Possibly the coolest talk I heard at Cosyne, the annual computational and systems neuroscience conference, this year was by David Heeger, who's at NYU. Those of you who know my general distaste for functional MRI imaging -- or rather, the vast majority of experiments that make use of it -- will probably be somewhat surprised to hear this. The talk was on how different areas of the brain integrate information temporally. The expectation is that more peripheral areas, which are more directly connected to sensory inputs and motor outputs (e.g. primary visual cortex, primary auditory cortex, etc), will tend to reflect more of the moment-to-moment structure of the world, whereas higher processing centers have to integrate information over longer periods of time in order to make sense of what's going on. In the visual system, for example, the early stages of visual processing are responsible for the cinematography -- what's there, what direction is it moving -- while higher areas take care of the plot, the interactions between elements, and so forth.

A very elegant prediction of this hypothesis is that if you remove the longer-term temporal structure of a stimulus, lower areas should continue processing things as before, but the higher areas will fail to be engaged. Heeger and his colleagues tested this by measuring fMRI signals from subjects while they watched several versions of movies. One of the versions was played in the normal direction, one was played backwards, and several of the others were shuffled. The shuffled versions made use of the same cuts as the original version, but the order of the cuts was randomized, so in one scene you'd see Charlie Chaplin roller-skating in a department store and in the next he'd be working in a factory, and so forth. Heeger assessed how the brains of his subjects were processing this data by measuring the correlations between multiple presentations of the different movies. High degrees of correlation in a particular area indicate that the circuits in that area are processing the information the same way in each trial. In other words, the information in the stimulus is driving the activity in that area. A low degree of correlation, on the other hand, indicates that the region is not being driven by the stimulus. The results were more or less as expected. The normal movie produced activity that was highly correlated in almost all the areas involved in visual processing, whereas the time-reversed and shuffled movies produced low correlations in regions of the brain associated with processing higher levels of structure.

But the really interesting result came when they compared the responses across subjects. In other words, how similar is the activity in your brain when watching a movie that of the person sitting next to you? It turns out to depend, as in the previous result, on what areas of the brain you look at. But it also depends, to an almost shocking degree, on the movie. If you play subjects a video that doesn't have any plot -- a bunch of people walking through Central Park, for instance -- the degree of correlation is fairly low except at the earliest stages of processing. Some movies, like "The Good, the Bad, and the Ugly", produce much higher levels of correlation across a larger proportion of the brain. And some movies, like one directed by Alfred Hitchcock, induced high correlations across 70% of the brain.

It would be easy to overinterpret this finding, which Heeger doesn't do. Once it's published I expect the mainstream media will read that 70% figure as meaning that when you and your buddy watch Alfred Hitchcock your mental states are 70% the same. In order for that to be the case, the correlations would have to be perfect, which they're not. The low temporal and spatial resolution of fMRI imaging also means that the similarity is only on a fairly gross level. But even with those caveats, it's still kind of an incredible finding. The huge difference between the effects of an unstructured video and the effects of a Hollywood video indicate just how good the movie industry is at specifying the experience you're going to have when you go to a movie.

On my drive back from Salt Lake I happened to hear Bob Edwards interview Orhan Pahmuk, the Turkish author and Nobel Prize winner. Pahmuk made the observation that the rise of the novel coincides very nicely with the rise of nationalism. Novels are indeed highly cultural beasts. The best of them are highly idiomatic and difficult to translate. They are deeply embedded in the history of a place and a people. Movies are much more universal. Translation is much less of an issue, because so much of the content of a movie is in the cinematography, the acting, and the synergy of music and visual representation. Movies may be just as concerned with a time and place as a novel, but the language they use to discuss those concerns is entirely different. Pahmuk said that movies have a place in our new globalized culture analagous to that of the novel in the new nationalistic culture of the early nineteenth century. He seemed to see the ascendency of this art form as a good thing. I'm not so sure. I love movies, too, but there's something sad about the image of people around the world giving up music, verbal innovation, and the plastic arts to sit mutely in front of a DVD player, minds all running in parallel.

Update: The results have been published in the March 5 edition of the Journal of Neuroscience. Link here, although I don't think the full text is freely available yet.