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Perception block 11 > Parallel Processing > Flashcards

Parallel Processing Flashcards

1
Q

Difference between parallel processing and serial processing

A

Serial is sequential and parallel is running side by side

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2
Q

What are all of the systems that go to the LGN in parallel

A 
Magno cells 
-2 most ventral layers
Parvo cells 
-4 most dorsal 
Konio cells 
-interlaminar regions
-between principal layers 
-smallest of 3 LGN
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3
Q

Where does LGN project to

A

Primarily to visual cortex

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4
Q

What is the smallest of the 3 LGN cells

A

Konio

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5
Q

Parvo cells are sensitive to _____

A

R/G color contrast

  • not sensitive to movement
  • 70% of retinogeniculate pathway
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6
Q

70% of th retinogeniculate pathway

A

Parvo

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7
Q

Magno cells are sensitive to

A

Rapid movement

  • 10% of retinogeniculate pathway
  • mostly monochromatic
  • rods primarily feed into the magno pathway
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8
Q

10% of the retinogeniculate pathway

A

Magno

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9
Q

Konio cells respond to _____

A

B/Y color contrast

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10
Q

Cortical projection of parvo neurons

A

4Cb

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11
Q

Cortical projections of magno neurons

A

4Ca

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12
Q

Both parvo and konio neurons are characterized by

A

Color oppnency

  • They are excited by cortina wavelengths and inhibited by others
  • the sign of the response (excitatory or inhibitory) encodes info about the stimulus wavelength
  • these cells play critical role in wavelength based discrimination
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13
Q

These cells play a critical role in wavelength based discrimination

A

Parvo and konio

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14
Q

Many cells in parvo layers manifest

A

R-G opponency

-input from the midget ganglion cells

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15
Q

Input to the parvocellualr layers

A

Midget ganglion cells

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16
Q

Konio cells exhibit ____ opponency

A

Blue yellow

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17
Q

Input to konio presumed to originate from

A

Small bistratisfied ganglion cells

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18
Q

Onion cells confined to the interlaminar regions of the LGN

A

May not be confined

  • certain cells in the parvocellualr region of the LGN manifest B-Y properties
  • unknown if these are true parvo cells or konio cels
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19
Q

Show weak or no color opponency

A

Magno cells

  • generally give a response of the same sign (regardless of the stimulus wavelength)
  • not capable of contributing significantly to wavelength based discriminations
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20
Q

Temporal properties of parvo

A

Sustained response to long-duration stimulus

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21
Q

Temporal properties of magno

A
  • transient response to long-duration stimulus
  • brief burst of activity at onset and offset
  • may be due to input from transient amacrine cells
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22
Q

Spatial properties of parvo

A

S-spatial properties similar to retinal midget cells

-smaller receptive field centers provide higher spatial resolution

23
Q

Spatial properties for magno

A
  • spatial properties similar to retinal parasol cells
  • larger diamter axons transmit APs faster than konio or parvo (Myelin)
  • stimuli that isolate magno pathway have shorter visual latency than those that isolate parvo or konio pathways
24
Q

What system has larger diameter axons to allow for faster transmitting of APs?

A

Magno

25
Q

The division of parvo and magno in the retinogenicualte pathway

A

The clear division into distinct parvo and magno pathways seen in the retinogeniculate pathway is not so apparent in the cortex
-parvo and magno retinogenicualte pathways may be the predominant inputs to the cortical ventral and dorsal processing streams

26
Q

May be the predominant inputs to the cortical ventral and dorsal processing streams

A

Parvo and magno

27
Q

Magno and parvo communicating with cortical processing stream

A

Neither retinogenicualte pathway appears to communicate exclusively with a particular cortical processing stream

28
Q

Lesion in the parvocellualr region of LGN

A
  • vision altered in predictable manner
  • reduced wavelength discrimination
  • reduced high spatial frequency contrast sensitivity
  • detection of high temporal frequency flicker and other visual capabilities remain unaltered
29
Q

Lesion in magnocellualr region of LGN

A
  • reduction of high temporal frequency flicker
  • reduction of low spatial frequency contrast sensitivity
  • unaltered wavelength discrimination
  • unaltered high spatial frequency contrast sensitivity
30
Q

This pathway is key to color discrimination and vVA

A

Parvo pathway

31
Q

This system encodes fast movements and low spatial frequencies

A

Magno

32
Q

Isoluminant gratings

A
  • bars of varying chromaticities
  • same luminance
  • may isolate the parvo system
  • bars are visible only due to chromatic contrast
33
Q

Why isoluminant gratings isolate the parvo system

A
  • spectral Sensitivity of a magano neuron is similar in form to the photopic luminance function
  • a green bar of the isoluminant grating activates a magno cell to the same extent as a red bar
  • border formed by the bars become invisible to the magno cell
  • the magno pathway is “silenced” by isoluminant stimuli
  • the perceptual distortions noted when viewing isoluminant stimuli-for instance, abnormal motion perception- are consistent with reduced magno contribution
34
Q

Why is the isoluminant grating strategy limited?

A
  • spectral sensitivity of magno cells varies slightly from cell to cell
  • therefore unlikely that isoluminant stimuli silcene all magno neurons
  • perceptions obtained using isoluminant stimuli proabably do not reflect the parvo system in isolation
35
Q

Do the isoluminant gratings isolate the parvo systems?

A

Mostly, not 100%

36
Q

Diseases and parvo, magno, konio

A

Certain disease can impact different pathways

  • noninvasive psychophysical produces could be useful for their early and differential diagnosis
  • procedures must isolate these pathways
37
Q

Dx of glaucoma

A
  • VF loss
  • ONH appearance
  • IOP
  • VF loss already indicates a substantial proportion of ganglion cells have died

May lead to blindness
Early treatment delays progression of visual loss

38
Q

Key to preventing vision loss in glaucoma

A

Treat early

39
Q

Autopsies of POAG reveals what

A

Axons of larger neurons are damaged earlier than those of smaller neurons (Magno)

40
Q

Which pathway is more susceptible to glaucoma damage>/

A

Magno

41
Q

Tests to look at magno pathway in glaucoma

A

Frequency doubling

42
Q

Healthy patient in frequency doubling

A

As temporal rate is increased, the patient will note the apparent spatial freqnwcy of the grating doubles

43
Q

PAOG and frequency doubling

A

Ledimpaired

-led to the adoption of frequency doubling tech as a clinical tool

44
Q

Original FDT perimeter threshold testing

A
  • employed a four-reversal staircase procedure known as the modified binary search algorithm (MOBS)
  • contrast increased until a stimulus is detected
  • contrast is decreased if the stimulus is detected at a higher level
45
Q

N30-1 screening test

A
  • presents stimuli that can be detected by 99% of normal population
  • if initial target not detected, it will be repeated
  • if again not detected, it will be presented at a level detected by 99.5% of the normal population
  • if thus target is not seen the stimulus is presented as max contrast
  • sensitivity for the N30-1 test is been reported to be 78-92% and specificity between 85-100%
  • the high specificity associated with this test suggests it may be useful option for large population
46
Q

Why is N30-1 good for screening

A

High sensitivity

47
Q

N30-5

A

Diagnosis and following glaucoma

  • first stimuli presented at 95%
  • repeated if not detected
  • if not still, presented one that is detected by 98%, then 99% detection level
  • 30s per eye

High sensitivity better for detecting VF loss for glaucoma

48
Q

Humphrey matrix 800

A
  • for early VF loss detection
  • people fall asleep easily
  • detects damage to M cells (magno)
  • fast and easy
  • doesn’t need dark room, no trial lenses or eye patches
  • small
49
Q

Tests with high contrasts targets are more specific for

A

Detecting patients with VF defects

50
Q

Tests with lower contrast levels

A

Are more sensitive

51
Q

Physiological underpinnings of FDT

A

Based on assumptions

  • could find no characteristics of the magno cell neural response that could account for frequency doubling
  • dont know why or how it works, but it does
52
Q

Dyslexia

A
  • selective impairment of reading skills in spite of normal
  • intelligence
  • vision
  • hearing
  • instruction
  • motivation
53
Q

Origins of dyslexia

A

Remain controversial

  • prevailing view: primarily cognitive disorder
  • there are some who believe it is due to sensory defects
54
Q

Dyslexia and temporal information

A

Deficits in it

  • magno
  • flicker fusion rates abnormalities

Perception block 11 (8 decks)

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