Object motor representation and language.

Results of kinematic studies on the control of the reaching-grasping motor act (Gentilucci 2003, Exp Brain Res 149:395-400) suggest that grasp is guided by a single motor representation, which codes all the possible types of interactions with the objects. Neuroimaging studies in humans (Chao and Martin 2000, Neuroimage 12:478-484; Grabowski et al. 1998, Neuroimage 7:232-243; Grafton et al. 1997, Neuroimage 6:231-236; Martin et al. 1995, Science 270:102-105) suggest that these representations are coded in the premotor cortex and are automatically activated when naming the object or viewing it without the execution of an overt action. If an object motor representation is accessed by language, naming of object properties related to sensory-motor transformation can automatically influence the object motor representation. This hypothesis was verified by behavioural experiments (Gentilucci and Gangitano 1998, Eur J Neurosci 10:752-756; Gentilucci et al. 2000, Exp Brain Res 133:468-490; Glover and Dixon 2002, Exp Brain Res 146:383-387), which showed that automatic reading (and probably silent naming; MacLeod 1991, Psychol Bull 109:163-203) of adjectives related to object properties analysed for planning the reaching-grasping motor act influenced the control of the arm movement. In a new study it was determined whether the class of a word can be a factor selectively influencing motor control. Participants were required to reach for and grasp an object located either on the right or on the left, and to place it on the opposite side. Either a verb ("place" SPOSTA versus "lift" ALZA) or an adjective ("lateral" LATERALE versus "high" ALTO) was printed on the target. A greater influence of the verbs than of the adjectives was observed on the kinematics of the action. In particular, when the verb ALZA was printed on the object, hand-path height and vertical component of arm velocity were higher than when the adjective ALTO was presented on the object. The data support the hypothesis that the object motor representation is mainly coded in terms of possible interactions with the object.