MCAT Psychology Outline 6A
Gestalt principles - proximity
elements that are close to each other tend to be grouped together
Eye anatomy - iris
colored portion of the eye that surrounds the pupil
What is meant by top-down processing?
model of visual processing that posits the brain goes from forest to trees, i.e. formulates perceptual hypothesis about the nature of the stimulus as a whole, selects and examines specific features to check hypothesis, recognizes stimulus
What is meant by bottom-up processing?
model of visual processing that posits the brain goes from trees to forest, i.e. combines the specific features of stimuli it detects into more complex forms until the stimuli are recognized. The brain detects specific features of stimulus -> combines specific features into more complex forms -> recognizes of stimulus
Eye anatomy - cornea
"anterior-most ""window"" portion through which light initially passes"
Describe the visual pathway from eye through the brain.
1) Light from the left half of the visual field hits the right side of each retina and the information is eventually transmitted to the right side of the brain. Right half to left retina to left side of brain. 2) Information travels from retina, along the optic nerves (4 in total, L & R for both eyes) to lateral geniculate nucleus (LGN) of the thalamus. 3) LGN processes and distributes to the primary visual cortex (contained in the occipital lobe). 4) Secondary pathway from the optic nerves to the visual cortex goes through superior colliculus. It is believed that this pathway is responsible for coordination of visual inputs with other sensory inputs. 5) Signals are further transmitted to the temporal and parietal lobes. Dorsal stream - information from primary visual cortex goes to the parietal lobe to process for perception of motion and depth. Ventral stream - information from primary visual cortex goes to the temporal lobe to process for information about color and form.
Describe how the cells of the visual cortex work to understand visual stimuli.
Cells of the visual cortex are feature detectors, neurons that respond selectively to specific features of more complex stimuli. The basic theory is that the cells of the visual cortex work collectively to piece together a coherent image of otherwise complex images
Name the muscles that move the eye and the cranial nerve that enervates them.
Lateral rectus (6), medial rectus (3), superior rectus (3), inferior rectus (3), superior oblique (4), inferior oblique (3)
What are the 5 gestalt principles?
Proximity, closure, similiarity, simplicity, continuity
What are the 3 types of cells in the visual cortex?
Simple cells, complex cells, hypercomplex cells
Fechner's law/scale
Subjective sensation is propotional to the logarithm of stimulus intensity
Weber's Law
The just-noticeable difference between two stimuli is proportional to the magnitude of the stimulus
Eye anatomy - fovea
a spot in the center of the retina that contains only cones
Eye anatomy - pupil
black portion in the middle which may dilate and contract to regulate the amount of light passing into the eye
optic chiasm
crossing point for R optic nerve of L eye and L optic nerve of R eye
Gestalt principles - similarity
elements that are similar tend to be grouped together
Eye anatomy - retina
neural tissue lining the interior of the eye that actually senses and processes light for transmission to the brain
Visual cortex - complex cells
respond to correct width and orientation, but less picky about location in visual field. Some are most responsive to lines sweeping across the field in the "correct" direction
Visual cortex - hypercomplex cells
respond to the correct length of the stimulus line
Visual cortex - simple cells
respond to very specific stimuli lines of correct width, oriented at the correct angle and in the correct place in the visual field
Define perception
the selection, organization and interpretation of sensory input
Eye anatomy - lens
transparent structure responsible for focusing and refracting light coming into the eye and falling on the retina
Gestalt principles - simplicity
viewers tend to organize elements in the simplest way possible
Gestalt principles - continuity
viewers tend to see elements in ways that produce smooth continuation
Gestalt principles - closure
viewers tend to supply missing elements to complete or close a familiar figure
Eye anatomy - cones
visual receptors of the retina that are specialized for color detection and daytime/bright light vision
Eye anatomy - rods
visual receptors of the retina that are specialized for peripheral vision and nighttime/low light vision