Functional MRI correlates of real and imagined tool-use pantomimes

Objective: To study the pattern of cerebral activation related to the performance of tool-use pantomimes with functional MRI (fMRI) using a task-subtraction design. Background: Tool use comprises a particular category of transitive actions. Inability to pantomime the use of tools has been classically associated with retrorolandic dominant hemisphere damage. However, where in the left hemisphere these transitive representations are generated is unclear. Methods: Echoplanar images were acquired in eight alternating task and control periods. Sixteen right-handed normal adults pantomimed the use of common tools and utensils with each hand. The control condition consisted of a sequence of nonsymbolic complex movements of forearm, hand, and fingers at a self-paced rate. Eight individuals also imagined the execution of the real task and control actions. A repeated measures ANOVA compared activations in five regions of interest in each hemisphere. Results: Regardless of which hand was used, the left hemisphere was more active than the right in both real (p < 0.02) and imagined (p < 0.04) tasks. Activations clustered in the left intraparietal cortex and posterior dorsolateral frontal cortex. Conclusions: Pantomiming the use of tools is associated with activation of the left intraparietal cortex and dorsolateral frontal cortex. The left intraparietal cortex may store the representations of tool-use formulae, whereas the dorsolateral frontal cortex activation may reflect the switching between innervatory motor programs.