Body Representation Flashcards
what are the requirements for representing our body?
1) pre-existing stored model of body
2) on-line representation of body at any one moment
3) anatomical structure of body leads to recalibration of visual and tactile system
4) subjective conscious experience of ownership of body
what does pre-existing stored model of body mean?
- have to have a pre-existing stored model of our body: have to have some memory of what our body is, allows us to distinguish between our body from others’ bodies
what does on-line representation of body at any one moment mean?
- have to have on-line representation of our body at one moment, on-line moment to moment representation needs to be flexible and allow us to give control to our body movements efficiently. brain needs to modulate the interaction of multisensory information from: vision, touch, proprioception, interoception.
what does anatomical structure of body leads to recalibration of visual and tactile systems mean?
- anatomical posture rep of body leads to recalibration of vis and tactile coordinates systems, need to align with spatial framework and touch and vision uses in order to kick ball.
what does subjective conscious experience of ownership of body mean?
-subjective conscious exp of body ownership, where we are and our limbs are in space, awareness takes in peripersonal states and how large they are and what factors interfere with peripersonal space around us. it’s the space that’s reachable around us and is highly plastic and extent of peripersonal space there are huge ID’s.
what is interoception?
interoception, the perception of the state of ourselves like ability to perc our heart rate or other internal cues to our state, breathing rate etc., great ID’s in our ability to perc our internal state! some are strong at this and some are poor at this!
to what extent do we perc control and ownership over our own bodies?
- body image: shape of body, type of dimensions that pertains to body image, body image can change and there are ID’s in the way that we perc image of our own bodies.
- interoceptive cues like whether we feel hungry contribute to perc of bodily self.
- action system can have knock on effect on our moment to moment rep of our bodily self, schema of our body: how big are our hands and knowledge of this helps us interact with objects. agency is sense of voluntary and involuntary actions on the world, all aspects feed into a global rep of ourselves.
actions would not work well on static reps of ourselves is what researchers are interested in.
what are examples of psychiatric disorders associated with inefficient rep of one’s own body?
- Cotard syndrome is the illusion that they are dead and don’t exist, no sense of internal self, one has lost their blood and internal organs.
- Interoceptive agnosia is the loss of sense of pain.
- Mirror sign is the inability to recognise one’s own image in the mirror.
- Misoplegia is hatred towards one’s own body parts.
- Somatoparaphrenia/ Alien Head is the denial of ownership of one’s body part.
- Body integrity identity disorder (BIID) is the urge to be amputated of one’s own perfectly healthy limbs.
- Heautoscopy is visual hallucination of a double of oneself at a distance.
…range from benign to the rare, but v curious disorders.
what are the neural substrates involved with body representation?
- EBA/ extra-striate body area in visual cortex.somatosensory cortex maps out body into what we call homunculus, role of vision is to represent one’s own body in homunculus, what we see can affect what we tactically feel and affect the rep of body is homunculus.
- Proprioception is the perception of limb position in space and on body.
- Perception-for-action: the role of the parietal cortex in body representation
Downing, Jiang, Shuman and Kanwisher, 2001? discovery of EBA
visual area involved in rep own body is the EBA/extra-striate body area.
noticed there is a region of visual cortex that responds only to shapes of bodies, strong activation in right occipitotemporal cortex (EBS) to bodies and body parts more so than objects and object parts.
Downing et al, 2001?
category-specific activation to human bodies..like the silhouette of a body, isolated body parts etc.
Astafiev, Stanley, Shulman and Corbetta, 2004: does EBA respond to v specific representations of bodies i.e. static representation, or does it respond to bodies that actually move?
EBA was sensitive to changes in body motion, activated to goal-directed movement in participants.
- doesn’t matter which body part was about to move towards target area, the intention to move caused greater activation in EBA area. - depicts the shape of a body in ventral region of vis cortex (cortical stream, ie. ventral stream goes to temporal cortex…object recognition, so this is body (object) recognition) so we know its related to shape.. also responds to movements that are goal directed.
Peelen and Dowling, 2005?
they argued that it’s not the EBA that is responding to movements and that it just represents anatomical shape. argued a region slightly adjacent to the EBA called the Action Related Region. debate continued between two groups about whether EBA incorporated motion or not.
Striem-Amit and Amedi, 2014: whether EBA is acc a visual area or not?
diff sensory systems can modulate activation in regions of the visual cortex, can EBA be activated by other inputs?
- trained blind for 70hrs using vOICe technology, system that converts visual images into a soundscape.
- Used fMRI to measure brain responses to soundscapes of body-shape silhouettes, objects faces and abstract patterns.
- EBA was activated in both groups, region that codes for shape of bodies but doesn’t have to be visually presented shape, can be shapes that are applied through other sensory systems.
- Both blind and sighted groups showed larger responses to body-shape silhouettes than to other images in the EBA… why would blind have part of brain that would represent body shapes if they’d never make use of it?
…findings were interpreted as evidence that the specialisation found in the visual cortex may exist independently of experience.
Constantini, 2011: somatosensory system has rep of body, does EBA receive input from tactile system about our body shape?
EBA is activated through haptic exploration of body parts.
- doesn’t activate to objects similar in scale or texture but body parts do…blind may have region in vis system dedicated to anatomical representation of bodies through tactile system!
Urgesi, Candidi, Ionta and Aglioti, 2007: is EBA involved in action perception?
Representations of static anatomically correct portrayals of the body or motion of the body. body form and body action are represented in separate neural substrates. if interfere with EBA then impairs the discrimination of bodily forms (body identity). interference with ventral premotor cortex impairs with perception of bodily actions….basically that there is a body form and body action section of cortex.
Longo, 2009; visually induced analgesia, viewing body can also have effect on somatosensory cortex.
if you see body prior to receiving the painful stim that attenuates the perceptual effect of painful stimulus. seeing body reduces pain! Infrared lazer stimulus applied to left hand to induce pain. nociceptive evoked potentials measured the pain as well as asking for person to subjectively rate the pain, the pain then was attenuated relative to previewing an object! but not if you viewed another person’s hand!!! has to be sight of own body to attenuate pain.
Mancini, 2001: visual distortion of body size modulates pain perception.
vision increases the representation of the part of body being viewed, increases the somatosensory representation of body part being viewed.
change in this cortex of the body being viewed through vision.
relative effect of painful stimulus has then decreased when viewing body part receiving pain. do not look at the needle because then you’re over-representing the needle!!!
if you preview arm then you got a higher pain threshold, works in same principal.
tactile representation of body in somatosensory system in flexible and amenable to modulation from other sensory systems.
Culham, 2006? parietal cortex/ PC
parietal cortex, moment to moment movement of body in interacting with world, sensory control of action which requires a representation of body to voluntary actions to the world,
- eye and head movements; reaching, pointing and grasping.
- damage to parietal lobe leads to optic ataxia which is an inability to reach for visual targets.
- The PPR/Parietal Reach Region is activated in humans when arm reaches or points.
- The AIP/Anterior Intraparietal Area is activated in humans when the hand grasps
Head and Holmes, 1911? distinction between body image and body movements
old study that proposed one body schema for the appreciation of posture or passive movement, and another schema for localisation of stimulated spots on skin.
Paillard, 1999? in response to Head and Holmes
1) A sensorimotor map of the body space is based on
2) proprioception that body image is a pictorial description of body based on vision. what extent do anorexics perc of own body image, line up diff types of body shape to pick one best matches theirs, distorted body representations and are a lot more incorrect about what their body shape is. none of us is good in recognising body shape from warped shapes of bodies.
what two studies did Paillard do as evidence for double associations in patients?
- Patient had left parietal infarct and had complete sensory paralysis of left hand. But when blindfolded she could touch with her left hand the exact spot that had been touched on paralysed hand. “Blind touch”
- Patient was deprived of proprioception and fine touch in 4 limbs by a large-fibre peripheral neuropathy…could consciously identify body parts touched out of sight but couldn’t point to them unless aided by vision.
how can we alter the topographic map of body in body representation?
we can change way in which bodies are topographically mapped through training, amputation and multisensory illusory conditions made in the lab.
Schaefer?
Illusory feeling of an elongated arm, illusion that they have a third arm can be instilled in the lab!
