M2 Sensory Contributions

types of sensory info

types of sensory info

exteroceptive

proprioceptive

sensory receptors for movement

tactile/cutaneous (4 types)

exteroceptive

• visual (2 types)

• auditory

proprioceptive

exteroceptive

sensory info perceived from the environment

proprioceptive

sensory info perceived from within the body

• movement-produced feedback

• sensing movements of joints, tension in muscles…

exteroceptive info

two main types of exteroceptive feedback:

• vision

• audition

vision

ability to see

• defines physical environment

• info about one’s movements in relation to environment

  • helps in judgment, anticipation of upcoming events

audition

ability to hear

• sound cues related to motor skills

  • e.g playing an instrument

proprioceptive info

includes:

• vestibular (2 types)

• joint receptors

• muscle spindles (2 types)

• Golgi tendon organs

• cutaneous receptors

vestibular apparatus

• in inner ear

• provides signals related to movement and orientation

  • detects accelerations of head w/ respect to gravity

• impt. in posture and balance

joint receptors

• located in joint capsules

• provide info abt extreme positions of joints

muscle spindles

• embedded within belly of skeletal muscle

• oriented parallel w/ and changes length w/ muscle fiber

  • monitors muscle length

  • indirect info on joint position

Golgi tendon organs

• located near junction b/w muscle and its tendon

• sensitive to tension

  • indicates amount of force produced by a muscle

tactile receptors

located near skin; detects pressure, temperature, touch

• Merkel cell

• Meissner corpuscle

• Ruffini corpuscle

• Pacinian corpuscle

tactile receptor types

tactile receptors classified by two types:

• slowly adapting (SA)

  • maintains response as long as stimulus is present

  • detects constant pressure and texture

• fast adapting (FA)

  • responds only when stimulus starts and stops

  • detects dynamic stimuli (like vibrations or change in textures)

Merkel cell

slow adapting (SA)

superficial receptor found in epidermis

detects sustained pressure, fine textures, shapes

Ruffini corpuscle

slow adapting (SA)

deep receptor found in the dermis

detects sustained pressure, skin stretch

Meisnner corpuscle

fast adapting (FA)

superficial receptor found in fingertips, palms, lips

detects light touch, low-frequency vibrations, change in texture

Pacinian corpuscle

fast adapting (FA)

found deeper in dermis or subcutaneous tissues

detects deep pressure, high frequency vibrations, change in pressure/texture

visual receptor types

parvocellular neurons

magnocellular neurons

lateral geniculate nucleus

located in the thalamus, acts as a relay center for visual info coming from retina before being sent to the primary visual cortex

• aka LGN

parvocellular neuron

associated w/ parvocellular pathway which is responsible for colour and fine details

• receive input from cone cells in retina, sends signals to LGN

• smaller cell bodies than magnocellular neurons

magnocellular neuron

associated w/ magnocellular pathway which is responsible for vision in low-light conditions and detecting movement

• receive input from rod cells in retina, sends signals to LGN

• *primary source of info for voluntary actions

  • processes motion, spatial awareness, and broad visual patterns

dorsal stream

“where” pathway; helps us understand where objects are located

• involved in processing spatial info, motion, depth, and location of objects

located in primary visual cortex

ventral stream

“what” pathway; helps us understand what objects are

• involved in object identification, shapes, colours, features

located in primary visual cortex

Milner and Goodale (1995)

case study of a lady who had a heater in her washroom (when she went to take a shower, door was shut and CO2 built up)

• suffered from agnosia as a result

• could not consciously recognize objects or describe their shapes; however, could still perform actions involving those objects

suggests ability to interact with objects (dorsal stream) can remain intact even when object recognition (ventral stream) is impaired

optical array

rays of light which enter the eye at specific angles

optical flow

optical arrays undergo this process; arrays are transformed into a “flow of light” across the retina

• provides numerous kinds of info about one’s movement through the environment

  • time before collision w/ objects, direction of movement, movement of environmental objects, stability and balance, velocity

time-to-contact

involves processing visual information to estimate how long it will take for an object to reach a specific location

• optical flow creates a pattern of expanding visual info on the retina; allows brain to determine how quickly objects are approaching

focal vision

type of visual processing that allows for detailed examination and recognition of objects

• primarily concerned w/ features, shapes, colours, object identification

ambient vision

type of visual processing that provides a broad awareness of the environment, encompassing spatial orientation and movement

• primarily concerned w/ where objects are in space and where they are in relation to each other

closed loop closed system

a way to think abt how sensory info is processed during movement; relies on feedback to correct errors

4 parts:

• executive for decision making on errors

• effector for carrying out decisions

• reference of correctness

• error signal which executive takes to act upon

reference of correctness

feedback from sensory info is used against this to compare and define error

room temp in house example

an example to understand the closed-loop system

desired state: warm up house

• sensory info abt system output (house’s actual temp) measured by thermometer and compared to expected temp

• difference b/w expected and actual temp represents an error and is sent to executive

• executive decides how to reduce or eliminate error

• executive sends command to effector, which carries out action (turning on furnace)

• actual state equals expected state (temp in house and desired temp reaches equilibrium), executive sends command to switch off heat production

feedforward

anticipated sensory feedback; anticipated sensory consequences of movement that should be received if movement is correct

closed-loop control limitations

has flexibility in movement control but is slow, especially when there is high demand for processing time and resources

system can only produce responses at a maximum rate of ~3 per second

discrete tasks

tasks that are very quick, ballistic actions (throwing, kicking) or pressing a key during texting

• movement is fully planned out to achieve goal before being initiated

proprioceptive closed-loop control

closed-loop control can act beyond our own consciousness

• (patellar tendon reflex/monosynaptic reflex)

patella tendon reflex (M1)

also known as the knee-jerk reflex; monosynaptic reflex arc

• patella hammer hits patella tendon (attached to patella and tibia)

• patella tendon stretches and brings patella downward

• patella stretches quadriceps muscle and quadriceps muscle spindles

• muscle spindles send a signal to spinal cord via afferent neurons which synapse w/ efferent neurons

• efferent neurons lead back to quadriceps and cause a brief contraction

biceps reflex (M2)

also known as the biceps-jerk reflex; monosynaptic reflex arc

• person holding a book in a supinated palm, book must be held at a certain height

• all of a sudden someone comes along and places a heavy weight on top of the book

• arm begins to drop, but corrects itself quickly in order to not drop the book

• after a slight delay, inc load is compensated for and books are held at the desired height

Daniel Kish

(that one ducking dude who uses echolocation to see)

• clicks his tongue to gauge distance of objects

  • can be discrete (quiet tongue click) or loud

• he equates it to seeing with “dim flashes of light”

those who use echolocation are still encouraged to use a cane in case of uneven surfaces which sound can not properly distinguish from flat surfaces

McGurk-McDonald effect

demonstrates that visual info can impair the perception of auditory cues

• e.g an outfield in baseball may be fooled into predicting a ball from a batter’s bat will go over their head when in fact the sound of the bat-ball contact correctly indicates it was a softly hit ball

0.1s

lowest acceptable estimate of visual feedback processing delay

sensory integration

refers to the brain’s ability to organize, process, and respond to information gathered by the senses