2: Sensory and Perception Flashcards
sensation
conversion of physical, electromagnetic, auditory, and other information from our internal and external environments to electrical signals in the nervous system
perception
the processing of sensation information to make sense of its significance
sensory receptors
neurons that respond to stimuli and trigger electrical signals; photoreceptors respond to light and encode brightness and color/shape of light
ganglia
collections of neuron cell bodies found outside the CNS that transmit sensory data to CNS
projection areas
further analyze sensory information sent from ganglia
threshold
minimum amount of a stimulus that renders a difference in perception
absolute threshold
minimum of stimulus energy needed to activate a sensory system
difference threshold
“just noticeable difference”
minimum difference in magnitude between two stimuli before one can perceive this difference
Weber’s Law
there is a ratio between change in stimulus magnitude needed to produce a jnd and the magnitude of original stimulus
(louder sound=bigger magnitude for jnd)
signal detection theory
focuses on the changes in our perception of the same stimuli depending on both internal (psychological) and external (environmental) context
stimulus–>conscious perception pathway
sensory receptor–>afferent neuron–>sensory ganglion–>spinal cord–>brain (projection areas)
sclera
white of the eye
choroidal vessels
blood vessels that supply nutrients to the eye between sclera and retina
retinal vessels
also supply nutrients to eye
retina
innermost layer of eye
contains actual photoreceptors that transduce light into electrical information that the brain can then process
cornea
clear domelike window at front of eye that gathers and focuses incoming light
anterior chamber
lies in front of iris
posterior chamber
between iris and lens
iris
colored part of eye
dilator pupillae
opens pupil under sympathetic stimulation
constrictor pupillae
contricts pupil under parasympathetic stimulation
ciliary body
produce aqueous humor
lens
right behind iris
helps control refraction of incoming light
accommodation
when ciliary muscle contracts and changes shape of the lens
retina
at back of eye
converts incoming photons of light into electrical signals
cones
used for color vision and to sense fine details
most effective in bright light and are named for wavelength of light they absorb (S, M, L)
central section of retina contains high concentration of cones even though there is a higher amount of rods in the retina
*convert physical stimulus into electrical signal
(in retina)
rods
only allow for sensation of light and dark
low sensitivity to details
not involved in color vision
involved in night vision
many more rods than cones
*convert physical stimulus into electrical signal
fovea
Center of the macula, which is the center of the retina
Contains only cones
As you move away from the fovea, the concentration of rods increases while the concentration of cones decreases
THEREFORE: visual acuity is best at the fovea
Most sensitive in normal daylight vision
optic nerve
blind spot where the optic nerve leaves the eye b/c there are no photoreceptors here (in the retina)
ganglion cells
link between bipolar cells and optic nerve
must represent activity of many rods and cones
visual pathway
all fibers corresponding to the left visual field from both eyes project to the right side of the brain, and all fibers corresponding to the right visual field project into the left side of the brain
parallel processing
The ability to simultaneously analyze and combine information regarding color, shape, and motion, which can then be used to compare to memories.
parvocellular cells
Responsible for shape detection
High color spatial resolution–allow for fine detail discrimination
Low temporal resolution–can only work with stationary or slow moving objects
magnocellular cells
Responsible for motion detection
High temporal resolution
Low spatial resolution
pinna/auricle
Outer part of ear
Funnel sound into external auditory canal
external auditory canal
Directs sound waves to tympanic membrane
tympanic membrane
Vibrates in phase with incoming sound waves
Velocity of vibrations depends of frequency of sounds (high frequency=fast, low=slow)
Louder sounds=greater intensity=increased amplitude
Divides outer ear from middle ear
ossicles
Middle ear
Smallest bones in the body
Transmit and amplify the vibrations from the tympanic membrane to the inner ear
a) malleus (hammer): attached to TM, acts on…
b) incus (anvil): which acts on…
c) stapes (stirrup): rests in oval window of cochlea, which is entrance to inner ear
Eustachian tube
Connects middle ear to nasal cavity
Equalizes pressure b/w middle ear and environment
cochlea
spiral shaped organ divided into three parts called scalae
membranous labyrinth
Contain (continuous) cochlea, vestibule, and semicircular canals
Filled with potassium rich fluid called endolymph
Suspended within bony labyrinth by thin layer of perilymph fluid
perilymph
Suspends membranous labyrinth in bony labyrinth
Simultaneously transmits vibrations from outside world and cushions inner ear structures
bony labyrinth
Inner ear sits within this structure
organ of corti
Part of cochlea
Sits on basilar membrane
Composed of thousands of hair cells bathed in endolymph
Tectorial membrane sits on top
*Hair cells convert physical stimulus into electrical stimulus (like rods and cones of eye), which is then carried to CNS via auditory (vestibulocochlear) nerve
round window
Membrane covered hole in the cochlea
Permits perilymph to move within the cochlea b/c fluid is ~incompressible
vestibule
Essential to balancing and orientation in 3D space
Contains utricle and saccule, which are sensitive to linear acceleration
lateral geniculate nucleus
Located in the thalamus
One of the final destinations for light signals
Lateral=light
medial geniculate nucleus
Located in the thalamus
One of the final destinations for sound signals
Medial=music
visual pathway
cornea–>pupil–>lens–>vitreous–>retina (rods and cones–>bipolar cells–>ganglion cells)–>optic nerve–>optic chiasm–>optic tract–>lateral geniculate nucleus (LGN) of the thalamus–>radiations through parietal and temporal lobes–>visual cortex (occipital lobe)
auditory pathway
pinna–>external auditory canal–>tympanic membrane–>malleus–>incus–>stapes–>oval window–>perilymph in cochlea–>basilar membrane–>hair cells–>vestibulocochlear nerve–>brainstem–>medial geniculate nucleus (MGN) of thalamus–> auditory cortex (temporal lobe)
olfactory pathway
nasal passageway–>olfactory nerves in olfactory epithelium–>olfactory bulb–>olfactory tract–>brain (limbic system)
somatosensation
“Touch”
4 modalities: pressure, vibration, pain, and temperature
somatosensory pathway
various receptors–>CNS–>somatosensory cortex (parietal lobe)
two point threshold
minimum distance necessary between two points of stimulation on the skin that the two points will be felt as two distinct stimuli
gate theory of pain
There is a special “gating” mechanism that can turn pain signals on and off, affecting whether or not we perceive pain.
Theoretically: spinal cord can preferentially forward signals from other touch modalities (pressure, temp) to brain, thus reducing the sensation of pain
kinesthetic sense
“Proprioception”
Ability to tell where one’s body is in space
Receptors critical in hand-eye coordination, balance, and mobility
bottom-up processing
Logical processing type #1: object recognition via parallel processing and feature detection
“Data-driven processing”
Brain takes sensory information and combines them to create cohesive image before determining what the object is
Without bottoms-up processing, we would have difficulty discriminating slight differences between similar objects
top-down processing
Logical processing type #2: object recognition via memory recall and expectations
“Conceptually driven processing”
Allows brain to recognize the whole object and then recognize the components based upon expectations
Brain can quickly recognize objects without analyzing specific parts–without it, we would have a hard time recognizing objects
Deja-vu: when brain top-down processes too quickly
perceptual organization
Ability to use top-down and bottom-up processing in tandem to create a complete picture or idea about an object
Gestalt principles
There are ways for the brain to infer missing parts of a picture when the picture is incomplete
Law of proximity
Gestalt principle
Elements close to each other tend to be perceived as one unit
Law of similarity
Gestalt principle
Objects that are similar tend to be grouped together
Law of good continuation
Gestalt principle
Elements that appear to follow one pathway seem to be grouped together
Subjective contours
Gestalt principle
Mind perceives shapes or contours in a stimulus that aren’t actually present
Law of closure
Gestalt principle
When a space is enclosed by a contour it tends to be perceived as a complete figure
Four right angles=square even if sides aren’t closed or complete
