The overall goal of the Sensorimotor Neuroscience Lab is to understand how the nervous system integrates and uses visual input to control and to adapt walking in healthy as well as neurologically and visually impaired adults. Essentially, we try and understand how the brain uses what it sees.
Vision contributes to movement by allowing us to detect and define properties of the environment, receive and process self- and object-motion cues, and determine the position of the limbs and body relative to our surroundings. An intact visual system and appropriate gaze behaviour facilitates the identification of hazards, negotiation of obstacles, and goal-directed limb movement. For optimal control of movement, the nervous system must integrate the input it receives from vision with vestibular and somatosensory sources to accurately estimate limb state.
The following describes our three primary research themes:
How the Brain Adapts to Movement Errors: Visuomotor Learning
The ability to adapt to our surroundings and retain what is learned is essential for survival and performing many daily activities. When moving, however, we must contend with the effects of aging, injury, disease, and an ever-changing environment. These effects can change the normal relationship (or mapping) between sensory input and motor output, thus causing errors in movement. Experience suggests we can learn and retain new mappings. For instance, we can quickly determine how to control a cursor on a screen using a mouse or trackpad. We can also transfer (or generalize) mappings to new situations; for example, this can allow us to switch between different tablets or cell phones. Learning, retention, and transfer of new mappings are especially relevant following neurological injury or disease.
We study these processes, usually in the context of walking, by systematically exposing the nervous system to perturbations that shift the visual field. This technique artificially alters ones visuomotor mapping, resulting in a mismatch between the expected and actual outcome of a movement. Over time, individuals adapt to this change in mapping and become more accurate. Our research is focused on identifying factors that enhance how we learn, retain, and transfer these mappings. This insight may assist in the development of more effective rehabilitation strategies and the design of human-machine interfaces, such as virtual reality technologies.
Select Related Publications:
- Maeda RS, O'Connor SM, Donelan JM, Marigold DS. Foot placement relies on state estimation during visually guided walking. J Neurophysiol 117: 480-491, 2017.
- Maeda RS, McGee SE, Marigold DS. Consolidation of visuomotor adaptation memory with consistent and noisy environments. J Neurophysiol 117: 316-326, 2017.
- McGowan K, Gunn SM, Vorobeychik G, Marigold DS. Short-term motor learning and retention during visually guided walking in persons with multiple sclerosis. Neurorehabil Neural Repair 31: 648-656, 2017.
- Alexander MS, Flodin BW, Marigold DS. Prism adaptation and generalization during visually guided locomotor tasks. J Neurophysiol 106: 860-871, 2011.
Factors Guiding Gaze During Natural Behaviour
Visual Impairment and Mobility
The inability to properly see makes activities of daily living difficult to perform. Decreased quality of vision, which affects hundreds of millions of people worldwide, increases the risk of colliding with objects, tripping, falling, and the likelihood of injury. Aging, macular degeneration, glaucoma, cataracts, and hemianopia are simply a few conditions that can affect vision.
As a consequence of poor vision, people change the way they look at, or visually sample, the environment. This can prevent the formation of an accurate representation of their surroundings, such as the location of objects. Because when and where a person looks is tightly related to limb movement, this also disrupts how vision guides goal-directed actions. For instance, one must be able to direct gaze to a sidewalk curb at the correct time and for sufficient duration in order to decide when and how high to step.
In one aspect of our research, we study how older adults with glaucoma navigate around obstacles and step precisely onto particular locations on the ground. We have found that when and where these individuals look during these tasks relates to greater object collisions and reduced foot-placement accuracy. This suggests that these individuals are using their remaining visual function ineffectively, which provides an avenue for intervention. We are currently developing a gaze training program to improve mobility in individuals with glaucoma.
Importantly, we collaborate with a variety of clinicians (i.e., ophthalmologists, optometrists, and orientation & mobility specialists) to facilitate our research in this area.
Select Related Publications:
- Miller AB, Lajoie K, Strath RA, Neima DR, Marigold DS. Coordination of gaze behavior and foot placement during walking in persons with glaucoma. J Glaucoma 27: 55-63, 2018.
- Alexander MS, Lajoie K, Neima DR, Strath RA, Robinovitch SN, Marigold DS. Effects of macular degeneration and ambient light on curb negotiation. Optom Vis Sci 91: 975-989, 2014.
- Alexander MS, Lajoie K, Neima DR, Strath RA, Robinovitch SN, Marigold DS. Effect of ambient light and macular degeneration on precision walking. Optom Vis Sci 91: 990-999, 2014.
Other Research Interests
How non-visual sensory input is integrated with normal or degraded vision during walking
The role of the posterior parietal cortex in visually guided movement
Current and/or Past Research Funding
Natural Sciences and Engineering Research Council of Canada (NSERC)
Glaucoma Research Society of Canada
Canadian National Institute for the Blind (CNIB)
Simon Fraser University - Office of the VPR