Different effects in tactile attention between the thumb and its metacarpus and the palm.

The aim of this study is to establish whether the thumb is represented independently of the palm. An exogenous spatial cueing paradigm was used, where participants had to detect a tactile stimulus that could appear on the proximal and distal phalanges or metacarpus of the thumb (thenar area; Experiment 1) and the metacarpus of the thumb or hypothenar area of the palm (Experiment 2) of the left hand. Our results suggest the thumb and its metacarpus share the same mental representation, which is distinct from the representation of the palm.