Cerebrum Winter 2022

en people the idea caught on that the networkwas the default state of the brain.”

internal constructions. We have these networks and brain systems that allow us to tend to the external world, act, and survive the here and now. But we have other networks—default networks—that may be used when we detach from the outside world and mentally explore. When networks or interactions between them break and seem to be fragile, one might see devastating, cognitive dysfunction. It’s also the case that we might have stumbled into seeing some of the networks that are highly expanded and evolved in the human lineage, networks that allow us to do these extraordinary human faculties, such as remember, or imagine what we’re going to do tomorrow, and work in social groups, where we can envision what somebody else might be thinking. Another key insight is that higher-order networks involved in mental thought may be specialized for specific domains of information. It’s easy to appreciate the idea if we begin by thinking about parallels in sensory brain systems. We have different domains and specializations for sensory processing. For example, specialized visual regions deal with where things are, and others with what they are. It’s easy to translate that and tell people that there are parts of the brain’s visual system that become particularly specialized when taking in different bits of sensory and visual information. I suspect that the higher-order networks that we uncovered in our journey to understand the brain’s default network are also specialized, but in more abstracted domains—such asfor remembering and, separately, for making social inferences.

What inspired you to devote your career to studying the default network, or should I say “networks?” BUCKNER: In graduate school, I was more interested in targeted memory functions and using imaging to compare brain functions of people doing tasks. Marcus Raichle was the person going around the lab, saying, ‘You folks, look at this stuff. You should pay attention to it.’ He was referring to the pattern of activity we now know as the default network, but at the time, I personally was slow to appreciate the significance. One of my earliest papers in graduate school demonstrated this. We had data in 1992, ’93, but it wasn’t until my paper in 1995 that the default network was shown. It wasn’t because of any special insight, but more due to my eagerness to present all the data from an experiment. So just the tendency to describe our methodology and results very thoroughly made for one of the first presentations of the network. In retrospect, it was mother nature saying, ‘Here I am.’ When I’m asked, ‘How was it discovered?’ The answer: Serendipitously. It was just in all the study data. Imaging has certainly changed neuroscience in so many ways. But how in particular have the default network revelations changed neuroscience? BUCKNER: It’s relevant to psychiatry in particular. Tracking the competition and boundaries between networks may lead to some of the more profound symptoms you see in mental illness. This is a hypothesis. In active psychosis, for example, one can confuse reality with



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