From contact to cortex: Exploring the neural dynamics of sensorimotor interactions

This thesis is a detailed study of the neural mechanisms of sensorimotor integration. It is mainly focused on the interaction between tactile information and action imagination and its regulation by neural circuits, including the primary motor cortex (M1), the primary somatosensory cortex (S1), and the dorsal premotor cortex (dPMC). Through a sequence of experiments, this research reveals how tactile feedback and the imagination of specific activities that require force and precision are handled and incorporated into the brain’s motor system, showing the facilitatory role of touch on motor control and the selectivity of these effects in relation to the imagined action. The initial study addresses the effects of tactile stimulation during action imagination on motor system activity, showing that tactile feedback increases motor evoked potentials (MEPs) in a force-dependent manner and that this effect is bodypart specific. This improvement is associated with the vividness of motor imagery, suggesting a close link between sensory feedback and motor imagination. Subsequent research extends these results to the social area by looking at the role of different types of touches (self-touch, touches of another individual, and a nonliving surface) in the excitability of the motor cortex. Findings demonstrate the role of biological sources of touch, particularly in a social context, in the enhancement of motor system activation, thereby highlighting the social aspect of touch in action and its neural correlates. Expanding the current knowledge, the final study focuses on the neural dynamics of motor imagery and uses continuous Theta Burst Stimulation (cTBS) to temporarily reduce the activity in S1 and dPMC. This approach allows for a nuanced understanding of these regions' roles in motor imagery, especially in tasks involving precision grip. The results indicate that the inhibition of S1 and dPMC activity influences task performance and motor system excitability. Thus, the role of these areas in the cognitive control of motor imagery is emphasized. Altogether, these studies offer a comprehensive view whereby tactile feedback and motor imagery become integrated through the motor system, with specific neural circuits playing a significant part in facilitating this process. The research contributes significantly to our understanding of sensorimotor integration, offering implications for enhancing motor control through tactile feedback and informing the development of interventions and technologies to improve motor function.