Defining the common network of number processing and hand motor actions through an fNIRS investigation

The relationship between number processing and hand motor actions has been widely studied and is well-established through previous literature consisting mostly of behavioral studies, which hint at common neural mechanisms for the processing of these two domains. However, despite the extensive behavioral research that has provided insights, the specific neural mechanisms underlying how and where this interaction happens in the brain is currently unclear and require further investigation. In this thesis, we aimed to unveil the common brain network of number processing and hand motor actions using functional near-infrared spectroscopy (fNIRS). To that end, we recorded 30 healthy adults (mean age = 23 y/o; 10 M) while they were performing a series of hand motor tasks (consisting of an experimental grasping task, and a control squeezing task) and numerical tasks (consisting of an experimental number magnitude comparison and a control color naming task). The fNIRS array was placed on frontoparietal brain areas so as to cover number and grasping cortical networks. Our analyses revealed that frontal and parietal channels were commonly activated by both number comparison and hand motor tasks (both grasping and squeezing). Specifically, the overlap has been found around the left superior parietal sulcus, within the left precentral gyrus, and in the left middle frontal gyrus. These results underline the existence of a common cortical network that is shared between these two cognitive domains.