Whoa! I know ferret-fu!
October 21, 2004 7:03 AM   Subscribe

Idle your visual cortexes on this ... There's some interesting science in here about how much of our brains we humans use, but for the rest of today I'll be using my spare brainwidth to picture "The Matrix" with ferrets. (via Dynamist, via PunditDrome!)
posted by allaboutgeorge (7 comments total)
[This is fascinating!]
posted by shoepal at 7:40 AM on October 21, 2004

Very cool

*sits back, imagines ferrets watching The Matrix*
posted by TungstenChef at 8:28 AM on October 21, 2004

very interesting!

::wanders off to a darkened room to ponder::
posted by kamylyon at 8:48 AM on October 21, 2004

I am not a neurobiologist, but I'd like to play one on TV.

The first couple of paragraphs seem to be a bit misleading, and I'm not very surprised at this result. The basic research seems very cool, and I wonder how they did it.

The press release implies they are measuring the amount of 'usage' a brain gets. Reading further it seems what they're actually measuring is patterned behavior occurring in the visual cortex only. The 80% -- 100% values they're describing. Since the visual cortex is only a small part of the brain, expanding the claim to the whole shebang seems strange.

First sentence of the abstract is "During vision, it is believed that neural activity in the primary visual cortex is predominantly driven by sensory input from the environment". I'm not sure who believe this. It corresponds pretty well to the single-nerve theory of sensation -- there's not much going on in a single nerve cell (say, in your finger tip) when there's not much to sense.

But, they're expanding this theory to the visual processing center of the brain (well, primary visual cortex anyway).
Given the amount of visual processing humans do which is unrelated to direct visual input, it doesn't seem too surprising to me that the primary visual cortex is busy much of the time, even when no physical stimulus is present. I'm not sure that I'm comfortable w/ using the human mind to model ferret brains, but I'll go with it for now.

For example, when I read this article I immediately thought of the movie "Until the End of the World", imagining the scenes in which dreams begin to emerge out of the static on the screen. The very fact that I was able to 'see' the images without them actually being present would point towards some sort of visual processing going on despite the lack of physical stimulation.

The other result -- not much correlation between infant ferrets visual cortex activity patterns and physical stimulus... Not really surprised at that either. I thought it was pretty much general knowledge that the brain learns how to interpret visual stimuli after birth (or at least after the start of physical stimulus). I know folks who've had their vision disrupted by strokes, who've had to learn how to see again, for example.

In any case, I wonder how they did this? They seem to be saying that they're measuring the activity of many if not all of the neurons in the visual cortex, it's hard to imagine that they wired them all up, but I don't know how else they'd do it? I don't think functional MRI gives fine enough resolution to see what they're taking about, but then again I have no real clue...

And, in terms of basic research, it's cool they actually verified this. All my opinions come from theories about how the brain works, not from real strong evidence. This seems like real strong evidence.

The thing that was surprising to me is that this sounds like confirmation of several of the theories I've heard about rather than ground breaking new work...
posted by daver at 9:42 AM on October 21, 2004

For your edification... here's the abstract.

Nature. 2004 Sep 30;431(7008):573-8.

Small modulation of ongoing cortical dynamics by sensory input during natural vision.

Fiser J, Chiu C, Weliky M.

During vision, it is believed that neural activity in the primary visual cortex is predominantly driven by sensory input from the environment. However, visual cortical neurons respond to repeated presentations of the same stimulus with a high degree of variability. Although this variability has been considered to be noise owing to random spontaneous activity within the cortex, recent studies show that spontaneous activity has a highly coherent spatio-temporal structure. This raises the possibility that the pattern of this spontaneous activity may shape neural responses during natural viewing conditions to a larger extent than previously thought. Here, we examine the relationship between spontaneous activity and the response of primary visual cortical neurons to dynamic natural-scene and random-noise film images in awake, freely viewing ferrets from the time of eye opening to maturity. The correspondence between evoked neural activity and the structure of the input signal was weak in young animals, but systematically improved with age. This improvement was linked to a shift in the dynamics of spontaneous activity. At all ages including the mature animal, correlations in spontaneous neural firing were only slightly modified by visual stimulation, irrespective of the sensory input. These results suggest that in both the developing and mature visual cortex, sensory evoked neural activity represents the modulation and triggering of ongoing circuit dynamics by input signals, rather than directly reflecting the structure of the input signal itself.

I have no clue what the first sentence of the press release has to do with anything -- it seems to me that the "10% myth" was the only thing the journalist knew about brains, so they stuck it in there. As far as I know, we use 100% of our brains, but I'm just a lowly grad student at Penn's Center for Cognitive Neuroscience...
posted by dmd at 1:28 PM on October 21, 2004

Our brains use about 30 watts whether we're solving differential equations or watching TV. When people talk about an increase in activity of the ventral post medial neo hippobrebrum its typically no more than a few percent.
posted by euphorb at 1:37 PM on October 21, 2004

metafilter : "....We found neural activity that frankly surprised us"

"Weliky, in a bit of irony, set 12 ferrets watching the reality-stretching film The Matrix. He recorded how their brains responded to the film, as well as to a null pattern like enlarged television static, and a darkened room." - this needs to tie into, somehow, the upcoming election.
posted by troutfishing at 9:26 PM on October 21, 2004

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