Differential Functional Predominance of the Frontal and Parietal Areas during Performance of Isolated or Combined Eye and Hand Reaching Movements

Introduction: Reaching movements are combined of different subcomponents consisting of information regarding the position in space or the effector of the movement itself. Separate cortical areas seem to exert a differential influence. Whereas premotor and prefrontal areas are hypothesized to code for the motor effector, the parietal areas code for position in space. We compared the fMRI activations during combined eye-hand reaching movement with respect to the quality of information given before the execution of the task. Methods: We investigated 14 volunteers at 3 T (EPI-Sequences, whole brain). Each task consisted of the performance of saccades or reaching movements towards a target presented on a screen in front of the scanner. The target, a computer-generated laser point, was presented in horizontal positions at 10° left and right in the visual field. The event-related experimental paradigm consisted of performance of isolated or combined fixation of the laser point and reaching movements towards the target with their right hand after a cue 1500 ms before preparing the movement by presenting information about either the position (left or right), or the effector (eye, hand, combined) or both (full information). Saccade performance was controlled with an MR-compatible infrared-oculography (Cambridge Research Systems) during the scan. Activation was determined by individual and group analysis using SPM 2. Results: Isolated eye movements activated the saccade related areas (i.e., frontal and supplementary eye field, intraparietal sulcus) and reaching movements related areas including the motor cortex, the supplementary motor area, prefrontal and parietal cortex. Information about the effector before movement execution resulted in a relative increase in premotor and prefrontal activation, information about the position in space in parietal areas. Analysis of saccade measurements demonstrated good compliance and correct performance of the volunteers during the scan and resulted in exclusion of faulty performance before data processing. Conclusion: Apart from the activation of the saccade and hand movement related networks during isolated or combined reaching, we could demonstrate a differential predominance of the premotor, prefrontal and parietal areas with respect to the different subcomponents during reaching movements in space.