Kevin Weiner: If you met someone on the street who had no idea what brain mapping was, how would you describe your research and what you do for a living?
Tim Behrens: I play with brains and computers. I try to figure out how the world is represented in your brain and how you use these representations to guide your behaviour. I have whiteboards with boring looking equations on them. I have computers with lots of data on them. I try to see if the data on my computer matches the equations on my whiteboards. The data on my computer often comes from humans playing games in an MRI scanner, where we can watch as big patterns of brain activity change from moment-to-moment, but some of it also comes from recording what individual cells are doing when animals play similar games in the lab. Actually, that is a description of what all my friends and colleagues do. I mostly get to work and wonder what to do because my colleagues are doing all the work. Sometimes I also play candy crush.
KW: What should the non-expert be wary of when reading about brain mapping articles in the lay press?
TB: They shouldn’t. What does it matter if some of the nuances are not captured in the article? OK, often the article is just wrong, but that isn’t special to articles about neuroimaging. That’s just bad journalism. They should look at the amazing brain pictures, and they should say: "My god. That is a picture of activity inside someone’s brain. And that person was having lunch an hour later. That is amazing. Let’s give them our money”.
KW: If you weren't talking to brain mappers or scientists, how would you describe your most proud scientific accomplishment?
TB: Like all scientists, I think the coolest thing I have done is the stuff we are working on now, so I’ll describe 3 papers in one paragraph - one just published and two in submission. It’s also what I’ll be talking about at the meeting. Obviously, the next paragraph will sound very pretentious to any scientist reading it!
So - we figured out something about the languages that the brain uses to store knowledge about how things are related in the world. We figured out that brain regions can store relationships with positive (excitatory) connections between neurons but that these connections must be balanced by mirror-image negative (inhibitory) connections - kind of like “antimemories”. We figured out that many of these connections can then be organised into structures that represent knowledge in different parts of the brain, and that these neural structures are probably encoded in a language that other people have discovered for encoding our knowledge of space. This language is called a “grid cell code” and it is a very beautiful language. If this turns out to be true, it will be important for understanding how abstract concepts are represented in our brains, and how we can navigate through abstract concepts to understand the world around us.
Also, I used operant conditioning to train my son to respond “Dada” to the question “Who is the coolest?” when he was a year old. This was deeply satisfying both personally and scientifically.
KW: What do you think is the future of neuroimaging for basic research? For translational research and application?
TB: I think neuroimaging is in an awesome phase. Really awesome. We have moved to a stage where we can do really big experiments really well, and really study the organisation of cortex. New technologies are allowing us to study neural representations at the mesoscopic scale. These come both from new high resolution imaging technologies, but also from an increased understanding of how to design experiments that study representations rather than just average activity levels. I think there needs to be some work validating this stuff with electrophysiology and understanding how these things relate to cellular codes (but that is happening) and obviously there is still a lot of stuff we can’t see. But basically, I think that these two massive innovations (big data driven imaging with extremely high quality data, and the ability to study representations) will transform the current and next decade of human neuroscience. On top of this, MEG is really working at the “source” level now, so we can study dynamics. The kinds of questions that will be answered by neuroimaging experiments in the next years will be really about how stuff is organised, how computations happen etc. etc. I think this will bring us closer to animal experiments, so we can test whether neural codes found in animals can explain higher human cognitive behaviours that can’t be studied in animals. I think it will mean that interesting neuronal mechanisms discovered in animals, will be testable in real clinical populations for the first time, as candidates for disease. Being able to study representations across the whole brain simultaneously is new to neuroscience in any species. How is the same stuff represented in different areas? How do signals in one area change representations in another? I think it’s really an exciting time to be doing human neuroscience for people who want to think deeply about neural mechanisms and their organisation throughout the brain. Obviously, it’s also a very exciting time to be doing nonhuman research with a buffet of new techniques available that have extraordinary levels of precision and control. I think we need to make sure that the different fields stay in touch with each other as we are figuring out how neural computation happens across species.
KW: What motivated you to study frontal cortex and connectivity?
TB: I mostly just drift towards things that, or people who, are interesting. For example, things that seem new and cool and people who are fun to talk to. The people who I work with in Oxford and UCL are just about the most clever people I know. And some of the most exciting work in the world is happening in the function of frontal cortex and neural representations; in behavioural control; and in brain connectivity. It’s no coincidence that I copied these clever people in choosing these topics to study… I get to hang out with cool people and talk about interesting things.
KW: When you first started out, what was the most inspiring/motivating paper you read? How about the same question, but in the last 5 years?
TB: Bit of a weird question for me, because I started out making new methods for measuring brain connections from diffusion imaging, and now I am studying representations and computations. The classic papers in the diffusion field were obviously influential early. From people like Peter Basser, David Tuch, Geoff Parker, Derek Jones, Danny Alexander and many of the other early pioneers of diffusion imaging. Nowadays, I often have fun reading papers about how computations work. For example, you always learn something cool when you read papers by Peter Dayan, Nathaniel Daw, Yael Niv and their colleagues. I also like learning about how cool representations can enable computation. I loved Tim Vogels’ 2011 Science paper about simple inhibitory hebbian mechanisms for storing memories, for example. When I want to know how the frontal cortex works more broadly, I often turn to the views of people like Matthew Rushworth, Betsy Murray, Dick Passingham, Chris Frith, amongst many others. Recently when I have been interested in how computations work between frontal and temporal cortices, I have been very influenced by ideas from Howard Eichenbaum and Neil Burgess and their respective sets of awesome colleagues (as well as the league of extraordinary papers about how the hippocampal formation encodes space).
Rather than papers, however, I have mostly been inspired by people. I have been lucky enough to work with awesome sets of people. My group has always been stuffed with really clever students and post-docs, many of whom have become long term friends and colleagues. I won’t name individuals from my group here because they are all special :). From the very early days, though, I was lucky enough to work with people like Heidi Johansen Berg, Matthew Rushworth, Steve Smith, Mark Woolrich, Christian Beckmann, Mark Jenkinson. These guys have taught me how to think about science, data and the brain. They are endlessly curious and inventive. Who needs more inspiration than that?
KW: Thank you, Dr. Behrens!
Dr. Behrens will be giving the Wednesday afternoon Keynote lecture at the 22nd Annual Meeting of the OHBM Organization for Human Brain Mapping (June 29th, 4:15pm) later this month in Geneva. The topic of his lecture will encompass storing, using, and updating knowledge for behavioral control. All in all, we hope you will enjoy his lecture and have enjoyed getting to know him a bit better.
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