In a path-breaking study scientists at UC Santa Barbara have mapped the process that enables the human brain to transform sensory inputs into action, be it kicking a football or shaking a hand. Reported in the latest edition of The Journal of Neuroscience, the study is based on detailed imaging of the train of events that starts with an input and ends with an action.
The human brain is a repository of imagery of both external environments and motor maps that define our behaviour within those environments. By a beguilingly complex process the brain is able to correlate points of reference in those two sets of imagery to ensure that we don’t end up shaking hands when we in fact meant to kick a ball!
How this happens is the subject of this study led by doctoral student in UCSB’s new Interdepartmental Graduate Program in Dynamical Neuroscience. The experiments used customized scanning techniques to measure brain activity even as participants made wrist movements in different directions.
In the technique LED lights placed on the right hand to record even the finest of movements during brain scanning. This ultimately yielded a rich set of movement data to relate to brain activity. By using advanced analytical methods the researchers were then able to parse out the specific patterns of brain activity corresponding to different aspects of movement.
Building on previous research, they tracked down an area of the brain that facilitates the transformation of an input into an action. Called superior parietal lobule this area contains information for both location and direction. More interestingly, they found that the movement-related maps are hyper-sensitive to a hand’s posture, indicating that posture-dependent planning is more widespread in the brain than previously thought.
The study is expected to help explain the deficits seen in patients with neurological damage, which damage the process of visuo-motor transformations. It may also lead to the development of therapies for patients with optic ataxia (an inability to accurately reach to objects) and ideomotor apraxia (a deficit in imitating gestures under command).