Charan Ranganath: commitment

Transcript context

…It does seem to be that fMRI is a good way to study activation. So with these astrocytes, even though there’s a latency, it’s pretty reliably coupled to the activations. Oh, well, this gets me to the other part. So now let’s say for instance, if I’m just kind of I’m talking to you, but I’m kind of paying attention to your cowboy hat, right? So I’m looking off to the… Or I’m thinking about the [inaudible 01:26:12], even if I’m not looking at it. What you’d see is that there’d be this little elevation in activity in areas in the visual cortex, which process vision around that point in space, okay? So if then something happened like a suddenly a light flashed in that part of… right in front of your cowboy hat, I would have a bigger response to it. But what you see in fMRI is even if I don’t see that flash of light, there’s a lot of activity that I can measure because you’re kind of keeping it excitable [inaudible 01:26:46] that in and of itself, even though I’m not seeing anything there that’s particularly interesting, there’s still this increase in activity. So it’s more sensitive with fMRI. So is that a feature or is it a bug? People who study spikes in neurons would say, “Well, that’s terrible, we don’t want that.” Likewise, it’s slow, and that’s terrible for measuring things that are very fast. But one of the things that we found in our work was when we give people movies and when we give people stories to listen to, a lot of the action is in the very, very slow stuff. Because if you’re thinking about a story, let’s say you’re listening to a podcast or something, you’re listening to Lex Fridman Podcast, right? You’re putting this stuff together and building this internal model over several seconds. Which is basically we filter that out when we look at electrical activity in the brain because we’re interested in this millisecond scale, it’s almost massive amounts of information, right? So the way I see it is every technique gives you a little limited window into what’s going on. fMRI has huge problems, people lie down in the scanner. There’s parts of the brain where… I will show you in some of these images where you’ll see kind of gaping holes because you can’t keep the magnetic field stable in those spots. You’ll see parts where it’s like there’s a vein, and so it just produces big increase and decrease in signal or respiration that causes these changes. There’s lots of artifacts and stuff like that. Every technique has its limits. If I’m lying down in an MRI scanner, I’m lying down. I’m not interacting with you in the same way that I would in the real world. But at the same time, I’m getting data that I might not be able to get otherwise. And so different techniques give you different kinds of advantages. What kind of big scientific discoveries, maybe the flavor of discoveries have been done throughout the history of the science of memory, the studying of memory? What kind of things have been understood?…

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