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40 Cards in this Set

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Law of Specific Nerve Energies
Mueller held that whatever excited a particular nerve establishes a special kind of energy unique to that nerve. Sooo, any activity by a particular nerve always conveys the same kind of info (brain sees activity from optic nerve and hears activity from auditory nerve)
If the optic nerve is directed into what is ordinarily the auditory portion of the brain, very early in development, what happens?
What would have been auditory thalamus and cortex reorganized to become visual coretex, developing some (but not all) of the characteristic appearance of a visual cortex. Stimulation there produces visual experience. (Ferret study!)
pupil
light enters the eye through an opening in the center of the iris called the pupil
lens
focuses light; adjustable
cornea
focuses light; not adjustable
retina
rear surface of the eye lined with visual receptors; light from left visual field strikes right side of retina and vice versa;image on retina is reversed
bipolar cells
located in retina; receptors on back of the eye send messages toward biopolar cells whcih are neurons located closer to the center of the eye
amacrine cells
get info from biopolar cells and send to other biopolars, other amacrine cells or ganglion cells. located in retina closer to center than recepors, bipolar and ganglion
ganglion cells
get info from bipolar cells, located in retina but closer to the center of the eye than receptors and bipolar cells; axons join one another to loop around and travel back to the brain, forming the optic nerve
blind spot
point at which optic nerve exits the eye and therefore contains no receptors at this point
fovea
central portion of the macula; "pit"; specialized for acute detailed vision-the most precise visionl blood vessels and ganglion cell axons are absent here and receptors packed tightly leads to least impeded vision and therefore great pereception of detail; all cones
macula
greatest ability to resolve detail; center of retina
ciliary muslces
controls the lens;
rods
one type of receptor in the retina; most abundant in the periphery of the human retina, respond to faint light but are bleached by bright light and thus not very useful in bright daylight; more rods than cones; periphery vision is mostly rods and each receptor shares a line with tens or hundres of others
cones
one type of receptor in retina; most abundant in and around the fovea, are less active in dim light, more useful in bright light and essential for color vision; more direct route to brain than rods; each has own line to the brain
Why can you see a faint star in your periphery better than when looking directly at it
the light falls on the part of the retina with more rods which are more sensitive to faint light-more convergence of input, magnifying sensitivity to faint light
trichromoatic theory of color vision
aka Young-Helmholtz theory; we perceive color through the relative rates of response by three kinds of cones, each kind maximally sensitive to diff set of wavelengths; long wavelenth cones, short wavelenth and medium wavelength cones distributed randomly within the retina
Opponent-process theory
trichromatic theory doesn't account for all color vision like negative color afterimage; we perceieve color in terms of paired opposites:red vs green, yellow vs.blue and white vs black...no such thing as reddish-green, etc;
Retinex Theory
the two other theories don't explain color and brightness constancy; the cortex compares info from various parts of teh retina to determine the brightness and coor perception of each area (ex: if cortex notes a certain amount of green throughout a scene, it subtracts some green from each object to determine true color
Color constancy
ability to recognize the color of an object despite changed in lighting
Long wavelength cones
responds well to red or yellow
medium wavelength cones
responds best to green, less to yellow
short wavelength cones
responds best to blue
horizontal cells
rods and cones make synaptic contact with horizontal cells and bipolar cells; horizontal make inhibitory contact wit bipolar
optic chiasm
the optic nerve from left eye and from right eye meet at the optic chiasm; half the axons from each eye cross to the opposite die of the brain
lateral geniculate nucleus
axons from ganglion cells go here; it's a nucleus of the thalamus specialized for visual perception
optic nerve
starts at the ganglion cell axons and can lead to the lateral geniculate nucleus of the thalamus (most do) or the superior colliculous or hypotahlamus or elsewhere
receptive field
part of the visual field to which any one neuron responds is that neuron's receptive field; receptive field for ganglion cellwould be the combined receptive fields of all the receptors that are connected to it
lateral inhibition
reduction of activity in one neuron by activity in neighboring neuron
parvocellular neurons
type of ganglion cell; smaller cell bodies and small receptive fields, mostly in or near fovea; highly sensitive to detail because small receptive field; highly sensitive to color (excited by some and inhibited by others); connect only to LGN of thalamus
magnocellular neurons
ganglion cell; larger cell bodies and receptive fields, distributed fairly evenly thoughout retina; not color sensitive, respond strongly to moving stimuli and overall patterns but not details; throughout retina, including periphery; most connect to LGN but a few connect to other visual areas of thalamus
koniocellular neurons
ganglion cell; small cell bodies, similar to parvo but they occur throughout retina instead of clustered near fovea; connect to LGN, other parts of thalamus, and superior colliculus
visual pathway
photoreceptors to LGN to primary visual cortex(aka V1 or striate cortex) then goes to secondary visual cortex (V2; but V1 and V2 are reciprocal)
primary visual cortex
V1; responds to any kind of visual stimulus and is active even when we close our eyes and imagine visual stimuli
secondary visual cortex
V2; process info further and transmits to additional areas
ventral stream
visual paths in the temporal cortex, aka "what" pathway bc it is specialized for identifying and recognizing objects
dorsal stream
visual path in the parietal cortex, aka "where" or "how" pathway bc it helps motor system find objects and how to move toward them, grasp them and so forth
simple cells
only found in primary visual cortex; receptive field of a simple cell has fixed excitatory and inhibitory zones
complex cells
located in either V1 or V2 have receptive fields that cannot be mapped into fixed exciatory or inhibitory zones; it responds to a pattern of light in a particular orientations anywhere within its large receptive field, regardless of the exact location of the stimulus
end-stopped or hypercomplex cells
resemble complex cells but it has a strong inhibitory area at one end of its bar shaped receptive field