2. Vision Flashcards
Law of Proximity
elements close together perceived as one
Law of Similarity
similar objects are grouped together
Law of Good Continuation
elements that follow on the same pathway are grouped together
Law of Subjective Contours
perception of shapes that are not actually present
Law of Closure
figures tend to be perceived to be more complete than they actually are
Gestalt Principles
“gaps” in knowledge are filled by gestalt principles; help w/ object recognition
Bottom-Up Processing (def, steps)
- Refers to object recognition by parallel processing and feature detection; brain takes individual sensory stimuli and combines them together to create a cohesive image before determining what the object is
- (DATA-DRIVEN)
- Steps:
- Stimuli
- Attention
- Perception
- Thought processes
- Decision
- Response of action
Top-down processing (def, steps)
- driven by memories and expectations that allow the brain to recognize the whole object and then recognize the components based on these expectations
- CONCEPTUALLY DRIVEN
- allows us to quickly recognize objects w/o needing to analyze their specific parts
*Steps of Visual Processing
- LGN –> SUPERIOR COLLICULUS –> OCCIPITAL LOBE
- Involves:
- Lateral geniculate nucleus of the thalamus: “light”; a relay center in the thalamus for the visual pathway
- Superior colliculus: autonomic reflexes; orients vision
- *inferior colliculus orients in response to sound
- Visual cortex (occipital lobe):
Which optic fibers cross over at optic chiasm?
Nasal fibers crossover @ optic chiasm, so PERIPHERAL VISION would be affects by a lesion @ optic chiasm (e.g. pressure by pituitary tumor)
Which fields of vision are perceived by the temporal fibers?
The temporal fibers see the nasal fields of vision
Without the temporal fibers, you’d only have peripheral vision
What is the optic deficit seen with pituitary tumor/pressure on optic chiasm?
You would lose the peripheral vision; the pituitary tumor puts pressure on optic chiasm, which is where nasal fibers cross over –> nasal fibers see peripheral fields of vision –> w/o these, you’d only have central vision
What is the optic deficit seen if there was a lesion in the RIGHT OPTIC NERVE?
The right optic nerve wouldn’t be able to send any information to the visual cortex, so the right eye would be blind
Bipolar cells
receive direct input from rods/cones, highlight gradients, and synapse w/ ganglion cells
*Amacrine and Horizontal cells
both types of cells receive info from multiple retinal cells; allow for edge detection and contrasts
Ganglion cell
receives info from many cells; they group together to form optic nerve
pupil
a hole located in the centre of the iris of the eye that allows light to strike the retina
why does the pupil appear black?
It appears black because light rays entering the pupil are either absorbed by the tissues inside the eye directly, or absorbed after diffuse reflections within the eye that mostly miss exiting the narrow pupil
Cornea
a clear, domelike window in the front of the eye, which gathers and focuses incoming light
anterior chamber
lies in front of the iris
posterior chamber
between the iris and the lens
choroid
produces the aqueous humor that bathes the front part of the eye before draining into the canal of Schlemm
iris
colored part of the eye; consists of 2 muscles (dilator and constrictor pupillae)
two sets of blood vessels in the eye
- choroidal vessels: a complex intermingling of blood vessels between the sclera and the retina
- retinal cells
