PSY2002 W5 Multisensory integration 1 (L) Flashcards
What is body schema ?
“a representation of the positions of body parts in space, which is updated during body movement”
Sensorimotor representation that guides action
Does not require awareness
What are disorders of body schema?
Alice in Wonderland syndrome, Autopagnosia, phantom limbs
What is reference frame?
Player perspective: Coordinates of snake in the world, e.g. upper left corner
Snake perspective: Sees world through its eyes, can turn left or right
Problem: Sensory input in player perspective and Controls in snake perspective
What is coordinate transformation?
Eye-to-head: need to know orientation of eyes.
Head-to-body: need to know orientation of head.
→ Converting between reference frames requires us to know the position and orientation of body parts. In other words, we need a body schema
What is eye-/head-centred reference frames?
Head-centred frame is where you head is directed towards ()–a
Eye-centred frame is where your eyes are looking no matter the head is (¤) –
What is body image?
how do you imagine your body
how do you feel about your body
conscious (mostly visual) representation
What is alice in wonerland syndrome?
Distortion in size perception. Body parts might appear smaller (microsomatognosia) or larger than their true size (macrosomatognosia). Can affect whole body. Associated with childhood and migraines.
What is Autotopagnosia?
Inability to locate body parts. Loss of spatial unity of body. Patients can name body parts but relative order lost. Finger agnosia: Fused percept of fingers
What is Phantom limbs?
After limb loss, presence of limb is still felt. Can include agency over limb (movement). Often associated with pain. Phantom limb can change size over time (e.g. shrink: telescoping)
What is temporal-order judgements?
Heed & Azañón, Front Psychol, 2014
Does body posture affect perception?
Setup: stimulate both hands in random order
Task: Indicate which hand was stimulated first
Conditions: Arms uncrossed/crossed
Participants mix up which hand was stimulated when arms are crossed. Solving the task does not need input from body schema
-> Body schema affecting basic perception
What is peripersonal space?
The space immediately surrounding our bodies. Objects within peripersonal space can be grasped and manipulated immediately. Extent not fixed: can contract and expand.
What is the moravec’s paradox?
“It is comparatively easy to make computers exhibit adult level performance on intelligence tests or playing checkers, and difficult or impossible to give them the skills of a one-year-old when it comes to perception and mobility.” - Moravec, 1998
What are computers good at?
Computers are good at “hard” task – like playing chess, but are bad at seemingly “easy” tasks such as walking
Reasoning (high-level cognitive) ==> relatively easy to reproduce into a machine
Perception, Action (low-level) ==> surprisingly hard to reproduce into a machine
Does blocking the sensations from the fingers affect motor control?
Johansson, 2005
Blocked sensations from the fingers: anesthetize the fingers. Block all touch sensation from the fingers, does not affect motor control. After doing so the participant had to pick a match up and light it, in a normal condition it only takes a few seconds but after losing sensation in fingers it took around 25 seconds.
What is multisensory perception?
“I see and feel that I am touching this object.” – coordination of vision and touch. What robots have a difficulty integrating is the multisensory integration.
What are challenges in multisensory integration?
- How to transform representations from different senses into a common representational space? [W5 Lecture]
- How to integrate information from different senses into a coherent percept? [W6 Lecture]
Where are sensory percepts located?
Vision → eye-centered/retinal: location of visual stimulus on the retina
Audition → head-centered: location of sound source with respect to the ears
Touch → body-centered: location of tactile stimulus on skin
Need to convert between these reference frames and to external space (world coordinates)!
What characterise body schema?
1- Spatially coded
2- Modular
3- Updated with movement
4- Adaptable
5- Supramodal
6- Coherent
7- Interpersonal
What is spatially coded?
Body Schema
position of each body part in external space
What is modular?
Body schema
different body parts processed separately
What is adaptability ?
Body schema
Changes when the body changes
What is supramodal?
BOdy schema
Combines input from multiple senses, e.g. proprioception, touch, vision, audition
How are body schema’s coherent?
Body schema
patial continuity when resolving perceptual conflicts
How are body schema’s interpersonal?
observed actions are represented within the same body schema
How are body schema’s Updated with movement?
Body schema
automated and “always on”
What are some bodily illusions?
Pinocchio illusion, rubber hand illusion
What is the pinocchio illusion?
If arm is extended, but we are grasping our nose:
-> nose must be really long
Vibrating the biceps will make arm feel extended
What is rubber hand illusion ?
Setup
* Participant’s real hand hidden from view
* Experimenter strokes real and rubber hand simultaneously
* Participant sees and FEELS rubber hand being stroked
* Participant starts to feel as if rubber hand is real hand
-> Vision and touch: multisensory integration
How does the body schema develop?
At 6 months old, the body schema starts to interfere with tactile orienting.
What is the cross-modal integration and body schema?
Maravita et al. 2003
Participants receive a tactile stimulus and respond with the location (up or down).
Visual distractor (up or down) is presented nearby on the same hand or the other hand.
A Congruency effect exists for both hands – evidence for cross-modal integration and visual interference.
But: effect greater for same hand
Is the grater interference based on hand location (body schema) or visual field?
Body schema - cross model integration
Arm-crossing
Changing the mapping of the body schema:
-tactile stimulus on same side of the body
-visual stimulus on different side of body
Effect of visual distractor moves with the hand during arm-crossing
The body schema (not visual representation of external space) mediates the integration between vision and tactile stimulation.
==> Cross-modal interactions are mediated by body schema.
How are neurons incorporating tools?
Expansion of peripersonal space during tool use reflected in neural responses
Tools are used for what?
Extending the body
Tools are incorporated into the body schema during use.
Cross-modal congruency effects apply during tool use
● No crossing of body parts, only tools are crossed
● Same delay effects as seen during arm crossing
→ Tools become part of body schema
