Pantomiming tool use with an imaginary tool in hand as compared to demonstration with tool in hand specifically...

Neuropsychological lesion studies evidence the necessity to differentiate between various forms of tool-related actions such as real tool use, tool use demonstration with tool in hand and without physical target object, and pantomime without tool in hand. However, thus far, neuroimaging studies have primarily focused only on investigating tool use pantomimes. The present fMRI study investigates pantomime without tool in hand as compared to tool use demonstration with tool in hand in order to explore patterns of cerebral signal modulation associated with acting with imaginary tools in hand. Fifteen participants performed with either hand (i) tool use pantomime with an imaginary tool in hand in response to visual tool presentation and (ii) tool use demonstration with tool in hand in response to visual-tactile tool presentation. In both conditions, no physical target object was present. The conjunction analysis of the right and left hands executions of tool use pantomime relative to tool use demonstration yielded significant activity in the left middle and superior temporal lobe. In contrast, demonstration relative to pantomime revealed large bihemispherically distributed homologous areas of activity. Thus far, fMRI studies have demonstrated the relevance of the left middle and superior temporal gyri in viewing, naming, and matching tools and related actions and contexts. Since in our study all these factors were equally (ir)relevant both in the tool use pantomime and the tool use demonstration conditions, the present findings enhance the knowledge about the function of these brain regions in tool-related cognitive processes. The two contrasted conditions only differ regarding the fact that the pantomime condition requires the individual to act with an imaginary tool in hand. Therefore, we suggest that the left middle and superior temporal gyri are specifically involved in integrating the projected mental image of a tool in the execution of a tool-specific movement concept.