Research

Overview

The overall goal of the Sensorimotor Neuroscience Lab is to determine how the brain acquires, deals with changes in the quality of, and uses visual information to control and adapt walking (and movement in general). Essentially, we try to understand how the brain uses what it sees to move.

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. Thus, an intact visual system and appropriate gaze behaviour facilitates the identification of hazards, negotiation of obstacles, and goal-directed limb movement. For optimal control, though, the nervous system must integrate the input it receives from vision with vestibular and somatosensory sources to accurately estimate limb state; only then can we efficiently interact with the world.

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:

  1. Maeda RS, McGee SE, Marigold DS. Long-term retention and reconsolidation of a visuomotor memory. Neurobiol Learn Mem 155: 313-321, 2018.
  2. 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.
  3. Maeda RS, McGee SE, Marigold DS. Consolidation of visuomotor adaptation memory with consistent and noisy environments. J Neurophysiol 117: 316-326, 2017.
  4. 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.
  5. Alexander MS, Flodin BW, Marigold DS. Prism adaptation and generalization during visually guided locomotor tasks. J Neurophysiol 106: 860-871, 2011.

 

How We Use Vision to Navigate the World

Our environment presents an array of challenges for walking. This is particularly the case when navigating a crowded sidewalk or shopping mall, or when hiking through the cluttered terrain of a forest. Visual information about the world helps the brain make good decisions as to where to move in these situations. This visual information is actively sampled by shifts in gaze, which makes the eyes unique as sensors because the brain can direct them to points of interest. Our research in this area poses the question: what factors influence the decision of where, when, and for how long to allocate gaze for guiding movement?

Select Related Publications:

  1. Domínguez-Zamora FJ, Gunn SM, Marigold DS. Adaptive gaze strategies to reduce environmental uncertainty during a sequential visuomotor behaviour. Sci Rep 8: 14112, 2018.
  2. Lajoie K, Miller AB, Strath RA, Neima DR, Marigold DS. Glaucoma-related differences in gaze behavior when negotiating obstacles. Transl Vis Sci Technol 7(4):10, 2018.
  3. 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.

 

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:

  1. Lajoie K, Miller AB, Strath RA, Neima DR, Marigold DS. Glaucoma-related differences in gaze behavior when negotiating obstacles. Transl Vis Sci Technol 7(4):10, 2018.
  2. 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.
  3. 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.
  4. 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