CH5 VISION Flashcards
How far one sees is dependent on how far light travels before it strikes one’s eyes
Visual Coding
This states that activity by a particular nerve always conveys the same type of information to the brain
Law of specific nerve energies
___ is the mechanism of communication within (internal) while ____ is the mechanism of communication between (external) to the neurons.
electrical, chemical
Is the central portion of the retina and allows for acute and detailed vision
The Fovea
most abundant in the periphery of the eye and respond to faint light (120 million per retina)
Rods
most abundant in and around the fovea (6 million per retina)
Cones:
Two major interpretations of color vision
Trichromatic theory/Young-Helmholtz theory
Opponent-process theory
Color perception occurs through the relative rates of response by three kinds of cones
Trichromatic Theory
the ability to recognize color despite changes in lighting, is not easily explained by these theories
Color constancy
An impairment in perceiving color differences
Color Vision Deficiency
Chemicals contained by both rods and cones that release energy when struck by light
Photopigments
Mostly located in or near the fovea
Have smaller cell bodies and small receptive fields
Highly sensitive to detect color and visual detail
Parvocellular Neurons
Distributed evenly throughout the retina
Have larger cell bodies and visual fields
Highly sensitive to large overall pattern and moving stimuli
Magnocellular Neurons
Have small cell bodies
Found throughout the retina
Have several functions, and their axons terminate in many different places
Koniocellular Neurons
receives information from the lateral geniculate nucleus and is the area responsible for the first stage of visual processing
visual cortex (area V1)
refers to the path that goes through temporal cortex
The “what” path
Specialized for identifying and recognizing objects
ventral stream
refers to the visual path in the parietal cortex
The “how” path
Important for visually guided movements
dorsal stream
can see where objects are but cannot identify them
Ventral stream damage
can identify objects but not know where they are
Dorsal stream damage
A method of perceiving distance in which the brain compares slightly different inputs from the two eyes
Relies on retinal disparity or the discrepancy between what the left and the right eye sees
The ability of cortical neurons to adjust their connections to detect retinal disparity is shaped through experience
Stereoscopic Depth Perception
A condition in which the eyes do not point in the same direction
Usually develops in childhood
Also known as “lazy eye”
Strabismus
The inability to recognize objects despite satisfactory vision
Caused by damage to the pattern pathway usually in the temporal cortex
Visual Agnosia
receives information from area V1, processes information further, and sends it to other areas
visual cortex (area V2)
The impaired ability to recognize faces
Occurs after damage to the fusiform gyrus of the inferior temporal cortex
The fusiform gyrus responds much more strongly to faces than anything else
Prosopagnosia
The inability to determine the direction, speed and whether objects are moving
Likely caused by damage in area MT
Motion Blindness
Several mechanisms prevent confusion or blurring of images during eye movements
Saccades are a decrease in the activity of the visual cortex during quick eye movements
Neural activity and blood flow decrease 75 milliseconds before and during eye movements
Saccades
