Role of the posterior parietal cortex and primary motor cortex in gesture representation

A hand gesture may be defined as a dynamic movement referring to a sequence of hand postures connected by continuous motions over a short time span (Garg et al., 2009). Depending on whether they are associated or not with semantic content, gestures are said to be meaningful or meaningless. The absence of semantic value means that gestures do not convey any information, or simply are not specifically related enough to a semantic context to evoke any idea when presented in isolation. Conversely, meaningful gestures stem from cultural contexts and are loaded with significance. Among them, gestures serving to manipulate objects particularly make sense when they are used to actually manipulate them. The proper manipulatory patterns for using an object are strongly associated with its function and vary little between individuals, at least for some tools (e.g., scissors). Likely because of our material culture, object use gestures are the most developed in humans. Whether they are meaningless or meaningful, gestures may be observed, executed or imagined. The latter case corresponds to motor imagery, and constitutes a broad area of research in the gesture literature. This is likely due to the fact that motor imagery shares numerous neural mechanisms with motor execution. In the context of this thesis, we were primarily interested in how gestures are computed in the brain, as well as in the specific status of tool-use gestures. The present work is articulated in four chapters, preceded by an introduction about the general context in which the experimental work is inscribed. The first chapter investigates the relationship between motor imagery (MI) and the primary motor cortex (BA4). The second chapter concerns the role of the posterior parietal cortex in visual imagery (VI) and MI. The third chapter investigates the mechanisms underlying prospective action judgments regarding tool-hand interactions. Finally, the fourth chapter explores the relationship between the functional and manipulation knowledge of object use.(SBIM 3) -- UCL, 201