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bpk 207 > sensory contributions 3b > Flashcards

sensory contributions 3b Flashcards

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1
Q

vestibular system components

A

called end organs

otoliths
- saccule, utricle

semicircular canals
- superior, posterior, horizontal

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2
Q

vestibular system function

A

in inner ears

detects head acceleration

helps determine head position/motion and body orientation

detects acceleration when head moves

can detect head movement in all directions/rotations

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3
Q

vestibular apparatuses

A

on both sides of the head

work together to signal movement or orientation
- allows for greater signal to noise ratio and thus increases sensitivity to motion

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4
Q

otoliths

A

sense linear head acceleration (ie/ changing translational motion through environment) and changes in head orientation relative to gravity

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5
Q

saccule

A

detects acceleration in vertical plane

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6
Q

ultricle

A

detects acceleration in horizontal plane as well as head tilt

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7
Q

semicircular canals

A

sense angular head acceleration
- turning or tilting
- rotatory body movements

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8
Q

hair cells

A

stereocilia

located in vestibular apparatus get deflected by otolithic membrane (in otoliths) or endolymph (in semicircular canals)

depolarization ocurs because of an influx of potassium

resting discharge allows afferents to respond to bi-directional motion

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9
Q

positive mechanical deformation

A

towards the kinocilium which opens potassium channels in the stereocilia

calcium enters the cell allowing for vesicle fusion and the release of transmitter

tip links open the ion channels more

depolarixation - increased afferent discharge

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10
Q

negative mechanical deformation

A

away from the kinocilium causes potassium channels to close

tip links close the ion channels

hyperpolarization - decreased afferent discharge

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11
Q

tip links

A

connect individual hair cells together and are connected to spring-gated ion channels

slightly open the ion channel and allow a small amount of potassium inside

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12
Q

how do semicircular canals signal angular acceleration

A

canals are filled with viscious fluid which is rich in potassium called endolymph

because of its inertia, when the head rotates the endolymph displaces a gelatinous structure call the cupula which has hair cells embedded in it which are deflected

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13
Q

cupula

A

displaced by the flow of endolymph when the head moves

as a result the hair bundles are also displaced

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14
Q

endolymph flow

A

thick liquid when we move head it deflects cell to show which direction we are going

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15
Q

how do the otoliths signal head acceleration

A

linear (translational) head motion through environment or change in head orientation relative to gravity causes movement of the otolithic membrane

key is having an inertial substance (endolymph or otolithic membrane that is not rigidly attached to the rest of the body

when the body accelerates, inertia cause the substance to lag behind and hair cells detect this relative motion

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16
Q

otolithic membrane

A

contains otoconia stones

lags behind head motion

deflects hair cells (which project up into this membrane)

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17
Q

main function of vestibular system

A

postural stabilization
gaze stabilization (in conjunction with visual system)
perception of self motion
role in spatial navigation

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18
Q

postural stabilization in the vestibular system

A

maintenance of balance
- via vestibulospinal reflexes
- vestibular afferents project to vestibular nuclei in brainstem, which gives rise to descending tracts that activate muscles

helps keep head upright (and perception of spatial orientation when head is not upright)

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19
Q

gaze stabilization in the vestibular system

A

via vestibular-ocular reflect
- this reflex compensates for head movement - loops eyes in opposite direction ie/ when fixated
- when the head moves, the eyes rotate in orbits to maintain gaze fixation on target of interest

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20
Q

perception of self motion in vestibular system

A

head motion can tell CNS about you motion

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21
Q

vestibular system’s role in spatial navigation

A

linked with self motion as well as knowing orientation

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22
Q

GVS (galvanic vestibular stimulation)

A

used to study the vestibular contribution to balance

activates the vestibular afferents and and hair cells of the otoliths and semicircular canals causing illusory perception of head (and body) tilt and compensatory tilt in the opposite direction

gives the illusary perception of sway towards cafe and their is resulting compensatory sway towards anode

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23
Q

the eye

A

designed to focus the visual image on the retina with minimal optical distortion

light is focused by the cornea and lens onto photoreceptors in the retina

light rays must converge at the retina for light to be in focus

light is refracted when it passes through the cornea (2/3 of refection here) then at the lens (1/3 of total refraction here)

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24
Q

lens

A

can change its shape to alter the distance at which objects will be in focus
- known as accommodation
- due to the contraction/relaxation of the ciliary muscles

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25
retina
contains numerous cells in multiple layers has photoreceptors fovea retinal ganglion cells for the optic nerve and propagate the signal to visual areas in the brain lies in front of pigment epithelium that lies in the back of the eye
26
photoreceptors
transduce light into electrical signals
27
fovea
contains only cones; rods dominate elsewhen in retina part of the retina that allows for vision of fine details
28
cells in the pigment epithelium
filled with a black pigment, melanin, which absorbs any light not captured by the photoreceptors this prevents light from being reflected off the back of the eye, which would degrade the visual image light must travel throguh the layers of other retinal neurons before striking the photoreceptors cell bodies of the proximal retinal neurons in the fovea are shifted to the side, enabling the photoreceptors to recieve the visual image in its least distorted form
29
visual field
the region of space where the eyes sees shifts with eye movement
30
central vision
deals with identifying details central ~5 degrees of visual field predominently contains cones
31
peripheral vision
deals with where things are info regarding environmental context and moving limb contains mostly rods and sparse cones
32
binocular retinal disparity
refers to the difference in image location of an object seen by the left and right eyes, resulting from the eyes horizontal seperation (parallax) can be used to process object motion if object moves and the eyes remain fixed the image activates the reitina progressively more laterally
33
depth perception
facilitated by the different in image location of an object as viewed by the left and right eyes
34
primary visual cortex
about 2mm thick and has 6 layers - neurons carrying visual input from LGN enter layer 4 also known as visual striate cortex striate means striped - this area has a prominent layer 4 that gives rise to a striped appearence in V1 cross sections contralateral visual field representation is preserved in V1 has cells with many different visual receptive fields like layer 4c, simple, and complex cells
35
retinotopic representation
light (images) from specific areas of visual field hits a specific part of retina; each specific part of the retina is mapped onto the visual cortex, adjacent points in sensory space are represented at adjacent points in the brain
36
retinal ganglion and lateral geniculate nuclus (LGN) neurons
have receptive fields such that each neuron responds to a tiny spot of light (like a tiny region of the visual field) layer 4c neurons in V1 (onto which LGN neurons synapse ) are similar
37
simple cells in V1
have elongated receptive fields sense lines/edges of a particular location respond to bars of light and borders between light and dark can detect an edge of an object converge info into complex cells
38
complex cells in V1
have larger receptive fields sense lines/edges of a particular orientation anywhere within the receptive fields many also are sensitive to moving lines/edges - respond to moving bars of light
39
hierarchial organization in neurons in visual pathway
receptive fields get bigger as you move from LGN to visual cortex (from layer 4c to simple to complex cells) at each step of the hierarchy, when receptive fields get more complex, a receptive field is the sum of multiple, smaller receptive fields from "upstream" neurons (those that synapse onto the "downstream" neuron retinal ganglion to LGN cells to layer 4c - simple V1 - complex V1 fundamental principle of how info is integrated (and expanded) from one level to another within the nervous system the idea applies to many brain areas and many different senses
40
tuning curve
shows what orientation the neuron responds best to by measuring its discharge frequency
41
extrastriate
refers to all cortical areas outside of V1
42
cortical regions important for processing visual motion (optic flow)
middle temporal (MT) region [also called area V5] medial superior temporal (MST) region
43
middle temporal region
neurons have large receptive fields neurons have preference for a certain direction of motion neuronal activity is sensitive to speed of motion project to MST region- medial superior temporal area
44
medial superior temporal region
divided into two sub-regions that process object-motion or self-motion neurons have larger receptive fields (larger than MT)
45
optic flow
the continuous change over time of the spatial pattern of light (variations in intensity and wavelength composition) reaching a point as it moves through its surroundings
46
whole field motion
motion of an image sweeping across the eye when an eye rotates in its socket with the head stationary (from the image moving relative to the retina) like looking left to right without moving head
47
optic flow components
whole field motion image flow caused by the eye moving through the environment as a person moves and the eye turning in its socket simultaneously - translational flow and rotational flow
48
translational flow
referred to as radial outflow motion due to movement of eye through environment
49
rotational flow
motion due to the eye turning within the environment
50
what are the two factors important for generating optic flow
1. the speed and direction of the eye's movement through the surrounding 2. the distances from the eye to the points in the surroundings that hit the retina. images of closer objects flow across the eye faster when the eye moves through space
51
what does optic flow provide info on
stability and balance velocity and direction of movement movement of objects in the environment time-to-contact
52
several ways to calculate TTC
optic flow - calculate ratio of the object's image size to the rate of its radial expansion on the retina; a variable called tau binocular retinal disparity oculomotor vergence feedback - feedback from muscle spindles in eyes as the eyes rotate inward or outward to track an object
53
ventral visual stream
primary visual cortex to temporal lobe
54
vision-for-perception system
ventral visual stream responsible for fine analysis of the visual scene (form, colour) and object recognition uses object-centred frame of reference - ie/ the laptop is X distance to the coffee mug aka the what stream
55
dorsal visual stream
primary visual cortex to posterior parietal cortex and beyond
56
vision-for-action system
dorsal visual stream for guiding movement and spatial characteristics of the environment uses various egocentric frames of reference how or where stream
57
same-different discrimination task
two shapes presented together, and participant asked to determine visually if they are the same or different
58
object manipulation task
grasp shape appropriately grasp requires placing thumb and index finger at stable points
59
damage to dorsal stream
results in an improper grip of object even through able to visually discriminate
60
damage to ventral stream
results in an inability to discriminate between shapes but proper grasping
61
vision contributes to locomotion
implementing avoidance stategies accommodating different terrain navigation and determining the direction of walking planning and controlling precise foot placement - people tend to fixate where they eventually step, look-ahead distance depends on the complexity of the terrain (distance decreases with more complex terrain vision is used to monitor lower limb trajectory when stepping over obstacles vision is used both to plan upcoming movement and as sensory feedback to correct the movement on-line
62
vision contributes to reaching
vision provides extrinsic, world-based coordinate information - used to plan spatial features of movements toward visual targets vision also provides information regarding initial limb (hand/arm) configuration absense of vision of hand/arm during reaching results in changes in movement kinematics and decreased accuracy research suggests that we use visual feedback continuously during the movement or after the initial (very early) phase of the movement

bpk 207 (5 decks)

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