Touching the World With a Cane: Cognitive and Neural Processes

A touch sensitive computer screen either displaying a downscaled (45cm long) image of the rod (for the sighted), or supporting a same sized wooden rod (for the blind), will be placed on the table in front of the participant to record their localization performance. They will be instructed to use their left index fingertip to indicate on the image of the screen (for sighted) or on the wooden rod (for the blind) the position where they have felt the touch provided to the 90 cm long they held in their right dominant hand. Participants will wear a headset playing white noise to prevent any auditory localization cues when the long rod will be touched. The rod will be touched by a computer controlled solenoid. Thus, participants will respond with a hand gesture on the image or rod and will be asked to validate the position by pressing a foot-pedal with their left foot.

"The EEG protocol will be similar as the behavioral one described above, with the distinction of taking place in two separate sessions: one where the rod are touched, and one where their hand is touched. The participant will hold a rod in each hand and he will have to indicate on which rod he felt the touch.~Additionally electrophysiological responses will be continuously recorded using a 65 channel ActiCap system (Brain Products)."

"The same behavioral task and procedures of the behavioral protocol described above will be applied, adapted to take into account the constraints posed by the magnetic environment of the MR scanner. The participant will be placed on the scanner bed and provided with earphones that will both protect against the noise of the machine (80dB) and ensure a continuous communication with the participant.~During the fMRI sessions, the participant will solve the same rod localization behavioral task while we will record brain activations by measuring the brain oxygen level dependent signal via Echo Planar Imaging sequences. We will use an MRI compatible tactile stimulator to touch the hand-held rod and participants location judgement will be recorded by using an MRI-compatible tablet, positioned on their abdomen, where the participant will have to indicate the judged position."