Bruni Stefania, Giorgetti Valentina, Fogassi Leonardo, Bonini Luca
Department of Neuroscience, University of Parma, Parma 43125, Italy.
Istituto Italiano di Tecnologia (IIT), Brain Center for Social and Motor Cognition (BCSMC), Parma 43125, Italy.
Cereb Cortex. 2017 Jan 1;27(1):522-533. doi: 10.1093/cercor/bhv246.
Visuo-motor neurons of the ventral premotor area F5 encode "pragmatic" representations of object in terms of the potential motor acts (e.g., precision grip) afforded by it. Likewise, objects with identical pragmatic features (e.g., small spheres) but different behavioral value (e.g., edible or inedible) convey different "semantic" information and thus afford different goal-directed behaviors (e.g., grasp-to-eat or grasp-to-place). However, whether F5 neurons can extract distinct behavioral affordances from objects with similar pragmatic features is unknown. We recorded 134 F5 visuo-motor neurons in 2 macaques during a contextually cued go/no-go task in which the monkey grasped, or refrained from grasping, a previously presented edible or inedible target to eat it or placing it, respectively. Sixty-nine visuo-motor neurons showed motor selectivity for the target (35 food and 34 object), and about half of them (N = 35) exhibited congruent visual preference. Interestingly, when the monkey grasped in complete darkness and could identify the target only based on haptic feedback, visuo-motor neurons lost their precontact selectivity, but most of them (80%) showed it again 60 ms after hand-target contact. These findings suggest that F5 neurons possess a multimodal access to semantic information on objects, which are transformed into motor representations of the potential goal-directed actions afforded by them.
腹侧运动前区F5的视觉运动神经元根据物体所提供的潜在运动行为（如精准抓握）对物体进行“实用主义”表征编码。同样，具有相同实用主义特征（如小球体）但行为价值不同（如可食用或不可食用）的物体传达不同的“语义”信息，因此提供不同的目标导向行为（如抓握进食或抓握放置）。然而，F5神经元是否能从具有相似实用主义特征的物体中提取不同的行为可供性尚不清楚。在一项情境提示的“是/否”任务中，我们记录了2只猕猴的134个F5视觉运动神经元，在该任务中，猴子分别抓握或不抓握先前呈现的可食用或不可食用目标以进食或放置。69个视觉运动神经元对目标表现出运动选择性（35个针对食物，34个针对物体），其中约一半（N = 35）表现出一致的视觉偏好。有趣的是，当猴子在完全黑暗中抓握且只能根据触觉反馈识别目标时，视觉运动神经元失去了接触前的选择性，但其中大多数（80%）在手部与目标接触60毫秒后再次表现出该选择性。这些发现表明，F5神经元对物体的语义信息具有多模态访问能力，这些信息被转化为物体所提供的潜在目标导向动作的运动表征。
