Begliomini Chiara, Sartori Luisa, Di Bono Maria G, Budisavljević Sanja, Castiello Umberto
Dipartimento di Psicologia Generale, Università degli Studi di Padova, Padua, Italy.
Padua Neuroscience Center, Padua, Italy.
Front Neurosci. 2018 Apr 3;12:192. doi: 10.3389/fnins.2018.00192. eCollection 2018.
Neurophysiological studies showed that in macaques, grasp-related visuomotor transformations are supported by a circuit involving the anterior part of the intraparietal sulcus, the ventral and the dorsal region of the premotor area. In humans, a similar grasp-related circuit has been revealed by means of neuroimaging techniques. However, the majority of "human" studies considered movements performed by right-handers only, leaving open the question of whether the dynamics underlying motor control during grasping is simply reversed in left-handers with respect to right-handers or not. To address this question, a group of left-handed participants has been scanned with functional magnetic resonance imaging while performing a precision grasping task with the left or the right hand. Dynamic causal modeling was used to assess how brain regions of the two hemispheres contribute to grasping execution and whether the intra- and inter-hemispheric connectivity is modulated by the choice of the performing hand. Results showed enhanced inter-hemispheric connectivity between anterior intraparietal and dorsal premotor cortices during grasping execution with the left dominant hand (LDH) (e.g., right hemisphere) compared to the right (e.g., left hemisphere). These findings suggest that that the left hand, although dominant and theoretically more skilled in left handers, might need additional resources in terms of the visuomotor control and on-line monitoring to accomplish a precision grasping movement. The results are discussed in light of theories on the modulation of parieto-frontal networks during the execution of prehensile movements, providing novel evidence supporting the hypothesis of a handedness-independent specialization of the left hemisphere in visuomotor control.
神经生理学研究表明，在猕猴中，与抓握相关的视觉运动转换由一个涉及顶内沟前部、运动前区腹侧和背侧区域的神经回路支持。在人类中，通过神经成像技术也发现了类似的与抓握相关的神经回路。然而，大多数“人类”研究仅考虑右利手者执行的动作，因此关于左利手者在抓握过程中运动控制的潜在动力学相对于右利手者是否简单反转这一问题仍未解决。为了解决这个问题，一组左利手参与者在使用左手或右手执行精确抓握任务时接受了功能磁共振成像扫描。采用动态因果模型来评估两个半球的脑区如何对抓握执行做出贡献，以及半球内和半球间的连接性是否会因执行手的选择而受到调节。结果显示，与使用右手（例如，左半球）执行抓握任务相比，在使用左手主导（例如，右半球）执行抓握任务时，顶内前皮质和运动前背侧皮质之间的半球间连接性增强。这些发现表明，左手虽然在左利手者中占主导且理论上更熟练，但在视觉运动控制和在线监测方面可能需要额外的资源来完成精确抓握动作。根据在执行抓握动作过程中对顶叶 - 额叶网络调节的理论对结果进行了讨论，提供了新的证据支持左半球在视觉运动控制中具有与利手无关的特化这一假设。
