ch. 10 - central visual system Flashcards
conscious visual perception pathway
retina to lateral geniculate nucleus (LGN) of thalamus to primary visual cortex (area 17, V1, striate cortex)
retinofugal projection is made up of…. (in order)
- optic nerve
- optic chiasm
- optic tract
optic nerves
- travel through fatty tissue behind the eyes and pass through holes in the floor of the skull
- form optic chiasm
optic chiasm
- anterior to pituitary
- axons from nasal retina cross here
decussation
the crossing of a fiber bundle from one side of the brain to the other
optic tracts
run under pia mater along lateral diencephalon
left visual field
objects appearing to the left of the midline
right visual field
objects appearing to the right of the midline
binocular visual field
the central portion of both visual hemifields, viewed by BOTH retinas
where is the left visual hemifield in each eye?
RIGHT: temporal side
LEFT: nasal side
which hemisphere views information from the left visual hemifield?
right hemisphere
which hemisphere views information from the right visual hemifield?
left hemisphere
optic tract is most connected to…
LGN of dorsal thalamus
optic tract projects to the primary visual cortex via…
optic radiation
T or F: lesions ANYWHERE in the retinofugal projection from eye to LGN to visual cortex cause blindness in humans
TRUE
damage to the left optic nerve causes…
blindness in entire left eye only
damage to the left optic tract causes…
blindness in the right visual field in both eyes
optic tract connecting to pretectum
controls the size of the pupil and certain types of eye movement
optic tract connecting to hypothalamus
synchronize sleep and wakefulness with light-dark cycle and other biological rhythms
10% connect to superior colliculus
orient eyes in response to new stimulus
another name for super colliculus
optic tectum
which of the 6 layers of LGN is the more ventral?
layer 1
LGN neurons receive synaptic input from..
retinal ganglion cells
the left visual field is viewed by…
left nasal and right temporal
right LGN, right eye (ipsilateral) axons synapse on…
LGN layers 2, 3, 5
right LGN, left eye (contralateral) axons synapse on…
LGN layers 1, 4, 6
LGN layers 1 and 2
larger, called magnocellular (M cells)
LGN layers 3-6
smaller, called parvocellular (P cells)
koniocellular layers
small layer inbetween, receive input from nonM-nonP cells
major input to LGN comes from
primary visual cortex
retinotopy
an organization whereby neighboring cells in the retina feed information to neighboring places in their target structures
spiny stellate cells
small neurons with spine-covered dendrites that radiate out from the cell body
- in layers IVc
- axons make local connections
- golgi type II
pyramidal cells
covered with spines, characterized by a single thick apical dendrite that branches as it ascends toward the pia mater and by multiple basal dendrites that extend horizontally
inhibitory neurons
lack spines and are found in all layers
- form ONLYA local connections
which type of cells send axons out of striate cortex to form connections with other parts of the brain?
ONLY pyramidal
M cells project to
IVc alpha
P cells project to
IVc beta
koniocellular project to
layers II and III
ocular dominance columns
left and right eye inputs in stripes
layer IVc neurons project radially to
layers IVb and III, where left and right eye inputs mix
IVc alpha projects to
IVb
IVc beta projects to
layer III
in which layers can an axon form synapses with pyramidal cell dendrites from all layers?
III and IVb
layer III blobs receive input from
LGN directly
cytochrome oxidase
mitochondrial enzyme used for cell metabolism
Hubel and Wiesel
receptive fields in layer Ivc are similar to M cell and P cell LGN inputs
which layer is insensitive to wavelength?
IVc alpha
which layer has center-surround color opponency?
IVc beta
orientation selectivity
most of the receptive fields in the retina, LGN, and layer Ivc are circular and respond best to spot of light matched in size to receptive field center
V1 responds best to
elongated bar of light moving across their receptive fields
orientation-selective neurons are thought to be specialized for…
analysis of object shape
radial column of cells through which layers have the same preferred orientation?
II through VI
direction selectivity
respond when a bar of light at the optimal orientation moves perpendicular to the orientation in one direction but not in the opposite
sensitivity to the direction of stimulus motion is a hallmark of neurons receiving input from…
magnocellular layers of LGN
direction-selective neurons are thought to be specialized for…
analysis of object motion
simple cells
V1 neurons receiving a converging input from three or more LGN cells with receptor fields that are aligned along one axis
properties of simple and complex cells
- binocular
- sensitive to stimulus orientation
- direction selective
- relatively insensitive to wavelength
complex cells
- do NOT have distinct on and off regions
- may receive input from several simple cells
magnocellular pathway
- type of parallel pathway
- project to IVC alpha, which then projects to IVb
- analysis of object motion and guidance of motor actions
parvo-interblob pathway
- type of parallel pathway
- project to IVC beta, which then project to layer II and III
- analysis of fine object shape
blob pathway
- type of parallel pathway
- nonM-nonP to koniocellular layers II and III
- color, monocular, no orientation selectivity
- analysis of object colors
dorsal stream
- visual control of action and motion analysis
- extension of V1 magnocellular pathway
ventral stream
- perception and object recognition
- extension of V1 parvo-interblob and blob pathways
MT or V5
- dorsal stream
- all cells are direction selective
- important role in motion perception
MST
- linear motion
- radial motion
- circular motion
dorsal stream uses information for…
- navigation
- directing eye movements
- motion perception
V4
- ventral stream
- orientation and color selective
- important for shape and color perception
area IT
- ventral stream
- colors and abstract shapes
- some respond to faces
- important for visual perception and memory
achromatopsia
characterized by a parietal or complete loss of color vision despite the presence of normal functional cones in the retina
prosopagnosia
difficulty recognizing faces even though vision is otherwise normal
visual perception
the task of identifying and assigning meaning to objects in space