The Brain Area That Tracks Your Limbs in Space
Author: University College London
Published: 16 Jul 2010 - Updated: 16 Jun 2026
Publication Details: Peer-Reviewed, Research, Study, Analysis
Contents: Synopsis - Definition - Introduction - Main - Insights, Updates - Related Publications
Synopsis: This research, published in the journal Current Biology, reports that scientists from University College London and partner institutions in Barcelona pinpointed the posterior parietal cortex as the brain area that builds a constantly updated map of where our limbs are in space. The findings are authoritative because they come from a controlled experiment using magnetic brain stimulation and were funded and peer-published through established scientific channels, and they are useful because they show how the brain merges touch with our internal sense of body position to guide movement, even with the eyes closed. The work is of particular interest to people in the disability community, parents, and clinicians, since it may help explain the coordination difficulties seen in children with developmental coordination disorder, who can struggle to sense where their limbs are.*
At a Glance
- 1 - Volunteers rested a forearm in an adjustable sling and judged whether a tap on the arm landed above or below a tap on the face, a task that only works by combining skin sensation with limb position.
- 2 - A brief magnetic pulse delivered to the right-hemisphere posterior parietal cortex, timed between the two taps, clearly disrupted those spatial judgments.
- 3 - The same stimulation had no effect when participants judged arm position alone or touch location alone, isolating this region as the place where the two signals are merged.
- Topic Definition: Proprioception
Proprioception is the body's internal sense of where its parts are positioned and how they are moving, without needing to look at them. It draws on signals from receptors in the muscles, tendons, and joints, which the brain combines with touch and other information to build a continuously updated map of the body in space. This is what lets you know the posture of your arms and legs with your eyes closed, climb stairs without watching your feet, or bring a fork to your mouth in the dark. According to the research described here, a region called the posterior parietal cortex plays a central role in merging touch with limb position to create that body map, and when this sense is weak - as it can be in some developmental coordination conditions - everyday movements that most people perform without thinking become noticeably harder.
Introduction
When a mosquito lands on your hand, you can rapidly and effortlessly make a movement of the other hand to brush it away, even in darkness. But performing this seemingly simple action involves a surprisingly complex coordination of different types of sensory information in order for your brain to construct a constantly updated 'map' of the body in space.
Now, scientists from UCL (University College London) and Barcelona (Pompeu Fabra University, ICREA and University of Barcelona) have identified an area of the human brain called the parietal cortex that constructs this body model from the combination of tactile information from your skin (for example, where the mosquito is on your hand) with "proprioceptive" information about the position of your hand relative to your body.
Main Content
In an experiment they found that impairing the parietal cortex, using a brief pulse of magnetic stimulation, significantly impaired volunteers' judgments about the spatial relationship between their face and arms, but not their perception of touch or location alone. The research is published in the journal Current Biology, and was funded by the Biotechnology and Biological Sciences Research Council (BBSRC).
Professor Patrick Haggard, UCL Institute of Cognitive Neuroscience, who led the UCL team, said "Our brain constantly keeps track of the movements of the limbs, so that we always know the posture of our body, even with our eyes closed. Our results show, for the first time, how the brain updates this 'body space'.
"Our findings may be particularly relevant to children with developmental coordination disorder: these children have difficulty in coordinating their movements, but recent evidence suggests that one underlying problem is their poor sense of where their limbs are in space. Our result identifies the specific part of the parietal cortex needed to construct this map of body space."
In the experiment volunteers' forearms were placed in a sling which could be raised and lowered. Researchers then applied a brief tap at one of many locations on the forearm of volunteers, shortly followed by a brief tap at one of many locations on the face. Participants were asked to judge if the location of the arm tap was above or below the face tap, a judgment that could only be done by combining information about the tap location on the skin, and about the position of the arm relative to the body.
Researchers then disrupted the activity of the posterior parietal cortex (PPC) in the right hemisphere of the brain by delivering a brief pulse of magnetic stimulation after the arm tap and before the face tap. The stimulation was delivered through a coil placed on the scalp just over the location of the posterior parietal cortex indicated on a brain scan taken of each participant.
The stimulation significantly impaired volunteers' judgments about the spatial relation between the arm tap and the face tap. Crucially, when the volunteers just judged arm position alone, or touch location alone, the same stimulation had no effect. The scientists concluded that the posterior parietal cortex is the key brain area that combines touch and limb position, to produce a map of where the tap is in egocentric space.
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Insights, Analysis, and Developments
Editorial Note: It is easy to take for granted that we can swat away a mosquito in the dark or touch a finger to our nose with our eyes shut, yet this study shows just how much quiet computation underpins that ease, and by tracing it to a single, identifiable patch of the parietal cortex, the researchers have not only mapped a piece of how the body knows itself but also opened a practical avenue toward understanding and one day helping children whose sense of their own limbs does not come so naturally.*Attribution/Source(s): This peer reviewed publication was selected for publishing by the editors of Disabled World (DW) due to its relevance to the disability community. Originally authored by University College London and published on 16 Jul 2010, this content may have been edited for style, clarity, or brevity.
* Editorial additions by Ian C. Langtree.