32 lines
5.6 KiB
Markdown
32 lines
5.6 KiB
Markdown
---
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title: "Body schema"
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chunk: 2/3
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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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=== Updated with movement ===
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A working body schema must be able to interactively track the movements and positions of body parts in space. Neurons in the premotor cortex may contribute to this function. A class of neuron in the premotor cortex is multisensory. Each of these multisensory neurons responds to tactile stimuli and also to visual stimuli. The neuron has a tactile receptive field (responsive region on the body surface) typically on the face, arms, or hands. The same neuron also responds to visual stimuli in the space near the tactile receptive field. For example, if a neuron's tactile receptive field covers the arm, the same neuron will respond to visual stimuli in the space near the arm. As shown by Graziano and colleagues, the visual receptive field will update with arm movement, translating through space as the arm moves. Similar body-part-centered neuronal receptive fields relate to the face. These neurons apparently monitor the location of body parts and the location of nearby objects with respect to body parts. Similar neuronal properties may also be important for the ability to incorporate external objects into the body schema, such as in tool use.
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== Extended body schema ==
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The idea of the extended body schema is that, aside from the proprioceptive, visual, and sensory components that contribute to making a mental conception of one's body, the same processes that contribute to a body schema are also able to incorporate external objects into the mental conception of one's body. Part philosophical and part neuroscience, this concept builds upon the ideas of plasticity and adaptation to attempt to answer the question of where the body schema ends.
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There is debate as to whether this concept truly exists, with one side arguing that the body schema does not extend past the body and the other side believing otherwise.
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=== Supporting arguments ===
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The perspective shared by those who agree with the theory of the extended body schema follow reasoning in line with such that supports theories on tool use.
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In some studies, attempts at understanding tool assimilation are used to argue for the existence of the extended body schema. In an experiment involving the use and interaction with wool objects, subjects were tested on their ability to perceive afterimages of wool objects in varying contexts. Subjects accustomed their eyes to a dark room and then were shown a brief (1 millisecond) flash of light, intending to produce an afterimage effect of their arms which they held out in front of them during the experiment. Moving an arm afterwards would make the afterimage "fade" or disappear as it moved, thus indicating that the feature (the arm) was being tracked and integrated into the person's body schema. To test integration of the meaningless wool objects, subjects experienced four different contexts.
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Subjects held the wool objects in each hand and one hand (the active hand) would move, still holding the object (the active object).
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Using the active hand, the active wool object would be dropped once an afterimage was perceived.
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Using the active hand, one would grab the active wool object once an afterimage was perceived.
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The subjects were to hold onto a mechanical device which held the wool object. Once an afterimage was perceived, a subject's active hand would cause the mechanical device to drop the wool object.
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In all situations but the fourth, the subjects experienced the same "fading" effect as they did with their arm alone. This would thus indicate that the wool objects had been integrated into their body schema and contributes support towards the idea of the body's using proprioceptive and visual elements to create an extended body schema. The mechanical device acted as an intermediate between the subject and the active object, and the subjects' failure to detect an afterimage in that context indicates that this concept of extension is limited to being sensitive to only what the body is directly in contact with.
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=== Dissenting arguments ===
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The alternate perspective is that the body is the limit of any sort of body schema.
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An example of this division is found in a study and discussion on personal and extrapersonal attention, where personal relates to the body's sense of itself (the body schema) and extrapersonal relates to all external of such. Some research supports the claim that these two categories are purely distinct and do not intermingle, contrary to what the extended body schema theory describes. Evidence for such is primarily found in subjects with unilateral neglect, such as in the case of E.D.S., who was a middle-aged man with right hemisphere brain damage. When he was tested for hemispatial neglect using traditional measures such as sentence reading and cancellation tests, E.D.S. showed few signs and upon later examination showed no signs whatsoever, leading doctors to believe he was normal. However, he constantly had issues with physical therapy because he would claim to not be able to see his left leg; upon further examination, E.D.S. was known to have a particular type of hemispatial neglect that only affected the perception of his body. The motor function of the left side of his body was negatively affected though not totally compromised, yet when attempting tasks such as shaving, he would invariably not shave the left side of his face. This led some researchers to believe that there is a distinction between personal and extrapersonal neglect, which would thus reflect a similar distinction with body schema itself.
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== Associated disorders == |