Our new case study has been published in Neuropsychologia. We report an individual with subcortical damage who had excellent detection of light touch on the contralesional hand. However, his tactile localization on the contralesional hand was severely impaired, with his responses clustering on the left side of his hand.
Interestingly, “side” depended on the position and orientation of his hand. Regardless of whether his hand was positioned palm-up or palm-down, his errors were always on the left side of the hand relative to the participant’s viewpoint (i.e. towards the 5th finger with palm down, towards the thumb with palm up). When the hand was turned 90 degrees, his errors were made towards the left side of the hand in a hand-centered frame of reference.
This provides strong evidence for a dissociation of tactile detection and localization, shows that body position can modulate tactile localization, and provides evidence for hand-centered representations for touch. You can read the manuscript here.