MCAT P/S KA Lazy OCD

retinal disparity

a binocular cue for perceiving depth by comparing images from the retinas in the two eyes, the brain computes distance—the greater the disparity (difference) between the two images, the closer the object.

convergence

when things are far away, eyes are relaxed. When we see things closer to us, the eye muscles contract

Types of binocular cues

retinal disparity and convergence

types of monocular cues

relative size

interposition (overlap)

relative height (things taller seem farther away)

shading and contour (light and shadows give shape of an object)

motion parallax (things farther away move slower)

Constancy: our perception of an object doesn't change even if looks different on the retina

types of constancy

size, shape, color

sensory adaptation

diminished sensitivity as a consequence of constant stimulation

Sensory adaptation in hearing

small muscle in inner ear contracts with loud noise and dampening the vibrations that go into the inner ear

doesn't work with a gunshot or single really loud noise--remember that sensory adaptation has to involve constant stimulation!

sensory adaptation in touch

temperature receptors get saturated and are desensitized

sensory adaptation to smell

sensory receptors become desensitized to molecules

sensory adaptation to proprioception

mice raised upside down would accommodate over time and flip it over

sensory adaptation to sight

down regulation: light adaptation, pupils constrict, and rods and cones become desensitized to light

upregulation: dark adaptation, pupils dilate. rods and cones start upregulating light-sensing molecules

Weber's Law

the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount)

∆I/I = K (Weber's Law)

∆I = IK (linear relationship

I is the intensity ( like 2 lb or 5 lb)

∆I is the JND

If you plot I against ∆I, it's constant.

just noticeable difference (JND)

the threshold at which you're able to notice a change in any sensation that can be detected 50% of the time

absolute threshold of sensation

The minimum intensity of stimulus needed to detect a particular stimulus 50% of the time. At low levels of stimulus, some subjects can detect and some can't (differences are based on the individual)

don't confuse this with the JND

Factors that can influence absolute threshold

expectations

experience

motivation

alertness

subliminal stimuli

stimuli below the absolute threshold

balance and spatial orientation

What is the vestibular system used for?

Semicircular canals

posterior, lateral, and anterior ( all at right angles to each other--x, y , z axes) in the inner ear. filled with endolymph and otolithic organs

endolymph

fluid within the semicircular canals that detect which direction our head is moving and the strength of rotation when shifting positions.

doesn't stop spinning at the same time as we do, so it continues moving and indicates to the brain that we're still moving even when we stop (dizziness)

otolithic organs

Utricle and saccule. Detect linear acceleration and head positioning

calcium carbonate crystals attached to hair cells in viscous gel. When moving up and down, they move and pull on the hair cell to trigger an action potential to carry information to the brain

signal detection theory

how we make a decision under conditions of uncertainty--discerning between important stimuli and unimportant noise; at what point we can detect a signal.

Strength of a signal is variable d’, and c is strategy

- d’: hit > miss (strong signal), miss

role of signal detection theory in radar

signal a small vfish vs large whale

role of signal detection theory in psychology

which words on second list were present on the first list

real world example of signal detection theory

traffic lights--signal is present (green light) or absent (red light)

signal detection theory: present , yes

hit

signal detection theory: present, no

miss

signal detection theory: absent, yes

false alarm

signal detection theory: absent, no

correct rejection

conservative strategy

Always say no unless 100% sure a signal is present, might get misses

liberal strategy

always say yes, even if get false alarms, get all hits, but also some false alarms

C=0, ideal

C<1, liberal (says no less often that the ideal observer)

C>1, conservative (says no more often than an ideal observer)

When is a participant an ideal observer? Liberal? Conservative?

bottom up processing

no preconceived idea of what you're looking at, data driven

stimulus influences our perception.

processing sensory information as it's coming in--built from the smallest piece of sensory information

top down processing

background knowledge influences perception

driven by cognition (brain applies what it knows and what it expects to perceive and fill in the blanks)--where's waldo

Five Gestalt principles

similarity

pragnanz

proximity

continuity

closure

seek to understand why we perceive things the way we do

similarity

items similar to one another are 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

Cornea

Delicate membrane lining the eyelids and covering the eyeball

first layer light hits

cornea

transparent thick sheet of tissue, anterior 1/6th

anterior chamber

space filled with aqueous humour, which provides pressure to maintain shape of eyeball; allows nutrients and minerals to supply cells of cornea/iris.

pupil

hole made by the iris (which determines eye color)

lens

bends the light so it goes to the back of the eyeball

cilliary body

suspensory ligaments attached to a cilliary muscle, change the shape of the lens

iris

determines eye color

two muscles that control size of the pupil

posterior chamber

area behind the ciliary muscle, filled with vitreous humor

vitreous chamber

filled with vitreous humor, jelly like substance to provide pressure to eyeball and gives support to lens

retina

filled with photoreceptors that send signals to the brain through the optic nerve

macula

special part of retina rich in cones

fovea centralis

the central focal point in the retina, around which the eye's cones cluster

no axons in way of light, so cones get higher resolution because light hits it directly

choroid

pigmented black in humans, a network of blood vessels

sclera

whites of the eye, thick, fibrous tissue that covers posterior 5/6th of eyeball. attachment points for muscles

light (stimulus)

Neural impulse by a photoreceptor

What does vision require?

electromagnetic

Light is an _______ wave

violet (400 nm) to red (700 nm)

Visible light

rods

night vision, black and white

120 million

contain optic discs, large membrane bound structures that contain rhodopsin that fire APs to the brain.

1000x more sensitive to light than cones (whether light is present)

slow recovery time

photoreceptor

specialized nerve that take light and convert to a neural impulse

light comes in, goes through the pupil and hits the rod

normally the rod is turned on, but when light hits, it turns off

when the rod is off, it turns on a bipolar cell, turns on a retinal ganglion cell, and goes into the optic nerve and enters the brain

How do rods detect light?

when light hits rods and cones, process of turning off the cells in the retina, allows brain to comprehend the stimulus.

1. rods are a lot of disks stacked on top of each other, with proteins in the discs (rhodopsin) and retinal. Light hits retinal and causes it to change in conformation from bent to straight (11-cis retinal to 11-trans retinal)

2. retinal changes shape, causes rhodopsin to change shape

3. Transducin (protein, alpha, beta, gamma subunits) breaks from rhodopsin. Alpha subunit goes to disk and binds to phosphodiesterase

4. PDE takes cGMP and converts it to GMP. Na+ channels open when cGMP is bound (Na+ channels close without it)

5. As less Na+ enters the cell, rods hyperpolarize and turn off. glutamate is no longer released, no longer inhibits ON-center bipolar cells (excitatory to OFF-center bipolar cells)

6. causes bipolar cells to turn on and activates retinal ganglion cell, which sends a signal to optic nerve to brain

similar in cones, just with a different protein

phototransduction cascade

cones

three types: red, green, blue (60%/30%/10%)

6-7 million cones

almost all centered in fovea

contain photopsin

fast recovery time

less sensitive

blind spot

point where the optic nerve leaves the eye because there are no receptor cells located there

left, right

All right visual field goes to the ____ side of the brain. All Left visual field goes to the ____ side of the brain

optic chiasm

Optic nerves of both eyes Meet at the ____ _______

Components of feature detection

color

form

motion

trichromatic theory of color vision

presence of cones allows you to see color

,

Red -sensitive to red light: 60%

Green- sensitive to green light: 30%

blue -sensitive to blue light 10%

parvocellular pathway

ability to see the form/shape

good at spatial resolution, but poor at temporal (motion)

magnocellular pathway

has high temporal resolution and poor spatial resolution, but no color. we're able to track and see an object in motion.

parallel processing

the processing of many aspects of a problem simultaneously; the brain's natural mode of information processing for many functions, including vision. Contrasts with the step-by-step (serial) processing of most computers and of conscious problem solving.

sound waves

air molecules that are pressurized, which create areas of high and low pressure

add different frequency waves together. sound waves travel different lengths along the cochlea

How are you able to listen to different frequencies?

outer ear

pinna to tympanic membrane

middle ear

malleus , incus, stapes

inner ear

cochlea and semicircular canals

Organ of corti

Center part of the cochlea, containing hair cells, canals, and basilar/tectorial membranes, splits cochlea into 2 and fluid in the cochlea flows around the organ, causing hair cells to move back and forth.

hair bundle

stereocilia of one inner hair cell, filiments made of kinocilium, connected by a tip link and attached a K channel, which when moves, allows K to flow inside the cell.

spiral ganglion cell

activates auditory nerve when hair bundles are moved and K flows in and Ca channels are activated, causing an AP

chochlea

differentiates between two different sounds

basilar tuning

base: stimulated by high frequencies

apex: stimulated by low frequencies

also referred to as tonotypical mapping

varying hair cells detect different frequencies of sounds,and send an AP to the brain

primary auditory cortex

the region of the superior temporal lobe whose primary input is from the auditory system

sensitive to various frequencies in different locations, so you can distinguiush different frequencies

cochlear implants

a surgical procedure that allows sound waves to bypass the hair cells and go directly to the acoustic nerve

sound-->microphone-->transmitter (outside to the reciever-->cochlea, converts electrical impulse into neural impulse that goes to brain

types of sensations

temperature, pressure, pain, position

timing of sensations

non-adapting, slow adapting, fast-adapting

location of sensation

location-specific nerves to brain

adaptation

change over time of receptor to a constant stimulus (downregulation)

ex: if you push down with hand, receptors experience constant pressure. after a few seconds, receptors no longer fire

amplification

up regulation of a stimulus

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.

somatosensory homunculus

Broad areas of primary somatosensory cortex devoted to particular body regions, a topological map of the body in the cortex.

one part of your body sends sensory information to a specific part of the body in the somatosensory cortex

proprioception

the sensory processes that tell us about the location of our body parts and what each is doing

- Tiny little sensors located in our muscles that goes up to spinal cord and to the brain. It's sensitive to stretching.

- Sensors contract with muscles - so we're able to tell how contracted or relaxed every muscle in our body is.

kinaesthesia

movement of the body (behavioural)

does not include sense of balance

pain detection

nocicpetion

temperature detection

thermoception

TrypV1

Which receptor detects temperature?

TrypV1

detects temperature. heat causes a conformational change in the protein. When a cell is poked, thouususands of cells are broke and release different molecules that bind to TrypV1, causes conformational change,a ctivates the cell and sends signals to the brain

Three types of pain fibers

A-beta : ·       Fast ones are thick and covered in myelin (less resistance, high conductance)

A-delta: smaller diameter, less myelin.

C fibres - small diameter, unmyelinated (lingering sense of pain).

a-beta fibers

fast, thick and covered with myelin (less resistance, high conductance)

A-delta fibers

smaller diameter, less myelin. quick, sharp pain

C fibers

small diameter, unmyelinated (lingering sense of pain)

olfactory epithelium

a thin layer of tissue, within the nasal cavity, that contains the receptors for smell

receptors are sensitive to one type of molecule, so there are thousands of types in epithelial cells.

olfactory bulb

bundle of nerves that sends projections through the cribiform plate into the olfactory epithelium, which branch off.

Events that lead to olfaction

1. molecule binds to its specific receptor (receptor is a GPCR attached to an ion channel)

2. triggers events that cause cell to fire

3. AP ends up in olfactory bulb. All cells sesnitive that that particular molecule will fire to one olfactory bulb (glomerulus

4. they synapse on a mitral/tufted cell that projects to the brain.