Standard body-space relationships: Fingers hold spatial information

- Fingers have preferential associations with relative spatial positions.
- Finger-space associations are found in tactile tasks with and without vision.
- Finger-space associations are identifiable at the conceptual level.
- The thumb is associated with bottom and the index finger is associated with top.
- The relationship between body and space mapping is bi-directional.

The representation of the body in the brain is constantly updated to allow optimal sensorimotor interactions with the external world. In addition to dynamic features, body representation holds stable features that are still largely unknown. In the present work we explored the hypothesis that body parts have preferential associations with relative spatial locations. Specifically, in three experiments, we found consistent preferential associations between the index finger and the top position, and between the thumb and the bottom position. This association was found in a tactile sensory discrimination task, which was conducted both with and without vision, as well as at the implicit conceptual association level. These findings show that body parts and spatial locations are stably associated. Therefore, not only are body segments dynamically mapped in space for perception and action, but they also hold intrinsic spatial information that contributes to somatosensory spatial processing.