Sense and Perception Flashcards
What does our sense of sight allow us to do?
Allow us percieve the world around us
How much of the human brain is involved in vision and other things?
About 1/4 of the human rbain is involved in visual processing
How does vision being?
Wiht light passing through the cornea which does 3/4 of the focussing and then the lens which adjusts the focus. Both combine to produce a clear ima
What do the cornea and lens combine to produce?
A clear image of the visual world o the sheet of photoreceptors in the retina.
As in a camer, the image on the retina is
reversed. Objects to the right of center project images to the left part of the retina and vce verse. Objects above the center project to the lower pat and vice versa.
The size of the pupil which regulates how much ligth enters the eye is controlled by the r
Iris.
How many photoreceptors are in each eye?
About 125 million are neurons specialized to turn light into electrical signals
What two forms do photoreceptors occur in?
Cones and rods
What are rods ensitive to
dim light and do not convy color
Cones
work in brigt light and are responsibe for acute detail, black and white vision and color vision
The cones occur in three,….
Differnt range of colors. Because thier sensitivities overlap, cones work in combination to convey information about all visible colors. Red, Green and Blue
What is binocular vision?
Well developed vision using two eyes, called binocular vision. Visual signals pass form each eye along the million or so fibers of the optic nerve to the optic chism hwhere some nerve fobers cross over so both sides of the brian revcieve signals
Basically, how are your brain and eyes wired?
Your right brain sees your left and your left brain sees your right
Scientists know much about he way cells encode visual information in th retina–whch is also called:
The retinal contians how many stages of neurons
3
The first, thelayer of rods and cones sends it signals to the
middle layer which relays ignals to the third layer which conssits of the ganglion cells whose axons form the optic nerve
Each cell in the middle and third layer recieves input from
many cells in the previous layer, but the number of in puts varies widely across the retina.
Near the center of the gaze, where visual acuity is highest, each cell i nthe third layer recieves inuts from
the middle layer
Near the margins of the retina, each cell inthe third layer receives signals form a cluster of many
rods and cones
An area of visual space, providing inputto a visual neuron is calle..
a receptive field
About 55 years ago, what did scientists discover?
That the receptive field of a vision cell is activated when light hits a tiny region in its receptive field center and its inhibted when light hits the part of the receptive field around the center
Visual information form the retina is relayed through the lateral geniculate nucleus of the thalamus to the primary visual cortex, a thin sheet of tissue
The primary visula cortex is densely packed iwht cells in many layers, n its middle layer which recieves messages form
the lateral geniculate nucleus, scientits hav ound resonses similart to those observed in the retina and in lateral geniculate cells
Cells above and below this layer respond differently hOw?
They prefer stimuli in the shape of bars, or edges and those at a praticular angle
Although the process is not completely understood,recent finding suggest that visual signals are fed into at least
three seperate processing systems
One system is about
shape
What is the second system
color
What is the third system about?
It is about movement, location and spatial organization
Thes findings of seperate processing systems come form what studies
anatomical and physiological
What is Gestalt psychology says ( Its about movemen t and depth perception)
IT says that perception requirs various elements to be organized so that relatedones are grouped together . This stems from the brain’s ability to group the parts of an image together and also separate images from on another
How do all of these system combine to produce the vivid images of solid objects?
That htis involves extracting biologicaly relevant information at each state and associating firing patterns of neuronal populations
