A critical barrier to progress in understanding the nervous organization of movements, the defining capacity of animals, is a paucity of data on the function of connections between neurons within motor-related networks, particularly in intact freely behaving mammals. The proposed study will fill this gap by revealing inter-neuronal interactions in the cortical circuitry for control of visually guided locomotion. Thereby it will make a critical step toward a mechanistic understanding of the cortical mechanisms underlying complex everyday movements. Accomplishing the aims of this project will constitute a substantial advancement in mammalian motor neurophysiology and will have direct impact on and can be transformative for understanding the basic principles of how vision is used to adapt movements. In addition, data from this project will be added to open databases of brain structure and function to further facilitate research of the brain. This will ultimately lead to a better understanding of neurological disorders affecting vision and movements and development of new treatments for them. The project will also have an educational impact by providing students at various levels an opportunity to participate in research.
The specific goal of this project is to understand the motor, premotor, and parietal cortex mechanisms that are involved in adaptation of locomotion to the visually perceived features of complex natural environments. Experimental data will be obtained from cats, which are classic subjects for research in both motor and visual systems. Cats will walk on a flat surface where no visuo-motor coordination will be required and along a horizontal ladder where visuo-motor coordination for accurate foot placement on the cross-pieces will be required. Visual information will be made available to cats at different phases of the approach. The activity of neurons in the motor, premotor, and parietal cortex will be recorded. Axonal projections of the neurons will be identified. Optogenetic tools will be then used to reversibly block or activate various inputs to the neurons in order to understand the contribution that these inputs make to the formation of cortico-spinal signals for control of visually guided stepping. There are two interlocking objectives. Objective 1 is to reveal the role of projection from posterior parietal area 5 to premotor cortex in modulation of its descending signals during simple and visually-guided locomotion. Objective 2 is to reveal the role of projection from premotor area 6 to motor cortex in modulation of motor cortical signals to the spinal cord during simple and visually-guided locomotion. Results will provide novel insights into the basic neural principles of perception to action conversion during the defining function of animals, locomotion.