NJIT students work with Associate Professor Eric Fortune at the leading-edge of neurophysiological research in the lab and in the field. Here Monica Khattak (left) and Hannah Gattuso are helping to gather data about the behavior of weakly electric fish in Fortune's lab in the Central King Building.
Fortune’s work, which could yield new insights into neurological disorders as well as the complexities of normal behavior, is supported by major funding from the National Science Foundation (NSF). In 2016, he was awarded a new NSF grant of more than $380,000.
Fortune says that his research reflects a long-standing interest in the evolution of behavior. “Like a lot of kids, I was fascinated by dinosaurs, which led to a general interest in evolution. In college, as a biology major at the University of Chicago, I took a class in animal behavior and learned that the evolution of behavior is an especially complex and interesting phenomenon. This became my focus from then on.”
Another class at the University of Chicago, this time a class in neurophysiology at the graduate level, clarified the direction he would take toward his Ph.D. “What I liked about neuroscience was that it gave immediate and broadly relevant answers that my evolutionary studies weren’t providing. I learned that you can perform neuroscience experiments that provide insights about how the brain works which also address questions about the process of evolution.”
The Wild Neurophysiological West
Essentially, Fortune says, he is asking questions about how the brain makes computations based on input from different senses and how those computations control behavior. “For example, how is information from our eyes integrated with information in myriad receptors in our skin and muscles when we walk down a flight of stairs? Attempting this commonplace behavior with my eyes closed or my feet anesthetized with lidocaine would make it a quite a dangerous adventure.”
Critically, as Fortune explains, we don’t understand how information from our eyes and feet is fused to control what is a complex behavior. “The field is the ‘Wild West’ when it comes to what we don’t know,” he says. “We have mathematical hypotheses that describe the kind of computations that must go on in the brain, but we don’t understand how the brain implements those computations. Thus far, even the most sophisticated robots we are able to build cannot duplicate behavior that we take for granted every day.”
Part of the challenge for researchers is due to characteristics fostered by evolution. “Evolution did not design humans and other animals to do anything optimally. Rather, evolution has made us ‘robust,’ to use an engineering term. We have both multiple sensors and multiple compensatory systems. You can ‘perturb’ a robust system, do something disruptive or unexpected, and it will continue to function normally.
“The nervous system can absorb quite a bit of damage and compensate for it. This is, in part, what makes it difficult to understand the neurophysiological mechanisms of behavior. Everything is connected, with many parts functioning in parallel. So if you alter or eliminate a part, the results often do not provide valid insights about the phenomena you want to study.”
Help from Electric Fish and Wrens
Although researching sensory integration and behavior presents complex challenges, there are animals with special characteristics that can help to advance knowledge in this area. This is why Fortune is working with weakly electric fish in the laboratory at NJIT and in the field in Ecuador, as well as with a species of wren native to the same South American country.
The electrosensory capability of electric fish, such as the glass knifefish, allows these creatures to control complex behavior using only electricity, the “currency of the nervous system,” as Fortune says. Because this control does not involve the intervening and complicating mechanics of systems like muscles, the fish are an important ally in determining how neural codes are integrated in the brain to control behavior.
Fortune’s study of electric fish has provided new information about phenomena that include the neurophysiological computations associated with “direction-selective neurons,” which respond only to movement in a particular direction. These neural circuits allow various vertebrates and invertebrates to encode and comprehend motion in the surrounding world — very useful for activities such as finding a mate or prey, or to avoid being eaten. Although the researchers who first identified direction-selective neurons earned a Nobel Prize, how the related computations occur in the brain remained mysterious. In studying direction-selective neurons in electric fish, Fortune and his colleagues have described the computations in substantial detail.
The plain-tailed wren is another animal that demonstrates a unique behavior that can help us understand how neural codes influence behavior, including how the brain enables complex cooperative activities. The behavior of special interest in this species of wren is the duet song that males and females produce so precisely and quickly that it can sound as if only one bird is singing. The great majority of birds do not duet in this manner.
The wrens that Fortune is studying in Ecuador rely on sensory feedback to control their parts of the duet. It’s analogous to what takes place in the brain when two people dance, Fortune says.
“When we dance, our brain has to encode and integrate input from sight, touch and sound. These streams of information change very quickly, and they have to be processed in just the right way if we are to avoid stepping on a partner’s foot.” With a further touch of humor he adds, “With a bit of practice, the complex behavior of dancing becomes routine. Of course, some of us need more than a little practice.”
As Fortune goes on to explain, the neurophysiology of such cooperative behavior is even more mysterious than the navigation of stairs mentioned earlier. “We don’t even have mathematical hypotheses that describe the computations involved. This is really a leading-edge of neuroscience.”
Fortune’s plan for continued exploration of this scientific frontier, work that he anticipates will also engage NJIT students, involves recording neurophysiological data during the plain-tailed wrens’ unique duets. The technically challenging neurophysiological experiments that this groundbreaking effort requires must be conducted in the wrens’ natural habitats on the slopes of the Andes. As with Fortune’s investigation of how electric fish process information about the environment they inhabit, examination of such tuneful cooperation promises to fill in spaces that are still blank on a complicated and valuable behavioral map.
By Dean Maskevich