Slide Week 2 Flashcards
Vestibular System
- Which senses are responsible for the sensation of falling
- Acceleration and Deceleration or a car?
- What about leaning to the right or left with your eyes closed?
Equilibrium
- None of the traditional 5 Senses can account for the sense of falling, acceleration or tilt.
- Often overlooked but evolutionaily very old
- Composed of multiple reflexes and perceptual modalities
- Begin with Vestibular orgarns in the inner ear
Vestibular System
- Organs and Neural Pathways that sense head motion and head orientation with respect to gravity
- Help us by providing sense of
- linear Motion
- Angular Tilt
- Tilt
Spatial Orientation
- A sense consisting of three interacting sensory modalities
- Perception of linear motion, angular motion and tilt
- Below is a coordinate system for classifying direction

Three Directions for Sense of Rotation
- Roll:
- Pitch
- Yaw
Directions for Sense of Rotation: Roll
Rotation around x-axis

Directions for Sense of Rotation: Pitch
Rotation around y-axis

Directions for Sense of Rotation: Yaw
Rotation around z-xis

What receptors does the vestibular system use?
- Any cell that has steriocilia for transducing mechanical movement
- In the inner ear
- transmits neural activity sent to the brain

Stereocilia
- In the inner ear
- Mechano-sensing organelles of hair cells
- Respond to fluid motion in numerous types of animals for various functions, including hearing and balance
- About 10–50 micrometers in length
- Share some similar features of microvilli.
Semicircular Canals
- Three tubes in the vestibular system that sense angular accelaration
- Source of our sense of angular motion - Head Spinning in Pitch, Roll and Yaw

The push-pull relationship
- The Semicircular canals function in pairs that have a push-pull relationship
- Neural Activity in is sensitive to changes in rotation velocity
- Constant rotation leads to decreased responding from the canal neurons after a few seconds

Otolith Organs
- The mechanical structures in the vestibular system that sense both linear accelaration and gravity
- source of our sense of linear velocity and gravity
- sense of up, down, left, right, front and back

Utricle Macula
- Macula of the utricle, or utricular macula
- Region of the utricle that receives the utricular filaments of the vestibulocochlear nerve
- The portion of the utricle that forms the macula forms a sort of pouch or cul-de-sac, with a thickened floor and anterior wall.
- Utricle contains about 30,000 hair cells

Saccular Macula
- Anterior part exhibits an oval thickening of the macula of saccule
- Distributed the saccular filaments of the acoustic nerve.
- The vestibule is a region of the inner ear which contains the saccule and the utricle
- Each of which contain a macula to detect linear acceleration.

The Otolith Organs
- Otoconia
- Otolithic Membrane (gelatinous membrane)
- Reticular membrane
- Supporting cells
Define Spatial Orientation
the ability to perceive and adjust one’s location in space in relation to objects in the external environment
Three experimental paradigms to investigate spatial orientation perception
- Threshold Estimation
- Magnitude Estimation
- Matching
Threshold Estimation
What is the minimum motion needed to correctly perceive motion direction?
Magnitude Estimation
Participants report how much they think they tilted, rotated or tranlsated
Matching
- Participants are tilted and then orient a line with the direction of gravity
- Done in a dark room with the only line visible to avoid any visual cues orientation
Rotation Perception
- At first, constant rotation (in the dark) is perceived accurately
- Soon, subjects feel as if they are slowing down
- After 30 secs they no longer feel as if they are rotating
- When rotation stops they feel as if they are rotating in the opposite direction
Translation Perception
- When peole are translated in the dark they are able to use a joystick to reproduce the distance they traveled accuratly
- They can also reproduce the velocity of the passive motion trajectory

Tilt Perception
- We are very accurate when perceiving tilt for angles between 0 degrees and 90 degrees (lying down)
















