TICKLE ME · Self and others in the sensorimotor system: a computational neuroanatomy of sensory attenuation

Self and others in the sensorimotor system: a computational neuroanatomy of sensory attenuation

Try to tickle yourself. No matter how hard you try, the resulting sensation will always feel less ticklish and less intense compared to the sensation produced by somebody else tickling you. Since the early 70s, several behavioural studies have shown that self-generated touch – as when touching our hand with the other– feels systematically less intense and less ticklish compared to touch of the exact same intensity and frequency applied to our hand but generated by another person or machine. Sensory attenuation (SA) refers to this phenomenon and TICKLEME was an EU project funded by the Marie Skłodowska-Curie actions that aimed to a better computational and neuroanatomical understanding of SA. From a computational perspective, prevalent theories of motor control have proposed that SA is due to the ability of our brain to predict the sensory feedback of our movements. That is, when we move one hand to touch (or tickle) the other, our brain predicts that our two hands will get in contact and thus, tactile sensations are expected. Consequently, when we perform the movement and we touch our hands, the received touch feels less intense because it has been predicted. In contrast, externally generated touch cannot be predicted and therefore it is not attenuated. However, how and when the brain computes these tactile predictions remains unknown. From a neuroanatomical perspective, earlier neuroimaging studies on SA have provided conflicting results about which brain areas are involved in the phenomenon and the pattern of their activations. Consequently, we know too little about the brain processes that are responsible for SA. TICKLEME had three objectives: 1. to clarify (a) whether an active movement is necessary for SA, (b) whether mental simulation of a movement would be sufficient for SA and (c) whether an illusion of having the two hands in contact –while they are physically distant– would elicit SA. 2. to identify the brain areas that are involved in SA by studying the brain activation and brain connectivity in relation to the participants’ perception. 3. to study whether a prolonged experience of delays between a movement and its tactile feedback can reverse SA and make self-generated touch feel more intense. By understanding when and how the brain computes these movement-related tactile predictions, TICKLEME was expected to bring novel insights into the human motor control field in general. Moreover, SA was shown to be reduced in schizophrenic patients that report auditory hallucinations (i.e., the patients hear ‘voices’) or delusions of control (i.e., the patients report that their actions are controlled by external forces). Therefore, TICKLEME was expected to show strong clinical relevance, since understanding the SA mechanism within the healthy population could substantially benefit our understanding about which processes are disturbed in the schizophrenic brain.

Data: CORDIS, © European Union