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.

Activation of left intraparietal sulcus using a fMRI conceptual praxis paradigm.

The present paper reports the results of a fMRI subtraction study of the pattern of cortical activation induced by an ideational praxis paradigm in six normal right-handed subjects. The control task consisted of a sequence of complex meaningless hand movements. A complete study was done for each hand in each subject. The left intraparietal sulcus was the only structure activated in all subjects regardless of the hand used in the task. These findings, albeit preliminary, suggest that the organization of actions involving the mediation of tools and utensils are strongly lateralized to the left hemisphere and that damage to the dominant intraparietal sulcus may be critical for the development of the clinical syndrome of conceptual apraxia.