Psych Chapter 2 Sensation and Perception

Sensation (transduction)

taking the physical, electromagnetic, auditory and other info from internal and external environment and converting it into electrical signals in the nervous system; the raw signal that is unfiltered and unprocessed until entering the CNS

perception

processing information within the CNS in order to make sense of the information’s significance

distal stimuli

physical objects outside the body

proximal stimuli

sensory-stimulating byproducts of distal stimuli; e.g. heat, pressure, sound waves, photons

Ganglia

collections of neuron cell bodies found outside the CNS

photoreceptors

sensory receptors that respond to electromagnetic waves in the visible spectrum (sight)

mechanoreceptors

sensory receptors that respond to pressure or movement

nociceptors

sensory receptors that respond to painful or noxious stimuli (somatosensation)

thermoreceptors

sensory receptors that respond to changes in temperature (thermosensation)

osmoreceptors

sensory receptors that respond to osmolarity of the blood (water homeostasis)

olfactory receptors

sensory receptors that respond to volatile compounds (smell)

taste receptors

sensory receptors that respond to dissolved compounds (taste)

Threshold

minimum amount of stimulus that renders a difference in perception

absolute threshold

minimum of stimulus energy needed to activate a sensory system

threshold of conscious perception

level of intensity a stimulus must pass in order to be consciously perceived by the brain

subliminal perception

information received by the CNS but does not cross the threshold of conscious perception

difference threshold

sometimes called the just-noticeable difference (JND); minimum change in magnitude required for an observer to perceive that two different stimuli are actually different

discrimination testing

participant presented with a stimulus which is then varied slightly and ask whether a change was perceived

Weber’s law

difference thresholds are proportional and must be computed as percentages

applies to the perception of many senses, sounds, light, weight of objects for example

signal detection theory

how internal and external factors influence thresholds of sensation and perception

sclera

white of the eye; a thick structural layer covering the exposed portion of the eye

choroidal vessels

a complex intermingling of blood vessels between the sclera and retina

retinal vessels

blood vessels in the retina

retina

innermost layer of the eye, contains actual photoreceptors that transduce light into electrical information the brain can process; considered part of the CNS develops as an outgrowth of brain tissue

cornea

clear, domelike window in the front of the eye, gathers and focuses the incoming light

anterior chamber

lies in front of the iris

posterior chamber

lies between the iris and the lens; where aqueous humor is produced

iris

colored part of the eye, composed of two muscles, dilator pupillae and constrictor pupillae

dilator pupillae

part of iris that opens the pupil under sympathetic stimulation

constrictor pupillae

part of the iris that constricts the pupil under parasympathetic stimulation

choroid

continuous with the iris; vascular layer of connective tissue that surrounds and provides nourishment to the retina

ciliary body

continuous with the iris; produces aqueous humor that bathes in the front part of the eye before draining into the canal of Schlemm

lens

lies behind the iris and helps control the refraction of the incoming light

suspensory ligaments

pulled on as ciliary muscle contracts and changes the shape of the lens to focus on an image as distance varies (accommodation)

vitreous humor

lies behind the lens, a transparent gel supporting the retina

duplexity theory of vision

the retina has two kinds of photoreceptors, those for light and dark and those for color detection

cones

used for color vision and to sense fine details; most effective in bright light and comes in three forms blue, green, and red, or short, medium, and long respectfully (wavelengths they best absorb)

rods

better than cones in reduced illumination; only allow sensation in light and dark; spread over much larger area of the retina so less useful for detecting fine details

rhodopsin

all rods contain only this single pigment type

macula

central section of the retina that has a high concentration of cones

fovea

central most section of the macula, contains only cones; going further from this increases the number of rods and decreases the number of cones; so visual acuity is best here and is most sensitive in normal daylight vision

optic disk

region of the retina devoid of photoreceptors and gives rise to a blind spot

bipolar cells

synapse with rods and cones and highlight gradients between adjacent rods or cones

ganglion cells

synapse with bipolar cells and have axons that group together to from the optic nerve

amacrine and horizontal cells

receive input from multiple retinal cells int he same area before info is passed onto ganglion cells; accentuating slight differences between the visual information in each bipolar cell, so they are important for edge detection as they increase our perception of contrasts

visual pathways

refers to both the anatomical connections between the eyes and brain and to the flow of visual information along these connections

optic chiasm

nasal fibers from left and right eyes cross paths; routing visual info to the correct side of the brain

parallel processing

brain’s ability to analyze information regarding color, form, motion, and depth simultaneously using independent pathways in the brain

Form

shape of an object and our ability to discriminate an object of interest from the background by detecting its boundaries

parvocellular cells

cells in the lateral geniculate nucleus (LGN); have very high color spatial resolution and allow us to detect very fine detail when thoroughly examining an object; but can only work with stationary or slow-moving objects since they have very low temporal resolution

magnocellular cells

cells in distinct layers of the lateral geniculate nucleus (LGN) and are well-suited for detecting motion because they have very high temporal resolution; no fine details however sense they have low spatial resolution

depth perception

ability to discriminate 3D shape of our environment and judge the distance of objects within it, largely based on discrepancies between inputs brain receives from our two eyes

binocular neurons

responsible for comparing inputs to each hemisphere and detecting differences for depth perception

feature detectors

detects a very particular, individual feature of an object in the visual field

vestibular sense

our ability to both detect rotational and linear acceleration and to use this info to inform our sense of balance and spatial orientation

pinna (auricle)

cartilaginous outside part of the ear; channels sound waves into the external auditory canal

external auditory canal

directs sound waves to the tympanic membrane (eardrum)

eardrum (tympanic membrane)

vibrates in phase with incoming sound waves with a rate determined by the frequency of the sound wave, higher rate for higher frequency; divides the outer ear from the middle ear

ossicles

three smallest bones in the body, help transmit and amplify vibrations from the tympanic membrane to the inner ear; located in the middle ear

stapes, incus, and malleus

malleus (hammer)

ossicle affixed to the eardrum

incus (anvil)

ossicle that acts on the stapes

stapes (stirrup)

ossicle that rests on the oval window of the cochlea

cochlea

entrance to the inner ear; spiral shaped organ containing the receptors for hearing; divided into three parts called scalae

eustachian tube

connects the middle ear to the nasal cavity, helping to equalize pressure between the middle ear and the environment

bony labyrinth

hollow region of the temporal bone containing the cochlea, vestibule and semicircular canals

membranous labyrinth

collection of tubes and chambers resting inside the bony labyrinth; contains receptors fro the sense of equilibrium and hearing

endolymph

a potassium rich fluid filling the membranous labyrinth

perilymph

suspends the membranous labyrinth in the bony one; a thin layer of fluid that simultaneously transmits vibrations from the outside world and cushions the inner ear structures

Organ of Corti

housed by the middle scala, it is the actual hearing apparatus; rests on a thin, flexible membrane called the basilar membrane; composed of thousands of hair cells bathed in endolymph

tectorial membrane

relatively immobile membrane on top of the organ of Corti

round window

a membrane covered hole in the cochlea permitting the perilymph to move within the cochlea

auditory nerve

carries the electrical signal transduced by hair cells in the organ of Corti to the CNS

vestibule

portion of the bony labyrinth that has the utricle and saccule; structures sensitive to linear acceleration and used as part of the balancing appartus

otoliths

resists motion as the body accelerates; bends ad stimulates underlying hair cells, signaling the brain; found covering utricle and saccules

semicircular canals

sensitive to rotational acceleration; arranged perpendicularly to each other and ends in a swelling called an ampulla (where hairs are located)

stereocilia

on top surface of hair cells; sway back and forth within the endolymph opening ion channels which causes receptor potential

place theory

location of a hair cell on the basilar membrane determines the perception of pitch when that hair cell is vibrated; high frequencey pitches cause vibrations close to the oval window while low ones cause them at the apex, away from the window

tonotopical organization

hair cells vibrating gives the brain an indication of the pitch of the sound

pheromones

chemicals secreted by one animal, which, once bonded with chemoreceptors, compel or urge another animal to behave in a specific way

pacinian corpuscles

somatosensory receptors that respond to deep pressure and vibration

meissner corpuscles

somatosensory receptors that respond to light touch

merkel cells (discs)

somatosensory receptors that respond to deep pressure and texture

ruffini endings

somatosensory receptors that respond to stretch

free nerve endings

somatosensory receptors that respond to pain and temperature

two point threshold

minimum distance necessary between two points of stimulation on the skin to be felt as two distinct stimuli; size depending on density of nerves in particular area of skin being tested

physiological zero

normal temperature of skin; between 86 to 97 degrees farenheit

gate theory of pain

proposes that a special mechanism can turn pain signals on or off, affecting whether or not we perceive pain; spinal cord can preferentially forward signals from other touch modalities

kinesthetic sense (proprioception)

ability to tell where one’s body is in space; receptors in muscle and joints that play critical roles in hand-eye coordination, balance, and mobility

perceptual organization

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

monocular cues

only require one eye and include relative size, interposition, linear perspective, motion parallax, and other minor cues

relative size

objects appear larger the closer they are

interposition

when 2 objects overlap, the one in front is closer

linear perspective

convergence of parallel lines at a distance, the greater the convergence, the further the distance

motion parallax

perception that objects closer to us seem to move faster when we change our field of vision

binocular cues

primarily involve retinal disparity, referring to the slight difference in images projected on the two retinas

convergence

binocular cue in which the brain detects the angle between the two eyes required to bring an object into focus

constancy

our ability to perceive that certain characteristics of objects remain the same

gestalt principles

set of general rules that account for the fact that the brain tends to view incomplete stimuli in organized, patterned ways

law of proximity

elements close to one another tend to be perceived as a unit

law of similarity

objects that are similar tend to be grouped together