Proprioception, Vestibulation, and Mental Representation

Proprioception

  • The brain integrates information from multiple sources:
    • Vestibular organs: Located in the inner ear, they provide data about rotation, acceleration, and position.
    • Eyes: Provide visual information.
    • Stretch receptors: Found in skin, muscles, and joints, they transmit data about the position of body parts.

Somatosensory Cortex (S1)

  • The area associated with the sense of touch.
  • Located at the Parietal-Occipital Junction.
  • The mapping of the body is not perfectly topographic but is reasonably close.
  • Demonstrates body magnification, reflecting the density of sensory receptors in different body areas.

Proprioception (Detailed)

  • Definiton: Sense of body position.
  • Source: Relies on information from muscles and joints.
  • Function: Allows us to build a model of self in space.
  • Projection: Bodily information projects to the motor cortex.
  • Pathway: Uses the dorsal stream.
  • Integration: Integrates where you are and your directed goal.

Vision vs. Proprioception

  • Conflict: Occurs when visual cues contradict proprioceptive cues.
  • Dominance: Generally, vision has a greater influence than proprioception.

Vestibulation

  • Definition: Sense of movement and gravitational uprightness.
  • Location: Vestibular organs are located in the inner ear.
  • Components: Includes semicircular canals and otolith organs.
  • Function: Works with proprioception (kinesthesia) for posture control and balance.
  • Aspect: Essential for spatial orientation.

Inner Ear Components

  • Semicircular canals and otolith organs:
    • Fluid-filled chambers.
    • The fluid moves as the head moves.
    • Contain hair cells (similar to those in the auditory system).
    • Respond to roll, pitch, and yaw (X, Y, and Z planes).
    • Respond to acceleration but are less responsive at constant velocity.
    • Primarily sensitive to angular acceleration.

Vision and Vestibulation

  • Integration: Combines acceleration information from the vestibular system with visual input.
  • Induced Self-Motion Illusions: A large part of the visual field in motion can create the illusion of self-motion.
  • Vection: The illusion of self-motion induced by visual stimuli.

Tumbling Room Experiments

  • Setup: A person is strapped into a chair in a fake room that can flip independently of the chair.
  • Observations:
    • Chair upright, room upside down: Feels like you are upside down; this sensation disappears when eyes are shut.
    • Chair and room upside down: Feels like you aren’t upside down because gravity appears to be pulling you up.

Anti-Gravity Hills

  • Cause: Lack a clear view of the horizon and have multiple surface planes in sight.
  • Effect: Observers judge slopes based on misleading visual cues.
  • Perception: The slope of the middle plane is influenced by the other two.

Mystery Spots

  • Mechanism: Similar to anti-gravity hills, they lack a clear view of the horizon for visual calibration.
  • Features:
    • No surfaces are actually horizontal or vertical (everything is slanted).
    • Assumption that slight tilt is not present.
    • All angles are slightly more or less than 90 degrees (non-rectilinear).
    • Examples: Changing heights (Ames room), rolling balls (anti-gravity hills).

Tilt Illusion

  • Greatest effect: Occurs when backgrounds are tilted around 15 degrees.
  • Average difference: The difference from right angles in mystery spots.

Hanging Ball at Mystery Spot

  • Observation: The ball appears to hang at an angle.
  • Effect: Pushing the ball towards what looks like vertical is more difficult.
  • Explanation: Expectations about gravity influence perception; it should be easier to push something if working with gravity (Bridgeman, 2005).

Mental Representation

  • Process: A physical stimulus leads to a mental representation of that stimulus.
  • Example: A donut leads to a mental representation containing everything one knows about donuts.
  • Components of Representation related to Donuts:
    • "Donut" [ˈdoʊ.nʌt][ˈdoʊ.nʌt]
    • Edible and tasty.
    • Source of nutrition.

Perception, Representation, and Action

  • Sequence: Perception leads to representation, which in turn leads to action.

Representations (Detailed)

  • Definition: An internal model linked to external stimuli or information.
  • Types:
    • Analog representation: Sensory-based.
    • Propositional representation: Symbolic-based.

Types of Representations

  • Analog Representation: Sensory
  • Propositional Representation: Symbolic.
  • Example: Imagine a red apple.

Analog vs. Propositional Representation

  • Analog representation/addition:
    • 1 red apple + 1 green apple = 2 apples.
  • Propositional representation/addition:
    • 1+1=21 + 1 = 2

Propositional Representations

  • Nature: Abstract assertions that maintain relationships of referents.
  • Modality: Not tied to a particular sensory modality.
  • Type: Purely symbolic representation.
    • Example: "A" is left of "B".

Analog Representations

  • Nature: Representation has the same relationships as properties of the referent.
  • Modality: Tied to a sensory modality (e.g., visual).
  • Type: Non-symbolic representation.

Kosslyn, Ball, & Reiser (1978) - Map Experiment

  • Task: Participants memorize a map.
    • Assessed how long it takes participants to mentally "travel" between landmarks on a memorized map.
    • How: Imagine a small dot zipping from one location to another and hit a button when the dot arrives.

Findings of Island Experiment:

  • Reaction time (seconds), is proportional to distance (cm).
  • Alternative: Asked to just answer questions to control.
    • Is there a tree on the island?
    • Is there a beach on the island?

Mental Rotation

  • Definition: First scientific investigation into imagery.
  • Task: Determining if two objects are identical or mirror images when rotated.

Mental Rotation Results

  • Response Time: Varies linearly as a function of the degree of rotation (Shepard & Metzler, 1971).

Imagery vs. Reality

  • Relative Size and Imagery: Imagine a rabbit standing next to an elephant; it’s harder to visualize the rabbit’s features.
  • Imagine a rabbit standing next to a fly; it’s easier to visualize the rabbit’s features.

Imagination and Perception

  • Relationship: Mentally rotating objects is related to the time needed to physically rotate objects.
  • Mental movement: Mentally moving across a map is related to the time needed to physically move across a map.
  • Mental scanning: Mentally scanning an image is related to the time needed to physically scan the image.
  • Question: What are the similarities and differences between imagination and perception in the brain?

Visualization

  • Definition: Using imagination to simulate a task.
  • Application: "Visualize success."
  • Effectiveness: It actually works.
  • Basis: Imagination can be highly reflective of reality.
  • Mechanism: We are very good at predicting outcomes of actions and adjusting behavior based on predictions.

Mental vs. Physical Practice (Trombone)

  • Ross (1985) - Results:
    • Mental practice can lead to improvement, although typically less than that achieved through physical practice.

Mental Muscle Building

  • Ranganathan et al. (2003)
  • Groups:
    • ABD: Imagine finger abduction exercises (flexing pinky).
    • ELB: Imagine elbow flexion.
    • Control group.
    • Actual muscle movement groups for ABD/ELB.
  • Findings:
    • Mental training groups improved strength over the control group but less than the actual movement group (35% vs. 53%).
    • Imagery resulted in ERP increase in the finger, stimulating muscle growth.

Myth of Imageless Thought

  • Old Myth: Thought is separate from perception.
  • Truth: Thought relies on perceptual systems and mental imagery.
  • Evidence: Eye movements during imagery tasks.

Vividness of Imagery

  • Variability: There is variability in how vivid people’s imagery is.
  • Aphantasia: Lack (or extreme impoverishment) of willed visual imagery.
  • Assessment: Difficult to study due to reliance on self-report.
  • Tool: Vividness of Visual Imagery Questionnaire (VVIQ; Marks, 1973).

Some interesting VVIQ correlates

  • Correlations:
    • Positive correlations:
      • Frequency and intensity of flashbacks in PTSD patients (Bryant & Harvey, 1996).
      • Levels of anxiety when imagining phobias (e.g., spiders) (Pratt et al., 2004).
    • Scores on social desirability scales – a measure of subject bias (uh-oh) (Allbutt et al., 2011).

Aphantasia

  • Characteristics: VVIQ scores are extraordinarily low; individuals subjectively report being unable to will mental imagery.
  • Speculation: Thinking occurs in words/monologue only; processing might occur unconsciously.

Varieties of Thought

  • Key point of aphantasia: imagery ("thinking in images") is never present
    • Aphantasia (can only think in facts):
      • -red
      • -round
      • -tasty
      • -smooth
      • -fruit
      • -yellow
    • Aphantasia (only internal monologue):
      • "I'm thinking about an apple. I know that apples are red so the one I'm thinking about is too. What else do I know about apples?"…
    • Normal person (example) (good visualizer)
    • Normal person (bad visualizer, has internal monologue)

Inner Monologue and Speech

  • Assessment: VISQ-R questionnaire.
  • Variability: People vary greatly in the degree to which they engage in inner speech.
  • Cognitive Ability: No reported differences in cognitive ability between those with high/low inner speech.
  • Caveat: Differences in thought patterns =/= differences in the value of thought.