Begliomini Chiara, Caria Andrea, Grodd Wolfgang, Castiello Umberto
Centre for Mind and Brain Sciences, University of Trento, Rovereto, Italy.
PLoS One. 2007 Oct 31;2(10):e1108. doi: 10.1371/journal.pone.0001108.
Neurophysiological studies showed that in macaques, grasp-related sensorimotor transformations are accomplished in a circuit connecting the anterior intraparietal sulcus (area AIP) with premotor area F5. Single unit recordings of macaque indicate that activity of neurons in this circuit is not simply linked to any particular object. Instead, responses correspond to the final hand configuration used to grasp the object. Although a human homologue of such a circuit has been identified, its role in planning and controlling different grasp configurations has not been decisively shown. We used functional magnetic resonance imaging to explicitly test whether activity within this network varies depending on the congruency between the adopted grasp and the grasp called by the stimulus.
METHODOLOGY/PRINCIPAL FINDINGS: Subjects were requested to reach towards and grasp a small or a large stimulus naturally (i.e., precision grip, involving the opposition of index finger and thumb, for a small size stimulus and a whole hand grasp for a larger stimulus) or with an constrained grasp (i.e., a precision grip for a large stimulus and a whole hand grasp for a small stimulus). The human anterior intraparietal sulcus (hAIPS) was more active for precise grasping than for whole hand grasp independently of stimulus size. Conversely, both the dorsal premotor cortex (dPMC) and the primary motor cortex (M1) were modulated by the relationship between the type of grasp that was adopted and the size of the stimulus.
CONCLUSIONS/SIGNIFICANCE: The demonstration that activity within the hAIPS is modulated according to different types of grasp, together with the evidence in humans that the dorsal premotor cortex is involved in grasp planning and execution offers a substantial contribution to the current debate about the neural substrates of visuomotor grasp in humans.
神经生理学研究表明，在猕猴中，与抓握相关的感觉运动转换是在连接顶内前沟（AIP区）和运动前区F5的回路中完成的。猕猴的单神经元记录表明，该回路中神经元的活动并非简单地与任何特定物体相关联。相反，其反应对应于用于抓握物体的最终手部构型。尽管已经确定了人类中存在这样一个回路的同源物，但其在规划和控制不同抓握构型中的作用尚未得到明确证实。我们使用功能磁共振成像来明确测试该网络内的活动是否会根据所采用的抓握方式与刺激所要求的抓握方式之间的一致性而发生变化。
方法/主要发现：要求受试者自然地伸手去抓握一个小的或大的刺激物（即，对于小尺寸刺激物采用精确抓握，涉及食指和拇指相对，对于大尺寸刺激物采用全手抓握），或者采用受限抓握方式（即，对于大刺激物采用精确抓握，对于小刺激物采用全手抓握）。无论刺激物大小如何，人类顶内前沟（hAIPS）在精确抓握时比全手抓握时更活跃。相反，背侧运动前皮质（dPMC）和初级运动皮质（M1）均受到所采用的抓握类型与刺激物大小之间关系的调节。
结论/意义：hAIPS内的活动根据不同抓握类型进行调节的这一证明，以及人类中背侧运动前皮质参与抓握规划和执行的证据，为当前关于人类视觉运动抓握的神经基础的争论做出了重大贡献。
