Sensation and Perception

absolute threshold

minimum of stimulus energy that is needed to activate the sensory system

threshold of conscious perception

minimum of stimulus energy that will create a signal large enough in size and long enough in duration to be brought into awareness

difference threshold or just-noticeable difference

minimum difference in magnitude between 2 stimuli before one can perceive the difference

webers law

jnd for a stimulus is proportional to the magnitude of the stim, and that this proportion is constant over most of the range of possible stimuli

cornea

gathers and filters incoming light

iris

divides the front of the eye into the anterior and posterior chambers

• contains two muscles (dilator and constrictor pupillae) to open and close the pupil

lens

refracts incoming light to focus it on the retina and is held in place by suspensory ligaments connected to the cillary muscles

ciliary body

procudes aqueous humor, which drains thru the canal of Schlemm

rods

detect light and dark; found at the center of the macula in the fovea

cones

direct colors; mostly in the macula

visual pathway

optic nerves → optic chiasm → optic tract → lateral geniculate nucleus of the thalamus → visual cortex

optic chiasm

contains fibers crossing from the nasal side of the retina (temporal visual fields) of both eyes

parvocellular cells

detects shape with high spatial resolution and low temporal resolution

magnocellular cells

detects motion with low spatial resolution and high temporal resolution

outer ear

pinna, external auditory canal, and tympanic membrane

middle ear

contains ossicles (malleus, incus, stapes)

malleus

hammer

incus

anvil

stapes

stirrup; footplate of the stapes rests on the oval window of the cochlea

middle ear

connected to the nasal cavity via eustachian tube

inner ear

contains the bony labryinth inside of it is the membranous labryinth

bony labryinth

filled with perilymph

membranous labryinth

filled with the endolymph and consists of the cochlea (detects sound), utricle and saccule (detect linear acceleration), and semicircular canals (detect rotational accel)

auditory pathway

cochlea → vestibulocochlear nerve and medial geniculate nucleus of the thalamus → auditory cortex of temporal lobe

superior olive

localizes the sound

inferior colliculus

involved in the startle reflex

law of pragnanz

perceptual organization will always be as regular, simple, and symmetric as possible