(e)motion: The interplay between emotional processing and the sensorimotor system

This thesis aimed to explore the relationship between emotional processing and the sensorimotor system, mainly focusing on one information source derived from emotional body language (EBL). We investigated such a relationship in four different experiments and through several methodologies ranging from behavioral to neurophysiological techniques, by means of transcranial magnetic stimulation (TMS) and high-density electroencephalography (hdEEG), in healthy subjects (experiments 1, 2 and 3) and patients affected by Parkinson’s Disease (PD) (experiment 4). In the first experiment, whose aims were to explore the ability to process, discriminate and recognize emotional information carried by body language and to test motor response through response times (RTs) to emotional stimuli (i.e., EBL and IAPS), we found that fearful EBL is rapidly recognized and processed, probably because of a rapid and instinctual activation of several brain structures involved in defensive reactions. In the second experiment we investigated the effects of emotion processing (i.e., Fear, Happy and Neutral) on the sensorimotor system through a TMS protocol assessing short-latency afferent inhibition (SAI) at two timepoints (i.e., 120 and 300 ms). Our results showed that sensorimotor inhibition in the first 120 ms after stimulus onset is increased during processing of fearful emotional stimuli, reflecting the fact that automatic processing of threatening information can modulate attentional resources and cholinergic activity. In the third experiment, were a protocol involving hdEEG and a source localization workflow was implemented in the study of event-related potentials (ERPs) and mu-alpha and beta-bands rhythms during EBL processing, we confirmed what observed in the second experiment by showing that during processing of fearful body expressions there was an increased activity in the β frequency band in the somatosensory cortex which in turn may be one of the factors responsible for reducing the activation of motor related areas and, hence, increase sensorimotor inhibition. Lastly, in the fourth experiment we partly replicated the experimental design of the first experiment but in patients with Parkinson’s disease and using not only emotional body language stimuli and emotional scenes, but also emotional facial expressions. Our results showed that motor responses in PD patients are speeded when observing a potential threat, for both the embodied set of stimuli (EBL and facial expressions). We discussed this finding in relation to the “Kinesia paradoxa” phenomenon, defined as “the sudden transient ability of a patient with PD to perform a task he or she was previously unable to perform”.