depth, form, motion, constancy
Vision involving two eyes that give humans the ability to receive visual cues from the enviornment
What are two components of binocular vision?
Retinal Disparity Convergence
The fact that eyes are 2.5 inches apart allowing humans to get slightly different views of objects --> provides depth
Provide humans depth through using eye muscles - Far objects cause the eye muscles to relax -Close objects cause the eye muscles to contract
Visuals cues that use one eye that provide the form of an object
What are examples of monocular cues?
Relative Size Interposition (overlapping) Relative Height - things higher away are further Shading/Contour Motion parallax - Things further away appear slower
Our perception of object doesn’t change even if it looks different on retina
What is sensory adaptation?
Our senses are adaptable and they can change their sensitivity to stimuli
List the 5 Types of Sensory Adaptation
Hearing Touch Smell Proprioception Sight
Muscles in the inner ear contract at higher noises
Temperature receptors become desensitized over time
Desensitized receptors in your nose to molecule sensory information over time
the sense of the position of the body in space
Mice raised upside down would accommodate over time, and flip it over
Eyes can adapt to various degrees of light via up and down regulation - light adaptation: pupils constrict down-regulate cones and rods - dark adaptation: pupils dilate to up-regulate cones and rods
Just Noticeable Difference (JND)
The threshold at which you’re able to notice a change in any sensation i.e. can notice the change in weight from 2 lb to 2.2 lb but not if you go up to 2.05 lb
JND for a stimulus is proportional to the magnitude of stimulus
Weber's Law Equation
Delta I/I = k Intensity Change(or JND)/Intensity=Constant
What describes the relationship between incremental threshold and background intensity?
Absolute Threshold of Sensation
The minimum intensity of stimulus needed to detect a particular stimulus 50% of the time
Why is absolute threshold of sensation important?
It is more accurate than determining the absolute level something can be sensed when taking into account variations within or across individuals
Absolute Threshold of Sensation vs Just Noticeable Difference
ATS is when you can notice a stimulus while JND is when you can notice a change in the intensity of a stimulus
What influences the absolute threshold of sensation?
Different psychological states - Expectations - Experience (how familiar you are with it) - Motivation - Alertness
Stimuli below the absolute threshold
The vestibular system
System that involves the inner ear and limbs to help with the sense of balance and spacial orientation
Which structure within the inner ear is involved in balance?
Semicircular canals - posterior, lateral, and anterior
Fills the canal that allows us to detect what direction our head is moving in, and the strength of rotation
Helps us to detect linear acceleration and head positioning. In these are Ca crystals attached to hair cells in viscous gel.
Vestibular System and Dizziness
Endolymph doesn’t stop spinning the same time as we do, so it continues moving and indicates to brain we’re still moving even when we’ve stopped – results in feeling of dizziness
Signal Detection Theory
Looks at how we make decision under conditions of uncertainty – discerning between important stimuli and unimportant “noise”
How do we determine signals?
Hit - Signal present and recognize Miss - Signal present and don't recognize it False Alarm - Signal isn't present but recognize it Correct Rejection - Signal isn't present and recognize it isn't there
d' = strength hit > miss (strong signal) miss
Strategy of Determining Strength
c; how do you determine if signal is present
Two types of signal strategy
conservative (always say no unless 100% sure signal is present. Bad thing is might get some misses). Or liberal (always say yes, even if get false alarms)
Signals have two distributions
- Noise distribution - Signal distribution
How is signal strength determined?
d' is the difference between noise distribution and signal distribution
What are the shifts in the signal distribution graphs?
So if signal shifted to right, d’ would be big and easy to detect. If left, d’ very small and more difficult to detect.
List the various strategies
- The strategy C can be expressed via choice of threshold – what threshold individual deems as necessary for them to say Y vs. N. Ex. B, D, C, beta, just dif variables. - If we were to use B, let’s say choose this threshold – 2. So anything greater than 2 will say Y to, anything less say N. So probability of hit is shaded yellow, and false alarm is pink. - D = d’-B, so let’s say d’ in this example is 1, so 2-1=1. So if we use D strategy, anything above 1 = Y. - C strategy is an ideal observer. Minimizes miss and false alarm. C = B – d’/2. So in our example, it’s 2- ½ = 1.5. So anthing above a 1.5 When C = 0, participant is ideal observer. If <1, liberal. If >1, conservative. - Beta, set value of threshold = to the ratio of height of signal distribution to height of noise distribution. ln beta = d’ x C = 1 x 1.5 = 1.5
stimulus influences our perception
Background knowledge influences perception --> i.e. where's waldo
Idea that humans can group images/objects in an organized fashion
Gestalt (shape, form)
List of Gestalt Principles
Similarity – items similar to one another grouped together Pragnanz – reality is often organized reduced to simplest form possible (Ex. Olympic rings) Proximity – objects that are close are grouped together Continuity – lines are seen as following the smoothest path Closure – objects grouped together are seen as a whole
The first layer where light hits
transparent thick sheet of tissue, anterior 1/6th
space filled with aqueous humour, which provides pressure to maintain shape of eyeball.
hole made by iris, which determines eye color
bends the light so it goes to back of eyeball
area behind the ciliary muscle, also filled with aqueous humor.
filled with vitreous humour, jelly-like substance to provide pressure to eyeball
Region of the eye filled with photoreceptors.
- Macula – special part of retina rich in cones.
- Fovea – completely covered in cones, no rods. → Helps with finding fine details and pictures (Helps you see where waldo is)
pigmented black in humans, a network of blood vessels. Bc all of the light to the eye is reflected off of it
whites of the eye, thick fibrous tissue that covers posterior 5/6th of eyeball. Attachment point for muscles.
Suspensory ligaments attached to a ciliary muscle
secrets the aqueous humor
A neural impulse that created from a neural impulse
Helps convert light into a neural impulse in the eye
What is light?
What is the EM spectrum?
A electromangentic wave that is part of the EM spectrum
Spectrum that contain everything from gamma rays to AM/FM waves --> visible light is in the middle
What is the visible light spectrum?
Part of the EM spectrum that ranges from 400 nm to 700 nm
Violet to Red
Path of light into the eye
Light enters pupil and goes to retina, which contains rods and cones
There are 120 million rods, for night vision
- Light comes in, goes through pupil, and hits rod. Normally rod is turned on, but when light hits turns off.
- When rod is off, it turns on a bipolar cell, which turns on a retinal ganglion cell, which goes into the optic nerve and enters the brain.
Way for the brain to recognize that light is entering the eyeball. Involves initially turning off the rods in the retina so other molecules can turn on
A multimeric protein with 7 discs that contains retinal
a small molecule that changes conformation from bent to straight when it is hit by light
Phototransduction Cascade Process
- Light hits the retinal causing it to change shape so rhodopsin also changes shape.
- This begins a cascade of events with transducin
- Transducin breaks from rhodopsin, and alpha part comes to disk and binds to phosphodiesterase (PDE).
- PDE takes cGMP and converts it to regular GMP. Na+ channels allow Na+ ions to come in, but for this channel to open, need cGMP bound. As cGMP decreases, Na channels closes.
- As less Na+ enters the cell, rods hyperpolarize and turn off. Glutamate is no longer released, and no longer inhibits ON bipolar cells (it’s excitatory to OFF bipolar cells).
- Bipolar cells turn on. This activates retinal ganglion cell which sends signal to optic nerve to brain.
retinal ganglion cell
Cell that sends signal induced by light to optic nerve
What is inside a rod?
optic discs, large membrane bound structures – thousands of them. In membrane of each optic disc are proteins that fire APs to the brain.
Similarities and Differences between Cones and Rods
Similarities - Have the same structure and both trigger phototransduction cascade
- Rods have rhodopsin while cones have photopsin
- More rods than cones in the eye
- Rods are more sensative to light
- Cones detect color
- Rods have a slower recovery time than cones
- Rods are in the periphery in the eyeball while cones are in the fovea
Where optic nerve connects to retina where no photoreceptors are present
One of the contributing factors to the eye having such a high resolution?
There are no axons in the fovea so little is obstructing light from hitting the cones directly --> this is not the case for rods in the periphery
Use a graph to describe photoreceptor distribution
X axis = Location within the eye
Y axis = Density of particular receptor
Rods are highest in the periphery and lowest in the Fovea
Cones are highest in the fovea and lowest in the periphery
Describe Visual Processing
- All light from the left visual field goes to the left side of the brain, all light on the right visual field goes to the right side of the brain
- The light that hits the nasal side of the eye cross at the optic chiasm to go to the opposite side of the eye
When looking at an object, you need to break it down into its component features to make sense of what you are looking at
Look at 3 components - color, form motion
Trichromatic theory of color
Color vision comes in 3 forms - red, green, and blue - due to the 3 types of cones
RED (60%), GREEN (30%), BLUE (10%).
How does the eye processes color?
object reflects red --> red light hits red cone in eye --> fire axon potential -->
brain is like OH RED!! ),
Method of the eye to detect form
Very good with spacial resolution but poor temporal resolution
Method of detecting motion
High temporal resolution and poor spatial resolution --> no color present
The ability to utilize all 3 forms of feature detection at the same time
Simulatnious processing of incoming stimuli taht differs in quality
What are the two major compontents of hearing?
- Pressurized sound wave
- Hair cell
Areas of high and low pressure that form when air molecules are pressurized and try to escape
Frequency of Sound Waves
How close the peaks of the sound waves are
How are humans able to listen to different frequencies at the same time?
Ear has to breaks up the various frequencies. Able to do that because sound waves travel different lengths along cochlea.
outer part of ear where sound waves first hit
external auditory meatus
auditory canal, next place where sound wave travels after hitting the pinna
Another name for Eardrum
tympanic membrane, place where sound wave travels after hiting exernal auditory meatus (auditory canal)
Process of Hearing
- Sound wave first hits the pinna
Then it goes to external auditory meatus (aka auditory canal)
- Then hit the tympanic membrane (Eardrum)
- As pressurized wave hits eardrum, it vibrates back and forth, causes these 3 bones to vibrate – malleus, incus, and stapes. (MIS - 3 smallest bones in the body
- Stapes is attached to oval window (aka elliptical window).
- As the oval window gets pushed gets pushed, the fluid pushes fluid and causes the fluid to go around cochlea
- At tip of cochea, the fluid can only go back, but goes to the round window and pushes it out.
Reason fluid doesn’t go back to oval window, is because in middle of cochlea is a membrane – the organ of Corti
- Keeps happening until energy of sound wave is dissipated. Meanwhile hair cells in cochlea are being pushed back and forth and send info to auditory nerve.
Classicification of ear
Where is the outer ear?
What makes up the middle ear?
What makes up the inner ear?
Outer Ear - Pinna to Tympanic Membrane
Middle Ear - Malleus to Stapes
Inner Ear - Cochlea and semilcircular canals
What determines the rate at which the stapes moves?
The stimulus which causes the sound wave
Organ of Corti
Membrane in the cochlea tha splits it into two
In both the lower and upper membrane of the organ of corti, there are hair cells that help the fluid move back and forth
Hair Bundle in the Organ of Corti
Little filament that make up the hairs in the
What structure in the ear is used to differentiate 2 different sounds?
Frequencies and Hearing
Humans can hear between between 20-20000Hz
Low frequency example is a base drum
High frequency example is that of a bee
there are varying hair cells in cochlea. Hair cells at base of cochlea are activated by high frequency sounds, and those at apex by low frequency sounds. --> long waves travel further
- Once the sound hits its designated hair cell, the hair cell is activated and an AP is sent to the brain
-AP reaches the primary auditory cortex in the temporal lobe --> hear time ticking, temperol lobe
Tones are mapped close together in the brain based upon their frequency
What are Cochlear Implants?
A surgical procedure that attempts to restore some degree of hearing to individuals with sensory narrow hearing loss
Sensory Narrow Hearing Loss
problem with conduction of sound waves from cochlea to brain
How do Cochlear Implants Work?
- Receiver goes to a stimulator which reaches the cochlea. Receiver receives info from a transmitter. Transmitter gets electrical info from the speech processor. Speech processor gets info from microphone.
- Sound -> microphone -> transmitter (outside the skull) sends info to the receiver (inside). Then it sends info to the stimulator, into the cochlea, and cochlea converts electrical impulse into neural impulse that goes to brain.
What are the parameters for somatosensation?
Types of Sensation
Intensity of Sensation
Timing of Sensation
Location of Sensation
List the types of Sensation
Timing of Somatosenation
- Non-adapting- neuron consistency fires at a constant rate
- Slow-adapting - neuron fires in beginning of stimulus and calms down after awhile
- Fast-adapting - neuron fires as soon as stimulus start...then stops firing. Starts again when stimulus stops).
change over time of receptor to a constant stimulus – typically downregulation
Ex. As you push down with hand, receptors experience constant pressure. But after few seconds receptors no longer fire.
Importance of Sensory Adaptation
if cell is overexcited cell can die. Ex. If too much pain signal in pain receptor (capsaicin), cell can die.
sensory receptor is upregulated
Ex. Light hits photoreceptor in eye and can cause cell to fire. When cell fires AP, can be connected to 2 cells which also fire AP, and so on.
Map of the body in the brain, specifically in the cortex
Where in the cortex is the homunculus?
The sensory strip of the cortex - specific areas in the strip are receiving information from specific parts of the body
How is tthe sensory strip useful for neurosurgery?
Used to make sure that the surgeon isn't removing a part of the brain that deals with sensation to a particular part of the body
Sense of balence/position in the body
Deals mostly with cognition
This is dictated by muscle spindles, which are sensative to stretch to alert the body how contracted muscles are
Deals with the movement of the body
Behavioral component of bodily movement - i.e. teaching yourself how to move successifuly to complete a task
Ability to sense Pain
Ability to sense temperature
receptors that sense temperature and are sensative to pain
sends a signal to the brain via confirmational change when it senses heat
What are the 3 types of nerve fibers?
A-beta fibres - Fast ones are thick and covered in myelin (less resistance, high conductance)
A-gamma fibres -– smaller diameter, less myelin.
C fibres - small diameter, unmyelinated (lingering sense of pain).
Molecule that can bind to TrypV1 receptor to trigger pain
Sometimes used for arthritis medication
Taste and smell
When you eat, molecules travel up back of throat and some go into back of your nose. So you’re using your sense of smell in conjunction with taste.
If your smell is knocked out, you can’t taste things as well.
specialized epithelial tissue inside the nasal cavity that is involved in smell
Separates the olfactory epithelium from the brain
A bundle of nerves that sends little projections through cribriform plate into the olfactory epithelium
There are receptors at the olfactory epithelium that is connected to the bulb for a particular molecule
How does a molecule bind to a receptor and cause an AP?
The molecule binds to the
GPCR receptor on odor molecule --> GPCR on olfactory epithelia --> G-protein dissociates
and causes a cascade of events inside the cell --> G protein binds to ion channel which
allows cells outside the cell to come inside--> opens and triggers an AP --> goes to
cribriform plate --> glomerulus --> activate mitral/tufted cell --> synapse to brain.
Location in the olifactory bulb where all of the AP from a specific molecule's receptors feed into
Cells within at the glomerulus where the receptors synapse to to project the smell to the brain.
Molecules released by animals that serves as special olfactory cues
What parts of the olfaction system are involved in pheramon processing
Specialized part of olfactory epithelium in animals – the accessory olfactory epithelium. It sends projections to the accessory olfactory bulb.
- Within the accessory olfactory epithelium, you have the vomeronasal system.
- In vomeronasal system, there are basal cells and apical cells. They have receptors at tips.
- Triangle will come in and activate receptor on basal cell here. Basal cell sends axon through accessory olfactory bulb to glomerulus, which eventually goes to the amygdala.
5 Tastes on Tongue
bitter, salty, sweet, sour, and umami (ability to taste glutamate)
Cells concentrated anteriorly on the tongue. Taste buds can be fungiform (anterior), foliate (side), and circumvallate (back)
- A taste bud has all 5 of the receptors used to detect taste
Labelled lines model
Each receptor has an axon, which all remain separate to the brain. And they all synapse on dif parts of the gustatory cortex
example - Glucose hits tongue, activates sweet cell (because it has sweet sensitive receptors), triggers cascade of events so cell depolarizes, and travels down axon to the brain
What type of receptors do each of the 5 tastes have?
Sweet, umami, and bitter cells GPCR receptors
Sour and salty rely on ion channels
What happens if we put salty receptor inside a sweet cell?
Receptors in membrane bind to glucose. But let’s insert a salty receptor. Since axon from cell leads to brain, if NaCl comes in, it activates the receptor, + ions go inside, sweet cell depolarizes and fires AP, and brain interprets it as a sweet signal.