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Neuroscience > Lecture 15: Vision > Flashcards

Lecture 15: Vision Flashcards

1
Q

what is the 7 step hierarchy of the visual system

A

eye and retina (photoreceptors)

optic nerve

optic chiasm

optic tracts

thalamus

Optic radiations

primary visual cortex

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2
Q

what is the retina

A

Receives light from the lens and converts it into neural signals that the brain can understand.

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3
Q

what are photoreceptors

A

cells in the retina that respond to light

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4
Q

what are the two kinds of photoreceptors

A

rods

cones

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5
Q

where are rods found

A

in the peripheral retina

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6
Q

what are rods

A

Achromatic (don’t process colour)

High light sensitivity, so we use these for Nighttime vision

a lot more rods than cones

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7
Q

where are cones found

A

in the central retina (fovea)

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8
Q

what are cones

A

High-acuity and colour vision during day-time when light levels are higher.

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9
Q

what is the optic disc

A

Region where the axons leaving the retina gather to form the optic nerve

*no photoreceptors here > blind spot

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10
Q

what is the region of the retina with the HIGHEST visual acuity

A

the fovea

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11
Q

what are the 2 kinds of ganglion cells

A

Parasol Ganglion Cells

Midget Ganglion Cells

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12
Q

what are Parasol Ganglion Cells

A
  • Gross stimulus features and movement
  • Large cell bodies, large receptive fields, large axons
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13
Q

what are Midget Ganglion Cells

A
  • Fine visual detail and color
  • Small cell bodies, small receptive fields, smaller axons…. More NUMEROUS
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14
Q

what is Age-Related Macular Degeneration

A

Damage to macula. Central vision affected.

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15
Q

what is Diabetic Retinopathy

A

Excess blood sugar damages retinal blood vessels. Patchy vision loss throughout visual field.

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16
Q

what is Cataracts

A

Loss of lens transparency.

17
Q

what is Glaucoma

A

Increased intraocular pressure = damage to optic nerve (often peripheral deficits).

18
Q

how is what we see changed

A

its flipped and inverted by the type it reaches the optic nerves

19
Q

once information has been flipped and upside down, where does it go

A

the optic chasm where 60% of fibres cross

20
Q

where does information go after the optic chiasm

A

the optic nerves become the optic tracts, which each have information from both eyes

21
Q

what is the path for anything to do with motion/spatial analysis

A

it goes through the parasol cells, then to the magnocellular layers of thalamus

it stays in its own channel

22
Q

what is the path for anything to do with form and colour

A

it goes through the midget cells, then to the parvocellular layers of thalamus

it stays in its own channel

23
Q

what is the retina-geniculate pathway

A

the primary visual pathway used for conscious vision

Information from the retina projects to four important subcortical regions in the thalamus

24
Q

what are the 3 extra-geniculate pathways

A

don’t go to thalamus, for subconscious vision

pretectum

superior colliculus

hypothalamus

25
Q

what are the where/what pathways

A

once information reaches the primary visual cortex, it can either go:

up to the parietal stream (where- analysis of motion and spatial relations)

down to the temporal stream (what-analysis of form and colour)

26
Q

what is Prosopagnosia

A

inability to recognize faces

issue with the “what” pathway

27
Q

what is Homonymous field deficits

A

a part of the visual field is missing

common after stroke

27
Q

what are the 6 muscles responsible for moving the eyes

A

Lateral Rectus

Medial Rectus

Superior Rectus

Inferior Rectus

Superior Oblique

Inferior Oblique

28
Q

what are brainstem gaze centres

A

responsible for the automatic control of our extra- ocular muscles

Direct the movements of two eyes together

Connected to output nuclei by inter-nuclear pathways (circuits)

29
Q

what is paramedian pontine reticular formation (PPRF)

A

the horizontal gaze center

gives information to the medial longitudinal fasciculus or MLF to yoke the right and left eye

30
Q

what are saccades

A

Rapid eye movements to bring targets of interest into the field of view

Refocus image on the fovea

31
Q

what are the 2 kinds of saccadic eye movements

A

reflexive (loud sound)

voluntary (looking for someone)

32
Q

what is Smooth pursuit

A

Require moving stimulus; cannot be carried out voluntarily without a stimulus

eyes track something as it moves

33
Q

what is Optokinetic Nystagmus

A
  • Slow phase (smooth pursuit) in one direction
  • Fast phase (saccade-like) eye movements in the other

“Train nystagmus”

34
Q

what is the Vestibulo-ocular reflex (VOR)

A

Eye movements maintain fixation on target when the head moves

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