Visual System Flashcards
Rods contain _____.
rhodopsin
Rhodopsin is extremely sensitive to _____.
light
Rods function _____ in dim light and _____ in bright light.
well, poorly
Rods do not distinguish _____.
color
Rods are located in the _____.
peripheral retina
Cones contain _____.
iodopsin
Iodopsin requires _____ to function.
bright light
Cones function _____ in daylight and _____ dim light.
well, poorly
Cones have three types of iodopsins to respond to _____.
different wavelengths of light
Cones are located in the _____.
central retina (fovea)
Receptive fields of rods are _____.
large
Receptive fields of cones are _____.
small
Many rods share a _____.
ganglion cell
Fewer cones than rods attach to each _____.
ganglion cell
In the _____ each cone has its own ganglion cell.
fovea
_____ contact photoreceptors and bipolar cells.
Horizontal cells
_____ contact bipolar and ganglion cells.
Amacrine cells
Ganglion cells create _____ potentials.
action
When light strikes rhodopsin, _____ is activated.
retinal (RPE65)
Leber’s congenital optic degeneration
RPE65 (retinal) is defective
photoreceptors degenerate
patient goes blind
Light closes sodium channels, causing _____.
rods are turned off
hyperpolarization
Lateral inhibition
inhibition of connected bipolar cells produces contrast
LGN (lateral geniculate nucleus) of the thalamus has _____ cell types.
three
Parvocellular cells consist of _____ dorsal layers and are _____ cells with _____ receptive fields.
four, small, small
Magnocellular cells consist of _____ ventral layers and are _____ cells with _____ receptive fields.
two, large, large
Koniocellular cells consist of layers with _____ cells, between _____ layers.
very small, main (P & M)
Most visual information first arrives in the _____.
Primary visual cortex (V1)
in occipital cortex
Brain maps of visual space are mostly devoted to the _____.
fovea
Simple cells are _____.
line detectors
Simple cells are more responsive to _____, than to static, steady illumination or diffuse illumination.
flashes of light
Complex cells are concerned more with _____ than with their precise localization.
recognizing external objects
Simple cortical cells, also called _____, respond to an edge or bar of a particular _____.
bar or edge detectors
width, orientation, and location
Complex cortical cells respond to _____, but may be located _____ in the visual field.
a bar of a particular width and orientation
anywhere
_____ receive input from neurons in lateral geniculate nucleus.
Simple cortical neurons
_____ receive input from simple cells.
Complex cortical neurons
Visual cortical cells do a _____ of the luminosity variations in a scene.
frequency analysis
Different visual cortical cells have different _____.
sensitivities
Visual cortical cells can detect not just _____ but _____ of luminosity change.
edges, grades
Area V1 (primary visual cortex) Is organized in _____ and _____.
columns, slabs
An ocular dominance column is a region of cortex with _____ from one eye.
greater synaptic input
Much of vision is _____ from what is actually ‘seen’.
extrapolating (predicting)
Cells in inferotemporal cortex respond to _____, including _____ we have learned to recognize.
complex forms, forms
Receptive fields in IT cortex develop through _____ and _____.
experience, learning
Hierarchy of visual processing
From simple edges and borders to complex forms as you move from V1 to IT.
The M-channel (magnocellular pathway) is _____ selective, _____ sensitive for movement, and has no _____ sensitivity
(analysis of object motion)
orientation, directional, color
The P-IB channel (parvocellular interblob pathway) has high _____ sensitivity, no _____ sensitivity, and _____.
(analysis of object shape)
orientation, color, small receptive fields
The blob channel (parvocellular blob and koniocellular pathway) has _____ sensitivity and no _____ sensitivity.
(analysis of object color)
color, orientation
Trichromatic hypothesis
Three types of cones
Each cone responds to a part of the spectrum
Each cone has a separate pathway to the brain
Opponent-process hypothesis
Three color axes (opposed pairs of colors)
red - green
yellow - blue
white - black
Akinetopsia
Motion blindness
Opponent Process: Cells in the _____ and thalamic _____ layers fire to some _____, and are inhibited by others.
retinal ganglion, parvocellular, wavelengths
Micropsia causes objects in the visual field to appear _____ than normal.
smaller
Macropsia causes objects in the visual field to appear _____ than normal.
larger
_____ is cause by alternating micropsia and macropsia.
Alice in Wonderland Syndrome
_____ results in the ability to see individual objects and the inability to perceive a visual scene as a whole.
Simultagnosia
_____ results in seeing afterimages, both as a reduced amount of time required to form an afterimage, and an increased duration of the afterimage.
Palinopsia
_____ results in normal speech, sensations, ability to use objects, and the the inability to name objects.
Visual agnosia
Blindsight is due to minor pathways leading into the _____ that bypass _____.
extrastriate cortex (V2 through V5) straite cortex (V1)
The _____ is associated with motion, representation of object locations, and control of the eyes and arms.
(the ‘where’ pathway)
dorsal stream
The _____ is associated with form recognition and object representation.
(the ‘what’ pathway)
ventral stream
Optic ataxia
The patient can’t use visuospatial information to guide arm movements.
Amblyopia
The loss of one eye’s ability to see details.
lazy eye
Hemispatial neglect
The patient is unaware of the contralesional half of space.
contralesional: the half of a patient’s brain or body away from the site of a lesion
Cells are classified as _____ or _____, depending on their _____.
simple, complex, receptive fields
Vitamin _____ is a precursor to retinal.
A
Hyperopia is known as _____ and can be corrected with a _____ lens.
farsightedness, convex
Myopia is known as _____ and can be corrected with a _____ lens.
nearsightedness, concave
The M-Channel is involved in _____ analysis.
motion
The P-IB Channel is involved in _____ analysis.
shape
The Blob Channel is involved in _____ analysis.
color
The optic nerve is composed of _____.
ganglion cells
