Kirupa Suthakar, Ph.D.
Meet the Researcher
Kirupa Suthakar, Ph.D., received her doctorate in physiology and pharmacology from the University of New South Wales in Sydney, Australia. She completed postdoctoral fellowships at Mass Eye and Ear/Harvard Medical School and then the intramural program of the National Institutes of Health/National Institute on Deafness and other Communication Disorders. Suthakar began her independent research program as an assistant professor of speech, language, and hearing at the University of Texas at Dallas. She is a 2027 Emerging Research Grants scientist.
My project grew from a longstanding interest in factors that shape perception and mental health, which began during my undergraduate studies in psychology, philosophy, and medical science. I was introduced to the concept of nature versus nurture and to twin studies exploring how genetic and environmental factors interact to influence disease. In mental health, genetic factors can contribute to an individual’s susceptibility to conditions such as depression, but whether and when a condition develops is also strongly influenced by the environment. Rather than nature versus nurture, I came to think of it more accurately as nature alongside nurture.
This idea also shaped my interest in individual differences in sensory perception. How we navigate the world is fundamentally influenced by how we perceive external stimuli. Why can two people encounter the same stimulus yet have completely different experiences of it? Consider things like music, art, facial expressions, and threats. As someone who grew up in Australia, for example, I can look at a huntsman spider and think: “This little guy is going to keep the insects in check and poses no danger to me—thanks, buddy!” I suspect that is not a universal reaction. The stimulus is the same, the perception is not.
Serotonin provided an intriguing connection between these interests. It is a major neuromodulator, important for regulating neuronal gain in the brain. Yet, its synthesis is dependent on an essential amino acid (tryptophan), meaning that serotonin signaling can be influenced by dietary factors. Serotonin signaling is also influenced by environmental factors such as sunlight, sleep, and exercise. Given the contributions of genetic and environmental factors in mental health, and the frequent co-occurrence of mood and auditory disorders, I became interested in how serotonin might influence auditory perception and hearing health. I was struck by how little we know about the role of serotonin in the earliest stages of auditory processing.
When I first learned of auditory efferent neurons, I was fascinated by their role in modulating the encoding of sounds. The peripheral auditory system is extraordinarily specialized, allowing us to detect tiny sound induced movements whilst also accommodating sounds many orders of magnitude more intense. The cochlea contains its own biological amplifiers that enhance and fine-tune these vibrations. I began to think of the auditory system as a high-performance supercar: exceptionally fast and precise, but potentially vulnerable if it cannot control its own power. Auditory efferent neurons provide some of that control—the brakes that help regulate the system and protect it from excessive stimulation.
This led to a simple question. Depression and other mood disorders occur at unusually high rates in people with tinnitus, hyperacusis, and other auditory disorders. Is this relationship simply an association, or could there be a unifying biological mechanism connecting the two? Returning to the supercar analogy, could altered serotonin signaling associated with depression also be weakening the 'brakes' of the auditory system, leaving it more vulnerable to damage from loud noise?
The genesis of this project can be traced back to that relatively simple thought: Could differences in a neuromodulatory system involved in mental health also determine how well the auditory system protects itself from intense sound?
Innately Curious
Like many people who pursue careers in science, I was an innately curious child. I was the type of youngster that would incessantly ask “why?” of those around me. I still vividly remember my father once telling me that the simplest way to get the root of a problem is to ask why no fewer than five times. My teachers in high school reinforced this curiosity-driven mindset and helped me develop it into an analytical one. They taught me the value of correctly articulating a question and knowing both where and how to look for the answers. I came to appreciate an important distinction: Knowledge is knowing things, wisdom is understanding how to know things. Different questions require different strategies.
As our family were first-generation immigrants to Australia, my formative years were filled with diverse and worldly experiences that nurtured my curiosity and love of the natural world. I spent much of my childhood reading, watching documentaries and exploring the dry, hot suburbs of Sydney. I was especially captivated by the wildlife: intelligent, calculating, and seemingly unafraid of humans. My acoustic environment filled with the screeches of cockatoos, galahs, rainbow lorikeets, and crimson rosellas, alongside the melody-rich songs of currawongs, butcherbirds, and Australian magpies. These birds who would routinely approach for food, interact playfully, make low fly-bys, and even swoop to defend their territory. As annoying as the latter could be, I was fascinated by their behavior. This early fascination with animal intelligence and communication has stayed with me throughout my career.
A photography class during high school provided an unexpected turning point. We built a camera obscura to help us understand the physical properties of light, and the chemical process of developing photo paper. We learned to develop black-and-white negatives and create photographic enlargements. I was captivated by the process of using light to capture and reveal a snapshot of the world frozen in time. The experience cemented my fascination with light and imaging, although at the time I did not realize how important those interests would become to my career.
In university, I spent a considerable amount of time studying philosophy. I am particularly grateful for the opportunity it gave me to think deeply about the mind, perception and metaphysics. Two thought experiments from that time have stayed with me: the Brain in a Vat and the Chinese Room. Both explore questions of reality, experience, perception, communication, meaning, and perspective. More broadly, they prompted me to reflect on how we perceive and interact with the world, and how we can know whether our understanding of the world is accurate.
Several philosophy courses ultimately helped point me toward a career in scientific research. Formal Logic taught me deductive reasoning and gave me tools for navigating ambiguity, constructing valid arguments and developing precision of thought. Philosophy of Science made me consider how we establish knowledge and how we can agree upon observable realities. Studying empiricism deepened my fascination with sensory experience and what external information is required to make sense of the world. Finally, in Philosophy of Cognitive Science, we explored concepts of neural networks and artificial intelligence. Together with my studies of psychology, this exposure to philosophy solidified my interest in sensory and systems neuroscience.
My first experience with a light microscope during my second undergraduate degree in medical science brought all these interests together. Looking through the microscope, I was reminded of my early photography exposure: manipulating light to reveal a the world through a different lens. Now, rather than simply capturing an image, I could use that application of light to ask questions about how living systems work. This was my “aha” moment. I realized that what I really wanted was not simply to ask questions or conduct thought experiments, but to test them. I was not only interested in why; I wanted to understand how.
Philosophy taught me the art of asking questions and thinking deeply about them. Science gave me the opportunity to pursue those questions through observation, experimentation and discover. I consider it a privilege to have a profession that allows me to think, do, and share—to lean into my innate curiosity while putting my observant nature to work.
My interest in auditory neuroscience was solidified by watching my mother navigate sudden sensorineural hearing loss in her late forties. In the early 2000s, she worked as a secretary and relied heavily on telephone communication. One day, she heard a “pop” in the ear she used for the phone, followed by discomfort. For several days, she tried to reach her doctor by telephone but could not get through. Eventually, she tried using her other ear and realized that the problem was not the phone, but her hearing.
Her doctor prescribed oral corticosteroids and referred her to an ear, nose, and throat (ENT) specialist. The earliest available appointment was a month away. During that time, she underwent several imaging studies, but no cause for the hearing loss could be identified. The ENT administered an intratympanic corticosteroid injection and told her about a bone-anchored hearing aid (BAHA) that might help. However, he was not yet trained to perform the procedure, so she had to wait for access to the implant.
She struggled with her newfound hidden disability and the stigma of not being able to communicate effectively. No longer able to rely on auditory input from both sides, everyday situations became precarious. When crossing the road, sirens approaching from one side could be completely inaudible. Even when she detected a siren, her inability to localize its source left her uncertain and hypervigilant, particularly when alone. At work, colleagues, largely unaware of the sudden change in her hearing, would call out to her while she was on the phone. With her “good ear” occupied, she could no longer acknowledge fleeting remarks without visual cues. As a person of color, her difficulty hearing was also sometimes mistaken for an inability to understand English—an especially frustrating experience for a polyglot whose English skills were so well developed that she routinely wiped the floor with most people during Scrabble.
She began attending every hearing health event she could find in search of answers. At one tinnitus event, a salesperson referred her to a clinical nurse who knew of another ENT surgeon who had been fitting patients with BAHA devices for more than two years. Three years after the initial “pop,” she received the implant. The device transmitted sound vibrations through her skull to stimulate the cochlea on her hearing side, allowing her to detect sounds originating from her deaf side. She understood that the BAHA would not restore sound localization nor her ability to hear speech in background noise, but she was desperate for any improvement.
In group environments, including at home, she struggled to follow multiple streams of conversation at the dinner table. Sometimes she would mishear something and respond with a completely unrelated comment. In social situations where people whispered, she struggled to catch subtle conversational cues and became increasingly isolated. She recalls receiving strange looks when she spoke up and eventually became embarrassed enough to stop trying to participate. At home, we adapted our behavior to help her remain engaged. Sometimes her unrelated interjections were hilarious and we could laugh together; other times, her frustration was palpable. She could not rely on the same accommodations at work and ultimately retired early out of “sheer frustration.” As is often the case, the implant was eventually tucked away in a drawer.
I began my research career during her retirement. She was excited that I was studying something related to her disability, and we talked about my work often. I practiced explaining complex neuroscientific ideas to her, learning to find the right words and analogies. She attended my research presentations and, by the time of my dissertation defense, she understood the work. One day she turned to me and asked, “Does your research mean that by not wearing my hearing aid, my neurons could be dying?” I replied, “Possibly. That’s what the data implies for our deaf mice.” The next time I saw her, the BAHA had been dusted off and was back in place.
Watching someone close to me become so profoundly affected by losing something most of us take for granted was a humbling experience. My mother’s experience taught me that hearing loss is not simply the loss of auditory input; it can alter how a person navigates safety, communication, relationships, and social belonging. Watching her withdraw from social situations and feel ashamed when she could not communicate effectively motivated my interest in studying the intersection of hearing dysfunction and affective health. I am grateful for the opportunity to contribute to a deeper understanding of hearing disorders and their broader consequences, and to pursue research that may one day help people like my mother not only hear but remain connected to the world around them.
Extraordinary Variety
Pursuing a career in scientific research has given me the opportunity to travel, work with people from different backgrounds and perspectives, share my own knowledge and bring what I have learned back to my community. Some of the most memorable moments of my career have therefore not been individual discoveries or achievements, but the people and connections that made them possible. It can be easy to forget that, despite its enormous size, Australia is relatively sparsely populated and geographically isolated. The Australian Government lists 42 universities nationally. By comparison, there are 44 institutions of higher education in the greater Boston area alone.
I am also grateful for the extraordinary variety that a career in science affords. On a given day, I might be an educator, student, technician, philosopher, communicator, artist, or statistician. Science continually asks me to learn something new, approach problems from different perspectives, and communicate ideas to people with varying levels of expertise. I consider it a privilege to spend my career challenging myself to understand the world a little better and, in doing so, contribute to our collective understanding of it. The individual advances may be incremental, but together they form the foundation on which future discoveries can be built.
As a child, I read voraciously, particularly fantasy and science fiction. I was fascinated by how different people could read the same words, yet construct subtly different worlds in their imaginations. I often wondered: Whose interpretation was closest to what the author envisioned? Why had the author chosen one adjective over another? What information did those choices give us, and what did they leave for us to infer?
In high school, this curiosity led me toward a career as a film director. Unlike books, film provides the opportunity to utilize tell stories using both visual and acoustic cues. I was intrigued by how different directors used both overt and subtle cues to construct a world and guide an audience through a narrative. Dialogue and framing were the obvious tools, but what intrigued me most was the deliberate control of what an audience was allowed to see or hear, when they were allowed to see or hear it, and what was left outside the frame.
The best directors seemed to understand that storytelling was not simply about what you show or say, but also about what you withhold, imply, and invite the audience to interpret. I was drawn to the idea that meaning can exist in the unseen and unheard, and that sometimes the most powerful part of a story is what the audience has to piece together for themselves.
In retrospect, I think that same curiosity about how people construct meaning from incomplete information ultimately drew me toward auditory research. I may not have become a film director, but I still spend my career asking how the brain makes sense of the signals it receives, and, from the information that is missing.
I enjoy travel, adventure, and food. I have been fortunate to visit over 25 countries and to live in seven cities across five countries. I consider myself an explorer and relish the opportunity to venture out into the unknown. Before smartphones made navigating unfamiliar places so easy, I did a great deal of solo travelling and savored the challenge of overcoming language barriers to connect with people from different walks of life. At other times, I sought out remote places where I could lose myself in nature, surrounded by little more than landscape and the knowledge that the nearest person could be hundreds or thousands of miles away. I enjoy both the stillness of untouched natural environments and the electric energy of bustling cities. Wherever I go, I have found that food is a great equalizer. Some of my favorite travel memories involve sharing a meal with someone I had just met.
I credit those early travel experiences with my love of cooking and baking . I find food preparation therapeutic and particularly enjoy hosting and cooking for friends and family. I love both the creative and procedural aspects of cooking: starting with a vision for a dish, breaking it down into flavors, aromas, textures, and working out how to bring those elements together. I rarely use recipes, instead relying on what I know about individual ingredients to build a meal. There is something deeply satisfying about transforming a collection of raw ingredients into something that can be shared.
Growing up in a household where freshly toasted and ground spices were a constant presence, I learned to trust my nose. I still sniff almost everything I cook, using familiar aromas to recall flavors and guide new combinations. Experimenting with unfamiliar ingredients and flavors brings me the same kind of job I find in exploration and science: There is a goal, a process of trial and error, and the possibility of discovering something unexpectedly wonderful. Cooking is chemistry, after all. I also love knowing that people enjoy something I have made for them. For me, cooking is both a creative outlet and one of the most tangible ways I can share a personal experience with the people I care about.
Another hobby I indulge in for relaxation is video games, particularly first-person, adventure-based games and cooperative strategy/world-building games with my husband. Video games offer the ultimate sandbox: a low-stakes space to test different strategies, fail, learn from those failures and try again without serious consequences. Like scientific experimentation, video games allow me to approach a difficult problem from several angles, discovering what does not work, and gradually developing an effective strategy for success. I enjoy both the visceral feeling of immersing myself in a different world, and the iterative process of exploration and experimentation, where failure is simply information that helps me adapt, try again, and do better.
A fun fact about me is that I enjoy working with my hands and love to create things. One of my favorite experiences was taking a Japanese knife-making course, where I had the opportunity to design, forge and finish two knives from high carbon spring steel. I loved learning about the chemistry underlying normalizing, annealing, hardening, and tempering, and how these processes felt both familiar and completely different from the chemistry I usually encounter at the biological scale. Working the forge was loud, hot and exhausting. But, it also felt surprisingly familiar, like a scaled-up version of the repetitive tasks we perform as part of wet-lab scientific experimentation. The rhythm of the work in the forge (heat, hammer, repeat) translated remarkably well to bench work (pipette, wait, repeat). Grinding the forged pieces into shapes I designed was equally gratifying as I watched the knives gradually emerge. I also enjoyed the more creative aspects of the process, particularly choosing the wood for the handles and complementary materials for the guards. Now when I cook, I love using my beautiful hand-forged Japanese gyuto to slice, chop, and dice.
Over the next five years, I see myself continuing to develop an independent research program exploring neuromodulation of the descending auditory pathway. My research program will investigate how neuromodulators such as dopamine and noradrenaline influence sound encoding in the auditory system, and consequences of alterations in neurodegenerative conditions such as Parkinson’s and Alzheimer’s disease. I hope to build complementary collaborations with researchers across disciplines, fostering long-term partnerships that will deepen our understanding of the mechanistic interactions between auditory and neuromodulatory systems in the brain. Beyond research, I want to continue developing as a mentor, teacher, and leader, creating an environment in which the people I work with can develop and thrive.
Over the next 10 years, I hope to expand this work toward more translational research, helping to bridge the gap between preclinical discoveries and strategies that can improve human health through early detection, prevention, and treatment of disease. In the longer term, I hope to contribute to a broader shift toward viewing human health holistically, particularly by encouraging greater consideration of how interactions between sensory and nonsensory systems influence disease, treatment, and well-being. Ultimately, I want my research to reinforce the idea that understanding the brain necessarily requires consideration of how its systems interact, rather than studying each system in isolation.
The Research
The University of Texas at Dallas
Serotonin signaling of auditory efferent neurons in noise-induced hyperacusis and tinnitus (NIHT)
A single exposure to loud noise can cause lasting changes in hearing. Tinnitus (the phantom perception of sounds such as ringing or buzzing) and hyperacusis (an increased sensitivity to everyday sounds resulting in discomfort or pain) can develop following exposure to loud sounds. Both conditions can have a profound impact on quality of life, affecting communication, concentration, sleep, mood and social interactions. Depression and other mood disorders also occur at unusually high rates in people with tinnitus and/or hyperacusis, suggesting that hearing and mental health may be biologically connected.
Serotonin is a chemical messenger in the brain best known for its role in mood, but it also regulates the activity of nerve cells throughout the brain, including those involved in hearing. Altered serotonin signaling is associated with depression and is targeted by antidepressant medications known as selective serotonin reuptake inhibitors (SSRIs). SSRIs increase serotonin signaling by blocking the serotonin transporter (SERT), a protein that normally removes serotonin from the spaces between neurons, known as synapses. By blocking SERT, SSRIs increase the amount of serotonin available to signal nerve cells.
A specialized group of nerve cells called medial olivocochlear (MOC) efferent neurons act as a volume control for the auditory system. When activated, MOC neurons reduce the ear’s sensitivity to sound, helping protect the auditory system from the effects of intense noise. Our previous work has shown that serotonin can increase MOC activity. However, it is not yet known if differences in serotonin signaling change an individual’s vulnerability to noise-related hearing problems.
We propose that altered serotonin signaling provides a mechanistic link between mood and auditory disorders. We hypothesize that serotonin influences the ear’s protective mechanisms, and, consequently, vulnerability to tinnitus and hyperacusis following exposure to loud sounds. Using mice with genetically altered SERT function, we will directly test this possibility. We will determine whether long- term disruption of serotonin signaling during development alters MOC activity, vulnerability to noise-induced hyperacusis and tinnitus, and measures of depression-like behaviors. By manipulating both serotonin signaling and noise exposure, we can test whether serotonin plays a causal role rather than simply being associated with hearing or mood disorders.
This research offers a new approach for understanding the neurobiological connection between auditory and mental health disorders. Our findings could help explain why some individuals are particularly vulnerable to noise-induced hearing problems, identify an underexplored protective pathway in the auditory system, and provide a foundation for investigating whether medications that alter serotonin signaling, including SSRIs, could eventually have utility in preventing or treating these disabling conditions.
Long-term goal of research: Our long-term goal is to understand how neuromodulatory molecules such as serotonin, dopamine and noradrenaline regulate the auditory system’s response to sound and influence auditory perception. Because changes in neuromodulatory signaling are associated with mood disorders such as depression and anxiety, as well as neurodegenerative disorders such as Parkinson’s disease and Alzheimer’s disease, our laboratory is interested in exploring non-invasive measures of auditory function that could provide earlier indicators of these disorders. We are also interested in determining whether existing neuronal circuits that protect the auditory system from loud sounds can be strengthened, providing new approaches to prevent damage resulting from loud noise exposures. Fundamentally, we aim to understand how neuromodulatory systems shape hearing health and vulnerability to auditory disorders.
The overarching goal of this project is to elucidate how serotonergic signaling of medial olivocochlear (MOC) efferent neurons contributes to protection from noise-induced hyperacusis and tinnitus. By combining measures related to depressive-like behaviors in rodents with assays of cochlear function and detailed analyses of auditory circuitry, this project will establish a mechanistic link between serotonin signaling, auditory protection, and vulnerability to noise-induced hearing disorders. More broadly, it will establish a pipeline for connecting cellular and circuit-level mechanisms identified in animal models with behavioral and clinical measures in humans.
The proposed research has clear translational potential to develop treatment strategies for tinnitus and hyperacusis. The next step in this progression will be to translate the mechanistic findings from studies in rodents into basic scientific research in humans. Leveraging pre- existing partnerships within the UTD ecosystem—the Callier Center for Communication Disorders, Clinical and Translational Research Center, Center for Vital Longevity, Center for Brain Health and UTSW Medical Center—we will study individuals with and without tinnitus and hyperacusis, including participants with different histories of depression and antidepressant use. We will combine genetic, physiological, behavioral and brain-imaging measures to determine whether differences in serotonin signaling are associated with auditory function and susceptibility to these conditions. These studies will help determine whether differences in serotonin signaling can identify individuals who are particularly vulnerable to noise-induced hearing problems, and whether this vulnerability is associated with mood disorders or antidepressant use. This information could provide a foundation for developing more personalized approaches to prevention and treatment, in which interventions are targeted to individuals most likely to benefit.
Building on these human studies, a subsequent phase of research will test whether targeted modulation of serotonin signaling can improve auditory outcomes in individuals who are at particularly high risk of noise-related hearing injury, such as active-duty military personnel, factory workers, and musicians. These early-stage clinical studies will provide an important test of whether mechanisms
identified in animal models and observational human studies can be translated into effective strategies for preventing or reducing tinnitus and hyperacusis.
Ultimately, this stepwise pathway—from basic mechanistic discovery, to human validation, to early-stage clinical testing—aims to improve our understanding of why some individuals develop persistent problems with auditory perception following noise exposure while others do not. By exploring underlying neurobiological factors that contribute to this vulnerability, this research could lead to the development of earlier identification of at-risk individuals, targeted preventative strategies and new treatments for tinnitus and hyperacusis. In the longer term these approaches could reduce the health burden associated with auditory disorders and their frequent co- occurrence with mood disorders.