40 lines
5.3 KiB
Markdown
40 lines
5.3 KiB
Markdown
---
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title: "Body schema"
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chunk: 3/3
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source: "https://en.wikipedia.org/wiki/Body_schema"
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category: "reference"
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tags: "science, encyclopedia"
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date_saved: "2026-05-05T15:12:55.941468+00:00"
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instance: "kb-cron"
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---
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=== Deafferentation ===
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The most direct of related disorders, deafferentation occurs due to the loss of sensory input from afferent sensory nerves, without affecting motor neurons. The most famous case of this disorder is "IW", who lost all sensory input from below the neck, resulting in temporary paralysis. He was forced to learn to control his movement all over again using only his conscious body image and visual feedback. As a result, when constant visual input is lost during an activity, such as walking, it becomes impossible for him to complete the task, which may result in falling, or simply stopping. IW requires constant attention to tasks to be able to complete them accurately, demonstrating how automatic and subconscious the process of integrating touch and proprioception into the body schema actually is.
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=== Autotopagnosia ===
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Autotopagnosia typically occurs after left parietal lesions. Patients with this disorder make errors which result from confusion between adjacent body parts. For example, a patient may point to their knee when asked to point to their hip. Because the disorder involves the body schema, localization errors may be made both on the patient’s own body and that of others. The spatial unity of the body within the body schema has been damaged such that it has incorrectly been segmented in relation to its other modular parts.
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=== Phantom limb ===
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Phantom limbs are a phenomenon which occurs following amputation of a limb from an individual. In 90–98% of cases, amputees report feeling all or part of the limb or body part still there, taking up space. The amputee may perceive a limb under full control, or paralyzed. A common side effect of phantom limbs is phantom limb pain. The neurophysiological mechanisms by which phantom limbs occur is still under debate. A common theory posits that the afferent neurons, since deafferented due to amputation, typically remap to adjacent cortical regions within the brain. This can cause amputees to report feeling their missing limb being touched when a seemingly unrelated part of the body is stimulated (such as if the face is touched, but the amputee also feels their missing arm being stroked in a specific location). Another facet of phantom limbs is that the efferent copy (motor feedback) responsible for reporting on position to the body schema does not attenuate quickly. Thus the missing body part may be attributed by the amputee to still be in a fixed or movable position.
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=== Others ===
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Asomatognosia, somatoparaphrenia, anosognosia, anosodiaphoria, allochiria and hemispatial neglect all involve (or in some cases involve) aspects of impaired body schema. Hemispatial neglect is not uncommon because strokes sometimes cause it.
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== Tool use ==
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Not only is it necessary for the body schema to be able to integrate and form a three-dimensional representation of the body, but it also plays an important role in tool use. Studies recording neuronal activity in the intraparietal cortex in macaques have shown that, with training, the macaque body schema updates to include tools, such as those used for reaching, into the body schema. In humans, body schema plays an important role in both simple and complex tool use, far beyond that of macaques. Extensive training is also not necessary for this integration.
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The mechanisms by which tools are integrated into the body schema are not fully understood. However, studies with long-term training have shown interesting phenomena. When wielding tools in both hands in a crossed posture, behavioral effects reverse in a similar way to when only hands are crossed. Thus, sensory stimuli are delivered the same way be it to the hands directly or indirectly via the tools. These studies suggest the mind incorporates the tools into the same or similar areas as it does the adjacent hands. Recent research into the short term plasticity of the body schema used individuals without any prior training with tools. These results, derived from the relation between afterimages and body schema, show that tools are incorporated into the body schema within seconds, regardless of length of training, though the results do not extend to other species besides humans.
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== Confusion with body image ==
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Historically, body schema and body image were generally lumped together, used interchangeably, or ill-defined. In science and elsewhere, the two terms are still commonly misattributed or confused. Efforts have been made to distinguish the two and define them in clear and differentiable ways. A body image consists of perceptions, attitudes, and beliefs concerning one's body. In contrast, body schema consists of sensory-motor capacities that control movement and posture.
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Body image may involve a person’s conscious perception of their own physical appearance. It is how individuals see themselves when picturing themselves in their mind, or when perceiving themselves in a mirror. Body image differs from body schema as perception differs from movement. Both may be involved in action, especially when learning new movements.
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== See also ==
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Body image (medicine)
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Multisensory integration
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Body transfer illusion
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Peripheral neuropathy
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Schema (psychology)
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Attention schema theory
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== References == |