Grasping How We Grasp: A "Virtual Lesion" Approach

Nichola J. Rice
Volen Center for Complex Systems
Brandeis University

Everyday we reach out and grasp objects in our environment, for example 
to pick up a coffee cup. To do so requires the fine calibration of the 
hand and arm to reach the target successfully and efficiently. Under 
certain conditions, patients suffering from optic ataxia are severely 
impaired at making such movements. Research from neuropsychological 
patients, as well as functional neuroimaging studies in healthy 
individuals have brought us a long way in understanding the neural 
circuits involved in grasping. However, many questions have remained 
unanswered. To determine the contribution of specific brain regions to 
grasping movements we have used transcranial magnetic stimulation to 
induce transient "virtual lesions" in the brains of healthy subjects. 
We have assessed the neural regions involved in: (1) planning and 
executing a grasp; (2) detecting and correcting a grasping error; 
(3) grasping with the left and right hands; (4) grasping based on 
either current information or a memory representation. Our studies 
have helped understand the organization and function of the neural 
regions mediating grasping movements.