Research Area: Behavioral Neuroscience; Faculty page
Joseph Bergan grew up in northern Minnesota—a setting that naturally fostered an interest in the natural world. Early interests in medicine, geology, and mathematics gave way to neuroscience during his first year at Macalester College. “Neuroscience has the questions that interest me most in science. You are studying how the brain works, how we interact and perceive the world. How we behave, feel, and think. Those questions are really interesting to me. It is a privilege to get to study these questions and introduce students to these concepts for a living.” says Bergan.
After a few years of college, he knew that he wanted to pursue graduate school in neuroscience. He contacted Peggy Mason at the University of Chicago who was studying how different behavior states modulate pain. Bergan was accepted into a Howard Hughes Medical Institute summer program working with Mason, which became his first formative experience with neuroscience research. Professor Mason proved to be a great mentor for Bergan and, in a short time, shaped much of how he approaches neuroscience questions.
Attending the Stanford Neurosciences Graduate Program, Bergan continued training as a systems neuroscientist and neuroethologist with Professor Eric Knudsen. The Knudsen lab is best known for its studies of barn owls, which have an unmatched ability to localize the sounds of prey scurrying over leaves in the dark. The evolutionary pressure on the owl’s ability to localize stimuli in three dimensions bestowed a crystalline pattern of responses to the underlying neural circuits. There is a very clear representation of the three-dimensional world present when recording the owl's neural activity evoked by sensory cues. Because this representation is one of the clearest known in the animal kingdom, it is possible to make insights that would not be possible otherwise.
Working with owls highlighted the importance of a strong relationship between sensory input and behavioral output. When this is true, sensory cues predict the behavioral outcome and provide insight into the neural computations that are needed to accomplish a specific goal. Having this strong relationship between input and output makes inferences about what is happening in between easier to recognize. Working with a nontraditional model system also highlighted the importance of studying neural circuits in the context of an animal's behavioral niche.
After graduate school Bergan was looking for a field of study where he could use what he had learned. He was excited about the latest developments in genetics. Procedures had emerged that allowed researchers to answer questions with finer resolution and higher reproducibility. Catherine Dulac, Bergan’s postdoctoral mentor, approached social neuroscience in animals from a genetic perspective. Dulac's lab offered many genetic tools that were at their disposal. “There is great genetic diversity in the cells that comprise social behavior networks in the brain. Scientists are now able to activate, silence, identify, and trace specific populations of genetically defined neurons. This allows one to understand the precise contributions of these neurons to specific behaviors,” notes Bergan.
He ultimately chose to focus his work on the social behavior network, a set of broadly conserved subcortical brain regions where social behaviors are mediated. In mice, these regions are driven heavily by the olfactory system. This is where a strong relationship exists between sensory stimuli, social cues, and behavior. The Bergan Lab at UMass studies the behaviors that occur between individuals with different experience, relationships between mates, offspring, predators, and aggression. Age, strain and the internal state of the animal can affect the way a neural circuit functions. The same sensory input can give you a different behavioral output.
The neuroscientists working in Bergan’s lab explore the innate behaviors of mice. By altering the activity of specific genetically-defined populations of neurons, they have found how to shift the social preference of a mouse model. For example, by activating groups of specific cells, specific social behaviors can be promoted within a mouse. Finding these groups of cells in core-conserved brain regions has been an exciting development, and the hope is that some of the principles they find are broadly conserved.
“I’ve always wanted to know what these cells are doing on a moment to moment basis. I want to know how they are processing sensory stimuli,” says Bergan. Using electrophysiology, his lab can record the activity of individual neurons and responses to sensory stimuli. How groups of cells process sensory stimuli is very different in young versus old animals, males versus females, animals with different sensory experience or neuroendocrine state. These factors strongly influence behaviors.
There is an emerging trend that studying brain regions is not enough to understand behavior. You need to understand the neurocircuitry at a finer resolution. To do that, the Bergan Lab is fluorescently labeling cells and working on techniques to render the brain transparent. Using techniques to extract the whole circuit, the researchers can look at neurons throughout the brain that provide input to these groups of cells. Bergan asks, “Where does this population of cells send their output to? What downstream targets are they talking to? What kind of variance is there in individual cells?”
In Bergan’s research, he tries to address questions that are both interesting and capable of being answered successfully. He explains that, “When we answer something, there’s often quite a bit of work left to know how that work will relate to humans. We try to understand the systems at work in animals and make predictions. The big question that motivates a lot of my research is whether we can understand circuitry, the functional properties, and activity of neurons at a level that will allow predictions about behaviors and why one individual animal behaves differently than another. Any chance I had to answer a question about individual differences in behavior, that’s what I went after. That is still one of the things I am most interested in.”