The candidate has a longstanding interest in how the brain learns, and studied song learning in songbirds for her doctoral thesis. The candidate decided to focus on the cerebellum-dependent motor learning in the vestibulo-ocular reflex (VOR) in mice for three reasons: the circuit is relatively simple, learning is easily quantifiable, and mice lend themselves well to molecular-genetic manipulation. In this award, she will learn one of the general methods employed by systems neuroscientists to study circuit function: stimulation. Moreover, she will be learning to use a novel method of stimulating neuronal activity: optogenetics. Optogenetics will allow her to perform detailed analyses of the specific contributions of different cerebellar circuit elements to VOR motor learning in awake, behaving animals. These analyses were previously not feasible;she will thus be a pioneer in her field of research. In this proposal, she will test the long-standing hypothesis that climbing fibers provide a key instructive signal for motor learning. Her short-term goal is to obtain a tenure-track faculty position. Her long-term goal is to map the function of each element of the cerebellar circuit to motor learning. The candidate will be conducting the proposed experiments in Dr. Raymond's laboratory in the Dept. of Neurobiology at Stanford. Dr. Raymond is her Mentor, an expert in in vivo electrophysiological recordings, who has the laboratory space, equipment, and resources to support the candidate's research during the award. Dr. Karl Deisseroth, a co-Mentor, is one of the pioneers of optogenetics, and is also at Stanford. He will provide the candidate with materials and advice for the optogenetics portion of the proposal. The Neuroscience community at Stanford provides many venues for intellectual stimulation and discourse, such as seminars, journal clubs, department-wide monthly meetings, annual retreat, as well as joint lab meetings. In addition, Dr. Raymond holds weekly lab and individual meetings. The School of Medicine and the Stanford community offer various courses and workshops that enhance the career development of scientists. Research Project The execution of any skilled movement requires accurate calibration of the amplitude and timing of that movement. This motor learning is heavily dependent on the normal function of the cerebellum. However, how the cerebellum computes motor learning is not well understood. The climbing fiber input to the cerebellum has been thought to provide a key instructive signal for motor learning. Climbing fiber activity, however, is not the only available instructive signal in the cerebellum. This proposal aims to determine which components (i.e., amplitude, timing, or both) of motor learning can be reliably predicted by the climbing fiber activity during induction of learning, which components can be induced by climbing fiber activity, and the nature of the climbing fiber instructive signal. These experiments will be conducted in mice and will use motor learning in the vestibulo-ocular reflex (VOR) as the learning paradigm. VOR is a reflexive eye movement that stabilizes image motion in the retina. To achieve the goals in this proposal, the climbing fiber activity will first be recorded in vivo during induction of motor learning using training paradigms that induce learned changes in the amplitude, timing, or both of the VOR. The climbing fiber activity will be correlated with the learned changes in the different components of motor learning. Second, the climbing fibers will be activated and/or inhibited using optogenetics, mimicking the patterns of climbing fiber activity recorded during each training paradigm, to determine which components of motor learning are sufficiently driven by climbing fibers. The optogenetic stimulation will replace the error signal that drives VOR motor learning, which is transmitted via climbing fibers in normal behavioral training. Lastly, simultaneous recording and optogenetic stimulation of climbing fiber activity in vivo will provide a causal link between different features of climbing fiber activity and motor learning. The highlight of this proposal is the use of optogenetics, or genetically targeted expression of light-activated proteins, to manipulate climbing fiber activity. Unlike other methods of stimulation, optogenetics allows regional specificity of climbing fiber activation with good precision and reliability in a millisecond-time scale. The results and insights on motor learning that will be obtained from this proposal will help guide rational designs of new therapy for cerebellar patients. Neurological disorders are diagnosed at the behavioral level, while most of the therapies employed are at the molecular level. What is needed to bridge the gap between the behavioral and molecular levels is an understanding of the circuit function, which links both levels. Investigating the patterns and features of neuronal activity sufficient to drive motor learning will open new avenues of treatments for motor dysfunction. Moreover, because the cerebellum is involved in other functions such as cognition (language), attention (autism), and perception of timing, the underlying principles of cerebellar function derived from this study can be generalized to these other cerebellar functions.
Neurological disorders are often diagnosed at the behavioral level, while most therapies employed are at the molecular level. What is needed to bridge the gap between the behavioral and molecular levels is an understanding of the function of the circuit which links both levels. Investigating the patterns and features of neuronal activity sufficient to drive motor learning will open new avenues of treatments for motor dysfunction, which can be generalized to other cerebellar functions such as cognition (language), attention (autism), and perception of timing.