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Organs Systems 3 Exam 1 > Visual Part 4 > Flashcards

Visual Part 4 Flashcards

1
Q

What are two ways in which the visual field is bissected?

A
  1. partial decussation of ganglion cells at optic chiasm. 2. R and L visual fields project to opposite LGBs and visual cortexes.
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2
Q

What is a cause of total blindness in one eye?

A

a lesion of the optic nerve before the optic chiasm

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3
Q

What is hemianopsia?

A

loss of half of the visual field

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4
Q

What is heteronymous hemianopsia?

A

loss of opposite visual fields due to a lesion at the central optic chiams (eg. from pituitary tumors)

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5
Q

What is homonymous hemianopsia?

A

loss of the same visual fields due to a lesion between the optic chiasm and the visual cortex

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6
Q

where is the lateral genticulate nucleus?

A

in the thalamus

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7
Q

What kind of visual information does the parvocellular pathway transmit?

A

color and shape information for object perception and information

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8
Q

What kind of visual information does the magnocellular pathway transmit?

A

movement related information for perception of motion, direction, attention and alerting

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9
Q

What kind of information does the koniocellular pathway transmit?

A

low acuity color information to the primary visual cortex for unconcsious visual behavior (eg. blindsight)

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10
Q

90% of axons in the optic nerve are a part of what pathway?

A

the parvocellular pathway (P or midget cells)

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11
Q

5% of axons in the optic nerve are a part of what pathway?

A

the magnocellular pathway (M or parasol cells)

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12
Q

Which pathway is high acuity? the parvocellular or the magnocellular pathway?

A

the parvocellular is high acuity

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13
Q

Which visual pathway recieves information mostly from cones?

A

the parvocellular pathway

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14
Q

Which visual pathway recieves information mostly from rods and is good in night vision?

A

the magnocellular pathway

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15
Q

How many layers does the lateral geniculate nucleus have?

A

six (four parvcellular and two magnocellular)

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16
Q

Where is the primary visual cortex (V1)?

A

medial surface of the occipital lobe

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17
Q

V2, V3 and V5 are what kind of areas?

A

association visual corteces

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18
Q

What do the LGN neurons project to the primary visual cortex?

A

information from the retinal center-surround receptive fields

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19
Q

What are four types of information that the primary visual cortex perceives?

A

form, color, motion, binocular vision

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20
Q

What do simple cells in the primary visual cortex do?

A

combine input from several geniculate cells that respond to the same bar of light

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21
Q

how do simple cell RFs differ from retinal or geniculate RFs?

A

they are more oval/rectangular that retinal/geniculate round RFs

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22
Q

How do complex cells differ from simple cells?

A

complex cells can respond to properly oriented edges/bars of light anywhere within the RF

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23
Q

What type of cells seem to reflect both parallel paths from the geniculate as well as interactions among simple cells and cortical neurons?

A

complex cells of the PVC (V1)

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24
Q

What type of PVC cells detect egdes only?

A

simple cells

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25
Q

What type of PVC cells detect position and orientation of a structure?

A

complex cells

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26
Q

What type of cells detect endpoints and crossing lines from position/orientation information?

A

hyper-complex cells

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27
Q

What cortex integrates information from simple, complex and hyper-complex cells to generate object familiarity?

A

association (secondary) visual corteces

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28
Q

What are visual cortical columns?

A

vertical zones of the cortex that combine simple and complex cells to sort information. used to provide feedback to LGN

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29
Q

What kind of information do the cortical columns sort?

A

edge orientation, color, shape/size, direction of movement and R/L eye dominance

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30
Q

How is color perception organized in the retina, LGN and cortical regions?

A

red-green or blue-yellow center-surrounds that get organized into ‘blobs’ in the cortex

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31
Q

What is stereopsis?

A

stereopis is binocularity

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32
Q

how is depth perception generated?

A

retinal disparity and binocular input from complex cells in upper and lower layers of primary and association visual cortices.

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33
Q

How is depth perception acquired in monocular vision?

A

visual clues such as interposition, shading, relative size, linear perspective, etc

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34
Q

What is the purpose of cortical feedback?

A

to shape sensory input according to behavior, enhance acuity, altering lateral inhibition-like mechanism. enhances responsiveness to a particular stimulus

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35
Q

LGN cells are modified by what structures?

A

cortical columns and brainstem pathways (from norepi, serotonin, Ach, NO) (reticular formation, eg)

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36
Q

How does cortical feedback work?

A

cortical cells that respond to a specific RF will sharpen the response of corresponding LGN cells. This increases the number of LGN cells responding to the same stimulus, enhancing LGN-cortical transmissions

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37
Q

What is the purpose of brainstem pathways that modulate the LGN?

A

modulate wakefulness, acuity, arousal, attention and focus. shifts between wakefulness and sleep states, eg. responds to intense emotions and flashes of light

38
Q

How does the brainstem communicate with the LGN and the cortex?

A

NO, ACh released from the parabrachial nucleus in the brainstem. Norepi and serotonin (5-HT) also released from the reticular formation

39
Q

What are the two visual association cortices?

A

The ventral (parvocellular) stream for color, acuity and object identification. The dorsal (magnocellular) stream for action, object manipulation and “where”/”how”.

40
Q

The ventral system receives information from what type of photoreceptors and where does that information go?

A

from cones, goes to the inferotemporal gyrus for identification of form, color, and “working memory”

41
Q

The dorsal system receives information from what type of photoreceptors?

A

rods

42
Q

The dorsal and ventral visual association streams form what?

A

the prefrontal cortex and become “working memory”

43
Q

What does the V1 cortex respond to?

A

orientation, spatial frequency, color

44
Q

What is the V2 cortex tuned to?

A

angles between lines, orientation of illusory contours

45
Q

What is the V4 cortex tuned to?

A

color, complex shape attributes such as corners, outline-shapes (human color center)

46
Q

What is the inferotemporal cortex tuned to?

A

form, color, scale, position invariance, emotional connections, faces, emotional expression

47
Q

What is the middle temporal cortex tuned to?

A

complex, global motion (part of the dorsal stream)

48
Q

How is information conveyed to the inferotemporal complex?

A

from both halves of the visual field, by interhemispheric axons via the corpus callosum

49
Q

How is IT stimulus organized? and how can the IT acuity be affected?

A

organized by the convergence of simple and complex cells. acuity is modulated by attention

50
Q

What kind of memory is shown in the IT?

A

short and long term

51
Q

What three structures are responsible for consolidating memory in the cortex?

A

the hippocampus, the amygdala and the limbic structures

52
Q

What did penfield find while performing neurosurgery on patients with epilepsy?

A

That stimulation of the IT gyrus cortex can elicit vivid scenes from the past

53
Q

What is visual neglect syndrome?

A

loss of function in the right visual association cortices. Thus, the patient sees only half of the world, does not recognize or intuit the other half

54
Q

What does the fusiform gyrus do?

A

face recognition, especially with emotional valence (is connected to the amygdala)

55
Q

Inappropriate activity in the fusiform gyrus can lead to what?

A

hallucinations

56
Q

What is synesthesia? How is it hypothesized to occur?

A

hereditary condition in which one experiences different sensations simultaneously. possibly due to cross-activation of neurons in the fusiform gyrus

57
Q

Why are emotional sensations often faster that recognition?

A

because emotional stimuli bypass the visual cortex and go straight to the fusiform gyrus/amygdala. thus they’re faster

58
Q

What are the two secondary visual (non-conscious) pathways? How are they different from conscious visual pathways?

A

the koniocellular and the melanopsin visual pathways. These differ because they bypass the LGN

59
Q

Koniocellular ganglion cells project to______ and do _____(4)

A

The superior colliculus. visual orientation, saccades, blindsight, emotion

60
Q

Melanopsin ganglion cells project to_____ and _____. There, they do what?

A

the pretectum (for pupillary reflex) and the suprachiasmatic nucleus (for circadian rythms)

61
Q

The superior colliculus receives information from:

A

the retinal koniocellular ganglia and visual, auditory, association and motor cortices.

62
Q

The superior colliculus projects information to:

A

cortical areas for eye movement (saccadic eye movement) and the brain stem and spinal cord (for head movement)

63
Q

What is the purpose of the koniocellular pathway via the superior colliculus?

A

to orient the eyes and head to the source of the stimulus

64
Q

How is the reflexive saccade initiated?

A

exogenously by peripheral stimuli

65
Q

How is the scanning saccade initiated?

A

endogenously for exploring the environment/reading

66
Q

When does seeing occur in saccadic eye movements?

A

during the pauses

67
Q

What is blindsight?

A

a lesion of the primary visual cortex that leads to complete lack of consciousness of visual information. (retain emotional responses, but are unaware of what is being seen)

68
Q

What pathway is proposed to generate blindsight?

A

the extrastriate/koniocellular pathway (bypasses the PVC). koniocellular ganglions –> SC –>pulvinar nucleus –>posterios parietal cortex (dorsal stream) and amygdala (emotions)

69
Q

What does the pulvinar nucleus do?

A

conveys emotional stimuli to the amygdala, the cingulate and orbitofrontal cortex for subcortical sensory input to the limbic system.

70
Q

What does the amygdala do?

A

stimulate norepi pathways from the reticular formation for mental arousal/awareness

71
Q

externally perceived things involve activation of what areas?

A

specialized visual areas (visual cortex, eg)

72
Q

internally perceived things involve activation of what areas?

A

mostly frontal and parietal areas, dorso-lateral prefrontal cortex

73
Q

What are three ways that hallucinations can occur?

A

Charles Bonnet Syndrome, Cholinergic or Serotonergic deficiency

74
Q

What happens in patients with Charles Bonnet Syndrome?

A

increased activity in the fusiform face area leads to hallucinations of faces and colors (V4 activation)

75
Q

What are the two levels of altered neural activity that are related to hallucinations?

A

activation of a specific cortex or intercortical connections. neuromodulation of cortical areas by cholinergic/serotonergic pathways from the reticula formation.

76
Q

Does Charles Bonnet Syndrome affect occipital visual or anterior ventral temporal lobe areas more? How does this affect the complexity/simplicity of hallucinations?

A

CBS affects occipital visual areas more, causing a predominance in simple hallucinations

77
Q

Does cholinergic/serotonergic neuromodulation affect occipital visual or anterior ventral temporal lobe areas more? How does this affect the complexity/simplicity of hallucinations?

A

influences anterior ventral temporal lobes regions more, resulting in a predominance of complex hallucinations

78
Q

What organic compound do intrinically photosensitive retinal ganglion cells have? What is it’s purpose? What do these cells do?

A

melanopsin, which absorbs blue light for ROS protection. This initiates APs that stimulate circadian rhythm and pupillary reflex

79
Q

intrinsically photosensitive retinal ganglion cells project information to:

A

the suprachiasmatic nucleus (circadian rhythms) and to the pretectum (pupillary reflex)

80
Q

Where is the suprachiasmatic nucleus?

A

hypothalamic nucleus just above the optic chiasm

81
Q

What is the pathway of the circadian rhythm stimuli?

A

ipRGCs–>SCN –>paraventricular hypothalamic nuclei –> (1)sympathetic IML and (2) parasympathetic DMV (vagus) systems and (3)pituitary hormone release

82
Q

where and how is melatonin released?

A

SCN regulated the pineal gland to release melatonin (symathetic nervous system stimulus)

83
Q

What is melatonin/what does it do?

A

regulates sleep/wake cycles, temperature and cortisol release. it’s released with decreased blue light, a sleep promoting factor

84
Q

What is the pathway of the consensual pupillary response?

A

light –> melanopsin ganglion cells –>pretectal nucleus –> E-W nucleus –>ciliary ganglion –> spincter pupillae m.

85
Q

What kind of nuclei are the erdinger-westphal nuclei? (parasympathetic or sympathetic?

A

parasympathetic

86
Q

How does sympathetic activity affect the pupil size?

A

increases pupil size

87
Q

What is the pathway for sympathetic activity in increasing light entry into the eye?

A

preganglionic T1-T2 –> superior cervical ganglion –>dilator pupillae and tarsal m.

88
Q

How is sympathetic control of the iris and upper eyelid controlled?

A

local reflexes and limbic/hypothalamic emotional signals

89
Q

What is the tarsal muscle? how is it innervated?

A

deep to levator palpebrae, attaches to the tarsal plate of the eyelid. opens the eye in response to sympathetic and emotional states.

90
Q

What is ptosis? when is it seens and what is it caused by?

A

drooping of the eyelid caused by damage to the sympathetic nervous system. seen in Horners syndrome.

Organs Systems 3 Exam 1 (5 decks)

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