Ch. 2: Sensation and Perception Flashcards
defn: sensation vs. perception
sensation = transduction = taking the physical, electromagnetic, auditory, and other information from our internal and external environment and converting this info into electrical signals in the nervous system = a raw signal
- performed by receptors in. the peripheral nervous system, which forward the stimuli to the central nervous system in the form of action potentials and neurotransmitters
perception = processing this information within the CNS in order to make sense of the info’s significance = includes both the external sensory experience and the internal activities of the brain and spinal cord
- helps make us make sense of the world
defn: sensory receptors
neurons that respond to stimuli by triggering electrical signals that carry information to the CNS
defn: psychophysics
the relationship between the physical nature of stimuli and the sensations and perceptions these stimuli evoke
defn: ganglia
collections of neuron cell bodies found outside the CNS
defn: projetion areas
further analyze sensory input after stimuli are transduced into electrical signals
func: photoreceptors
respond to electromagnetic waves in the visible spectrum (sight)
func: mechanoreceptors
respond to pressure or movement (hair cells respond to movement of fluid in the inner ear)
movement, vibration, hearing, rotational and linear acceleration
func: nociceptors
respond to painful or noxious stimuli
somatosensation
func: thermoreceptor
respond to changes in temperature
thermosensation
func: osmoreceptors
respond to osmolarity of the blood (water homeostasis)
func: olfactory receptors
respond to volatile compounds
smell
func: taste receptors
respond to dissolved compounds
taste
defn: threshold
the minimum amount of a stimulus that renders a difference in perception
defn: absolute threshold
the minimum of stimulus energy that is needed to activate a sensory system (how bright, loud, or intense a stimulus must be before it is sensed)
a threshold of sensation, not perception
defn: threshold of conscious perception
the level of intensity that a stimulus must pass in order to be consciously perceived by the brain
defn: subliminal perception
information that is received by the CNS but does not cross the threshold of conscious perception
what is the difference between absolute threshold and the threshold for conscious perception?
a stimulus below the absolute threshold will not be transduced and never reaches the CNS
a stimulus below the threshold of conscious perception arrives at the CNS, but does not reach the higher order brain regions that control attention and consciousness
defn: difference threshold (just noticeable difference)
the minimum change in magnitude required for an observer to perceive that two stimuli are diferent
defn: discrimination testing
participant is presented with a stimulus
stimulus is varied slightly and researchers ask the participant to report whether they perceive a change
the difference continues to be increased until the participant reports they notice the change, and this interval is recorded as the just noticeable difference
defn: Weber’s law
difference thresholds are proprotional and must be computed as percentages
defn: signal detection theory
how internal (psychological) and external (environmental) factors influence threshold of sensation and perception
defn: noise trials vs. catch trials
noise trials = trials in which the signal is presented
catch trials = trials in which the signal is not presented
after each trial, the subject is asked to indicate whether or not a signal was presented
defn: hit vs. miss vs. false alarm vs. correct negative
HIT = a trial in which the signal is presented and the subject correctly perceives the signal
MISS = a trial in which the subject fails to perceive the presented signal
FALSE ALARM = a trial in which the subject indicates perceving the signal, even though the signal was not presented
CORRECT NEGATIVE = a trial in which the subject correctly identifies that no signal was presented
defn: adaptation
our ability to detect a stimulus can change over time through this
can have a physiological (sensory) component and a psychological (perceptual) component
one way in which the mind and body try to focus attention on only the most relevant stimuli
Defn and func: sclera
Thick structural layer of the eye that covers the eye (this is the white of the eye)
Defn and func: choroidal vessels
Blood vessel intermingling complex between the sclera and the retina
What are the two sets of blood vessels that supply the eye with nutrients?
Choroidal vessels and retinal vessels
Defn and func: retina
Innermost layer of the eye (at the back of the eye); contains the actual photoreceptors that transduce light into electrical info for the brain
like a screen made of neural elements and blood vessels
considered to be part of the CNS
Defn and func: cornea
Clear, domed window at front of the eye
Gathers and focuses incoming light
What are the two divisions of the front of the eye and where are they located in relation to the iris?
Anterior chamber: in front of the iris
Posterior chamber: between the iris and the lens
Defn and components (and their functions): iris
Iris: colored part of the eye
Composed of 2 muscles: dilator pupillae (opens pupil under sympathetic)
constrictor pupillae (constricts pupil under parasympathetic)
Defn and func: choroid
Vascular layer of connective tissue that is continues with the iris
Provides nourishment and surrounds retina
Func: ciliary body
Produces the aqueous humor that bathes the front of the eye
Cont. with the iris
Func: canal of Schlemm
Where the aqueous humor drains
Loc and func: lens
Lies behind the iris
helps control refraction of incoming light
Func: ciliary muscle
Part of the ciliary body, under parasymp. control
When it contracts, it pulls the suspensory ligaments and changes the shape of the lens to focus on an image as distance varies
What is the process that the ciliary muscle executes called?
Accommodation (ciliary muscle contracts, pulling the suspensory ligaments, and changing the shape of the lens to focus on an image as distance varies)
Defn and loc: vitreous humor
Transparent gel that supports the retina
lies behind the lens
Defn: duplexity/duplicity theory of vision
The retina contains 2 kinds of photoreceptors: light-and-dark detection AND color detection
Mnemonic: cones v. rods
Cones are for Color
Rods function best in Roduced light
Func: Cones
Used for color vision and to sense fine details
Most effective in bright light
Types of cones
S: short (blue)
M: medium (green)
L: long (Red)
Cones are named for the wavelengths of light they best absorb
Func: Rods
Rods are highly sensitive to photos, easier to stimulate than cones so they work best in low light
Can be stimulated by light of any color, but only allow sensation of light and dark (not good for fine details –> rods are spread over a large area of the retina)
Defn and func: rhodopsin
The pigment type that all rods contain
Is part of why rods are so sensitive
Loc and defn: macula
the central section of the retina
high concentration of cones
Defn and loc and func: fovea
Contains only cones
The centermost region of the macula
most functional in normal daylight vision bc high concentration of cones
Defn: optic disc
A region of the retina where the optic nerve exits the eye
Devoid of photoreceptors –> so there is a blind spot
Neuronal pathway from rods and cones to the optic nerve + impact
Rods and cones synapse with bipolar cells which synapse with ganglion cells (axons group together to form optic nerve)
photos travel past several cell layers to reach rods and cones and then the info is transmitted forward as action potentials to reach the ganglion cells
Defn and func: bipolar cells
Neurons in the pathway of rods and cones to the optic nerve
highlight gradients between adjacent rods or cones
Are there more rods or cones in the eye?
Rods!
Defn and func: amacrine and horizontal cells
Receive input from multiple retinal cells in same area before info is passed to ganglion cells
accentuate slight differences in visual info in each bipolar cell
help with edge detection!
Overall rule of visual pathwasy
If an object is on your left, then photons from that object stimulate the right side of the retina in EACH eye
so visual info from objects to your left is processed by the right side of your brain and vice versa
Defn: the crossing over of visual information
nasal field stimulates temporal fibers
temporal field stimulates nasal fibers
recall: temporal and nasal visual fields
temporal and nasal visual fifbers
Defn and event: optic chiasm
The location at which nasal fibers from the left and right eyes cross paths on the way to the brain
nasal fibers have to be redirected by the optic chiasm to return to their correct side of the brain
result: the visual info coming from an object on your left is processed by the right side of your brain
Defn: optic tracts
the reorganized pathways after the cross of fibers at the optic chiasm
Where does visual info go after optic tracts?
lateral geniculate nucleus (LGN) of the thalamus then to the visual cortex in the occipital lobe
superior colliculi of the midbrain
Defn: parallel processing
the ability to analyze info of color, form, motion, and depth all at the same time under independent brain ptahways
Defn, loc, func: parvocellular cells
Cells with very high color spatial resolution (fine detail!)
low temporal resolution (only works for slow objects)
neurons carrying info from the fovea and surrounding central portion of retina synapse
in the LGN
DETECT FORM
Defn, loc, func: magnocellular cells
High temporal resolution (good for detecting motion)
Get most info from periphery
low spatial resolution (no detail, blurry)
Defn and corresp. cells: depth perception
Depth perception: our ability to discriminate shape of environment and judge the distance of objects within it
Mostly based on differences between inputs brain gets from both eyes
Binocular neurons in the visual cortex
Defn and loc: feature detectors
in the visual cortex
each feature detector cell type detects a particular, individual feature of an object
overall combo of feature detectors become activated in parallel so we can associate certain patterns of stimuli with expected outcomes
defn: vestibular sense
our ability to both detect rotational and linear acceleration and to use this info to inform our sense of balance and spatial orientation
defn + func + aka: pinna
the cartilaginous outside part of the ear
aka = auricle
channels sounds waves into the external auditory canal
where do sound waves go after the external auditory canal?
the tympanic membrane (eardrum) which vibrates in phase with the incoming sound waves
do louder sounds have greater or lesser intensity? greater or smaller amplitude of vibration?
greater intensity
increasesd amplitude of vibration
what does the tympanic membrane divide ?
the outer ear from the middle ear
defn + func: ossicles
the three smallest bones in the body
help transmit and amplify the vibrations from the tympanic membrane to the inner ear
explain the parts and pathway of the middle ear
the MALLEUS (hammer) is affixed to the tympanic membrane and acts on the INCUS (anvil) which acts on the STAPES (stirrup)
the baseplate of the stapes rests on the oval window of the cochlea, which is the entrance to the inner ear
defn + func: eustachian tube
connects the middle ear to the nasal cavity
helps equalize the pressure between the middle ear and the environment
explain the parts and pathways of the innear ear
the inner ear sits within a BONY LABRYINTH (a hollow region of the temporal bone containing the cochlea, vestibule, and semicircuar canals)
inside the bony labrythinh rests a continous collection of tubes and chambers THE MEMBRANOUS LABYRINTH which contains recetpros for the sense of equilibrium and hearing
defn: endolymph vs. perilymph
ENDOLYMPH = a potassium-rich fluid filling the membranous labyrinth
PERILYMPH = suspends the membranous labyrinth, transmits vibrations from the outside world and cushions the inner ear structures
defn: cochlea
a spiral-shaped organ that contains receptors for hearing, divided into three parts called scalae which all run its entire length
defn + loc: organ of Corti
the actual hearing apparatus
housed by the middle scala and resting on a thin, flexible membrane (the basilar membrane)
composed of thousands of hair cells, bathed in endolymph
on top: a relatively immobile membrane (the tectorial membrane)
what do the other two scalae do?
- filled with perilymph
- surround the hearing apparatus
are continous with the oval and round windows of the cochlea
defn + func: round window
a membrane-covered hole in the cochlea
permits the perilymph to actually move within the cochlea (bc fluids are essentially incompressible)
func + aka: auditory nerve
vestibulochoclear nerve
carries the electrical signal transduced from the physical timulus by the hair cells in the organ of corti to the CNS
defn: vestibule
the portion of the bony labyrinth that contains the utricule and the saccule which are sensitive to linear acceleration = used as part of the balancing apparatus, determine one’s orientation in 3-D space
defn + func: otoliths
modified hair cells in the utricle and saccule
as the body acclerates, these resist motion which bends and stimulates the underlying hair cells, which send a signal to the brain
defn + func: semicircular canals
sensitive to rotatioinal acceleration
arranged perpendicularly to each other
each ends in a swelling (ampulla) where hair cells are located
when the heat rotates, endolymph in the canal resits the motion, bending the hair cells, sending a signal to the brain
auditory pathway
sound info passes through the VESTIBULOCOCHLEAR NERVE to the BRAINSTEM where it ascends to the MEDIAL GENICULATE NUCLEUS (MGN = MUSIC) of the thalamus
NERVE FIBERS project to the AUDITORY CORTEX in the temporal lobe for sound processing
some info is sent to the SUPERIOR OLIVE (localizes the sound) and the INFERIOR COLLICULUS (involved in startle reflex, helps keep eyes fixed on a point while the head is turned (vestibulo-ocular reflex)
defn + func: hair cells
have long tufts of stereocilia on their top surface
as vibrations reach the basilar membrane underlying the organ of Corti, the stereocilia adorning the hair cells begin to sway back and forth within the endolymph
the swaing causes ion channel opening, which cause a receptor potential
certain hair cells are connected directly to the tectorial membrane –> involved in amplifying the incoming sounds
defn: place theory
the location of a hair cell on the basilar membrane determines the perception of pitch when that hair cell is vibrated
high-freq cause vibrations of the basilar membrane very close to the oval window
low-freq cause vibrations at the apex, away from the oval window
defn: tonotopical organization of the cochlea
which hair cells are vibrating gives the brain an indication of the pitch of the sound
What senses are there other than vision and hearing? (4)
- Smell (chemical)
- Taste (chemical)
- Somatosensation (touch)
- Kinesthetic sense
What does smell respond to?
Volatile or aerosolized compounds (chemicals from the outside world)
Loc, func, and aka: olfactory chemoreceptors
Aka: olfactory nerves
loc: olfactory epithelium at the upper part of the nasal cavity
func: chemical stimuli bind to respective chemoreceptors to cause a signal
Defn and func: pheromones
Chemicals secreted by one animal and once bonded with chemoreceptors, compel or urge another animal to behave in a spec. way
impacts on foraging, social, and sexual behaviors
Defn: olfactory pathway
- Inhale odor molecules into nasal passages
- Odor molecules contact olfactory nerves
- Receptor cells are activated, send signals to olfactory bulb
- Signals relayed via olfactory tract to brain higher regions
How is taste detected?
Chemoreceptors sensitive to dissolve compound
Defn and loc: taste buds
A group of cells that are the receptors for taste
found in little bumps on the tongue (papillae)
Defn: papillae
Little bumps on your tongue that house taste buds
Defn: taste pathway
Taste info travels from:
1. Taste buds to brainstem
2. To taste center in thalamus
3. To higher brain regions
Defn: somatosensation
Touch!
What are the four modalities of somatosensation?
Pressure, vibration, pain, temperature
What are the 5 types of receptors that receive touch info and what do they respond do?
- Pacinian corpuscles (deep pressure, vibration)
- Meissner corpuscles (light touch)
- Merkel cells (discs) (deep pressure, texture)
- Ruffini endings (stretch)
- Free nerve endings (pain and temperature)
Defn: somatosensation pathway
- Transduction in the receptors
- Signal sent to CNS
- Info travels to somatosensory cortex in the parietal lobe
Defn: two-point threshold
Related to: touch
the minimum distance necessary between two points of stimulation on the skin such that they are felt as distinct stimuli
Defn: physiological zero
Related to: touch
the normal temperature of the skin that temperature is judged relative to (an object feels cold bc its temp is less than physiological 0)
Defn and how: gate theory of pain
Related to: touch
a special gating mechanism can turn pain signals on or off, affecting whether or not we perceive pain
how? the spinal cord preferentially forwards signal from other touch modalities to reduce the sensatio nof pain
Defn and func: nociceptors
The majority of sensory receptors that receive info and send pain signals
Defn and aka: proprioception
Aka: kinesthetic sense
the ability to tell where you are in space
Defn, loc, func: proprioceptors
The receptors for proprioception (where are you in space)
mostly in muscles and joints
has roles in hand-eye coordination, balance, mobility
What are the two main theories of object recognition?
Bottom-up (data-driven) processing
Top-down (conceptually driven processing)
Defn: bottom-up processing
Data-driven processing
Object recognition by parallel processing and feature detection
brain takes individual sensory stimuli and combines into a cohesive image before determining what the object is
Defn and func: top-down processing
Conceptually-driven processing
Driven by memories and expectations that allow the brain to recognize the whole and then the components based on expectations
ALLOWS US TO quickly recognize objects without analyzing their parts
What would be the impact if we didn’t have bottom-up processing? Top-down processing?
If no bottom-up: difficulty discriminating between slight object differences
If no top-down: inefficient at recognizing objects (each time we look at something it would feel like the first time)
Defn: perceptual organization
the ability to create a complete picture or idea by combining top-down and bottom-up with all other sensory cues
What are monocular and binocular cues? (macro)
visual cues interpreted by the brain to help with depth perception
Defns: monocular cues (4)
Requires one eye
- Relative size: objects appear larger the closer they are
- Interposition: when two objects overlap, the front is closer
- Linear perspective: convergence of parallel lines at a distance
- Motion parallax: objects closer to us seem to move faster when we change our field of vision
Defns: binocular cues
- Retinal disparity: the slight diff. in images projected on the two retinas (exploited in VR to mimic depth)
- Convergence: the brain detects the angle btwn the 2 eyes required to bring an object into focus (used to perceive distance)
Defn: constancy
Our ability to perceive that certain characteristics of objects remain the same, despite environmental changes
What do we have constancy for?
Brightness, size, shape, color
Defn and list: Gestalt principles
A set of visual rules that account for the fat that the brain views incomplete stimuli in organized ways
- Law of proximity
- Law of similarity
- Law of good continuation
- Subjective contours
- Closure
6*. Law of pragnanz
Defn: law of proximity
A Gestalt principle
elements close to one another are often perceived as a unit
Defn: law of similarity
Gestalt principle
objects that are similar tend to be grouped together
Defn: law of good continuation
Gestalt principle
elements that appear to follow the same path tend to be grouped (there is a tendency to perceive cont. patterns in stimuli not abrupt changes)
Defn: subjective contours
Gestalt principle
you perceive shapes that are not actually a stimulus bc you perceive contours created by other shapes that do exist
Defn: law of closure
Gestalt principle
when a space is enclosed by a contour, it is often perceived as a complete figure
Defn: law of pragnanz
The governing rule of Gestalt principles
perceptual organization will always be as regular, simple, and symmetric as possible
