Surrounding your body is an invisible, flexible field that your brain constantly monitors. This area, known as peripersonal space (PPS), represents the space within your immediate reach. It is the zone where you can interact with objects, and where objects can interact with you. This differs from the more familiar concept of “personal space.” While personal space is a psychological construct dictated by social and cultural norms, peripersonal space is a neurological one generated by the brain to manage physical interactions and for defense.
The Brain’s Multisensory Map
The brain constructs its map of peripersonal space through multisensory integration, fusing information from different senses. Specialized neurons within the parietal and premotor cortices are responsible for this task. These cells respond to stimuli from sight, touch, and sound to create a unified awareness of objects near the body.
This network operates in a body-part-centered frame of reference. For example, neurons in brain regions like the ventral intraparietal area (VIP) respond to both a tactile sensation on the hand and a visual stimulus seen near that same hand. These bimodal neurons anchor a visual receptive field to a tactile one, meaning the brain’s map of near-hand space moves as the hand moves. This mechanism allows the brain to track objects relative to the body in real-time, regardless of gaze direction.
Different neurons show preferences for different body parts. Research in monkeys has identified distinct representations for the hands, face, and trunk, which are heavily interconnected. Neurons in the putamen also contribute to this network, showing similar visuo-tactile responses. The collective activity of this parieto-frontal network generates the coherent, operational map of the space immediately surrounding us.
The Malleable Nature of Peripersonal Space
The boundary of peripersonal space is not fixed; it is dynamic and can be reshaped by our actions, tools, and social environment. The brain continually updates this representation based on our capacity to interact with the world.
A classic example of this malleability is tool use. When you use a rake to reach a distant object, your brain extends its representation of peripersonal space to include the tool. Neurons that previously only responded to stimuli near your hand will begin to respond to stimuli near the tip of the rake. This functional extension incorporates the tool into the body schema, recalibrating the boundary of what the brain considers “near” space. This remapping is temporary and depends on the active, intentional use of the tool.
Social context also influences this neural bubble. The presence of another person can cause PPS to shrink or expand. Engaging in a cooperative task with a trusted individual can lead to a merging of spaces. In contrast, being approached by a stranger may cause your PPS to contract as a protective measure.
Protective and Interactive Functions
Peripersonal space serves two primary functions. The first is a defensive role, acting as an early-warning system that helps us avoid collisions and react to potential threats. Neurons in the PPS network activate when an object approaches, preparing the body for a defensive response before contact is even made. Electrical stimulation of these brain regions in monkeys has been shown to trigger defensive movements like withdrawing an arm.
The second function is to facilitate goal-directed action. The PPS map allows you to accurately reach for a cup, catch a ball, or manipulate objects. By encoding the location of objects in a body-centered reference frame, the brain can generate the appropriate motor commands for interaction. This links the perception of objects in near-space directly to the motor system, ensuring our movements are well-coordinated.
Individual and Situational Differences
The size and characteristics of peripersonal space vary between people and can be altered by specific conditions or expertise. For some, this neural representation can be a source of distress, while for others, it can be a finely tuned asset.
An altered PPS representation is linked to certain psychological conditions. For example, individuals with high claustrophobic fear tend to have a larger peripersonal space. This may contribute to feeling intruded upon in enclosed environments. Trait anxiety also correlates with an expanded PPS, suggesting a heightened state of defensive monitoring.
Expertise can also refine the boundaries of peripersonal space. Skilled athletes may develop a highly tuned representation of the space relevant to their sport. For example, the defensive peripersonal space of professional boxers is shaped by their training, modifying their perception of threat. This specialized experience molds the neural bubble to optimize performance.