Time: 14:00-15:30 on Tue.,Oct.31, 2023
Speaker: Dr.Baohua Liu
Host: Dr.Mu Zhou
Title: A Direction-selective Top-down Pathway Adaptively Modulates Innate Behaviors
Sensory cortices apply a top-down modulation of innate motor behaviours throughout corticofugal projections that target phylogenetically-old brainstem nuclei. However, it remains unknown whether the functional properties of these projections match the properties of the innate behaviours they modulate. Here, I will present evidence that visual cortical neurons projecting to the brainstem optic-tract and dorsal-terminal nuclei (NOT-DTN) transmit motion signals relevant to the optokinetic reflex (OKR), a brainstem-mediated innate eye movement that is paramount for vision. Remarkably, enriched in specific visual areas these neurons prefer temporo-nasal visual motion, sharing the direction bias of downstream NOT-DTN neurons. Furthermore, the activity of temporo-nasally biasing cortical neurons is selectively enhanced when OKR is potentiated. These functional specificities allow efficiently integrating cortical input in NOT-DTN neurons to support OKR potentiation. Lastly, I will pinpoint the synaptic target of the corticofugal projection by showing that the visual cortex innervates only one subpopulation of NOT-DTN neurons, which project specifically to the inferior olive (IO) in the brainstem. This IO projecting NOT-DTN population also prefers the temporo-nasal motion, and is critical for the cortical contribution to the OKR. Overall, our results provide compelling evidence that a direction-selective descending pathway connects the visual cortex and brainstem, which conducts functionally relevant information and specializes in adaptively modulating the OKR.
Assistant professor in the department of biology at the University of Toronto, Dr Baohua Liu uses mice to study how the visual circuits coordinate with the oculomotor circuits in mammals to achieve proper vision. Professor Liu received his bachelor and master degrees in biophysics from Nankai University in China. His academic journey began at the University of Southern California. He received his PhD in Physiology and Biophysics from Keck School of Medicine, USC. During this period, he worked in the Zhang and Tao labs at Zilkha Neurogenetic Institute, focusing on the roles of inhibition in cortical processing. During his postdoc training with Professor Massimo Scanziani at the University of California San Diego, he aimed to understand the roles of corticofugal projections from the visual cortex to the brainstem and discovered that this descending pathway can promote the plasticity of innate behaviors mediated by the brainstem. At University of Toronto, Dr Liu puts efforts to investigate the circuit mechanisms underlying the cortical modulation of brainstem functions, and to understand functional roles of inhibitory neurons in brainstem visual nuclei. Dr Liu has published 25 papers in top journals, such as Nature, Nature Neuroscience, Neuron, Nature communications. Outside of the lab, he enjoys hiking in the nature, playing table tennis and cooking.