Grant: Discovery Grants Program - Individual

Background: Locomotion in quadrupeds (animals) and bipeds (humans) consists of stance and swing phases to move a limb forward. In the cat, the primary motor and somatosensory (M1, S1), posterior parietal (PPC), and premotor cortical (PMC) regions are involved with sensorimotor processing and locomotor performance. While mounting evidence shows multiple brain regions are involved to produce locomotion in cats, the cortex of most mammals is not as developed as in humans, which precludes interpretation of the neural activation patterns that may support human locomotion. In humans, the reciprocal stepping pattern is driven in the spinal cord and brain stem. Yet, using mobile brain/body imaging, my work and that of others advanced our understanding of human locomotion by identifying a role for multiple regions in the cerebral cortex. This work uses functional near infrared spectroscopy (fNIRS) and electroencephalogram (EEG) to explore the neural mechanisms of gross human locomotion. Whether cortical regions function as a network to phasically control aspects of naturalistic locomotion is unknown. Objectives: The long-term objective of this research program is to uncover fundamental neural mechanisms that underpin naturalistic locomotion in humans. The short-term objectives are to identify cortical activation patterns in PMC-M1-S1-PPC circuitry: Objective 1) under manipulations to somatosensation,  Objective 2) under manipulations to motor performance,  Objective 3) and how patterns differ by flexion and extension phase based on somatosensory input, motor performance, and posture. Methods: For Objective 1, participants will receive somatosensory stimulation over various areas of the foot using fNIRS and EEG to measure spatial and phasic aspects of neural activation, respectively. Somatosensory stimuli will include manipulations to thermoception (hot vs cold), mechanoreception (sharp vs dull), and proprioception (flexed vs extended position sense). For Objective 2, motor performance conditions will include moving the foot under manipulations to movement speed, range of motion amplitudes, and posture. For Objective 3, to investigate how activation in one region may be phasically linked with another, this objective will explore the relationship between fNIRS and EEG responses. Novelty and Significance: In the short-term, tying somatosensory, motor, and postural manipulations to activation in neural circuitry will allow us to uncover new knowledge relevant to understanding foundational neural mechanisms of human locomotion. The wealth of data generated by this research program could have applications to computational models of human movement, brain/computer interfaces, wearable sensors, and rehabilitation of gait deficits. From the controlled methods in this DG, my long-term research program will move toward less constrained tasks with increasingly complex locomotor behaviours in environmental conditions that mimic the real-world.