Understanding the brain's role in movement

While people like to describe themselves as left- or right-brained, we all rely on both hemispheres to function normally.

However, neuroscientists haven't been certain whether both contribute equally to the production of skilled movements.

Dr. Claudia Gonzalez

"There is an abundance of literature on sensory-motor integration and on goal-directed movements like reaching and grasping, but there has been little written about whether there are differences between the contribution of each hemisphere to these kind of behaviours," says Dr. Claudia Gonzalez, a new researcher in the Department of Kinesiology and a Tier II Canada Research Chair (Sensorimotor Control).

But Gonzalez's research is helping to unravel this mystery.

To determine whether there is a hemisphere bias involved in goal-directed movements, she presented participants with an object embedded in a visual illusion and asked them to grasp the object using each hand. Regardless of whether people were right- or left-handed, their left hand was fooled by the illusion (i.e. their grip was scaled to the illusory size of the object) while their right grip reflected the real size of the object.

These results suggest that the left hemisphere, which controls the right hand, may play a more important role than the right side in the integration of visuo-motor information.

Gonzalez's work is relevant to how people recover from brain injury. A more sophisticated understanding of how the two hemispheres control different facets of action and perception could ultimately help tailor rehabilitation practices to specific injuries.

Her research may also explain why people favour one hand over the other ("handedness"). If the left hemisphere plays a more pivotal role in grasping – a primitive function crucial for survival – it makes sense that humans developed a more specialized right hand.

"This research doesn't only apply to people with brain injuries but to how we understand cerebral asymmetries," Gonzalez explains.