Lecture 25

What is orienting (vestibular sense)?
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What is orienting (vestibular sense)?
Your sense of balance, largely comes from your inner ear.
What are the semicircular canals?
Critical for balance, fluid filled chambers that cause hair cells to move and send information to the brain. Similar to hearing, but rather than sending information about sound, it sends information about orientation and acceleration.
We have three of these to pick up information about 3-D environments and rotations in 3 directions.
Semicircular canals are ______ ______ ______.
Smart Perceptual Devices. They pick up a higher-order parameter without picking up on a lower-order parameter. They pick up on acceleration without picking up on velocity. Our bodies do not perceive velocity, this allows us to fly in planes or drive without getting dizzy or sick. This gives us the sense of being stationary while in these transportation devices.
What is a statolith?
A fluid filled chamber with a calcium deposit and hair cell in it, connected to the semicircular canal. If you tilt your head, the calcium deposit will hit different hair cells to help tell your orientation. For other animals like lobsters, the stone is actually stuck at the end of the hairs rather than free-moving. There is a disorder where this gets stuck, causing dizziness and sickness.
What did the balance experiments on sea crustaceans show?
There is a crustacean creature that jabs stones into its ear to assist in vestibular sense. Experiments were run with magnets instead of stones, which led the creature to perceive down when it is up, up when it is upside down, etc, based on the orientation of a magnet.
What is haptic touch?
Multiple somatosensory systems used in combination. The skin + muscles and joints. Exploratory Procedures bring different somatosensory systems in play.

For example, touching a piece of bread: Lateral motion > pressure > enclosure with hands > contour following.
The somatosensory cortex contains ______ ______.
The Homunculus; Spatial Organization
What does spatial organization of touch on the brain show?
Much like sight, the left side of the somatosensory is mapped for the right side of the body, etc. We have a "little man" in our cortex mapped out for touch, with features for detail-oriented touch mapped larger (hands, face, etc). Touch is also mapped for the primary motor cortex.
Where is the somatosensory cortex located in context to the primary motor cortex?
Right next to the primary motor cortex, why you feel something as you move. They both show spatial organization and cortical magnification.
This is why when you have a stroke and can't move an arm, you also can't feel that arm.
In the primary motor cortex, the size of projection area (spatial organization), corresponds to what?
Corresponds to the fineness of motor control, we have finer motor control for our mouth and fingers, etc.
In the somatosensory cortex, the size of projection area (spatial organization), corresponds to what?Corresponds to degree of sensitivity, lips and fingers are more sensitive and have more touch acuity.Much of motor control at the major joints, like the elbows and knees, actually occurs in _____ _____.Subcortical areas.Why do we attend physical therapy after strokes or broken bones?If you were to break part of your hand, your cortex area dedicated to it will shrink and remap to accommodate, which is why you have to attend physical therapy to "relearn" or "remap" motor skills with that part of your hand.What did the third thumb experiment show?An experiment that gave an individual an additional thumb actually caused a loss in mapping of other fingers to make room for the additional thumb's mapping. This remapping gets harder with age.What is kinesthesis?The perception of the body, relative to the body, using muscles and joints. Object properties are perceived via kinesthesis but putting objects in motion with muscular torque. Ex: Moving your wrist to gauge how much liquid is left in a cup.What is the medium for the somatosensory systems?The body itself.What is the invariant for length detection in kinesthesis?Time varying motions and time varying torques (forces) are coupled by moments of inertia, which is invariant. Inertia is analogous to texture gradient and eye height. It is invariant to length perception using kinesthesis.Muscle sense picks up on _____.Inerita.