Chapter 10: The Central Visual System Flashcards
(25 cards)
central visual system
pathway serving conscious visual perception originates in the retina. Progresses to lateral geniculate nucleus, primary visual cortex, and higher order visual areas in occipital, temporal and parietal lobes.
retinofugal projection
the neural pathway that leaves the eye, beginning with the optic nerve.
decussation
the crossing of a fiber bundle from one side of the brain to the other.
optic nerves
exit the left and right eyes at the optic disks, travel through the fatty tissue behind the eyes in their bony orbits, then pass through holes in the floor of the skull.
optic chiasm
lies at the base of the brain, just anterior to where the pituitary gland dangles down from.
optic tracts
axons of the retinofugal projections form this which runs just under the pia along the lateral surface of the diencephalon.
left visual hemifield
objects appearing to the left of the midline are in the left visual hemifield.
right visual hemifield
objects appearing to the right of the midline are in the right visual hemifield
binocular visual field
by looking straight ahead with both eyes open and then alternately closing one eye and then the other, you will see that the central portion of both visual hemifields is viewed by both retinas.
lateral geniculate nucleus
most optic tract axons innervate the lateral geniculate nucleus of the dorsal thalamus. Neurons in the LGN give rise to axons that project to the primary visual cortex. Arranged into 6 distinct layers of cells.
optic radiation
projection from the LGN to the cortex.
targets of the optic tract
lesions anywhere in the retinofugal projection from the eye to the LGN to the visual cortex cause blindness in part or all of the visual field. Visual field deficits from lesions in the retinofugal projection.
superior colliculus
projections to a part of the midbrain tectum called the superior colliculus control saccadic eye movements.
hypothalamus
projections to part of the hypothalamus play an important role in synchronizing a variety of biological rhythms, including sleep and wakefulness.
pretectum
projections to part of the midbrain called the pretectum, control the size of the pupil and certain types of eye movement.
primary visual cortex
Brodmann’s area 17, located in occipital lobe of the primate brain. Also called V1 and the striate cortex.
retinotopic
neurons organized in V1 like a map of the retina, so they receive input from specific regions of retina.
V2/V3
further processing; combination of signals
V4
color interpretation
V5/MT
motion detection; direction processing. Neurons in area MT respond briskly if something moves relative to the background but show little response if the object and the background both move in the same direction and speed. MT neurons enable you to distinguish between the result of eye movements and the results of object movements.
motion blindness
an impaired ability to perceive movement after damage to area MT and surrounding areas
prospagnosia
inability to recognize faces, can result from damage to the fusiform gyrus, failure of the gyrus to develop fully, having small fusiform gyrus or few connections between the fusiform and occipital cortex.
dorsal stream
where/how, analysis of visual motion and the visual control of action. If damaged, can see objects but don’t integrate their vision with their arm and leg movements, cannot accurately reach out and grab an object.
ventral stream
what, perception of the visual world and the recognition of objects. If damaged, cannot name objects, recognize faces, or distinguish a square from a rectangle. Can use vision to guide actions.
