Ch. 6 ~ Sensation & Perception

How do we experience the world?

• physical energy entering our body/nervous system and converted into a neural signal that can be sent to your brain

What is transduction?

• the conversion of the physical energy to neural energy that is sent as a signal for your brain to process

What is the cornea?

• clear outer covering, protects our eyes, focuses image

What does the pupil do?

• controls the amount of light that gets into the eye

What is the iris?

• muscles that allow pupil to change size, the colored part of the eye

What do the lens in our eye do?

• focus a sharp image unto the back part of the eye (gets more rigid/less bending as older)

What is the retina and its role?

• curved projection screen, thin layer of cells, contains receptors (rods and cones) for light converting it into a neuro signal

What is the blind spot in your eye?

• a gap where visual signals leave eye and travel to back of the brain so we can perceive what we’re seeing

What is the fovea?

• central part of your visual field, right behind your retina

• the images that leave the eye and travel to the back of your brain are inverted images

What are two problems of Focus?

• Myopia/Near-sightedness: can get a sharp image up close, farther away is blurry

• Hyperopia/Far-sightedness: further image is sharp, closer= blurry

Why do the receptors have to pass the signal onto the ganglion cells?

• Because the axons of those ganglion cell form the fibers of the optic nerve

• Gets passed on to bipolar cells first because of the big distance

• Then the G-cells pass it on to the back of the brain

What does the 0 degrees represent in the distribution of rods and cones?

• represents the Fovea, the central image, moving away is moving into the periphery

Are there more rods or cones?

• wayyyy more rods

• *there are no rodes in the Fovea but are located along the periphery

What are the rods sensitive to?

• motion; allow us to detect motion in our visual field

• allow us to see in dimly lit conditions

What is the role of the cones?

*they are also in the periphery but line it

• to make images very sharp

• why is why when you want to see something clearly you look at it closely and directly, ensuring its in your central point of view

• allow us to process color

What is the point where the two optic nerves from each eye cross over?

• optic chiasm

  • from there they travel to the thalamus, then the back of the brain

How do we see color?

• physical energy in the environment does not have perceptual qualities

  • light waves are not colored but our nervous system is interpreting these colors

• Light being reflected off some object

How is a chameleon able to change it’s color?

• he has control over the pigments within his skin, so he can control the wavelengths that are reflected, vs the ones that are absorbed

What’s the most impressive animal that can change the color of their skin?

• the cuttlefish

What is trichromatic vision?

• the fact that we have three different types of cones in our retina and each respond to a diff range of wavelengths

• Long = upper spectrum, red

• Medium = middle, green

• Short = lower, blue

What does it mean if someone has dichromatism?

• they only have two types of cones of the wavelengths, limiting their access to the long//red and making them “color blind”

• even the greens they see are dull

What can’t trichromaticism explain about how we see images?

• color afterimages

What is opponent process?

• processing of the color signals within the visual cortex

• when you’re staring at the color it’s being exhausted, so when you remove it and look at white then it’s opposing color has a chance to be used and you see an opposite color

What are the two systems in which we see colors?

• Trichromatic (receptors in retina)

• Opponent-process (beyond the retina to brain)

How does the opposing-process allows us to do?

• make fine discrimination in colors that are very close to each other within a wavelength spectrum

  • e.g different shades of red

What are the two ways we perceive complex visuals?

• (Bottom Up): we build a perception from the sum individual parts, “sensations”

• (Top Down): Gestalt; see the entire image then look at it’s parts

  • proved that we see this way more

What was the one overall guiding principle that Gestalt used?

• simplicity

Principle of similarity?

• grouping things that look similar together

Principle of continuity?

• not four branches but two continuing from each side

Principle of Proximity?

• when images are closer together we group them as one

What is figure-ground segregation?

• when we look at an image we try to extract the object from it’s background

• *figure ground images don’t allow us to do this easily

What is binocular depth cues?

• result from binocular disparity

  • the fact that when we’re looking at something the image that enters our right eye is slightly diff from the one that enters our left

  • our brain can now process these diff images and extracts depth cues

Whats the best way to understand this depth perception?

• stereoscopes and 3d Movies

  • two images displaced slightly going into one eye each only, creating the image to pop out

  • use two cameras side by side

What was the visual cliff experiment?

*purpose was to see if babies noticed a diff in height

• placed on glass table: half checkerboard and half transparent glass

• very young babies actually can’t detect, their depth perception wasn’t fully developed

What are monocular depth cues?

• don’t require interaction between both used

• used to perceive depth from a 2D image

What is relative height?

• the fact that we use the relative height of images to determine how far away they are

  • the higher the image is the further away (on ground)

  • lower = further away (in the sky)

What is relative size vs familiar size?

• relative = bigger is closer and smaller is farther

• but it can be deceiving so we’ve go to know the familiar size of what we’re viewing

What is size constancy?

• a cognitive function of the visual system that allows us to perceive an object as its actual, constant size, even as its distance from us changes and the size of its image on our retinas shrinks or grows

• playing on our understanding that the farther away something is the smaller it is

What is the ames room?

• other visual illusions rely on restricted viewing angle and manipulation of depth cues

How do sounds travel?

• in waves

What are the two physical aspects of sound?

• physical = volume, perception = loudness

• physical = frequency, perception = pitch

What are the different sections of our ears?

• Outside, folds, groove: called pinna

• Eardrum: tympanic membrane (eardrum)

  • vibrates when sound reaches it

What are the three ossicles/bones in our ear?

• Malleus

• Incus

• Stapes

  • bangs against cochlea

*smallest bones in the human body

Why are the ossicles bone and not muscle or soft tissue?

• they have to transfer the sound from air, to fluid that is inside the cochlea

What is the basilar membrane?

• houses receptors for sound that are located on top of the membrane

• transmit signals to nerve fibers

• base = narrow, thick for high frequencies

• upper = wide, thin apex for low frequencies

What needs to happen for a sound to be perceived?

• must travel to the brain

• from cochlea to thalamus to auditory complex

What are the two hearing problems?

• Conductive: sound signals are not being transmitted properly

• Sensorineural: involves an issue with the neural processing of the sound waves (more serious)

What does a cochlear implant do?

• artificially sends neural signals that aren’t being transmitted themselves

• hearing SOME sounds and speech, but not all

  • one of a thing we need to speak is to hear ourselves

How are we able to taste food?

• the chemical contents of our food reacts with taste receptors located in our mouths

• where there are a lot of bumps, indicated that there are a lot of receptors there

What is umami?

• foods that are savory/meat

  • beef or steak

Supertaster vs non-taster?

• Super, more taste buds: picky eater

  • extra sensitive in spice

• Non-taster

• No difference in bitter foods

What is olfaction?

• we have to extract the chemicals from the air that we breathe into our nose, then they’re converted

Olfactory receptors and bulbs?

• sent from the receptors, to the bulb to the brain

Why do we also react to certain smells of food?

• the signal is also sent to two parts of our frontal lobe

  • Orbitofrontal cortex: decision making

  • Amygdala: affects our emotional state, giving an emotional reaction

How do we touch?

• receptors (mechanoreceptors) located in our skin

• can respond to changes in pressure or temp against skin and transfer it to the brain

What carries our touch signals to the brain?

• cranial and spinal nerves

What is the somatosensory cortex?

• has a map of areas of the body where the, diff regions of cortex respond to sections of the body where the signals are originating in

Which receptors allow us to distinguish everyday touch vs pain?

• Nociceptors

  • Fast fiber; reserved for very sharp immediate pain

  • Slow fiber; lingering, a slow aching

How do we recognize pain signals inside our body?

• Complicated explained by gate control body

  • can be influenced by our cognitive state

  • opening gate = more pain, closed = reduced to no pain

What can the gate control model explain?

• How we perceive placebo effects

• why a person can be injured but doesn’t feel the pain, because they’re focusing on other things

• Also why meditation, acupuncture and hypnosis effectively works when its really simple