Kathleen Cullen, PhD
Department of Physiology
McGill University
(October 15, 2014)
Neural Representations of Natural Self Motion: Implications for Perception and Action
How do we control our motions and orient our bodies in space? The vestibular system is critical to the control of balance and movement. Most people do not give much thought to their vestibular system until it malfunctions. Problems with the vestibular system can lead to dizziness and a loss of balance – both of which can lead to falls and broken bones. The Cullen laboratory examines how the brain processes information from the vestibular system and uses that information to predict the outcomes of self-motion. By measuring responses at the level of single neurons, Dr. Cullen is learning how patterns of neuronal firing change when a movement is self-generated compared to those externally directed. Dr. Cullen’s research will also have an impact on treatments for those with a loss of vestibular function.
To advance our understanding of brain disorders, it is necessary to identify the underlying neural circuits and determine how abnormalities in these circuits produce cognitive and behavioral symptoms. The overarching focus of my research program is to develop an understanding of neural circuits underlying vestibular disease, with an emphasis on translational approaches for restoring sensory function. The loss of vestibular function due to aging, injury, or disease produces dizziness, imbalance, and an increased risk of falls — all symptoms that profoundly impair quality of life. Thus, vestibular disorders impose a substantial burden on the economy in the form of increased medical costs, work-related absenteeism, and reduced productivity.
Recent research from my laboratory has advanced our fundamental knowledge about the neural circuits responsible for normal vestibular function and reveal how these circuits are altered by disease to develop innovative treatment options. The research program is aimed at addressing two central challenges.
The first is to understand how the brain processes vestibular information to ensure accurate perception and behavior in everyday life. I described recent progress made toward understanding the nature of the neural code that used to represent vestibular sensory input. Using computational modeling and experimental approaches, my group has shown through its work how heterogeneities in the intrinsic neural variability of early vestibular pathways determine the nature of the neural code (i.e., rate versus temporal coding). In addition, work from my laboratory has revealed how we distinguish between our own self-generated movements and those of the external world. While vestibular brainstem and cerebellar neurons show robust responses to externally applied motion, these responses are canceled when motion is self- generated. By completing trial-by-trial analysis of voluntary head movements, my laboratory has further shown that the brain performs this elegant neural computation by computing an internal expectation of the expected sensory consequences of active self-motion.
The second challenge of my lab’s research program is to understand the neurophysiology of vestibular/balance disorders and develop new treatment approaches. Specifically, by measuring activity in these circuits after vestibular loss at the level of single neurons, their recent findings establish how changes in coding, including altered multimodal integration, impact perception and behavior. In ongoing experiments, my lab is now using this information to drive novel rehabilitation strategies to treat patients in part through development of implantable vestibular prostheses.