Research in the Action and Cognition @ Trent (ACT) Lab:

All of our everyday activities – reaching for a cup of coffee, tossing a ball to a child, talking to a friend – require that we interact skillfully with the people and objects in our surroundings.

The goal of research in the ACT Lab is to understand how the brain uses sensory information (vision, touch, and proprioception) to learn and control limb and hand movements. We are also interested in how our action capabilities influence how we attend to and perceive our immediate surroundings.

To address these questions, we use specialized equipment to track precisely how participants’ eyes, head, and limbs move as they perform our experiments. We carefully manipulate what people see and feel as they reach for targets, learn new motor skills, or use tools. We also use brain stimulation techniques (transcranial magnetic stimulation) to help us understand how the brain coordinates sensory and motor information during movement.

Ultimately, our goal is to reveal strategies that can be used by people with brain injuries to help them regain and maintain their independence.

Some questions we are investigating:

Can we use our hands to augment vision?
New findings suggest that we can see targets more quickly and accurately when the target appears in the space near our hands. For example, MB - a young man who is blind in his upper-left visual field - could report object size in his blind field if his hand was placed near the target object (1). In studies of healthy participants, we've shown that pointing movements are performed more precisely if the target is shown on the participant's own real hand than on a similarly-positioned fake hand (2), and that pointing precision varies with the distance between target and the nearby hand (3). Can these effects be explained by attention or is there a role for special neurons that code space near the hands (visual-tactile bimodal neurons)? Are there other situations in which people can see better near their hands and can this effect be exploited to help patients overcome visual exploration deficits? Our current studies address these questions.

1. Brown, L. E., Kroliczak, G., Demonet, J.-F., & Goodale, M. A. (2008). A hand in blindsight: Hand placement near target improves size perception in the blind visual field. Neuropsychologia, 46, 786-802.

2. Brown, L. E., Morrissey, B. F., & Goodale, M. A. (2009). Vision in the palm of your hand. Neuropsychologia, 47, 1621-6.

3. Brown, L. E., Reynolds, A., & Gozli, D. (2009). Hand-target proximity improves target representation for reaching. Poster presented at Society for Neuroscience, Chicago, IL.

Does motor learning change the way we deal with sensory information?
The motor system helps us adapt to forces applied by the environment (strong wind and current) and by objects (gravity and object inertia). Is force information useful to other sensory systems? We recently showed that visual motion processing changes in response to motor adaptation to an environmental force field (4), and that the visual system may also use learned force information to make predictions about how far a hand-held tool can reach (5). Special regions of space near the hand grow to encompass the entire tool, but only after active tool use. What role does motor learning play in this adaptation?

4. Brown, L. E., Wilson, E. T., Goodale, M. A., & Gribble, P. L. (2007). Motor force field learning influences visual processing of target motion. Journal of Neuroscience, 27, 9975-9983.

5. Brown, L. E., Doole, R., & Malfait, N. (in press). The role of motor learning in spatial adaptation near a tool. PLoS One.

6. Gozli, D. G., & Brown, L. E. (in press). Agency and control for the integration of a virtual tool into peripersonal space. Perception.

Does motor learning occur by observing perfection or errors?
Common wisdom says that I will improve my own movement performance if I watch an expert perform, but most motor learning by observing research emphasizes the importance of observing errors. When do observers need to see a model of perfect performance and when do they need to see errors? Do they benefit from observing their own errors more than others' errors? What role do the visual and motor systems play in learning by observing?

7. Brown, L. E., Wilson, E. T., Obhi, S. S., & Gribble, P. L. (2010). The effect of trial order and error magnitude on motor learning by observing. Journal of Neurophysiology, 104, 1409-16.

8. Brown, L. E., Wilson, E. T., & Gribble, P. L. (2009). Repetitive transcranial magnetic stimulation to primary motor cortex interferes with motor learning by observing. Journal of Cognitive Neuroscience, 21, 1013-22.