Body schema

Body schema is a concept used in several disciplines, including psychology, neuroscience, philosophy, sports medicine, and robotics. The neurologist Sir Henry Head originally defined it as a postural model of the body that actively organizes and modifies 'the impressions produced by incoming sensory impulses in such a way that the final sensation of [body] position, or of locality, rises into consciousness charged with a relation to something that has happened before'.[1] As a postural model that keeps track of limb position, it plays an important role in control of action. It involves aspects of both central (brain processes) and peripheral (sensory, proprioceptive) systems. Thus, a body schema can be considered the collection of processes that registers the posture of one's body parts in space. The schema is updated during body movement. This is typically a non-conscious process, and is used primarily for spatial organization of action. It is therefore a pragmatic representation of the body’s spatial properties, which includes the length of limbs and limb segments, their arrangement, the configuration of the segments in space, and the shape of the body surface.[2][3][4][5] Body schema also plays an important role in the integration and use of tools by humans.[6][7][8][9]

A clear differentiation of body schema from body image has developed gradually.

History

Henry Head, an English neurologist who conducted pioneering work into the somatosensory system and sensory nerves, together with British neurologist Gordon Morgan Holmes, first described the concept in 1911.[10] The concept was first termed "postural schema" to describe the disordered spatial representation of patients following damage to the parietal lobe of the brain. Head and Holmes discussed two schemas (or schemata): one body schema for the registration of posture or movement and another body schema for the localization of stimulated locations on the body surface. "Body schema" became the term used for the "organized models of ourselves".[10] The term and definition first suggested by Head and Holmes has endured nearly a century of research with clarifications as more has become known about neuroscience and the brain.[2]

Henry Head
A portrait of Henry Head, the pioneering English neurologist who first defined and used the term "body schema".

Properties

Neuroscientists Patrick Haggard and Daniel Wolpert have identified seven fundamental properties of the body schema. It is spatially coded, modular, adaptable, supramodal, coherent, interpersonal, and updated with movement.[2]

Spatial encoding

The body schema represents both position and configuration of the body as a 3-dimensional object in space. A combination of sensory information, primarily tactile and visual, contributes to the representation of the limbs in space.[2][4] This integration allows for stimuli to be localized in external space with respect to the body.[6] An example by Haggard and Wolpert shows the combination of tactile sensation of the hand with information about the joint angles of the arm, which allow for rapid movements of said arm to swat a fly.[2]

Modular

The body schema is not represented wholly in a single region of the brain.[2] Recent fMRI (functional Magnetic Resonance Imaging) studies confirm earlier results. For example, the schema for feet and hands are coded by different regions of the brain, while the fingers are represented by a separate part entirely.[11]

Adaptable

Plastic changes to the body schema are active and continuous. For example, gradual changes to the body schema must occur over the lifetime of an individual as he or she grows and absolute and relative sizes of body parts change over his or her life span.[2] The development of the body schema has also been shown to occur in young children. One study showed that with these children (9-, 14-, and 19-month-olds), older children handled spoons so as to optimally and comfortably grip them for use, whereas younger children tended to reach with their dominant hand, regardless of the orientation of the spoon and eventual ease of use.[12] Short-term plasticity has been shown with the integration of tools into the body schema.[7][9] The rubber hand illusion has also shown the rapid reorganization of the body schema on the timescale of seconds, showing the high level of plasticity and speed with which the body schema reorganizes.[13] In the Illusion, participants view a dummy hand being stroked with a paintbrush, while their own hand is stroked identically. Participants may feel that the touches on their hand are coming from the dummy hand, and even that the dummy hand is, in some way, their own hand.

Supramodal

By its nature, body schema integrates proprioceptive, (the sense of the relative position of neighbouring parts of one's body), and tactile information to maintain a three-dimensional body representation. However, other sensory information, particularly visual, can be in the same representation of the body. This simultaneous participation means there are combined representations within the body schema, which suggests the involvement of a process to translate primary information (e.g. visual, tactile, etc.) into a single sensory modality or an abstract, amodal form.[2]

Coherent

The body schema, to function properly, must be able to maintain coherent organization continuously.[2] To do so, it must be able to resolve any differences between sensory inputs. Resolving these inter-sensory inconsistencies can result in interesting sensations, such as those experienced during the Rubber Hand Illusion.[13]

Interpersonal

It is thought that an individual's body schema is used to represent both one's own body and the bodies of others. Mirror neurons are thought to play a role in the interpersonal characteristics of body schema. Interpersonal projection of one's body schema plays an important role in successfully imitating motions such as hand gestures, especially while maintaining the handedness and location of the gesture, but not necessarily copying the exact motion itself.[11]

Updated with movement

A working body schema must be able to interactively track the movements and positions of body parts in space.[2] 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.[14][15] 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.

Extended Body Schema

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. [16] 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.

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.[17][18]

Supporting Arguments

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.

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.

  1. Subjects held the wool objects in each hand and one hand (the active hand) would move, still holding the object (the active object).
  2. Using the active hand, the active wool object would be dropped once an afterimage was perceived.
  3. Using the active hand, one would grab the active wool object once an afterimage was perceived.
  4. 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.

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.[19]

Dissenting Arguments

The alternate perspective is that the body is the limit of any sort of body schema.

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.[20]

Associated disorders

Deafferentation

The most direct of related disorders, deafferentation occurs when sensory input from the body is reduced or absent, without affecting efferent, or 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.[21]

Autotopagnosia

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.[22]

Phantom limb

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.[23] 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.[24] 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.[2]

Tool use

Rhesus Macaques - cropped
Rhesus macaques are able to be trained to use rudimentary tools, but have never been proven to use tools spontaneously in the wild.[9]

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.[9] 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.[9] In humans, body schema plays an important role in both simple and complex tool use, far beyond that of macaques.[6][8][9] Extensive training is also not necessary for this integration.[11]

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.[9] 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.[6]

Confusion with body image

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.[25] 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.

Body image may involve a person’s conscious perception of his or her 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.

See also

References

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  9. ^ a b c d e f g Maravita, A.; A. Iriki (2004). "Tools for the body (schema)". Trends in Cognitive Sciences. 8 (2): 79–86. doi:10.1016/j.tics.2003.12.008. PMID 15588812.
  10. ^ a b Head, H.; G. Holmes (1911). "Sensory disturbances from cerebral lesions". Brain. 34 (2–3): 102. doi:10.1093/brain/34.2-3.102.
  11. ^ a b c Chaminade, T.; A. Meltzoff & J. Decety (2005). "An fMRI study of imitation: action representation and body schema". Neuropsychologia. 43 (1): 115–127. doi:10.1016/j.neuropsychologia.2004.04.026. PMC 3648209. PMID 15488911.
  12. ^ Johnson, S. (2000). "Thinking ahead: the case for motor imagery in prospective judgements of prehension". Cognition. 74 (1): 33–70. doi:10.1016/S0010-0277(99)00063-3. PMID 10594309.
  13. ^ a b Lewis, E.; D. M. Lloyd (2010). "Embodied experience: A first-person investigation of the rubber hand illusion". Phenomenology and the Cognitive Sciences. 9 (3): 317–339. doi:10.1007/s11097-010-9154-2.
  14. ^ Graziano, M.S.A.; Hu, X.T. & Gross, C.G (1997). "Coding the locations of objects in the dark". Science. 277 (5323): 239–241. doi:10.1126/science.277.5323.239. PMID 9211852.
  15. ^ Graziano, M.S.A.; Yap, G.S. & Gross, C.G (1994). "Coding of visual space by premotor neurons". Science. 266: 1054–1057. doi:10.1126/science.7973661. PMID 7973661.
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  17. ^ Reed, C. L., & Farah, M. J. (1995). The psychological reality of the body schema: A test with normal participants. Journal of Experimental Psychology: Human Perception and Performance, 21(2), 334-343.
  18. ^ Yamamoto and Kitazawa. 2011. Reversal of subjective temporal order due to arm crossing. Nature Neuroscience 4: 759-765
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  20. ^ Guariglia and Antonucci. 1992. Personal and extrapersonal space: A case of neglect dissociation. Neuropsychologia, 30:1001-1009
  21. ^ Gallagher, S.; J. Cole (1995). "Body schema and body image in a deafferented subject". Journal of Mind and Behavior. 16 (4): 369–390. Retrieved 16 June 2012.
  22. ^ Sirigu, A.; et al. (1991). "Multiple representations contribute to body knowledge processing: Evidence from a case of autotopagnosia". Brain. 114 (1): 629. doi:10.1093/brain/114.1.629.
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  24. ^ Giummarra, M.; et al. (2007). "Central mechanisms in phantom limb perception: the past, present and future". Brain Research Reviews. 54 (1): 219–232. doi:10.1016/j.brainresrev.2007.01.009. PMID 17500095.
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Andrew N. Meltzoff

Andrew N. Meltzoff (born February 9, 1950) is an American psychologist and an internationally recognized expert on infant and child development. His discoveries about infant imitation greatly advanced the scientific understanding of early cognition, personality and brain development.

Anosodiaphoria

Anosodiaphoria is a condition in which a person who has a brain injury seems indifferent to the existence of their handicap. Anosodiaphoria is specifically used in association with indifference to paralysis. It is a somatosensory agnosia, or a sign of neglect syndrome. It might be specifically associated with defective functioning of the frontal lobe of the right hemisphere.Joseph Babinski first used the term anosodiaphoria in 1914 to describe a disorder of the body schema in which patients verbally acknowledge a clinical problem (such as hemiparesis) but fail to be concerned about it. Anosodiaphoria follows a stage of anosognosia, in which there may be verbal, explicit denial of the illness, and after several days to weeks, develop the lack of emotional response. Indifference is different from denial because it implies a lack of caring on the part of the patient whom otherwise acknowledges his or her deficit.

Artificial consciousness

Artificial consciousness (AC), also known as machine consciousness (MC) or synthetic consciousness (Gamez 2008; Reggia 2013), is a field related to artificial intelligence and cognitive robotics. The aim of the theory of artificial consciousness is to "Define that which would have to be synthesized were consciousness to be found in an engineered artifact" (Aleksander 1995).

Neuroscience hypothesizes that consciousness is generated by the interoperation of various parts of the brain, called the neural correlates of consciousness or NCC, though there are challenges to that perspective. Proponents of AC believe it is possible to construct systems (e.g., computer systems) that can emulate this NCC interoperation.Artificial consciousness concepts are also pondered in the philosophy of artificial intelligence through questions about mind, consciousness, and mental states.

Attention schema theory

The attention schema theory (AST) of consciousness (or subjective awareness) is an evolutionary and neuropsychological scientific theory of consciousness which was developed by neuroscientist Michael Graziano at Princeton University. It proposes that brains construct subjective awareness as a schematic model of the process of attention. The theory is a materialist theory of consciousness. It shares similarities with the illusionist ideas of philosophers like Daniel Dennett, Patricia Churchland, and Keith Frankish.One goal of developing the AST is to allow people to eventually construct artificial, conscious machines. AST seeks to explain how an information-processing machine could act the way people do, insisting it has consciousness, describing consciousness in the ways that we do, and attributing similar properties to others. AST is a theory of how a machine insists it is more than a machine, even though it is not.

Autotopagnosia

Autotopagnosia from the Greek a and gnosis, meaning "without knowledge", topos meaning "place", and auto meaning "oneself", autotopagnosia virtually translates to the "lack of knowledge about one's own space," and is clinically described as such.Autotopagnosia is a form of agnosia, characterized by an inability to localize and orient different parts of the body. The psychoneurological disorder has also been referred to as "body-image agnosia" or "somatotopagnosia." Somatotopagnosia has been argued to be a better suited term to describe the condition. While autotopagnosia emphasizes the deficiencies in localizing only one's own body parts and orientation, somatotopagnosia also considers the inability to orient and recognize the body parts of others or representations of the body (e.g., manikins, diagrams).Typically, the cause of autotopagnosia is a lesion found in the parietal lobe of the left hemisphere of the brain. However, it as also been noted that patients with generalized brain damage present with similar symptoms of autotopagnosia.As a concept, autotopagnosia has been criticized as nonspecific; some claim that this is a manifestation of a greater symptomatic complex of anomia, marked by an inability to name things in general—not just parts of the human body.

Body image

Body image is a person's perception of the aesthetics or sexual attractiveness of their own body. It involves how a person sees themselves, compared to the standards that have been set by society. The Austrian neurologist and psychoanalyst Paul Schilder coined the phrase body-image in his book The Image and Appearance of the Human Body (1935).Human society has at all times placed great value on beauty of the human body, but a person's perception of their own body may not correspond to society's standards.

The concept of body image is used in a number of disciplines, including psychology, medicine, psychiatry, psychoanalysis, philosophy, cultural and feminist studies; the media also often uses the term . Across these disciplines and media there is no consensus definition, but body image may be expressed as how people view themselves in the mirror, or in their minds. It incorporates the memories, experiences, assumptions, and comparisons of one's own appearance, and overall attitudes towards one's height, shape, and weight. An individual's impression of their body is also assumed to be a product of ideals cultivated by various social and cultural ideals.

The issues surrounding body image can be examined through body negativity and through body positivity. Negative body image consists of a disoriented view of one's shape; whereby one may often feel self-conscious or feel ashamed, and assume others are more attractive. Aside from having low self-esteem, sufferers typically fixate on altering their physical appearances. Long-term behavior could thus potentially lead to higher risks of eating disorders, isolation, and mental illnesses. Having a negative body-image may lead to a more serious mental illness such as body dysmorphic disorder: "Body dysmorphic disorder (BDD), occasionally still called dysmorphophobia, is a mental disorder characterized by the obsessive idea that some aspect of one's own body part or appearance is severely flawed and warrants exceptional measures to hide or fix their dysmorphic part on their person..."

Positive body image on the other hand, is described as a clear true perception of one's figure. In addition to celebrating and appreciating the body, it also requires an understanding that an individual's appearance does not reflect their character or self-worth.A 2007 report by the American Psychological Association found that a culture-wide sexualization of girls and women was contributing to increased female anxiety associated with body image. An Australian government Senate Standing Committee report on the sexualization of children in the media reported similar findings associated with body image. However, other scholars have expressed concern that these claims are not based on solid data.Body image can have a wide range of psychological effects and physical effects. Throughout history, it has been extremely difficult for people to live up to the standards of society and what they believe the ideal body is. Many factors contribute to a person's body image; some of these include: family dynamics, mental illness, biological predispositions and environmental causes for obesity or malnutrition, and cultural expectations (e.g., media and politics). People who are either underweight or overweight can have poor body image. However, when people are constantly told and shown the cosmetic appeal of weight loss and are warned about the risks of obesity, those who are normal or overweight on the BMI scale have higher risks of poor body image. This is something that can lead to a change in a person's body image. Often, people who have a low body image will try to alter their bodies in some way, such as by dieting or by undergoing cosmetic surgery. "We expected women would feel worse about their bodies after seeing ultra-thin models, compared to no models if they have internalized the thin ideal, thus replicating previous findings."

Body image (medicine)

Body image is a medical term, often used in the context of describing a patient's cognitive perception of their own body. The medical concept began with the work of the Austrian neuropsychiatrist and psychoanalyst Paul Schilder, described in his book The Image and Appearance of the Human Body first published in 1935.

Concentrative movement therapy

Concentrative movement therapy (CMT) is a psychotherapeutic method for group and individual therapy which is based on thought models stemming from psychodynamic psychotherapy and depth psychology. Taking as its point of departure the theory that perception is composed of sensation and experience (Viktor von Weizsäcker), CMT is interested in the conscious perception of the body in the "here and now" against the background of the individual life and learning story.

Cutaneous rabbit illusion

The cutaneous rabbit illusion (also known as cutaneous saltation and sometimes the cutaneous rabbit effect or CRE) is a tactile illusion evoked by tapping two or more separate regions of the skin in rapid succession. The illusion is most readily evoked on regions of the body surface that have relatively poor spatial acuity, such as the forearm. A rapid sequence of taps delivered first near the wrist and then near the elbow creates the sensation of sequential taps hopping up the arm from the wrist towards the elbow, although no physical stimulus was applied between the two actual stimulus locations. Similarly, stimuli delivered first near the elbow then near the wrist evoke the illusory perception of taps hopping from elbow towards wrist. The illusion was discovered by Frank Geldard and Carl Sherrick of Princeton University, in the early 1970s, and further characterized by Geldard (1982) and in many subsequent studies. Geldard and Sherrick likened the perception to that of a rabbit hopping along the skin, giving the phenomenon its name. While the rabbit illusion has been most extensively studied in the tactile domain, analogous sensory saltation illusions have been observed in audition and vision. The word "saltation" refers to the leaping or jumping nature of the percept.

Depersonalization disorder

Depersonalization disorder (DPD), also known as depersonalization/derealization disorder (DPDR), is a mental disorder in which the person has persistent or recurrent feelings of depersonalization or derealization. Depersonalization is described as feeling disconnected or detached from one's self. Individuals experiencing depersonalization may report feeling as if they are an outside observer of their own thoughts or body, and often report feeling a loss of control over their thoughts or actions. In some cases, individuals may be unable to accept their reflection as their own, or they may have out-of-body experiences. Derealization is described as detachment from one's surroundings. Individuals experiencing derealization may report perceiving the world around them as foggy, dreamlike/surreal, or visually distorted. In addition to these depersonalization-derealization disorder symptoms, the inner turmoil created by the disorder can result in depression, self-harm, low self-esteem, panic attacks, and phobias. It can also cause a variety of physical symptoms, including chest pain, blurry vision, visual snow, nausea, and the sensation of pins and needles in one's arms or legs.

Depersonalization-derealization disorder is thought to be caused largely by interpersonal trauma such as childhood abuse. Triggers may include significant stress, panic attacks, and drug use. It is unclear whether genetics plays a role; however, there are many neurochemical and hormonal changes in individuals with depersonalization disorder. The disorder is typically associated with cognitive disruptions in early perceptual and attentional processes.Diagnostic criteria for depersonalization-derealization disorder include, among other symptoms, persistent or recurrent feelings of detachment from one's mental or bodily processes or from one's surroundings. A diagnosis is made when the dissociation is persistent and interferes with the social and/or occupational functions of daily life. However, accurate descriptions of the symptoms are hard to provide due to the subjective nature of depersonalization/derealization and persons' ambiguous use of language when describing these episodes. In the DSM-5, it was combined with Derealization Disorder and renamed Depersonalization/Derealization Disorder (DDPD). In the DSM-5, it remains classified as a dissociative disorder, while the ICD-10 calls it depersonalization-derealization syndrome and classifies it as a neurotic disorder. Although the disorder is an alteration in the subjective experience of reality, it is not a form of psychosis, as the person is able to distinguish between their own internal experiences and the objective reality of the outside world. During episodic and continuous depersonalization, the person can distinguish between reality and fantasy. In other words, the grasp on reality remains stable at all times.While depersonalization-derealization disorder was once considered rare, lifetime experiences with it occur in about 1–2% of the general population. The chronic form of the disorder has a reported prevalence of 0.8 to 1.9%. While these numbers may seem small, depersonalization/derealization experiences have been reported by a majority of the general population, with varying degrees of intensity. While brief episodes of depersonalization or derealization can be common in the general population, the disorder is only diagnosed when these symptoms cause substantial distress or impair social, occupational, or other important areas of functioning.

Ideomotor apraxia

Ideomotor Apraxia, often IMA, is a neurological disorder characterized by the inability to correctly imitate hand gestures and voluntarily mime tool use, e.g. pretend to brush one's hair. The ability to spontaneously use tools, such as brushing one's hair in the morning without being instructed to do so, may remain intact, but is often lost. The general concept of apraxia and the classification of ideomotor apraxia were developed in Germany in the late 19th and early 20th centuries by the work of Hugo Liepmann, Adolph Kussmaul, Arnold Pick, Paul Flechsig, Hermann Munk, Carl Nothnagel, Theodor Meynert, and linguist Heymann Steinthal, among others. Ideomotor apraxia was classified as "ideo-kinetic apraxia" by Liepmann due to the apparent dissociation of the idea of the action with its execution. The classifications of the various subtypes are not well defined at present, however, owing to issues of diagnosis and pathophysiology. Ideomotor apraxia is hypothesized to result from a disruption of the system that relates stored tool use and gesture information with the state of the body to produce the proper motor output. This system is thought to be related to the areas of the brain most often seen to be damaged when ideomotor apraxia is present: the left parietal lobe and the premotor cortex. Little can be done at present to reverse the motor deficit seen in ideomotor apraxia, although the extent of dysfunction it induces is not entirely clear.

Mental image

A mental image or mental picture is the representation in a person's mind of the physical world outside that person. It is an experience that, on most occasions, significantly resembles the experience of perceiving some object, event, or scene, but occurs when the relevant object, event, or scene is not actually present to the senses. There are sometimes episodes, particularly on falling asleep (hypnagogic imagery) and waking up (hypnopompic), when the mental imagery, being of a rapid, phantasmagoric and involuntary character, defies perception, presenting a kaleidoscopic field, in which no distinct object can be discerned. Mental imagery can sometimes produce the same effects as would be produced by the behavior or experience imagined.The nature of these experiences, what makes them possible, and their function (if any) have long been subjects of research and controversy in philosophy, psychology, cognitive science, and, more recently, neuroscience. As contemporary researchers use the expression, mental images or imagery can comprise information from any source of sensory input; one may experience auditory images, olfactory images, and so forth. However, the majority of philosophical and scientific investigations of the topic focus upon visual mental imagery. It has sometimes been assumed that, like humans, some types of animals are capable of experiencing mental images. Due to the fundamentally introspective nature of the phenomenon, there is little to no evidence either for or against this view.

Philosophers such as George Berkeley and David Hume, and early experimental psychologists such as Wilhelm Wundt and William James, understood ideas in general to be mental images. Today it is very widely believed that much imagery functions as mental representations (or mental models), playing an important role in memory and thinking. William Brant (2013, p. 12) traces the scientific use of the phrase "mental images" back to John Tyndall's 1870 speech called the "Scientific Use of the Imagination". Some have gone so far as to suggest that images are best understood to be, by definition, a form of inner, mental or neural representation; in the case of hypnagogic and hypnapompic imagery, it is not representational at all. Others reject the view that the image experience may be identical with (or directly caused by) any such representation in the mind or the brain, but do not take account of the non-representational forms of imagery.

In 2010, IBM applied for a patent on a method to extract mental images of human faces from the human brain. It uses a feedback loop based on brain measurements of the fusiform face area in the brain that activates proportionate with degree of facial recognition. It was issued in 2015.

Phantom pain

Phantom pain sensations are described as perceptions that an individual experiences relating to a limb or an organ that is not physically part of the body. Limb loss is a result of either removal by amputation or congenital limb deficiency. However, phantom limb sensations can also occur following nerve avulsion or spinal cord injury.

Sensations are recorded most frequently following the amputation of an arm or a leg, but may also occur following the removal of a breast, teeth, or an internal organ. Phantom limb pain is the feeling of pain in an absent limb or a portion of a limb. The pain sensation varies from individual to individual.

Phantom limb sensation is any sensory phenomenon (except pain) which is felt at an absent limb or a portion of the limb. It has been known that at least 80% of amputees experience phantom sensations at some time of their lives. Some experience some level of this phantom pain and feeling in the missing limb for the rest of their lives.

The term "phantom limb" was first coined by American neurologist Silas Weir Mitchell in 1871. Mitchell described that "thousands of spirit limbs were haunting as many good soldiers, every now and then tormenting them". However, in 1551, French military surgeon Ambroise Paré recorded the first documentation of phantom limb pain when he reported that, "For the patients, long after the amputation is made, say that they still feel pain in the amputated part".

Proprioception

Proprioception ( PROH-pree-o-SEP-shən), is the sense of the relative position of one's own parts of the body and strength of effort being employed in movement. It is sometimes described as the "sixth sense".In humans, it is provided by proprioceptors in skeletal striated muscles (muscle spindles) and tendons (Golgi tendon organ) and the fibrous membrane in joint capsules. It is distinguished from exteroception, by which one perceives the outside world, and interoception, by which one perceives pain, hunger, etc., and the movement of internal organs.

The brain integrates information from proprioception and from the vestibular system into its overall sense of body position, movement, and acceleration. The word kinesthesia or kinæsthesia (kinesthetic sense) strictly means movement sense, but has been used inconsistently to refer either to proprioception alone or to the brain's integration of proprioceptive and vestibular inputs.

Proprioception has also been described in other animals such as vertebrates, and in some invertebrates such as arthropods. More recently proprioception has also been described in flowering land plants (angiosperms).

Schema

The word schema comes from the Greek word σχήμα (skhēma), which means shape, or more generally, plan. The plural is σχήματα (skhēmata). In English, both schemas and schemata are used as plural forms.

Schema may refer to:

SCHEMA (bioinformatics), an algorithm used in protein engineering

Schema (genetic algorithms), a set of programs or bit strings that have some genotypic similarity

Schema (Kant), in philosophy

Schema (psychology), a mental set or representation

Schema Records, a jazz record label in Milan, Italy

Schema.org, a web markup vocabulary

Axiom schema, in formal logic

Body schema, a neural representation of one's own bodily posture

Great Schema, a degree of Orthodox monasticism

Image schema, a recurring pattern of spatial sensory experience

Database schema

XML schema

Schema (fly), a genus of insects

Schema (psychology)

In psychology and cognitive science, a schema (plural schemata or schemas) describes a pattern of thought or behavior that organizes categories of information and the relationships among them. It can also be described as a mental structure of preconceived ideas, a framework representing some aspect of the world, or a system of organizing and perceiving new information. Schemata influence attention and the absorption of new knowledge: people are more likely to notice things that fit into their schema, while re-interpreting contradictions to the schema as exceptions or distorting them to fit. Schemata have a tendency to remain unchanged, even in the face of contradictory information. Schemata can help in understanding the world and the rapidly changing environment. People can organize new perceptions into schemata quickly as most situations do not require complex thought when using schema, since automatic thought is all that is required.People use schemata to organize current knowledge and provide a framework for future understanding. Examples of schemata include academic rubrics, social schemas, stereotypes, social roles, scripts, worldviews, and archetypes. In Piaget's theory of development, children construct a series of schemata, based on the interactions they experience, to help them understand the world.

Scotoma

A scotoma is an area of partial alteration in the field of vision consisting of a partially diminished or entirely degenerated visual acuity that is surrounded by a field of normal – or relatively well-preserved – vision.

Every normal mammal eye has a scotoma in its field of vision, usually termed its blind spot. This is a location with no photoreceptor cells, where the retinal ganglion cell axons that compose the optic nerve exit the retina. This location is called the optic disc. There is no direct conscious awareness of visual scotomas. They are simply regions of reduced information within the visual field. Rather than recognizing an incomplete image, patients with scotomas report that things "disappear" on them.The presence of the blind spot scotoma can be demonstrated subjectively by covering one eye, carefully holding fixation with the open eye, and placing an object (such as one's thumb) in the lateral and horizontal visual field, about 15 degrees from fixation (see the blind spot article). The size of the monocular scotoma is 5×7 degrees of visual angle.

A scotoma can be a symptom of damage to any part of the visual system, such as retinal damage from exposure to high-powered lasers, macular degeneration and brain damage.

The term scotoma is also used metaphorically in several fields. The common theme of all the figurative senses is of a gap not in visual function but in the mind's perception, cognition, or world view. The term is from Greek σκότος/skótos, darkness.

Self-image

Self-image is the mental picture, generally of a kind that is quite resistant to change, that depicts not only details that are potentially available to objective investigation by others (height, weight, hair color, etc.), but also items that have been learned by that person about themself, either from personal experiences or by internalizing the judgments of others.

Self-image may consist of four types:

Self-image resulting from how an individual sees oneself.

Self-image resulting from how others see the individual.

Self-image resulting from how the individual perceives others see them.

Self-image resulting from how the individual perceives the individual sees oneself.These four types may or may not be an accurate representation of the person. All, some or none of them may be true.

A more technical term for self-image that is commonly used by social and cognitive psychologists is self-schema. Like any schema, self-schemas store information and influence the way we think and remember. For example, research indicates that information which refers to the self is preferentially encoded and recalled in memory tests, a phenomenon known as "self-referential encoding". Self-schemas are also considered the traits people use to define themselves, they draw information about the self into a coherent scheme.

Self-schema

The self-schema refers to a long lasting and stable set of memories that summarize a person's beliefs, experiences and generalizations about the self, in specific behavioral domains. A person may have a self-schema based on any aspect of himself or herself as a person, including physical characteristics, personality traits and interests, as long as they consider that aspect of their self important to their own self-definition.

For example, someone will have an extroverted self-schema if they think of themselves as extroverted and also believe that their extroversion is central to who they are. Their self-schema for extroversion may include general self-categorizations ("I am sociable."), beliefs about how they would act in certain situations ("At a party I would talk to lots of people") and also memories of specific past events ("On my first day at university I made lots of new friends").

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