fMRI activation in grasp-related regions during naming of tools and other graspable objects

Abstract

Previous studies have shown that focal areas of parietal and frontal cortex are activated when subjects name tools (compared to when they name other categories such as animals). We investigated whether this activation corresponds to a focus in the anterior intraparietal sulcus (AIP) that is activated during visually-guided grasping (vs. reaching) and whether the activation was specific to naming only tools or extended to graspable objects in general. Subjects silently named 2D images of graspable tools (e.g., hammer), graspable objects (e.g., apple), non-graspable objects (e.g., tree), or viewed scrambled versions of the same images. Activation for tool naming overlapped with area AIP in the left hemisphere, as localized by visually-guided grasping. Left AIP showed significantly greater activation for tools than for graspable and non-graspable objects (which were not statistically different from each other). Similar activation patterns were observed in left ventral premotor cortex and a subregion of left lateral occipital cortex. Thus even when no explicit action is required, tool naming recruits an area critical to visually-guided grasping; however, tool-related activation can not be explained solely by whether an object affords grasping. The greater activation for tools than other graspable objects may be due to stronger associations with a sequence of hand actions.