Cortical Representation of Mechanical Problem Solving in Tool Use

• Applicants: Professor Dr. Joachim Hermsdörfer; Privatdozentin Dr. Afra M. Wohlschläger
• Subject Area: Human Cognitive and Systems Neuroscience ; Biological Psychology and Cognitive Neuroscience
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 454310791

The ability to operate tools skilfully and precisely has become an essential component of modern human life. Neurological patients often show deficits in using tools due to apraxia. Apart from im-paired knowledge of tool function and tool manipulation, deficits in mechanical problem solving (MPS) seem to contribute significantly to tool use apraxia. Understanding the physical and mechan-ical properties of objects is particularly important, if previously unknown tools are used to achieve a mechanical goal. However, also when interacting with familiar tools, MPS seems to be an important cognitive component. A variety of paradigms to assess MPS evolved, but the underlying cortical representations are far from clear. The central objective of the proposed project is therefore to use an established behav-ioural paradigm with two complementary brain imaging technologies to gain a better understanding of the neural organisation and the essential components of the neural network.We plan to use the “Novel Tool Test” (NTT) that requests users to select a novel tool and use it to manipulate an object by reasoning from the tool’s and object’s structure. We plan to examine the execution of the NTT in healthy participants during functional magnetic resonance imaging (fMRI) using a set-up established in previous studies, which enables actual execution of hand actions in the MRI environment (the “tool carousel”). The design will allow us to distinguish between planning and execution of the action, and we plan to test both hands for a better analysis of the laterality of the neural representation. Former fMRI studies of familiar tools use showed that a left-sided fronto-temporo-parietal network is activated. Moreover, primary visual and sensorimotor areas contribute. We expect to find the same activations plus additional patterns that are MPS specific. Choosing among novel tools presumably activates occipito-temporal areas. For both the selection and execu-tion, we expect strong activations in the left inferior and superior parietal lobule and in the left su-pramarginal gyrus with distinct differences in the activations depending on the condition. As the complementary method, we plan to use the same set-up and transcranial magnetic stimula-tion (TMS) to determine the distinct functions of key areas associated with MPS as revealed by the former fMRI experiment. After stimulation of these areas, we expect behavioural decrements in the healthy participants obvious from video scoring and kinematic analysis. We hypothesize prolonged reaction times and slowed executions during the selection among novel tools. For the use condition, we additionally expect higher movement variability and decreased movement fluency associated with TMS stimulation of specific brain areas.Our studies will foster the understanding of the neural mechanisms of MPS in tool use, which is one of the major prerequisites allowing humans to use tools promptly and skillfully.

• DFG Programme: Research Grants