Fig. 1

Experimental procedures. A represents the experimental procedure for each experimental condition. Before each condition, 10 proprioceptive judgements were collected by asking participants to point to the tested hand position, while being blindfolded. Then, 3 min of RHI was performed. Finally, the proprioceptive judgement procedure was repeated, and questionnaires were administered. In separate trials, during the RHI procedure, different VT- and VM-RHI conditions were performed. Note that, besides 16 age-matched controls, 32 PD patients were recruited. Specifically, 16 right and 16 left exordium PD patients were tested on both their right and left hands in order to account for possible exordium side-dependent confounds. B shows a schematic representation of the visuo-tactile RHI conditions performed in Experiment 1, while C shows those of the visuo-motor RHI performed in Experiment 2.