones. I was like "IS THERE SOMETHING HORRIBLY WRONG WITH ME? OH FUCK, THERE SHE IS!!!"

BTW, is there such a thing as a "young crone?"

ckc (not kc) said...

4 people at an intersection

Big Bad Bald Bastard said...

Holy shit, it took me soooooo long to see the crones. I was like "IS THERE SOMETHING HORRIBLY WRONG WITH ME? OH FUCK, THERE SHE IS!!!"

There is something horribly wrong with you- you are a slave to beauty!