Neuroscientist Joan Orpella studies speech and language

For nearly 2 decades, Joan Orpella, PhD, was a professional violinist and pedagogue. When a diagnosis of focal dystonia—a neurological condition that causes involuntary muscle contractions—ended that career, he shifted his passion to research on speech and language. Now an assistant professor of neuroscience at Georgetown University Medical Center, Dr. Orpella investigates the neural mechanisms underlying speech production, perception, and pathology.

I was always fascinated by how we learn—not just to play a musical instrument but also to use music as a means to communicate, to convey emotions and sensations, and to move people, often in profound ways. That curiosity about music making naturally extended to speech and language. While they differ in important respects, speech and music can also be seen as complementary systems of communication. And, like music, learning to speak requires an extraordinary degree of motor coordination, something achieved only through sustained practice. In that sense, my career as a cognitive neuroscientist is almost a continuation of my former life as a musician.

One fundamental similarity between playing an instrument and speaking is that both involve auditory goals. We aim to produce a particular sound or utterance. Yet the actions that will achieve these goals are defined in motor terms. So, the brain must constantly translate what we want to hear and communicate that into the movements required to produce those sounds. Establishing such sensorimotor links with maximal automaticity and minimal friction is one of the main goals of our daily practice as musicians. But it’s also an essential component when we speak and when we learn to speak. It also works in the opposite direction, from the motor to the sensory. As a violinist, you don’t just react to the sounds you produce. You’re constantly trying to anticipate them, predicting what particular movements will sound like before you make them, to make sure that you’ll hit the right notes and produce the intended sounds. Speech production works much the same way. We rely on predictive mechanisms that allow us to anticipate the sensory consequences of our vocal tract movements. This helps us to plan and produce consistently accurate and intelligible speech. Understanding how the brain learns and seamlessly implements these sensorimotor integration processes is one of the core questions we are pursuing in the lab. These questions are relevant to basic science and are also important because of the many ways these delicate neural processes can break down during development or after brain injury or stroke.

Regarding what underlies stuttering moments, converging evidence points to anomalies within the brain network that supports speech production. What remains unclear is how these anomalies translate into actual stuttering events and how they account for the variability when stuttering occurs. One major challenge in neuroimaging research on stuttering has been reliably eliciting sufficient stuttering in the lab to study what happens in the brain during those moments. In collaboration with researchers at New York University, our lab has developed an experimental design that allows us to obtain balanced amounts of stuttered and fluent speech from individuals who stutter. Using this new design and high-resolution neuroimaging, we’re beginning to identify the neural dynamics underlying stuttered speech. The results are very promising in indicating a dysregulation of the speech motor network occurring already during speech planning, prior to overt stuttering. One possibility, supported by growing evidence, is that predictive mechanisms critical for planning and production are disrupted. If the brain’s ability to anticipate the sensory consequences of speech movements is compromised, the system may become unstable, increasing the likelihood of fluency breakdowns.

The underlying causes of stuttering are less well understood, but several interesting theories have been proposed. We’re currently investigating how genetic mutations found in approximately 15% to 18% of individuals who stutter may lead to the structural and functional anomalies we observe in the speech network. Our goal is to identify the neural signatures associated with these mutations and to understand how the mutations might contribute to the development and persistence of stuttering. By clarifying that neurobiological pathway, we hope to shed light on broader mechanisms underlying the disorder.

The lab is currently engaged in various projects investigating different aspects of speech perception and production, spearheaded by two outstanding postdoctoral researchers, Dr. Chantal Oderbolz and Dr. Neeraj Kumar. I’m particularly enthusiastic about the project on the neural basis of persistent developmental stuttering because of its potential to yield important insights into the disorder at multiple levels by bridging genetics, cellular-molecular, and cognitive neuroscience. The project also seeks to link brain structure and function in individuals who stutter in unprecedented ways. Another project I’m very excited about, led by Dr. Oderbolz, examines the speech perception side of things. Specifically, we’re investigating how distributed brain representations of different components of speech—such as segmental phonology, prosody, and syntax—work together and connect with our knowledge and understanding of the world so we can extract the speaker’s intended meaning.

Our research aims to deepen our understanding of the neural mechanisms supporting speech production and perception. The intention is always that, by understanding these processes and mechanisms more precisely, we can contribute to more accurate diagnostics and targeted interventions for those who need them. I believe that the field of neuromodulation offers a promising avenue for translating our findings in the near future to promote recovery and return to function—a mission that lies at the heart of our work here at Georgetown University Medical Center.