Facial motor system: voluntary and emotional control

Face expressions have a crucial role in human nonverbal behaviour and can be either voluntarily or emotionally controlled. The variety of functions of facial muscles, is reflected in their anatomical and histological characteristics. Face muscles present a peculiar coordination, in fact also during voluntary movements, facial muscles’ groups are always recruited together to produce a facial posture, but how and at which level they are coordinated and controlled by the emotional system is still unknown. For long time was impossible to study the motor control of facial muscle in humans. Only recently several studies have demonstrated that it is possible to probe it using transcranial magnetic stimulation (TMS).This work thesis attempted to investigate: 1) the interhemispheric connections between facial motor cortices (fM1);2) the cerebellar-fM1 connectivity; and 3) the influence of emotional stimuli over fM1 and pre-motor cortices, using TMS protocols.Results provided the first demonstration that : 1) the corpus callosum plays a minor role in the coordination of bilateral face movements; 2) A clear cerebellar-fM1 connectivity operates in the facial motor system; 3) fM1 is directly connected with the emotional system and specifically modulated by stimuli with positive connotation.