Week 8 Flashcards
Process of how light enters the eye
Light enters the cornea
The light passes through the pupil
The lens focuses the light on the retina
Cornea
a clear covering that protects the eye and begins to focus the incoming light
pupil
a small opening in the centre of the eye
iris
The coloured part of the eye and controls the size of the pupil by constricting or dilating in response to light intensity
lens
A structure that focuses the incoming light on the retina
retina
the layer of tissue at the back of the eye that contains photoreceptor cells
Visual accommodation
the process of changing the curvature of the lens to keep the light entering the eye focuses on the retina.
Rays from the top of the image strike the bottom of the retina, rays from the left side of the image strike the right side of the retina, causing the image on the retina to be upside down and backward
Nearsighted
If the focus is in front of the retina
Farsighted
When the focus is behind the retina
Activation of rods and cones
The activation then spreads to the bipolar cells and then to the ganglion cells, which gather together and converge, like the strands of a rope, forming the optic nerve
optic nerve
a collection of millions of ganglion neurons that sends vast amounts of visual information, via the thalamus, to the brain
electromagnetic energy
pulses of energy waves that can carry information from place to place
Wavelength
the distance between one wave peak and the next wave peak.
Visbile spectrum
the part of the electromagnetic spectrum that our eyes detect (only the range from about 400 to 700 billionths of a meter)
Rods
Visual neurons that specialize in detecting black, white, and gray colours. There are about 120 million in each eye. They do not provide a lot of detail about the images we see, but because they are highly sensitive to shorter waved and weak light, they can help us see in dim light. Located primarily around the edges of the retina, so they are particularly active in peripheral vision.
Cones
Visual neurons that are specialized in detecting fine detail and colours. The five million in each eye allow us to see colour, but they operate best in bright light. Located in and around the fovea
Fovea
Central point of the retina
How sensory information is recieved
sensory information is received by the retina and then relayed through the thalamus to corresponding areas in the visual cortex, which is located in the occipital lobe at the back of the brain
Left and right eyes send information to both the left and right hemisphere, and the visual cortex processes each of the cues separately and in parallel
visual cortex turns the sensations they receive from the optic nerve into meaningful images
why do we have a blind spot
There are no photoreceptor cells at the place where the optic nerve leaves the retina, so a hole or blind spot in our vision is created
How is perception created
In a part through the simulataneous action of thousands of feature detector neurons, located in the visual cortex, that respond to strength, angles, and movements of a visual stimulus
Feature detectors work in parallel, each performing a specialized function. Activation is passed onto other parts of the visual cortex, where other neurons compare the information supplied by the feature detectors with images stored in memory
Many neurons fire together, creating the single image of the red square that we experience
Helmoltz trichromatic colour theory
what colour we see depends on the mix of the signals from the three types of cones: one that reacts primarily to blue light, one that reacts to green-light, and one that reacts to red light. If the brain receives messages from all three types of cones, it will perceive white
Opponent process theory
proposes that we analyze sensory information not in terms of three colours, but rather in three sets of “opponent colours”: red-green, yellow-blue, and white-black
Evidence comes from the fact that some neurons in the retina and in the visual cortex are excited by one colour
How do the tricolour and opponent process mechanisms work together to produce colour vision
When light rays enter the eye, the red, blue, and green cones on the retina respond in different degrees and send different strength signals of red, blue, and green through the optic nerve
colour signals are then processed by both the ganglion cells and by the neurons in the visual cortex
feature detector neurons
Specialized neurons, located in the visual cortex, that respond to the strength, angles, shapes edges, and movements of a visual stimulus
colour blindness
The inability to detect green and/or red colours
Gestalt
A meaningfully organized whole
Perceiving form
figure and ground, similarity, proximity, closure
figure and ground
we structure input so that we always see a figure (image) against a ground (background)
Similarity
stimuli that are similar to each other tend to be grouped together
proximity
we tend to group nearby figures together
Continuity
we tend to perceive stimuli in smooth, continuous ways rather than in more discontinuous ways
Closure
We tend to fill in gaps in an incomplete image to create a complete whole object