Peripersonal space boundaries around the lower limbs.

Area of Science:

• Neuroscience
• Human Sensory Perception
• Multisensory Integration

Background:

• Bi- and tri-modal neurons in primates integrate tactile and near-body stimuli.
• Peripersonal space (PPS) is a multisensory integration zone extending around the body.
• Previous research primarily focused on upper body PPS, leaving lower limb PPS understudied.

Purpose of the Study:

• To delineate the spatial boundary of peripersonal space (PPS) around the lower limbs in humans.
• To investigate how visual stimuli approaching or receding from the feet influence tactile processing.
• To understand multisensory integration mechanisms in the lower extremities.

Main Methods:

• A multisensory interaction task involving tactile vibration on the toes and a visual stimulus.
• Experiment 1: Visual stimulus approaching the feet; Experiment 2: Visual stimulus receding from the feet.
• Measuring reaction times to tactile stimuli under different visual stimulus conditions.

Main Results:

• Participants responded significantly faster to tactile stimuli when a visual stimulus approached within approximately 73 cm of the feet.
• This facilitatory effect was observed only for approaching visual stimuli, not receding ones.
• This study provides the first quantitative measure of PPS boundary for the lower limbs.

Conclusions:

• The findings define a peripersonal space boundary around the lower limbs, approximately 73 cm.
• Lower limb PPS shows sensitivity to approaching visual stimuli, suggesting a protective function.
• This research contributes to understanding multisensory integration and spatial representation in the lower body.