Processing the Environment Flashcards by modi Aldosari

Binocular Cues -

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Retinal disparity (eyes are 2.5 inches apart)

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Convergence

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things far away, eyes are relaxed. Things close to us, eyes contract.

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Monocular Cues

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relative size,

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interposition

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relative height

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things higher are farther away

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shading and contour,

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motion parallax

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things farther away move slower)

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our perception of object doesn’t change even if it looks different on retina.

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size constancy, shape constancy, color constancy.

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Sensory Adaptation

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temperature receptors desensitized

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

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down (ex. Light adaptation, pupils constrict, rods and cones become desensitized to light) and
upregulation (dark adaptation, pupils dilate)

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inner ear muscle: higher noise = contract.

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Weber’s Law

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2 vs. 2.05 lb weight feel the same.

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2 vs. 2.2 lb weight difference would be noticeable.

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The threshold at which you’re able to notice a change in any sensation is the just noticeable difference (JND)

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So now take 5 lb weight, in this case if you replace by 5.2 weight, might not be noticeable. But if you take a 5.5 lb
it is noticeable.

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I = intensity of stimulus (2 or 5 lb), delta I = JND (0.2 or 0.5).

Weber’s Law is delta I to intensity is constant, ex. .2/2 = .5/5 = .1.

Delta I/I = k (Weber’s Law)

- If we take Weber’s Law and rearrange it, we can see that it predicts a linear relationship bet

ween incremental threshold and background intensity.

• If you plot I against delta I it’s constant

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. Also differences in an individual.

Not the same as the difference threshold (JND) – that’s the smallest difference that can be detected 50% of the time.

- Absolute threshold can be influenced by a # of factors, ex. Psychological states.

Expectations

Experience (how familiar you are with it)

Motivation

Alertness

stimuli below the absolute threshold.

Subliminal stimuli –

The Vestibular System

Balance and spatial orientation

Focus on inner ear - in particular the semicircular canals (posterior, lateral, and anterior)

Canal is filled with endolymph, and causes it to shift – allows us to detect what direction our head is moving in, and the strength of rotation.

help us to detect linear acceleration and head positioning. In these are Ca crystals attached to hair cells in viscous gel. If we go from lying down to standing up, they move, and pull on hair cells which triggers AP.

Also contribute to dizziness and vertigo

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”

At what point can we detect a signal

Origins in radar – is signal a small fish vs. large whale.

Its role in psychology – which words on second list were present on first list.

Real world example – traffic lights. Signal is present or absent (red).

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

d’: hit > miss (strong signal), miss

c: 2 strategies – 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).

For any signal, have noise distribution. And get a second graph – the signal distribution.

The difference between means of the two is d’. So if signal shifted to right, d’ would be big and easy to detect. If left, d’ very small and more difficult to detect.

X-axis have intensity.

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. lnbeta = d’ x C = 1 x 1.5 = 1.5 2

stimulus influences our perception.

Processing sensory information as it is coming in (built from smallest piece of sensory information)

background knowledge influences perception. Ex. Where’s waldo

Driven by cognition (brain applies what it knows and what it expects to perceive and fill in blanks)

Top-down:

items similar to one another grouped together

reality is often organized reduced to simplest form possible (Ex. Olympic rings)

objects that are close are grouped together

lines are seen as following the smoothest path

objects grouped together are seen as a whole

Similarity

Pragnanz

Proximity

Continuity

Closure

first layer 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.

attached to a ciliary muscle. These two things together form the ciliary body, what secrets the aqueous humor.

area behind the ciliary muscle, also filled with aqueous humor.

filled with vitreous humour, jelly-like substance to provide pressure to eyeball.

filled with photoreceptors.

special part of retina rich in cones.

completely covered in cones, no rods.

pigmented black in humans, a network of blood vessels. Bc black all light is reflected.

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

Conjunctiva

Cornea

Anterior chamber

Pupil

Lens

Suspensory ligaments,

Posterior chamber

Vitreous chamber

Retina

Macula

Fovea

Choroid

Sclera

light -> neural impulse, by a photoreceptor

What is light?

Electromagnetic wave part of a large spectrum

EM spectrum contains everything from gamma rays to AM/FM waves. Visible light is in the middle

Violet (400nm) – Red (700nm)

The Sun is one of most common sources of light

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.

There are 6-7 million cones

• 3 types: red, green, blue

Almost all cones are centered in fovea

when light hits rods and cones

Phototransduction Cascade –

Retina is made off a bunch of dif cells – rods and cones.

As soon as light is presented to him, he takes light and converts it to neural impulse. Normally turned on, but when light hits it’s turned off.

PTC is set of steps that turn it off.

Inside rod are a lot of disks stacked on top of one another.

A lot of proteins in the disks. One is rhodopsin, a multimeric protein with 7 discs, which contains a small molecule called retinal (11-cis retinal). When light hits, it can hit the retinal, and causes it to change conformation from bent to straight.

When retinal changes shape, rhodopsin changes shape.

That begins this cascade of events – there’s a molecule in green called transducin made of 3 dif parts – alpha, beta, gamma

Transducin breaks from rhodopsin, and alpha part comes to disk and binds to phosphodiesterase (PDE).

Bottom up

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.

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).

So bipolar cells turn on. This activates retinal ganglion cell which sends signal to optic nerve to brain.

Photoreceptors (Rods and Cones)

photoreceptor is a specialized nerve that can take light and convert to neural impulse.

Cones are also specialized nerves with same internal structure as rod.

Inside rod are optic discs, which are large membrane bound structures – thousands of them. In membrane of each optic disc are proteins that fire APs to the brain.

Cones are also specialized nerves with same internal structure as rod.

Rods contain rhodopsin, cones have similar protein photopsin.

- If light hits a rhodopsin, will trigger the phototransduction cascade. Same process happens in a cone.

Differences

120 M rods vs. 6 million cones.

Cones are concentrated in the fovea.

Rods are 1000x more sensitive to light than cones. Better at detecting light – telling us whether light is present, ie. BW vision

Cones are less sensitive but detect color (60% Red, 30% Green, 10% Blue)

Rods have slow recovery time, cones have fast recovery time. Takes a while to adjust to dark – rods need to be reactivated.

Photoreceptor Distribution in Retina

Where optic nerve connects to retina, blind spot – no 4 cones or rods.

Rods are found mostly in periphery.

Cones are found throughout the fovea, and few in rest of eye.

If we zoom in on fovea – no axons in way of light, so get higher resolution. If light hits periphery, light has to go through bundle of axons and some energy lost. So at fovea light hits cones directly.

How our brain makes sense of what we’re looking at. Right side of body controlled by left side, vice versa.

Visual Field Processing

How does it work in vision?

All right visual field goes to left side of brain, all left visual field goes to right side of brain.

Feature Detection and Parallel Processing

cones, trichromatic theory of color visio

parvocellular pathway – good at spatial resolution, but poor temporal),

magnocellular pathway, has high temporal resolution and poor spatial resolution, no color)

Color

motion

form

see all at same time; simultaneous processing of incoming stimuli that differs in quality

Parallel processing

Sound (Audition)

Need 1) pressurized sound wave and 2) hair cell

Ex. In between your hands are a bunch of air molecules, and suddenly hands move towards each other, so space is a lot smaller.

Air molecules are pressurized and try to escape, creating areas of high and low pressure – known as sound waves

Sound waves can be far apart or close together

How close peaks are is the frequency.

see all at same time; simultaneous processing of incoming stimuli that differs in quality

Parallel processing

Sound (Audition)

Need 1) pressurized sound wave and 2) hair cell

Ex. In between your hands are a bunch of air molecules, and suddenly hands move towards each other, so space is a lot smaller.

Air molecules are pressurized and try to escape, creating areas of high and low pressure – known as sound waves

Sound waves can be far apart or close together

Different noises have different sounds

You can listen to different frequencies at same time – if you add dif frequency waves together, get weird frequency. Ear has to break this up. Able to do that because sound waves travel different lengths along cochlea.

Hair cells – first hit outer part of ear, known as the pinna. Then go 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.

Reason doesn’t go back to oval window, is because in middle of cochlea is a membrane – the organ of Corti (includes the basilar membrane and the tectorial membrane).

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.

Stapes is attached to oval window (aka elliptical window). As it gets pushed, it pushes fluid and causes it to go around cochlea. At tip of cochea, it can only go back, but goes to the round window and pushes it out.

From pinna to tympanic membrane is the outer/external ear.

From malleus to stapes, middle ear.

Cochlea and semicircular canals is the inner ear.

Focus on cochlea and inner ear

Let’s unroll the cochlea.

moving back and forth at same frequency as stimulus. It pushes the elliptical window back and forth.

There’s fluid inside the cochlea which gets pushed around cochlea, and comes back around. Organ of Corti splits cochlea into 2.

Cross section of Organ of Corti

Upper and lower membrane, and little hair cells. As fluid flows around the organ it causes hair cells to move back and forth.

The hair bundle is made of little filaments. Each filament is called a kinocilium.

Tip of each kinocilium is connected by a tip link.

Tip link is attached to gate of K channel, so when get pushed back and forth they stretch and allows K to flow inside the cell.

Ca cells get activated when K is inside, so Ca also gets activated, and causes AP in a spiral ganglion cell which then activates the auditory nerve.

Auditory Processing

Brain relies on cochlea to differentiate between 2 different sounds.

Base drum has low frequency, whereas bees have high frequency.

We can hear between 20-20000Hz.

Brain also uses basilar tuning – 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.

Apex = 25 Hz, base = 1600 Hz.

Only certain hair cells are activated and send AP to the brain – primary auditory cortex receives all info from cochlea.

Primary auditory cortex is also sensitive to various frequencies in dif locations.

So with basilar tuning, brain can distinguish dif frequencies – tonotypical mapping.

A surgical procedure that attempts to restore some degree of hearing to individuals with sensory narrow hearing loss – aka `nerve deafness`

Base drum has low frequency, whereas bees have high frequency.

We can hear between 20-20000Hz.

Brain also uses basilar tuning – 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.

Apex = 25 Hz, base = 1600 Hz.

Only certain hair cells are activated and send AP to the brain – primary auditory cortex receives all info from cochlea.

Primary auditory cortex is also sensitive to various frequencies in dif locations.

So with basilar tuning, brain can distinguish dif frequencies – tonotypical mapping.

They have a problem with conduction of sound 6 cochlea to brain.

Receiver goes to a stimulator which reaches the receives info from a transmitter. Transmitter gets from the speech processor. Speech processor gets microphone.

Sound -> microphone -> transmitter (outside the to the receiver (inside). Then it sends info to the the cochlea, and cochlea converts electrical neural impulse that goes to brain.

Somatosensation

Types of Sensation, Intensity, Timing, and Location

Temperature (thermoception), pressure (mechanoception), pain (nociception), and position (proprioception)

Non-adapting, slow-adapting, fast-adapting.

Location-specific nerves to brain

Types

Location

Timing

change over time of receptor to a constant stimulus – downregulation

As you push down with hand, receptors experience constant pressure. But after few seconds receptors no longer fire.

Important bc if cell is overexcited cell can die. Ex. If too much pain signal in pain receptor (capsaicin), cell can die.

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.

Adaptation

Amplification is upregulation

Somatosensory Homunculus

Your brain has a map of your body – the cortex.

This part of cortex is the sensory cortex – contains the homunculus.

Info from body all ends up in this somatosensory cortex.

there was a brain tumor, to figure out what part it’s in neurosurgeons can touch diff. parts of cortex and stimulate them. If surgeon touches part of cortex patients can say they feel it. Do it to make sure they aren’t removing parts in sensation.

This creates topological map of body in the cortex.

Proprioception and Kinaesthesia

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.

talking about movement of the body. Proprioception was cognitive awareness of body in space.

more behavioural.

Kinaesthesia

- In order for us to sense temperature, we rely on the TrypV1 receptor.

Interestingly, this receptor is also sensitive to pain.

There are thousands of these in membranes. Heat causes a conformational change in the protein.

When cell is poked, thousands of cells are broken up, and releases different molecules that bind to TrypV1 receptor. Causes change in conformational change, which activates the cell and sends signal to brain.

Fast ones are thick and covered in myelin (less resistance, high conductance)

3 types of fibres – fast, medium, slow.

smaller diameter, less myelin.

small diameter, unmyelinated (lingering sense of pain).

A-delta fibres -

A-beta fibres -

C fibres

Pain also changes conformation of receptors – capsaicin binds the TrypV1 receptor in your tongue, and triggers the same response.

Processing the Environment Flashcards

(260 cards)