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)
Sensory Integration
- The Process of combining different sensory signals
- Typically leads to more accurate information then can be obtained from individual senses alone
Visual-vestibular Integration
- Vection: an illusory sense of self motion produced when you are not in fact moving.
eg: being stopped in a train at the station. The train next to yu is moving and it feels like you are moving forward.
Do we have a Vestibluar Cortex?
- The portion of the cerebrum which responds to input from the vestibular system
- Location is not well defined
- Some research indicates a right hemisphere dominance
Vestibular Cortex
- No need to have a cortex for processing vestibular information
- Areas of the cortex respond to vestibular input
- Tend to respond to visual input as well
- Vestibulare information reaches the cortex via thalamo-cortical pathways.
- Contributes to all senses
What happens when the vestibular system fails
- Spatial disorientation
- Imbalance
- Distorted vision unless held perfectly still
- Motion Sickness
Mal de Debarquement Syndrome
- Swaying, rocking or tilting perceptions felt after spending time on a boat or in the ocean
- Aftereffect of adapting to the rocking motion of the ocean
- Usually goes away after a few hours
- Some people experience it continuously
- “Getting your sea legs”
Meniere’s Syndrome
- Sudden experience of dizziness, imbalance and spatial disorientation
- Can cause sudden falling down
- can cause repeated vomiting from sever motion sickness
- Unpredictable and terrifying attacks.
- Sometimes removal of vestibulare aparratus is a treatment
Gurvich et al., 2013
Common Neural Pathways for Vestibular Funcion and many psychiatric disorders
Staab 2016
- 30-50% of patients with vestibular disorders have a co-existing psychiatric disorder including anxiety, depression, PTSD, OCD
Carmeli, 2016
- Comorbidity relationships between vestibular disorders and Mental Health Disorder is bi-directional
Smith et al., 2016
- Vestibular system influences higher order cognitive processing including:
- Working memory
- Spatial memory
- Attention
- Executive functioning
Smith & Darlington, 2013
- Personality can be affected by vestibular disturbances.
- Patients with vestibular dysfunction report feelings of depersonalization and derealization
- This indicates that vestibular system makes a key contribution to the sense of self
Why do we need a sense of touch?
- detect damage
- Determine the position of our body parts and where our muscles are moving
- sensing temperature changes
- feeling deformations
- low and high frequency vibrations
- pressure on our skin
Autotelic NFT
- NFT = Need for touch
- measure the desire to touch objects just to enjoy the sensory experience
Instrumental NFT
- NFT = Need for Touch
- Measure the use of touch to evaluate products for potential purchase
Touch Physiology
- Touch receptors are embedded in outer layer of (epidermis) and underlying area (Dermis) of skin
- categorised by:
- type of stimulation to which receptor responds
- Size of receptive field
- Rate of adaptation (fast vs slow)
Touch Flowchart
- Tactile Sensations
- Kinesthesis
- Thermal Sensation
- Pain
Tactile Mechanoceptors
- Tactile Sensations
- Caused by mechanical displacements
Kinesthetic Mechanoceptors
- Kinesthesis
- Position and movement of limbs
Thermalceptors
- Thermal Sensation
- Heat and Cold
Nociceptors
- Pain
- Damage to body tissue
Kinesthesia
Perception of the movement of our limbs in space
Proprioception
Perception of the position of our limbs in space
Somatosensation
- Collective group of sensory receptors
- sensory signals from:
- skin
- muscles
- tendons
- joints
- internal recptors
Tactile Receptors
- Called mechanoreceptors because the respond to mechanical stimulation
Merkel Receptors (SA1)
- Merkel nerve endings are mechanoreceptors basal epidermis and hair follicles.
- They are nerve endings
- Provide information on:
- mechanical pressure
- position,
- deep static touch features, such as shapes and edges.
- Found in the basal epidermis of the skin
- store serotonin which they release to associated nerve endings in response to pressure.
Meissner Corpuscle (RA1)
A sensory nerve ending that is sensitive to mechanical stimuli, found in the dermis in various parts of the body.
Ruffini Cylinder (SA2)
- Ruffini endings are slow adapting, encapsulated receptors
- Respond to skin stretch
- Present in both the glabrous and hairy skin.
Glaborous
smooth, hairless, bald Skin
Pacinian Corpuscle (RA2 or PC)
Pacinian corpuscles are rapidly-adapting, deep receptors that respond to deep pressure and high-frequency vibration.
Kinesthetic Receptors
Mechanoreceptors in muscles, tendons and joints
Muscle Spindle
A sensory receptor located in a muscle that senses its tension
Thermoreceptors
- Sensory Receptors that signal information about changes in skin temperature
- Two distinct populations of thermoreceptors:
- Warmth Fibres
- Cold Fibres
- Body is constantly regulating internal temperature
- Respond when you make contact with an object warmer than 36o and colder than 30o
Nociceptors
- Transmit information about stimulation that causes damage to the skin
- Two groups of nociceptors
- A-delta fibres that are myelinated
- C fires that are unmylenated
- We feel sharp pain followed by throbbing sensation
Pain
- Pain sensations triggered by nociceptors
- Responses to harmful stimuli
- Can be moderated by:
- anticipation
- religeous belief
- prior experience
- watching others respond
- attention
- emotion
- excitment
Analgesia
- Decreasing pain sensation during conscious experience
- Endogenous opiates release in body to block release and uptake of neurotransmitters that transmit pain sensation to the brain
Gate Control Theory
- Gate neurons block pain transmission
- activated by harmful stimulation applied to another area of the body
- Top Down influence from the brain
eg: expection of pain
Pain Sensitisation
- Nociceptors provide signal when there is impending or ongoing damage to body’s tissue
- Once damage has occurred, site can become more sensitive
- Pain as a result of damage to or dysfunction of nervous system
- No single pain medication will alleviate all types of pain
Nociceptive Pain
Nociceptors provide signal when there is impending or ongoing damage to body’s tissue
Hyperalgesia
Once damage has occurred, a pain site can become more sensitive
Neuropathic pain
Pain as a result of damage to or dysfunction of nervous system
The Somatosensory Cortex
- Central Sulcus
- Lateral Sulcus
Somatosensory Cortex Anatomy
- Primary Somatosensory Cortex (S1)
- Secondary Somatosensory Cortex (S2)
Homunculus
- Map-like representation of regions of the body in the brain
- adjacent areas on the skin connect to adjacent areas in the brain
Haptic Perception - Pascual-Leone & Hamilton (2001)
- Volunteers blindfolded for days
- On day 1 the Braille patterns only activated S1
- By day 5 activation in S1 decreased and activation in V1 increased
- Removing the blind fold resulted in return to the previous activation pattern
Two Point Threshold
- How finely can we resolve spatial details
- The minimum distance at which two stimuli are just perceptible as separate
Tactile sensitivity
- Tactile sensitivity declines with age
- Not the case for people without sight, tactile sensitivity remains high into old age
- People who lose sight later in life may not be able to read braille
Haptic Perception
- Knowledge of the world derived from sensory receptors
- Usually involve active exploration
Exploratory procedure
- A stereotypical hand movement pattern used to contact objects to perceive them
- Lateral motion = texture
- Pressure = hardness
- Static contact = temperature
- Unsupported holding = weight
- Enclosure global shape = volume
- Contour following global shape = exact shape
- Described by Lederman & Klatzky
Tactile Agnosia
- Inability to identify objects by touch
- Reed & Caselli (1994)
- Caused by lesions in parietal lobe
Body Image
- The impression of our bodies in space
- Systematically distorted towards top heaviness
- Consistent with somatotopic mapping in cortex and sensory homunculus
Somatotopic Mapping
- point-for-point correspondence of an area of the body to a specific point on the central nervous system.
- Typically, the area of the body corresponds to a point on the primary somatosensory cortex
Out of body Experiences
- Reported experiences where the conscious self lies outside the physical body
- Ehrsson (2007)
- Showed it was easy to induce OOBE’s in healthy subjects
Phantom Limb
- Sensation perceived from a physically amputated limb of the body
- Amputees report feeling the amputated had when face or remaining limbs are stimulated
Neural Plasticity
- The ability of neural circuits to undergo changes in function or organisation as a result of previous activity
Haptic Perception – Pascual-Leone & Hamilton
- Volunteers blindfolded for days
- On day 1 the Braille patterns only activated S1
- By day 5 activation in S1 decreased and activation in V1 increased
- Removing the blind fold resulted in return to the previous activation pattern
Touch and the Vestibular System Flowchart
- Somatosensation
- Proprioception
- Vestibluar System
- Touch
- Tactile Sensations
- Kinethesis
- Thermal Sensation
- Pain
Define Somatosensation
All sensory signals from the body
Define Proprioception
Sense of how your own body is oriented in space
Define Tactile Sensations
Caused by mechanical displacements
Kinesthesis
Position and movement of limbs
Define Thermal Sensation
Heat and Cold perception
Define Pain
Damage to body and tissue
