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