Could you provide a quick description of your lab and why it is unique?
We are best known for the research subjects of our lab, which are bats, so the nickname for the Comparative Neural Systems and Behavior Laboratory is the “Batlab.” We have three different species of echolocating bats in the lab, each suited to answer particular research questions. We study the North American big brown bat that hunts insects. These bats are found in your own backyard, and, in fact, we collect them mostly from people’s homes. We also have Egyptian fruit bats, which came to us from my former postdoc, Nachum Ulanovsky, who has a research lab at the Weizmann Institute in Israel. And last, we have another, much smaller, fruit bat species that comes from Central America. These are our research subjects, and we study general problems in systems neuroscience. Our lab is also unique, because we have a large multimedia research space in which bats steer around obstacles, seek food, communicate with other animals, and navigate.
What interests you (and why bats are key in answering our research questions)?
The broad goal of our research is to understand the mechanisms that enable the acquisition and processing of sensory information to guide natural behaviors. We take a comparative approach, which allows us to identify species specializations and general principles of neural systems. Bat research models that rely on active sensing offer distinct advantages for this work, as they report directly to the experimenter the stimulus information they collect from the environment. Careful analysis of the echolocation signals gives us a window to stimulus acquisition that is largely unavailable in other animal research models. In the coming years, our team plans to use a variety of neuroscience tools to better understand local and long-range neural circuits mediating sensory processing and sensory-guided behaviors, natural scene perception, spatial attention, navigation, learning, memory, decision making, and social communication.
How does your research intersect with human behavior?
We do basic research to acquire new knowledge, and this new knowledge can have applications to human health, but we do not always know what those applications will be. There are blind humans who use echolocation. They make sounds, such as tongue clicks, and listen to echoes to localize and identify objects. Egyptian fruit bats produce echolocation signals with the tongue, like humans, but their clicks are outside the range of our hearing. Other echolocating bat species (and there are over 1,000) produce echolocation sounds with the voice box. There are some interesting parallels between human and bat echolocation. We have had the opportunity to interact with echolocating blind humans, and we have done some studies of their echolocation abilities in our lab.
Importantly, we can ask blind human echolocators what they experience through the world with sound, what strategies they use, and so on. And I have come to learn things from these individuals that inform what may be going on with the bats. One thing that is quite apparent for blind human echolocators is that they do not rely only on echoes to guide the echoes from their clicks to navigate. Because humans do not hear very high-frequency sounds, they have to produce sounds that return echoes they will hear. These lower-frequency sounds are not as well-suited for returning echoes from small objects, and blind humans use echolocation to steer around large objects. Many have learned to interpret the echoes from different objects, plants versus walls versus cars, and so on, to get a sense of what physical objects are in their environment. However, they rely on passive listening, such as the sounds produced in the environment. Also, they have experience in the environment, and that experience informs their interpretation of the echoes they get back. And they also rely heavily on memory to remember the path they walked, which helps them follow their way back experience.
So, I think all of these things: memory, prior experience, shapes, and possibly expectation are all important for the success of bats in steering around trees while going after insects at rapid speed to actually do what they do.
Image: Neural specializations support natural behaviors of echolocating bats. Schematic depicting auditory processing of natural sounds, audio-motor integration, navigation, and flight control, which are modulated by spatial attention and action selection in echolocating bats. Bat photo courtesy of Charles Francis.
What exciting projects have you worked on recently?
Much of the research on hearing involves simplified stimuli, with the subject being more or less stationary. In the real world, though, we know that organisms move around, and the information they receive depends upon their movement. To better understand real-world sound processing, it was, for decades, my dream to record echo-evoked activity from free-flying, echolocating bats. But that is a real challenge as big brown bats are quite small, weighing less than an ounce, placing limits on the hardware they can carry in flight. My graduate student, Ninad Kothari (now a postdoc in Shreesh Mysore’s lab), and postdoc, Mel Wohlgemuth (now a faculty member at the University of Arizona) and I tackled this challenge, and we were able to capture neural recordings from echolocating, big brown bats navigating in a large room, which was equipped with cameras and microphones to track and quantify the animals’ behavior moment to moment.
Central to the analysis of the neural recordings, Ninad developed an acoustic model to reconstruct the bat’s stimulus space, which quantified the direction and distance of objects returning echoes from sonar calls to the bat. This model allowed us to relate neural firing patterns to echo returns from objects in the room. We discovered that a class of neurons in the bat’s midbrain respond selectively to echoes from physical objects and encode their 3D location with respect to the bat. We also observed dynamic response areas of single neurons that depend on the features of the animal’s echolocation calls. That was very exciting for me and a big step forward, because there has been a lot of work on bat auditory processing, but in bats listening passively to sounds that experimenters play at them, not bats listening to echoes from their own calls. Our lab is the first to do this.
What inspired you to become a scientist, and specifically one who uses bat research models?
Early on in college, I became very interested in sensory systems, and that interest actually arose from an experience I had as a high school exchange student in Sweden. Students in my Swedish high school had the opportunity to do practica and other activities out in the world rather than just sit in the classroom. So I chose to work in several homes for autistic children and also a school for the deaf. Even though there was a lot of effort to provide the children with all kinds of enrichment and stimulation, what I observed seemed like a deficit in sensory information processing. Their sense organs were intact, but their nervous systems were somehow unable to process the information effectively. I was only 17, but that experience launched my initial inquiry into understanding sensory information processing.
Next, I attended an experimental college called Hampshire College. They’re part of a community of five-college cooperative: Mount Holyoke, Amherst, University of Massachusetts, Hampshire, and Smith College. I actually chose to go there because of this five-college consortium, where you design your own program, and the program I devised focused on children with special needs. I combined coursework in neuroscience, extensive reading of scientific papers, and research in special classrooms. I completed most of the requirements for graduation but came to realize that I wasn’t getting a broad education. I decided to take some time off and accepted a full-time job at an institution for the developmentally disabled. This was one of the hardest jobs I ever had. This institution was subsequently exposed in an episode of 60 Minutes and was closed soon after.
I returned to college and felt like I needed to find a new path for myself, more in the science realm than applied work. I did research in a number of labs during college and later as a research assistant, where I explored, among other things, visual sensitivity during eye movements, attention (in children watching television), color vision, and the development of spatial vision in human infants. My undergrad education was unusual in that I was able to take charge of my academic program and pursued a mode of inquiry of my own design.
I attended Brown University for grad school and focused initially on visual neurophysiology and psychophysics, and ultimately conducted my dissertation research on hearing in frogs. As I was in the process of looking for a postdoc position, I attended a talk on bat echolocation and was just blown away. This talk inspired me to go to Germany for my postdoctoral work to conduct experiments on echolocation in bats. It has turned out that there are so many interesting problems for which bats are good research models, and I have continued to use them in my research for decades.
Who are a few of your collaborators and partners?
Our work is interdisciplinary, and several of our valued collaborators at Hopkins include Uli Mueller, in neuroscience; Mounya Elhilali, in electrical engineering; Noah Cowan, Rajat Mital, and Joe Katz, in mechanical engineering; Kathy Cullen in biomedical engineering; Amanda Lauer in otolaryngology, and Kishore Kuchibhotla in my own department, Psychological and Brain Sciences. I still collaborate with some of my colleagues at the University of Maryland, and I have strong connections with scientists at the University of Southern Denmark and in Germany, as well as my former postdoc from Israel, Nachum Ulanovsky at the Weizmann Institute.
What are great qualities for a graduate student or postdoctoral fellow to have?
Having substantial research experience is very helpful; then immersing yourself in research and taking on the role of the creator of new knowledge. That is a big transition for many students who as undergraduates were primarily required to read and report back what they read, memorize facts, and take exams. For graduate students, it’s important to identify the scientific background you need to develop and research tools you need to acquire, and then, as a researcher, you’ll be able to make new discoveries and share knowledge.
Do you have any ideas to build the OneNeuro community?
Retreats are good spaces for people to get to know each other and then develop ideas for new collaborations, just spontaneously, through conversations. And frequent, informal gatherings may help build community.
What do you enjoy doing in your spare time?
I have lived abroad several times, so I love to travel. For example, I went to Australia and China recently. I also enjoy learning foreign languages, reading fiction, hiking, and spending time with my three grown children, of course.
