Chapter 2: Sensation and Perception Flashcards
What is transduction?
Taking the physical, electromagnetic, auditory, and other information from our internal and external environment and converting this information into electrical signals in the nervous system
What’s more like transduction, sensation or perception?
Sensation
Which receptors perform sensation and in what form do they deliver stimuli to the CNS?
Receptors in the PNS; action potentials and neurotransmitters
What is perception?
The processing of information within the CNS in order to make sense of the information’s significance
Sensory receptors are neurons that respond to ________ by triggering ____________ signals that carry information to the ____________ nervous system.
Sensory receptors are neurons that respond to stimuli by triggering electrical signals that carry information to the central nervous system.
Physical objects outside of the body are referred to as ____________ stimuli. They produce photons, sound waves, heat, pressure, or other stimuli that directly interact with sensory receptors.
Distal
The sensory-stimulating byproducts of distal stimuli are called ________ stimuli.
Proximal
What are ganglia?
Collections of neuron cell bodies found outside the central nervous system
What are nuclei?
Cluster of neurons in the central nervous system
Different types of receptors receive a stimulus, transduce the stimulus into electrical signals, and transmit the data to the CNS through sensory ________.
Ganglia
Once transduction from sensory ganglia occurs, the electrochemical energy is sent along neural pathways to various _______________ _______ in the brain.
projection areas
What do photoreceptors respond to?
Electromagnetic waves in the visible spectrum
What do mechanoreceptors respond to?
Pressure or movement
What do nociceptors respond to?
Painful or noxious stimuli
What do thermoreceptors respond to?
Changes in temperature
What do osmoreceptors respond to?
Osmolarity of the blood
What do olfactory receptors respond to?
Volatile compounds
What do taste receptors respond to?
Dissolved compounds
What is threshold
Minimum amount of stimulus that renders a difference in perception
What are the 3 main types of thresholds?
Absolute threshold
Threshold of conscious perception
Difference threshold
What is absolute threshold?
The minimum of stimulus energy needed to activate a sensory system
Is absolute threshold a threshold of perception or sensation?
Sensation
What is the threshold of conscious perception?
The level of intensity that a stimulus must pass in order to be consciously perceived by the brain
Sensory systems can send signals without someone perceiving the signals
What is the difference threshold?
The minimum change in magnitude required for an observer to perceive that 2 different stimuli are, in fact, different
What is another name for the difference threshold?
Just-noticeable difference (jnd)
What is a common technique researchers use to explore the difference threshold?
Discrimination testing
What is discrimination testing?
Participant is presented with a stimulus. Stimulus is varied. Participant is asked to report whether they perceive a change. It is varied until they do. The interval is the JND
Which is important - absolute difference or percent difference?
Percent difference!
How do you compute the just noticeable difference?
change in stimulus divided by magnitude of original stimulus
What is Weber’s Law?
Difference thresholds are proportional and must be computed as percentages
the change in a stimulus that will be just noticeable is a constant ratio of the original stimulus
What is signal detection theory?
Studies how internal and external factors influence thresholds of sensation and perception
What 2 types of trials does a basic signal experiment consist of?
Noise trial
Catch trial
What is a noise trial?
In a signal detection experiment, a noise trial is a trial in which the signal is presented
What is a catch trial?
In a signal detection experiment, a catch trial is a trial in which the signal is not presented
What are the 4 possible outcomes for a trial in a signal detection experiment?
Hit
Miss
False alarm
Correct negative
What is a hit in a signal detection experiment?
Signal is presented and subject correctly perceives signal
What is a miss in a signal detection experiment?
Subject fails to perceive the presented signal
What is a false alarm in a signal detection experiment?
Subject indicates perceiving the signal, even though the signal was not presented
What is a correct negative in a signal detection experiment?
Subject correctly identifies that no signal was presented
What is sensory adaptation?
Our ability to detect a stimulus can change over time
Why is sensory adaptation advantageous?
Helps us focus on only the most relevant stimuli, which are usually changes in the environment around us
The exposed portion of the eyes is covered by a thick structural layer known as the ____________, or the white of the eye.
Sclera
Which part of the eyes is not covered by the sclera?
The cornea, the frontmost part
Which 2 sets of blood vessels supply nutrients to the eyes?
- Choroidal vessels
- Retinal vessels
Where are the choroidal vessels located?
Between the retina and sclera
What is the innermost layer of the eye called?
Retina
What does the retina contain?
Photoreceptors that transduce light into electrical information
Where does light first pass when entering the eye?
The cornea
What does the cornea do?
Gathers and focuses incoming light
What are the 2 parts that the front of the eye is divided into?
The anterior chamber
The posterior chamber
What is the anterior chamber in front of?
The iris
What is the posterior chamber between?
The iris and the lens
What is the iris?
The colored part of the eye
What are the 2 muscles that comprise the iris?
dilator pupillae
constrictor pupillae
The dilator pupillae opens the pupil under ____________ stimulation.
Sympathetic
The constrictor pupillae opens the pupil under ____________ stimulation.
Parasympathetic
The iris is continuous with the ____________.
Choroid
What is the choroid?
A vascular layer of connective tissue that surrounds and provides nourishment to the retina
The iris is also continuous with the ____________ ________.
Ciliary body
What does the ciliary body produce and what is it for?
aqueous humor; bathes the front part of the eye
Where does aqueous humor drain into?
The canal of Schlemm
Where is the lens located?
Right behind the iris
What does the lens do?
Controls the refraction of incoming light
Contraction of the ____________ muscle, a component of the ciliary body, is under ____________________ control.
ciliary; parasympathetic
As the ciliary muscle contracts, it pulls on the ____________________ ligaments and changes the shape of the lens to focus on an image as the distance varies. This is a phenomen known as ____________________.
suspensory; accommodation
The transparent gel that supports the retina is called the? Where is it located?
Vitreous humor; behind the lens
Label the eye using the following terms: optic disc area, iris, sclera, retina, optic nerve, cornea, aqueous body, ciliary body, vitreous body, choroid, lens
Where is the retina located?
Back of the eye
What does the retina do?
Converts incoming photons of light to electrical signals
Is the retina part of the CNS or PNS?
It is part of the CNS - it is an outgrowth of brain tissue
How many types of photoreceptors does the retina contain and what are they called?
2 - rods and cones
Are there more rods and more cones? By how much?
6 million cones, 120 million rods - 20 times more rods than cones
What are cones used for? Best in bright light or darkness?
Color vision and fine details; bright light
What are the three forms of cones?
short (blue)
medium (green)
long (red)
Are rods better in light or dark and why?
Reduced light; they are highly sensitive to photons
How many pigment types are in rods and what are they called?
Only 1 - rhodopsin
Why does color vision require more light?
Each cone only responds to certain wavelengths of right
Which colors can stimulate rods?
Any color!
Are rods more or less useful for detecting fine details? Why?
Less useful - they are spread over a much larger area of the retina
What is the center of the retina called?
Macula
Where is the highest concentration of cones in the retina?
Macula, specifically the fovea, which is in the center of the macula
As one moves further away from the fovea, the concentration of rods ____________ while the concentration of cones ____________.
increases; decreases
Choose one
Visual acuity is (best/worst) at the fovea.
Best
The fovea is (most/least) sensitive in normal daylight vision.
Most
Some distance away from the retina the ________ nerve leaves the eye. This region of the retina has no ________________ and is called the __________ ______. It gives rise to a _________ _______.
optic; photoreceptors; optic disk; blind spot
What do rods and cones connect to?
They synapse with bipolar cells
What do bipolar cells synapse with?
Ganglion cells
The axons of ganglion cells group together to form the __________ _________.
optic nerve
Are the bipolar and ganglion cells located in front of or behind the rods and cones?
In front of
Are there more or less photoreceptor cells than ganglion cells?
Significantly more
As the number of receptors that converge through the bipolar neurons onto one ganglion cell increases, the resolution ________________.
Decreases
Choose one
On average, the number of cones converging onto an individual ganglion cell is (smaller/larger) than for rods.
smaller
This is why color vision has greater sensitivity to detail than B/W.
Which 2 sets of cells receive input from multiple retinal cells in the same area before the information is passed on to ganglion cells?
Amacrine and horizontal cells
What type of visual information are amacrine and horizontal cells important for?
Edge detection
Label the diagram of the cells of the retina using the following terms: bipolar cell, rod, horizontal cell, ganglion cell, cone, amacrine cell
Choose one
If an object is to your left, then photons from that object stimulate the (left/right) of the retina in each eye. From the retina, retinal fibers from each eye then project to the (left/right) side of your brain. This means that visual information from objects to your left is processed by the (left/right) side of your brain.
Right; right; right
If you look at at an object to your left, the photons strike the retinal fibers of your right eye on the (temporal/nasal side).
Temporal
fibers on right side of each eye go to the right.
If you look at at an object to your left, the photons strike the retinal fibers of your left eye on the (temporal/nasal side).
Nasal
fibers on right side of each eye go to the right.
If you look at at an object to your right, the photons strike the retinal fibers of your right eye on the (temporal/nasal side).
Nasal
fibers on left side of each eye go to the left
If you look at at an object to your right, the photons strike the retinal fibers of your left eye on the (temporal/nasal side).
temporal
fibers on left side of each eye go to the left
An object to the left of you is in the (temporal/nasal) visual field of your right eye. When the photons from this object enter your right eyes, they stimulate the (temporal/nasal) fibers on the (left/right) side of your right eye.
nasal; temporal; right
As the retinal fibers from each eye travel through the optic nerves toward the brain, (temporal/nasal) fibers from the left and right eyes cross paths at the __________ ____________.
nasal; optic chiasm
Only (temporal/nasal) fibers cross at the optic chiasm.
Nasal
This is because
An object to your left will stimulate the (temporal/nasal) fibers of your left eye, and then these fibers are routed through the optic chiasm to the (left/right) side of your brain.
nasal; right
After the nasal fibers cross the optic chiasm, the reorganized pathways are called optic _________.
tracts
An object to your right would be in the (temporal/nasal) field of your left eye. The photons would stimulate the (temporal/nasal) fibers of the left eye. Then these fibers would route directly back to the (left/right) side of the brain.
nasal; temporal; left
An object to the right is in the (temporal/nasal) field of your right eye and stimulates the (temporal/nasal) fibers of that eye. These nasal fibers are routed through the optic chiasm.
temporal; nasal
The temporal field of each eye stimulates the (temporal/nasal) fibers of each eye.
NASAL
From the optic chiasm, the info goes to several different places, such as ?
- Lateral geniculate nucleus (LGN) of the thalamus
- Superior colliculi in the midbrain
Where is the lateral geniculate nucleus (LGN) located?
Thalamus
Nerve fibers that pass to the LGN synapse with nerves that pass through radiations in the ________________ and ________________ lobes to the ____________ cortex in the ________________ lobe.
temporal, parietal; visual; occipital
Nerve fibers from the optic chiasm can branch off the optic tracts, skip the thalamus, and head directly to the ________________ ________________ in the midbrain, which control some reflexive responses to visual stimuli and reflexive eye movements.
Superior colliculi
List 4 aspects of vision
What is parallel processing?
Ability of the brain to analyze info regarding color, form, motion, and depth simultaneously using independent pathways in the brain
What is form?
Shape and ability to discriminate an object of interest from the background by detecting its boundaries
Neurons carrying info from the fovea and surrounding central portion of the retina synapse with ________________________ cells in the LGN. These cells have very high ____________ ____________ resolution, but low ________________ resolution. Gives us fine detail.
parvocellular; color spatial; temporal
____________________ cells are well-suited for detecting motion because these have very high ________________ resolution.
Magnocellular; temporal
Since form and motion are processed in parallel, magnocellular cells and parvocellular cells are located in ____________ layers of the ___________ ___________________ ____________.
distinct; lateral geniculate nucleus
________________ cells predominantly receive inputs from the periphery of our vision, allowing rapid detection of objects approaching from the sides.
Magnocellular
Choose between magnocellular and parvocellular
Which cells detect form? Which cells detect motion?
Parvocellular, magnocellular
What is depth perception?
Ability to discriminate 3D shapes of our environment and judge distance within it
Specialized cells in the visual cortex known as ____________ neurons are responsible for comparing the inputs to each hemisphere and detecting these differences.
binocular
___________ ___________ cells detect particular, individual features of an object in the visual field, e.g. the red color of a stop sign. Rather than individually processing each of these features every time, the overall combo of feature detectors become activated in parallel.
Feature detector
What is vestibular sense?
Ability to both detect rotational and linear acceleration to inform sense of balance and spatial orientation
What are the 3 parts of the ear?
Outer, middle, inner
A sound wave first reaches the cartilagionous outside part of the ear, called the ________ or ____________.
Pinna; auricle
The main function of the pinna is to channel sound waves into the ____________ __________ __________, which directs the sound waves to the _________________ ______________.
External auditory canal; tympanic membrane (eardrum)
Choose
The membrane vibrates (in/out) phase with the incoming sound waves.
In
What determines the rate at which the eardrum vibrates?
Frequency of the sound wave
High frequency = high rate
Low frequency = slow rate
Choose
Louder sounds have a (greater/lesser) intensity, which corresponds to (increased/decreased) amplitude of vibration.
greater; increased
What divides the outer ear from the middle ear?
Tympanic membrane
The middle ear houses the 3 smallest bones in the body, called the ____________, which transmit and amplify the vibrations from the tympanic membrane to the inner ear.
Ossicles
The ____________ (hammer) is affixed to the tympanic membrane; it acts on the ________ (anvil), which acts on the ________ (stirrup). The baseplate of the stapes rests on the oval window of the ____________, which is the entrance to the inner ear.
malleus, incus, stapes; cochlea
The middle ear is connected to the nasal activity via the ____________ tube, which helps equalize pressure between the middle ear and the environment.
Eustachian
The inner ear sits within a ______ ______________, which is a hollow region of the temporal bone containing the cochlea, vestbule, and semicircular canals.
Bony labyrinth
In side the bony labyrinth is a continuous collection of tubes and chambers called the ________________ labyrinth, which contains receptors for the sense of equilibrium and hearing.
Membranous
The membranous labyrinth is filled with a potassium-rich fluid called ____________, and is suspended within the bony labyrinth by a thin layer of another fluid called ____________.
endolymph; perilymph
What does perilymph do?
Transmits vibrations from the outside world and cushions the inner ear structures
What spiral-shaped organ contains the receptors for hearing?
Cochlea
What are the 3 parts of the cochlea collectively called?
Scalae
The middle scala houses the actual hearing apparatus, called the ________ of ________, which rests on a thin, flexible membrane called the ____________ membrane.
organ of Corti; basilar
What does the organ of Corti have thousands of? What are they bathed in?
hair cells; endolymph
What membrane is on top of the organ of Corti? What does it do?
tectorial membrane; amplifies incoming sound
The other 2 scala (besides the middle) are filled with ________________, surround the hearing apparatus, and are continuous with the ________ and ________ windows of the __________.
perilymph; oval and round; cochlea
Sound entering the cochlea through the oval window causes vibrations in ________________, which are transmitted to the ________________ membrane.
perilymph; basilar
Since fluids are incompressible, the ________ window (a membrane-covered hole in the cochlea) permits the perilymph to move within the cochlea. The hair cells in the organ of Corti then transduce the physical stimulus into an electrical signal to be carried to the CNS by the ________________ nerve.
round; vestibulocochlear
Which portion of the bony labyrinth contains the utricle and saccule?
Vestibule
What are the utricle and saccule sensitive to? What does this do for us?
Linear acceleration; determine orientation in space and for balance
The utricle and saccule have modified hair cells covered with ________. What do these cells do?
Otoliths; resist motion as body accelerates, which bends and stimulates the underlying hair cells to send a signal to the brain
What in the ears are sensitive to rotational acceleration?
Semicircular canals
Each semicircular canal ends in a swelling called an ________, where hair cells are located.
ampulla
When the head rotates, ________________ in the semicircular canal resists this motion, bending the underlying hair cells, which send a signal to the brain.
endolymph
Most sound information passes through the vestibulocochlear nerve to the brainstem, where it ascends to the ________ geniculate nucleus of the thalamus.
Medial
Medial = Music
Lateral = Light
Nerve fibers in the medial geniculate nucleus project to the ________ cortex in the temporal lobe for sound processing.
Auditory
Some information in the MGN of the thalamus is also sent to the __________ __________, to localize the sound, and the ________ ________, which is invovled in the startle reflex and helps eyes stay fixed when the head is turned.
superior olive; inferior colliculus
Hair cells have long tufts of ?
Stereocilia
The swaying of stereocilia causes the opening of ____ ____________, which cause a receptor potential.
ion channels
The basilar membrane changes thickness depending on its location in the cochlea. What effect does this have on sound perception? What is place theory?
The location of a hair cell on the basilar membrane determine the perception of pitch when that hair cell is vibrated
Highest-frequency pitches cause vibrations of the basilar membrane (close/far) to the oval window.
close
The cochlea is ________________ organized: which hair cells are vibrating gives the brain an indication of the pitch.
tonotopically
Where are olfactory chemoreceptors located?
Olfactory epithelium in the upper part of the nasal cavity
Smell can carry interpersonal info through the medium of ________.
Pheromones
Odor molecules are inhaled into the nasal passages and then contact the olfactory nerves in the olfactory epithelium. These receptor cells are activated, sending signals to the ________________ ________. These signals are then relayed via the ________________ ________ to higher regions of the brain.
olfactory bulb; olfactory tract
Tastes are detected by ________________, which are sensitive to dissolved compounds.
Chemoreceptors
The receptors for taste are groups of cells called ________ ____, which are found in little bumps on the gonue called ________.
taste buds; papillae
Taste info travels from taste buds to the brainstem, then ascends to the ________ ________ in the thalamus before traveling to higher-order brain regions.
taste center
What are the 4 modalities of somatosensation?
pressure, vibration, pain, temperature
What do Pascinian corpuscles respond to?
deep pressure and vibration
What do Meissner corpuscles respond to?
light touch
What do Merkel cells (discs) respond to?
Deep pressure and texture
What do Ruffini endings respond to?
Stretch
What do free nerve endings respond to?
pain and temperature
Transduction of touch occurs in the receptors, which send the signal to the CNS, where it eventually travels to the ______________________ __________ in the parietal lobe.
Somatosensory cortex
What is a two-point threshold?
Minimum distance necessary between 2 points of stimulation on the skin such that the points will be felt as 2 distinct stimuli
The size of the two-point threshold depends on the ________ of nerves in the particular area of skin.
density
Pain perception commonly results from signals sent by ____________.
Nociceptors
Temperature is judged relative to _____________ _____, or the normal temp of the skin (between 86 to 97 F).
physiological zero
What is the gate theory of pain?
A special “gating” mechanism can turn pain signals on/off, affecting whether or not we perceive pain. Spinal cord can preferentially forward the signals from other touch modalities (pressure/temp) to the brain, thus reducing the sensation of pain.
What is proprioception?
Ability to tell where one’s body is in space
Where are the receptors for proprioception found and what roles do the play?
Mostly in muscle and joints
Play critical roles in hand-eye coordination, balance, and mobility
What is bottom-up processing?
Parallel processing and feature detection
allows us to quickly recognize without having to analyze
What is top-down processing?
Driven by memories and expectations that allow the brain to recognize the whole object and then recognize the components based on these expectations
What is perceptual organization?
The ability to create a complete picture or idea by combining top-down and bottom-up processing with all of the other sensory clues gathered from an object
What are monocular cues?
Only require 1 eye; aid in depth perception
What are 4 examples of monocular cues?
(MILR)
Motion parallax
Interposition
Linear perspective
Relative size
What is relative size?
The idea that objects appear larger the closer they are
Monocular cue
What is interposition?
When 2 objects overlap, one in front is closer
Monocular cue
What is linear perspective?
Convergence of parallel lines at a distance: the greater the convergence, the further the distance
Monocular cue
What is motion parallax?
The perception that objects closer to us seem to movefaster when we change our field of vision
Monocular cue
What are binocular cues?
Require both retinas and relies on slight difference in images projected on the 2 retinas
What are 2 examples of binocular cues?
Retinal disparity
Convergence
What is retinal disparity?
Slight difference in images; gives depth perception
Binocular cue
What is convergence?
Brain detects the angle between the 2 eyes required to bring an object into focus
What is constancy?
Our ability to perceive that certain characteristics of objects remain the same, despite changes in the environment
What are Gestalt principles?
A set of general rules that account for the fact that the brain tends to view incomplete stimuli in organized, patterned ways
What are 5 examples of Gestalt principles?
Proximity
Similarity
Good continuation
Subjective contours
Closure
What is the law of proximity?
Elements close to one another tend to be perceived as a unit
What
What is the law of similarity?
Objects that are similar tend to be grouped together
Gestalt principle
What is the law of good continuation?
Elements that appear to follow in the same pathway tend to be grouped together
Gestalt principle
What are subjective contours?
Perceiving contours/shapes that are not actually present in the stimulus
Gestalt principle
What is the law of closure?
When a space is enclosed by a contour, the space tends to be perceived as a complete figure
Gestalt principle
Taken together, the Gestalt principles are governed by the _____ ___ __________, which says that perceptual organization will always be as regular, simple, and symmetric as possible.
law of Prägnanz
