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Abstract:
Our modern civilization provides a huge number of tools, which have been optimized for a specific purpose and goal. Some of these tools and their ways of usage are well known to each adult even if they have little practical experience with a respective tool. The integration of such highly familiar tools in sensorimotor and cognitive processing and planning can thus not only draw on currently available sensory information but also on long-term procedural and semantic memories associated with these tools. A so-called cortical tool network, consisting of the dorsal supramarginal gyrus (SMG), the inferior frontal cortex (IFC), and the inferior lateral occipito-temporal cortex (LOCT) has already been associated with the visual presentation, naming, and usage of tools. However, it is unknown through which structures or connections this tool network interacts with memory retrieval, thereby integrating semantic knowledge about tools.
We conducted three fMRI experiments comparing the processing of familiar with unfamiliar tools. In experiments 2 and 3, healthy participants decided whether a presented tool could be used or not used for a given task (e.g. crack a nut – nutcracker). For this task, we hypothesized and found increased signals in the SMG, IFC, LOTC for unfamiliar tools relative to familiar tools, most likely associated with visual and sensorimotor analysis of a currently presented tool. Additionally, we found signal changes at the anterior fronto-median cortex, a region which is associated with decision-making and error monitoring. A signal increase for familiar tools in the posterior middle temporal gyrus suggested a specific role for this region in the retrieval of previously established knowledge about such tools.
We confirmed these findings in a second experiment that looked more into the temporal sequence of activations across these networks using the same task but modified timing of events. In a third experiment, our participants were not explicitly instructed to evaluate the function of a given tool, but simply to categorize a variety of tools (e.g. kitchen vs. workshop). In agreement with our interpretation of experiments 1 and 2, we found signal increases at the posterior MTG in this categorization task relative to a sensory discrimination task. We assume that the posterior MTG connects long-term knowledge with ongoing motor cognition processing, representing a crucial hub in the integration of procedural and semantic memory, visual analysis, and motor cognition.
