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March 2018

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CANCELLATION: Bioengineering Spring 2018  Seminar Seried

Kathleen Cullen, Ph.D., Professor
Biomedical Engineering with Joint Appointment in the Departments of Neuroscience and Otolaryngology - Head and Neck Surgery, John Hopkins University

Johnson Center (JC), Room B
March 22, 2018
12:00 pm - 1:00 pm

Topic: Neural Representations of Natural Self-Motion: Implications for Perception & Action

The vestibular system detects self-motion and in turn generates reflexes that are crucial for our daily activities, such as stabilizing the visual axis (gaze) and maintaining head and body posture. In addition, the vestibular system provides us with our subjective sense of movement and orientation in space. The loss vestibular function due to aging, injury, or disease produces dizziness, postural imbalance, and an increased risk of falls – all symptoms that profoundly impair quality of life.

Abstract: In this talk, Dr. Cullen will describe how the brain encodes vestibular information in natural conditions. Notably, our work has established the relationship between neural variability, detection thresholds, and information transmission in the vestibular system. In addition, we have established how early stages of processing process vestibular stimuli and integrate them with extra-vestibular cues – for example proprioceptive and premotor information to ensure accurate perception and behaviour. Our experiments have revealed that while vestibular afferents respond identically to externally-generated and actively-generated self-motion, this is not the case at first central stage of sensory processing. Neurons mediating the vestibulo-spinal reflexes, as well as ascending thalamocortical pathways, are robustly activated during externally-generated motion, however their sensory response are cancelled during actively-generated movements. Our work has further revealed that this cancellation of actively-generated vestibular input occurs only in conditions where the actual sensory signal matches the brain’s internal estimate of the expected sensory consequences of active movement. Moreover, when unexpected vestibular inputs becomes persistent during voluntary motion, a cerebellar-based cancellation mechanism is rapidly updated to re-enable the vital distinction between self-generated and externally-applied stimulation to ensure the maintenance of posture and stable perception. In contrast, vestibular pathways mediating the vestibulo-ocular reflex, employ a different strategy. In this pathway, head velocity is robustly encoded whenever the goal is to stabilize gaze, but when the goal is to voluntarily redirect gaze an efferent copy of the gaze command suppresses the efficacy of this reflex pathway. Taken together, these findings have important implications for understanding the neural basis of perception and action during self-motion.

Biography: Dr. Kathleen Cullen received a bachelor’s degree in Biomedical Engineering and Neuroscience from Brown University and a PhD in Neuroscience from the University of Chicago. After doctoral studies, Dr. Cullen was a Fellow at the Montreal Neurological Institute where she worked in the Department of Neurology and Neurosurgery. In 1994, Dr. Cullen became an assistant professor in the Department of Physiology at McGill University, with appointments in Biomedical Engineering, Neuroscience, and Otolaryngology. In 2002, Cullen was appointed a William Dawson Chair in recognition of her work in Systems Neuroscience and Neural Engineering, and served as Director of McGill’s Aerospace Medical Research Unit comprising four faculty and their research labs.

In 2016, Dr. Cullen moved to Johns Hopkins University, where she is now a Professor in Biomedical Engineering, and holds joint appointments in the Departments of Neuroscience and in Otolaryngology – Head and Neck Surgery. In addition to her research activities, Dr. Cullen currently serves as the Program Chair and Vice President of the Society for the Neural Control of Movement. Dr. Cullen has been an active member of the Scientific Advisory Board of the National Space Biomedical Research Institute, which works with NASA to identify health risks in extended space flight. She has also served as a reviewing editor on numerous Editorial Boards including the Journal of Neuroscience, the Journal of Neurophysiology, and the Journal of Research in Otolaryngology. Dr. Cullen has received awards including the Halpike-Nylen medal of the Barany Society for “outstanding contributions to basic vestibular science”, the Sarrazin Award Lectureship from the Canadian Physiological Society (CPS), and was elected Chair of the Gordon Research Conference on eye movement system biology. Cullen has served as Communications Lead for the Brain@McGill, and was Chair of the 2016 Canadian Association for Neuroscience meeting. She has published over 120 articles, book chapters, and patent applications and given over 140 national and international invited lectures.







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