Visual System Flashcards
How do we see?
2-D–> 3-D
Major Structures of eye
- pupil: regulates the flow of light to the retina
- retina: converts light into electric signal then sends it to the optic nerve and then to the brain
iris: opens or closes the pupil to let in more or less light - lens: focuses the rays of light for the back of the eye(retina)
-fovea: focuses on sharp central vision optic nerve: carries visual messages
The Pupil and the Lens
- Light enters the eye through the pupil, a hole in the iris.
- Ciliary muscles adjust the lenses to focus visual images sharply on each retina, regardless of the distance of the image from the eyes; this focusing is
called accommodation.
Wavelength
perception of color
Intensity
perception of brightness
Humans see light between () and () nanometers
380- 760
Sensitivity VS Acuity
sensitivity: ability to see in dim light
Acuity: ability to see details
Ciliaty Muscles
alters shape of lens
Saccade
rapid eye movement
Fovea
- (has neurons) allows acuity
- high acuity area at the center of the retina
- where ONLY cones are found
Retina’s 5 layers (RHBAR)
receptor layer, horizontal cell layer, bipolar layer,
amacrine cell layer, and retinal ganglion cell layer.
receptor layer
The receptor layer is the farthest from light; therefore, incoming light is distorted by
four layers of neurons before reaching the receptors
Inverted vision
think of goggles in class
Blind Spot
no receptors where information
exits the eye
look @ mammalian retina
Cones Vs Rods
Cones: photopic (daytime vision)
Rods: scotopic (night vision)// increase in sensitivity and decrease in acuity
** look at the convergence of of cones and rods pic
Spectral Sensitivity Scale
shows relationship between brightness and wavelength
Fixations
pauses
Most visual system neurons respond to
change, not to steady input.
Temporal Integration
combining info overtime to improve detection
Visual Transduction
conversion of light to
neural signals by visual receptors
Transduction
conversion of one form of energy to another
Absorption spectrum
describes spectral sensitivity
Rhodopsin is the pigment found in rods
Bleaching reaction hyperpolarizes the rods
Sodium channels in the dark Vs in light
dark: sodium channels stay partially open (release glutamate)
light: sodium channels close (don’t release glutamate)
retina-geniculate-striate pathway
look at eye sight pathway
Retinotopic organization
neurons with receptive fields close together in visual space have cell bodies close together in the cortex
Contrast enhancement
improve the perceptibility of objects in the scene by enhancing the brightness difference between objects and their backgrounds.
Lateral inhibitions
neuron’s response to a stimulus is inhibited by the excitation of a neighboring neuron.
Dorsal Vs Ventral Stream
Dorsal: spacial perception (where)// behavioral control path
Ventral: pattern recognition (what)// conscious path
Retinex Theory
color is determined by the proportion of light of different wavelengths that a surface reflects
Component Theory (Trichromatic theory)
-Two cells types color, one brightness
- Accounts for color afterimages (colors that don’t mix)
