psych of perception chapter 3 Flashcards
visible spectrum for human
ranges from 400 to 700 nanometers
name the electromagnetic wave spectrum from short wavelenghts to long wavelengths
gamma, x-ray, ultraviolet, visible light, infrared, microwaves, radio waves
what is fovea
point of central focus
all-cone foveal vision results in high visual acuity
ligth patway in the eye
light enters the eye through the pupil and is focused by by the cornea and lens to sharp image on retina
distribution on retina
fovea consist solely of cones,
peripheral retina has both rods and cones,
more rods then cones in periphery
number of cones and rods
120 million rods and 6 million cones
blind spot
place where the optic nerve leaves the eye
lens
adjust shape for object distance (accomodation results when ciliary muscles are tightened, which causes the lens to thicken)
light focusing
cornea, which is fixed, accounts for 80% of focusing,
the lens, which adjust shape for object distance, accounts for the other 20%
presbyopia
presbyopia is the gradual loss of your eyes’ ability to focus on nearby objects
due to hardening lens and weakening of ciliary muscles
myopia
can’t see well from futher away (nearsightedness)
image is focused in front of the retina
myopia is caused by
cornea or lens bends too much light
eyeball is too long
hyperopia
can’t see objects from up close well
focus point is behind retina
eyeball too short
what is dark adaption
process of increasing sensitivity in the dark
dark adaptaion curve
sensitivity increases in two stages (3-4min)
then sensitivity levels off for 7-10min - the rod-cone break
stage two shows increased sensitivity for another 20 to 30min
threshold
threshold for light is lowest in the middle of the spectrum
use monochromatic light to determine threshold at different wavelenghts
rod spectral sensitivity
more sensitive to short-wavelenght light
most sensitive at 500nm
cone spectral sensitivity
most sensitive at 560nm
Purkinje shift
enhanced sensitivity to short wavelenghts during dark adaptaion when the shift from cone to rod vision occurs
rods and cones sends signals vertically through
bipolar cells
ganglion cells
ganglion axons
rods and cones sends signals horizontally through
between receptors by horizontal cells
between bipolar and between ganglion cells by amavrine cells
rods
rods are more sensitive to light than cones
take less light to respond
cannot distinguish detail
rods convergence
rods have greater convergence, which results in summation of the inputs of many rods into ganglion cels increasing likelihood of response
lateral inhibition
emphasizing the boundaries between things
simultaneous contrast
if surrounding region is brighter then cells that are covering this brighter region will create more suppresion signal to the center which makes it appear darker
receptive field
area of retina that affects firing rate of a given neuron in the circuit (imaginary spot on the retina)
center and surround ares of receptive field result in
excitatory-center-inhibitory surround
inhibitory-enter-excitatory surround
center-surround antagonism
when stimulated, the center and surround of RF cause the opposite responses to the corresponding ganglion cell