The standard posture of the hand is ready to grasp

The perception of limb position in space relies on sensory signals and motor commands. Another potential source of input is standard representations of body posture, which may bias perceived limb position towards more common positions. We recently found that tactile stimuli are processed more efficiently when they are delivered to a thumb in a relative low or to an index finger in a relative high position, supporting the existence of a standard posture of those two fingers. However they may have specific features because of their special roles in development. We investigated the existence of a standard posture of the entire hand testing: a) if similar associations are detectable for different finger contrasts; b) if associations are properties of each specific digit ; c) the role of intermanual competition, and d) the neurophysiological features of standard posture by means of somatosensory evokedpotentials (SEP). Results showed that the thumb is associated with low position, while the other fingers are associated with upper locations configuring the hand as a plier in a position ready to grasp. SEP analysis showed that preferential postures impact the P50 a component typically associated with the activity of primary somatosensory cortex.