Final Flashcards
Vision-energy type?
Electromagnetic
Vision
Electromagnetic Photons captured From extrastriate-->what/where pathways Cones. Rods. Photoreceptors. To measure optical power-diopter. Topographical mapping. Cortical rep of fovea greatly magnified compared to cortical rep of peripheral vision.
Audition
Mechanical forces
Energy-captured as air pressure.
Pathway for audition
Air pressure wave Pinnae Ear canal Tympanic membrane Ossicles Malleus Incus Stapes Oval window Vestibular Tectorial membrane Organ of corti Steric ilia Neurotransmitter- initiates action potentials in auditory nerve fibers that carried out to the brain
Decibel measures
Physical intensity of sound
Hertz
Frequency
Receptors in ears
Hair cells
Stereocilia
Ear organization
Tonotopic
Touch
Mechanical forces
Soma topically
Homonculus
Touch pathways
Skin and muscles-> spinal cord-
Spinothalamic
Temp pain
Dcml
Tactile
Smell is the only ________
Ipsilateral
Smell mapping
Topographical
Smell pathway
Odorants Receptor Olfactory cilia OSN Cribiform plate (olfactory bulb) Olfactory nerves Glomerulus Mitral Primary olfactory cortex/ other brain structures
Fourier analysis
Any complex sound can be broken down into individual sine wave components through this process.
taste
○ Type of energy: chemical diffusion
○ What form of energy captured: chemical senses
○ Sensory organ: tongue
○ Receptor: microvilli
○ Mapping:
○ Pathway: chewing breaks down food substances into molecules, dissolved in saliva → papillae which have taste buds embedded in them → Microvilli → cranial nerves → medulla → thalamus → insular cortex → orbitofrontal cortex
Vestibular (sense of balance)
○ Sensory organ: ear
■ 5 total: 3 semicircular and 2 otolith
Proprioception
(sense of limb positions)
○ Type of energy: mechanical forces
○ Sensory organ: muscles
Sound
■ different locations of cochlea for different frequencies
■ pressures relieved by round window
if I ask a ganglion cell, what do you know, what can you tell me about the visual word as opposed to a simple cell in v1,
all I know is if theres a spot of light in this one spot or not
● Index of Refraction
Indicates how much light ‘bends’ when it goes from one medium to another.
Responsible for image formation and rainbows
Cornea:
The front part of the eye; a transparent “window” into the eyeball
-● Presbiopia
“old sight”. Hardening of the crystalline lens. The lens becomes sclerotic (harder) and the capsule that encircles the lens (enabling it to change shape) loses its elasticity-
● Hyperopia:
When light entering the eye is focused behind the retina; farsightedness
● Myopia:
When light entering the eye is focused in front of the retina, and distant objects cannot be seen sharply; nearsightedness
diopter
unit of measurement of the optical power of a lens (or curved mirror). Reciprocal of focal length (in meters). D = 1/f(m)
Emmetropia:
No refractive error (no need for corrective eyewear)
Accommodation (change in focus):
The process in which the lens shape is changed, by the ciliary muscle, thus altering its refractive power
Retina:
A light-sensitive membrane in the back of the eye that contains rods and cones (and other neurons, supporting vessels, and structures), which receives an image from the lens and sends it to the brain through the optic nerve
● Aqueous Humor:
The watery fluid in the anterior chamber (between cornea and lens)
o Provides oxygen & nutrients; and,
o Removes waste from cornea & lens
● Crystalline Lens:
The lens inside the eye, which allows changing focus (Accommodation)
Pupil-
The circular opening (aperture) at the center of the iris in the eye, where light enters the eye
Iris:
The colored part of the eye, between the sclera (white part) and the pupil, consisting of a muscular diaphragm surrounding the pupil and regulating the light entering the eye by expanding and contracting the pupil
Vitreous Humor:
The transparent fluid that fills the large (vitreous) chamber in the posterior part of the eye (i.e., between the lens and the retina)
o Where floaters occur
● Astigmatism:
A visual defect caused by the unequal curving of one or more of the refractive surfaces of the eye, usually the cornea (requiring cylinder correction)
● Photoreceptors:
Cells in the retina that initially transduce light energy into neural energy
● Rods:
●
● :
●
● Horizontal Cells: located between photoreceptors and bipolar cells. Perform lateral inhibition. Responsible for center-surround receptive fields.
● Bipolar Cells: bridge between photoreceptors and ganglion cells. Two types: midget, 1:1 cone : ganglion (giving low convergence); and diffuse: connected to several photoreceptors (giving high convergence)
Photoreceptors that are specialized for night vision
o Respond well in low luminance conditions
o Do not process color
cones
-Photoreceptors that are specialized for daylight vision, fine visual acuity, and color
o Respond best in high luminance conditions
Duplex Retina
retina with cones and rods for day and night vision
● Pigment Epithelium:
Provides nutrients to photoreceptors. Usually opaque, sometimes reflective.
● Photoreceptors:
Rods: dim light, larger, more numerous, more sensitive, not in fovea; & Cones: better acuity, daylight, mostly in fovea, few in periphery, usu. 3 types (S, M, & L)
Horizontal Cells:
located between photoreceptors and bipolar cells. Perform lateral inhibition. Responsible for center-surround receptive fields.
● Bipolar Cells:
bridge between photoreceptors and ganglion cells. Two types: midget, 1:1 cone : ganglion (giving low convergence); and diffuse: connected to several photoreceptors (giving high convergence)
● Amacrine Cells:
● Ganglion Cells: Connection between eye and brain. Recieves information from bipolar cells (and amacrine cells) and sends info via the optic nerve.
● Age-related Macular Degeneration (AMD): A disease associated with aging that affects the macula. AMD gradually destroys sharp central vision
● Macula: The central part of the retina containing the fovea
● Scotoma: AMD causes central vision loss, resulting in a blind spot in this visual field
● Wet AMD: Abnormal blood vessels grow under the macula and can leak blood and fluid, raising the macula and impairing central vision. As the macula is displaced, straight lines may look wavy
● Dry AMD: More common. Occurs when macula cones degenerate. Sometimes dry AMD turns into wet AMD. Once dry AMD is advanced, no treatment can reverse the loss of vision.
less well understood. Seem to integrate information from groups of bipolar cells and communicate to ganglion cells.
Rhodopsin
-protein in rods
OFF-center ganglion cells
Inhibited by light falling on center, excited by light falling on surround
ON-center ganglion cells
Excited by light falling on center, inhibited by light falling surround
Cataracts
-loss of transparency in lens (solved with silicone implants)
Retinitis pigmentosa (RP):
Family of hereditary diseases involving the progressive death of photoreceptors and degeneration of the pigment epithelium
Receptive Field:
The region on the retina in which stimuli influence a neuron’s firing rate
Magnocellular
pathway is involved in motion processing. Excellent temporal resolution but poor spatial resolution
● M ganglion cells: Connect to the magnocellular pathway
o Receive input from diffuse bipolar cells
● P ganglion cells:
Connect to the parvocellular pathway
o Receive input from midget bipolar cells
o Parvocellular (“small cell”) pathway is involved in fine visual acuity, color, and shape processing. Poor temporal resolution but good spatial resolution
Vertical Pathway:
Photoreceptors, bipolar cells, and ganglion cells
Midget bipolar cell:
A small bipolar cell that receives input from a single cone
Diffuse bipolar cell:
A bipolar cell that receives input from multiple photoreceptors
Bipolar cell:
A retinal cell that synapses with one or more rods or cones (not both) and with horizontal cells, and then passes the signals on to ganglion cells
Amacrine cells: cells
●
These cells synapse horizontally between bipolar cells and retinal ganglion
Horizontal Pathway:
Horizontal cells & amacrine cells
● Horizontal cells:
Specialized retinal cells that run perpendicular to the photoreceptors and make contact with photoreceptors and bipolar cells
o Responsible for lateral inhibition, which creates the center–surround receptive field structure of retinal ganglion cells
● Ganglion Cells:
Connection between eye and brain. Recieves information from bipolar cells (and amacrine cells) and sends info via the optic nerve.
Age-related Macular Degeneration (AMD):
A disease associated with aging that affects the macula. AMD gradually destroys sharp central vision
Macula
-The central part of the retina containing the fovea
Scotoma
-AMD causes central vision loss, resulting in a blind spot in this visual field
Wet AMD:
Abnormal blood vessels grow under the macula and can leak blood and fluid, raising the macula and impairing central vision. As the macula is displaced, straight lines may look wavy
Dry AMD:
More common. Occurs when macula cones degenerate. Sometimes dry AMD turns into wet AMD. Once dry AMD is advanced, no treatment can reverse the loss of vision.
● Acuity:
the smallest spatial detail that can be resolved
● Measuring visual acuity
○ eye doctors use distance (20/20)
■ Numerator: the distance at which you can just identify the letters
■ Denominator: the distance at which a person with “normal” vision can just identify letters
■ 20/20 isn’t perfect, but normal
■ 20/8 is the physiological limit of human vision
● based on cone density
■ 20/200 while wearing corrective lens is legally blind in the US
○ Vision scientists use the smallest visual angle of a cycle of a grating
○ Other countries use Landolt Rings
Spatial Frequency and Contrast
● Spatial Frequency: the number of cycles of a grating per unit of visual angle
○ usually specified in degrees
● Contrast: the difference in illumination between a figure and its background
● Oriented grating appears to be gray if you’re far enough away because:
○ this striped pattern is a “sine wave grating”
○ the visual system “samples” the grating discretely
Threshold and Sensitivity
○ the minimum change in a stimulus that enables it to be correctly judged as different
● Sensitivity: a value that defines the ease with which an observer can tell the difference between either:
○ the presence or absence of a stimulus
○ the difference between stimulus 1 and 2
● Just Noticeable Difference (JND): a difference threshold
○ the smallest detectable difference between two stimuli
● Thresholds________ are to sensitivity
inversely proportional
● Contrast Sensitivity Function (CSF):
a plot of the threshold contrast to detect the grating (as opposed to seeing a uniform gray) as a function of spatial frequency
○ developed by Otto Schade
○ inverse of Contrast Threshold
○ if CT = 0.01, then contrast sensitivity is 1/0.01 = 100
○ For photopic vision, the CSF peaks around 2 to 4 cycles per degree
○ note how sensitivity is reduced for mesopic or scotopic vision
○ Photopic: daylight vision
○ Mesopic: twilight vision
○ Scotopic: nighttime vision
○ Contrast sensitivity is quite poor at birth, improves gradually with development
○ Contrast sensitivity is reduced with aging, primarily for high spatial frequencies
● Cycles per Degree:
the number of dark and bright bars per degree of visual angle
● Contrast Threshold:
the minimum difference in contrast for you to detect a pattern
Retinal Ganglion Cell
● Retinal cells like spots of light
● Low frequency yields weak responses
● Medium frequency yields strong responses
● High frequency yields weak responses
● Spatial frequency is important, but so is the phase
○ Phase: the phase of a grating refers to its position within a receptive field
Lateral Geniculate Nucleus
●
Two Lateral Geniculate Nuclei (LGNs): axons of retinal ganglion cells synapse there ● Two types of layers in LGN ○ Magnocellular ■ M Ganglion cells (Parasol cells) ■ Fast, large moving objects ○ Parvocellular ■ P Ganglion cells (Midget cells) ■ Details of static objects
● RETINAL PROJECTION
● The world is divided at the LGN:
○ Left side of space goes right
○ Right side of space goes left
● Each layer: input from ONE eye
○ Each layer = organized map of half of the visual world
● This is TOPOGRAPHICAL MAPPING
● LGN is not only a “relay” between eyes and visual cortex, but it also receives info from a number of other brain areas, functioning as a gate to the cortex
● Ipsilateral: referring to the same side of the body (or brain)
● Contralateral: referring to the opposite side of the body (or brain)
Striate Cortex
● Also known as the Primary Visual Cortex, area 17, or V1
● Major transformation of visual info takes place in striate cortex
○ Topographical Mapping
■ the organization of sensory surface matches the organization of the sensory world
● Neighboring “stuff” in the visual field will be processed by neighboring cells
○ Cortical Magnification
■ the dramatic scaling of info from different parts of visual field
■ 1 degree of visual angle at fovea is processed by 15 times more neurons than 1 degree of visual angle just 10 degrees away from fovea.
● Visual acuity declines in an orderly fashion with______
eccentricity
Receptive Field
●
Selective Responsiveness: orientation tuning: tendency of neurons in striate cortex to respond optimally to certain orientations and less to others
● Many cortical cells respond especially well to:
○ moving lines
○ bars
○ edges
○ gratings
○ certain motion directions
● Simple Cells
○ responds primarily to oriented edges and grating
○ simple cells in the primary visual cortex can be formed by the linking of outputs from concentric lateral geniculate nucleus cells with adjacent receptive fields
● Complex Cell
○ responds primarily to oriented edges and gratings, however it has a degree of spatial invariance
○ respond to bar, regardless of exact positioning within RF
● Each LGN cell responds to one eye or the other, but never to both
● End Stopping:
process by which cells in the cortex first increase their firing rate as the bar length increases to fill up its receptive field, and then decrease their firing rate as the bar is lengthened further
● Column:
a vertical arrangement of neurons
Hypercolumn
-a 1 x 1 mm block of striate cortex containing “all the machinery necessary to look after everything the striate cortex is responsible for, in a certain small part of the visual world” ●
Method of Adaptation-
the diminishing response of a sense organ to a sustained stimulus
Selective Adaptation
●
Tilt Aftereffect: perceptual illusion of tilt, provided by adapting to a pattern of a given orientation
○ supports the idea that the human visual system contains individual neurons selective for different orientation
● Selective Adaptation: evidence that human visual system contains neurons selective for specific stimulus properties
○ if adaptation to a stimulus occurs, then it must be that a group of neurons was coding that stimulus and became fatigued
● Adaptation experiments provide strong evidence that orientation and spatial frequency are coded by neurons somewhere in the human visual system
○ Cats, Monkeys: striate cortex, not in retina or LGN
○ Humans operate the same way as cats and monkeys with respect to selective adaptation
Sine waves
● Many stimuli can be broken down into a series of sine wave components using Fourier analysis
○ any sound, including music and speech
○ any complex image, including photographs, movies, objects, and scenes
○ any movement, including head and limb movements
● Our brains seem to analyze stimuli in terms of their sine wave components
○ vision
○ audition
● Properties:
○ Period or Wavelength: the time or space required for one cycle of a repeating waveform
○ Phase:
■ In vision, the relative position of a grating
■ In hearing, the relative timing of a sine wave
Color Perception
○ Detection: wavelengths of light must be detected in the first place
○ Discrimination: we must be able to tell the difference between one wavelength (or mixture of wavelengths) and another
○ Appearance: we want to assign perceived colors to lights and surfaces in the world and have those perceived colors be stable over time, regardless of different lighting conditions
Color
not a physical property but rather a psychophysical property
○ Most of the light we see is reflected
○ Typical light sources: sun, light bulb
○ Color on the surface depends on the mix of wavelengths that reach the eye from that surface
○ In the electromagnetic spectrum, we perceive light of a wavelength of 700 nm as a red
Four Photoreceptors
■ S- cones, M- cones, L-cones, Rods
○ Photopic:
light intensities that are bright enough to stimulate the cone receptors and bright enough to “saturate” the rod receptors
■ sunlight and bright indoor lighting are both photopic lighting conditions
○ Cone Photoreceptors → Three varieties:
■ S-Cones (420 nm): Cones that are preferentially sensitive to short wavelengths (“blue” cones)
■ M-Cones (525 nm): cones that are preferentially sensitive to middle wavelengths (“green” cones)
■ L-Cones (565 nm): cones that are preferentially sensitive to long wavelengths (“red” cones)
Problem of uniVariance
■ an infinite set of different wavelength-intensity combinations can elicit exactly the same response from a single type of receptor
● One type of photoreceptor cannot make color discriminations based on wavelength
Trichromacy
■ the theory that the color of any light is defined in our visual system by the relationships between a set of three numbers, the outputs of three receptor types now known to be the three cones
● (The Young-Helmholtz Theory)
■ Metamers:
different mixtures of wavelengths that look identical
● more generally, any pair of stimuli that are perceived as identical in spite of physical differences
■ Subtractive Color Mixture:
a mixture of pigments
● if pigments A and B mix, some of the light shining on the surface will be subtracted by A and some by B.
● Only the remained contributes to the perception of color
additive
a mixture of lights
● if light A and light B are both reflected from a surface to the eye in the perception of color, the effects of those two lights add together
Mixing/adding
● mixing wavelengths does not change the physical wavelengths
○ ADDING a wavelength of 500 to one of 600 doesn’t create a wavelength of 550 or 1100.
○ Produces a change in our psychophysical reality not in the physicals of light
● In order for a mixture of a red light and a green light to look perfectly yellow, you have to add just the right amount of red and green
RGB Color Spaces
defined by the outputs of long, medium and short wavelength lights
■
■
HSB color space:
defined by hue, saturation and brightness
● Hue: the chromatic (color) aspect of light
● Saturation: the chromatic strength of a hue
○ how much hue in light.
○ grey= zero saturation
● Brightness: the distance from black in color space
○ physical intensity of light
CMYK color space:
cyan, magenta, yellow and black
● used by printers
Opponent Color Theory
the theory that perception of color is based on the output of three mechanisms, each of them based on an opponency between two colors: red-green, blue-yellow, and black-white
■ some LGN cells are excited by L-cone onset in center, inhibited by M-cone onsets in their surround (and vice-versa)
● red vs. green
■ other cells are excited by S-cone onset in center, inhibited by (L+M)-cone onsets in their surround (and vice-versa)
● blue vs. yellow
Cone-Opponent cells
● these respond to RED-center/GREEN-surround and vice versa
● Cone-Opponent Cell ( or color-opponent cell): a neuron whose output is based on a difference between sets of cones
■ In primary visual cortex, Double-Opp Component color cells are found for the first time
● these are more complicated, combining the properties of 2 color opponent cells from the LGN
■ THERE IS NO WAY OF EXPLAINING THESE AFTER-IMAGES WITH ______ALONE
Trichromacy
● Subtractive Light:
○ take white light that contains a broad mixture of wavelengths
○ pass it through a filter that absorbs shorter wavelengths.
■ result will look yellowish
○ pass through a bluish filter that absorbs all but a middle range of wavelengths
○ the wavelengths that make it through both filters will be a mix that looks greenish
● Related color:
is seen only in relation to other colors
○ brown, gray
○ perception depends on surrounding colors
Color mixing with pigments
when a pattern of non-overlapping blue and yellow pigments is blurred, the resultant mixture is additive (gray) as opposed to subtractive (green)
● Pointillism:
which additive color mixtures are achieved by visually placing dots of diff colors in close proximity to each other, rather than the subtractive mixtures that are obtained when pigments are mixed together in the same location
● Achromatopsia:
an inability to perceive colors that is due to damage to the CNS
Tetrachromacy
the condition of possessing four different types of cone cells
○ some human females have a normal cone gene on one X chromosome and a mutated cone gene on the other X chromosome
○ one study suggested that 2-3% of the world’s women might have the kind of fourth cone that lies between the standard red and green cones, giving them a significant increase in color differentiation
■ this finding is still debated
○ Cultural Relativism:
in sensation and perception, the idea that basic perceptual experiences may be determined in part by the cultural environment
○ many languages do not differentiate between certain colors on the visible spectrum and do not have separate terms for blue and green
● 1 degree of visual angle where no ____, only ____
○ right behind the center of pupil
rods, cones
Extrastirate
region of cortex bordering the primary visual cortex and containing multiple areas involved in visual processing
o V2, V3, V4. etc
Structuralism
a school of thought believing that complex objects or perceptions could be understood by the analysis of components
● Gestalt Psychology:
“The whole is greater than the sum of its parts”
an organism’s attempt at breaking Gestalt rules so that its features are not perceived as an object on their own, but as parts of a larger object
Camouflage
● Global Superiority Effect:
“forest before the trees”, the properties of the whole object take precedence over the properties of parts of the object
● Receptive fields for cells in extrastriate areas are more sophisticated than those in striate cortex
True
Structural Description Theory
a description of an object in terms of the nature of its constituent parts and the relationships between those parts
o Exploit those properties that can distinguish most objects from on another, yet remain relatively stable over changes in views
● Middle Temporal Area:
area of the brain thought to be important in the perception of motion
● Geon:
In Biederman’s recognition-by-components model, any of the “geometric ions” out of which perceptual objects are built
● Recognition-By-Components Model:
Biederman’s model of object recognition, which holds that objects are recognized by the identities and relationships of their component parts
Viewpoint invariance
a property of an object that does not change when observer viewpoint changes o A class of theories of object recognition that proposes representations of objects that don’t change when viewpoint changes
● Double Dissociation:
the phenomenon in which one of two functions, such as hearing and sight, can be damaged without harm to the other and vice versa.
● Naïve Template Theory:
idea that we recognize objects by matching every pixel to a representation in memory
o Would take too many templates
● Structural Description Theory:
specification of an object in terms of its parts and relationships between parts
o Generalized Cones – David Marr
o Recognition-By-Components – Biederman
● Objects defined as configurations of qualitatively distinct parts called Geons
o Geons defined by configurations of non-accidental properties
▪ Number of straight and curved edges
▪ Which edges are parallel to one another
▪ Number of vertices of each type
▪ Presence of symmetries
● Non-accidental features provide clues to object structure
● Problems with Structural-Description Theories
● Object recognition is not completely viewpoint-invariant
● Geons aren’t always the best descriptions of objects
● Observers show some viewpoint effects in object recognition
o The farther an object is rotated away from a learned view, the longer it takes to recognize
● Prediction Recognition by components:
o
Deletion of contours in an image should have the greatest effect on recognition performance if it masks non-accidental properties or geons.
● Images projected onto the retina are
non-Euclidean
o When the three-dimensional world is projected onto the curved, two-dimension surface of the retina.
o Don’t necessarily remain parallel
o Angles of triangles don’t always add up
● Stereopsis:
the ability to use binocular disparity as a cue in depth
● Binocular Disparity: the differences between the two retinal images of the same scene
o Disparity is the basis for stereopsis, a vivid perception of the three-dimensionality of the world that is not available with monocular vision
● Anamorphosis:
a distorted projection or perspective; especially an image distorted in such a way that it becomes visible only when view in a special manner
o Convergence:
the ability of the two eyes to turn inward, often used to focus on nearer objects
o Divergence:
the ability of the two eyes to turn outward, often used to focus on farther objects
▪ Corresponding Retinal Points:
a geometric concept stating that points on the retina of each eye where the monocular retinal images of a single object are formed are at the same distance from the fovea in each eye
horopter
: the location of objects whose images lie on the corresponding points
● The surface of zero disparity
o The Vieth-Muller circle and the horopter are technically different, but for our purposes you may consider them the same
● Objects on the horopter are seen as single images when viewed with both eyes
o Panum’s Fusional Area: the region of space, in front of and behind the horopter, within which binocular single vision is possible
● Objects closer or farther away from the horopter fall on non-corresponding points in the two eyes and are seen as two images
o Diplopia: double vision
▪ if visible in both eyes, stimuli falling outside of Panum’s fusional area will appear diplopic
● Amount of diplopia of an object determines the distance from the horopter
▪ Relative Disparity
●
The bigger the disparity, the farther away from the horopter of the object is
▪ Crossed Disparity:
the sign of disparity created by objects in front of the plane of the horopter
● Image in front of the horopter are displace to the left in the right eye and to the right in the left eye
▪
Uncrossed Disparity:
the sign of disparity created by objects behind the plane of the horopter
● Images behind the horopter are displaced to the right in the right eye and to the left in the left eye
● How is stereopsis implemented in the human brain?
o Input from two eyes must converge onto the same cell
o Many binocular neurons respond best when the retinal images are on corresponding points in the two retinas: neural basis for the horopter
o Many other binocular neurons respond best when similar images occupy slightly different positions on the retinas of the two eyes (tuned to particular binocular disparity)
Stereoscope
a device for presenting one image to one eye and another image to the other eye
● Popular in the 1900’s
● ViewMaster is an example of a stereoscope
● 3D movies
o each eye must receive a slightly different view of the scene (just like in real life)
o Early methods for seeing 3D movies involved “anaglyphic” glasses with a red lens on one eye and blue on the other
o Current methods use polarized light and polarizing glasses to ensure that each eye sees a slightly different image
o Light waves involve oscillations in electric and magnetic fields
▪ Polarized lenses only pass light whose oscillations are oriented in a particular direction
▪ Cyclopean:
referring to stimuli that are defined by binocular disparity alone
● We live in a Cyclopean World, even though we have two eyes, we only perceive one world that is the combination of two
▪ Stereoblindness:
an inability to make use of binocular disparity as a depth cue
● About 5% of the population
● Can result from a childhood visual disorder, such as strabismus, in which the two eyes are misaligned
● Most people who are stereoblind don’t even realize it
● Ocular-Motor Cues
o Accommodation (Monocular) o Convergence & Divergence (Binocular)
● Binocular Depth Cues
o Binocular Disparity
▪ Stereopsis
● Psychological Qualities of Sound
-the psychological aspect of sound related to perceived intensity (amplitude)oPitch- the psychological aspect of sound related mainly to perceived frequency
the psychological sensation by which a listener can judge that two sounds with the same loudness and pitch are dissimilar.
o Timbre quality is conveyed by harmonics and other high frequencies
timbre
● : the canal that conducts sound vibrations from the pinna to the tympanic membrane
o Main purpose= protect tympanic membrane
Ear Canal
the eardum; a thin sheet of skin at the end of the outer ear canal.
o Vibrates in response to sound
Tympanic membrane
o Middle Ear
▪
Middle Ear: an air-filled chamber containing the middle bones
● Conveys and amplifies vibration from the tympanic membrane to the oval window
▪ Tympanic Membrane is the border between the outer and middle ear
▪ Consists of three tiny bones, the ossicles, that amplify sound waves
● Ossicle: any of three tiny bones of the middle ear
o smallest bones in the human body
o Amplify sound vibrations in two ways:
▪ The joints between the bones are hinged in a way that makes them work like levers: a modest amount of energy on one side of the fulcrum (joint) becomes larger on the other
● This lever action increases the amount of pressure change by about a third
▪ Concentrating energy from a larger to a smaller surface area: the tympanic membrane to the oval window
o Malleus: receives vibration from the tympanic membrane and is attached to the incus
o Incus: middle of the ossicles, conntecting the malleus and the stapes
o Stapes: connected to the incus on one end, the stapes pressed against the oval window of the cochlea on the other end
o Oval Window:
the flexible opening to the cochlea through which the stapes transmits vibration to the fluid inside
▪ Middle ear has two muscles:
●
Smallest muscles in the body
● Main purpose: to tense when sounds are very loud, restricting the movement of the ossicles and thus muffling pressure changes that might be large enough to damage the structures in the inner ear
● Tensor Tympani: muscle attached to the malleus; tensing the tensor tympani decreases vibration
● Stapedius: muscle attached to the sapes; tensing the spaedius decreases vibration
● However, this acoustic reflex, follows the onset of loud sounds by one-fifth of a second
o Acoustic Reflex: a reflex that protects the ear from intense sounds, via contraction of the stapedius and tensor tympani muscles
● NOT READY FOR ABRUPT SOUNDS
o Inner Ear
▪
-similar to the retina. Translates the information carried by waves into neural signals▪Major structure of the inner ear is the Cochlea●Cochlea- a tiny, coiled structure embedded in the temporal bone of the skulloContains the organ of CortioUncoiled would be about 35 mm longoFilled with watery fluids in three parallel canals▪Tympanic Canal- extends from the round window at the base of the cochlea to the helicotrema at the apex▪Vestibular Canal- extends from the from the oval window at the base of the cochlea to the helicotrema at the apex▪Middle Canal- sandwiched between the tympanic and vestibular canals and contains the cochlear partition●Helicotrema- the opening that connects the tympanic and vestibular canals at the apex of the cochleaoThree canals of the cochlea are separated by two membranes
▪ Reissner’s Membrane:
a thin sheath of tissue separating the vestibular and middle canals in the cochlea
▪ Basilar Membrane
: a plate of fibers that forms the base of the cochlear partition and separates the middle and tympanic canals in the cochlea
▪ Cochlear Partition:
the combined basilar membrane, tectorial membrane, and organ of Corti, which are together responsible for the transduction of sound waves into neural signals
● Complex structure
o Round Window:
a soft area of tissue at the base of the tympanic canal that releases excess pressure remaining from extremely intense sounds
▪ The Organ of Corti
● Structures in the O.C cause these movements of the cochlear partition to be translated into neural signals
● Made up of specialized neurons called hair cells
● Tectorial Membrane:
gelatinous, attached on one end, that extends into the middle canal of the ear, floating above inner hair cells and touching outer hair cells
○ Vibrations cause displacement of the tectorial membrane
■ bends stereocilia
■ causes release of neurotransmitters
● Stereocilia:
hairlike extensions on the tips of hair cells in the cochlea
○ initiate the release of neurotransmitters when they are fixed
○ tip of each is connected to the side of its neighbor by a tiny filament called a tip link
● Coding of Amplitude & Frequency in the Cochlea
○ Amplitude: the larger the amplitude, the bigger the shear of tectorial membrane
○ Place Code: tuning of different parts of cochlea to different frequencies, in which info about the particular frequency of incoming sound wave is coded by place along cochlear partition with greatest mechanical displacement
■ Coin sorting machine analogy
● smaller coins fall through smaller holes first
● quarters fall in the last hole
● The Auditory Nerve (AN)
○
responses of individual auditory nerve fibers to different frequencies are related to their place along the cochlear partition
○ Frequency Selectivity: clearest when sounds are very faint
○ Threshold Tuning Curve: map plotting thresholds of a neuron or fiber in response to sine waves with varying frequencies at lowest intensity that will give rise to a response
● Rate Saturation:
point at which a nerve fiber is firing as rapidly as possible and further stimulation is incapable of increasing the firing rate
○ Are AN fibers as selective for their characteristic frequencies at levels well above threshold as they are for barely audible sounds?
■ To answer this, look at Isointensity Curves: chart measuring an AN fiber’s firing rate to wide range of frequencies, all presented at same intensity level
○ Rate Intensity Function: a map plotting firing rate of an auditory nerve fiber in response to a sound of constant frequency at increasing intensities
○ Rate Saturation means:
■ We can NOT use a direction decoding rude like:
● If a 2000 Hz Auditory Nerve fiber is firing rapidly, the sound must be 2000 Hz○
Combinatorial Code:
■ The brain uses a pattern of firing rates across fibers to determine frequency
■ about 3,500 inner hair cell in each ear to describe each pattern
● Auditory Nerve Structures:
○ The auditory nerve carries signals from cochlea to brain stem
○ all auditory nerve fibers initially synapse in cochlear nucleus
○ Superior olive, inferior colliculus, and medial geniculate nucleus all play roles in the auditory process
○ Cochlear Nucleus: the first brain stem nucleus at which afferent nerve fibers synapse
■ Cells here fire to onset of sounds or coincidence of firing across frequencies
■ Some use lateral inhibition to suppress nearby frequencies
■ Some project to the superior olive
■ AN fibers PROJECT TO BOTH HEMISPHERES
● Tonotopic Organization: an arrangement in which neurons that respond to different frequencies are organized anatomically in order of frequency
○ Maintained up to primary auditory cortex (A1)
Comparing Overall Structure of Auditory and Visual Systems
● Auditory System: large portion of processing is done before A1
● Visual System: large proportion of processing occurs beyond V1
○ Differences may be due to evolutionary reasons:
■ hearing is probably an older sense than seeing
■ speech (recent in evolution) is in the cortex (the newer structure)
● Sensorineural Hearing Loss:
more common, most serious auditory impairment
○ due to defects in cochlea or auditory nerve, when hair cells are injured
○ as a result of antibiotics or cancer drugs
■ Common Hearing Loss: damage to hair cells due to excessive exposure to noise
● Conductive Hearing Loss:
caused by problems with the bones of the middle ear
○ Otosclerosis: more serious type of conductive loss.
■ caused by abnormal growth of middle ear bones; can be remedied by surgery
Weber & Rinne hearing tests
●
compare the perception of sound transmitted by air conduction to bone conduction
● determine type of hearing loss
○ conductive or sensorineural
● patient compares the loudness of a tuning fork at multiple locations
○ next to ear (air conduction)
○ touching mastoid (behind ears)
○ touching forehead
Beethoven
● partial deafness at 30, fully deaf at 44
● suffered from a form of tinnitus
○ perception of sound when no actual sound is present, ringing.
○ causes include: allergies, wax, foreign objects, infections, exposure to loud noises
Cochlear Implants:
● a microphone
● a speech processor
● a transmitter and receiver/stimulator
● NOT the same perception as normal hearing
● Azimuth:
the angle of a sound source on the horizontal plane relative to a point in the center of the head between the ears
o Measured in degrees, 0 being straight ahead
● Medial Superior Olive (MSO):
a relay station in the brain stem where inputs from both ears contribute to the detection of the interaural time difference
● Medial Superior Olive (MSO): a relay station in the brain stem where inputs from both ears contribute to the detection of the interaural time difference
● Cone of Confusion
: a region of positions in space where all sounds produce the same time and level (intensity) difference (ITDs and ILDs)
● Directional Transfer Function (DTF):
a measure that describes how the pinna, ear canal, head, and torso change the intensity of sounds with different frequencies that arrive at each ear from different locations in space (azimuth and elevation)
● Inverse-Square Law:
a principle stating that as distance from a source increases, intensity initially decreases, much faster than distance increases, such that the decrease in intensity is equal to the increase in distance squared
● Two ears are crucial for determining auditory locations
● ITD: determines direction sound is coming from by which ear receives the sound first
● MSO: first place in auditory system where inputs from both ears converge
● ILD: sounds are more intense at the ear that is closer to the sound
o Largest at 90 degrees and -90 degrees,
o Nonexistent at 0 & 180
o Between two extremes, ILD correlates with the angle of the sound source
o Because of the irregular shape of the head, it’s not as precise as ITD
o Head blocks high-frequency more effectively than low frequency
▪ Low frequency wavelengths bend around the head
▪ Inability to localize low frequencies is why it doesn’t matter where in a room you put the subwoofer
true
o Inhibitory inputs come from the
contralateral
● Vestibular Organs:
the set of five organs, three semicircular canals and two otolith organs, located in each inner ear that sense head motion and head orientation with respect to gravity
● Spatial Orientation:
a sense consisting of three interacting sensory modalities: the senses of linear motion, angular motion, and tilt
● Otolith Organ:
either of two mechanical structures (utricle and saccule) in the vestibular system that sense both linear acceleration and gravity
● Semicircular Canal:
any of three toroidal tubes in the vestibular system that sense angular motion
● Mechanoreceptor:
a sensory receptor that responds to mechanical stimulation (pressure, vibration, or movement)
● Ampulla:
an expansion of each semicircular canal duct that includes that canal’s cupula, crista, and hair cells, where transduction occurs
● Otoconia:
tiny calcium carbonate stones in the ear that provide inertial mass for the otolith organs, enabling them to sense gravity and linear acceleration
● Vestibular organs DO NOT respond to constant velocity
○
they only respond to CHANGES in velocity, acceleration
Push Pull symmetry
○ hair cells in opposite ears respond in a complementary fashion to each other
○ when hair cells in the left ear depolarize, those in the analogous structure in the right ear hyperpolarize
● Hair Cell Responses
○ in the absence of stimulation, hair cells release neurotransmitter at a constant rate
○ when hair cell bundles bend, change in hair cell voltage is proportional to the amount of deflection
■ bending toward tallest stereocilia: depolarization
■ bending away from tallest stereocilia: hyperpolarization
● Hair cells are encases in a gelatinous structure that contains calcium carbonate crystals called
otoconia (“ear stones”
● Angular VOR
○
-when the head turns to the left, the eyes are rotated to the right to partially counteract this motion
The Spins:
If you ingest too much alcohol and then you go to sleep, you get the spins
Alcohol changes the density of your blood, causes the cupula (jelly like thing embedded in the semi-circular canal hair cells in it) causes it to become lighter than the surrounding endolymph. Gradually starts to float. When you change orientation, they’re floating in the wrong place immediately.
Perceived as fluid circulating through the semi-circular canal, horiztonal, ampula, subtle wrong direction, you wont notice. But once you go to bed, it floats, but its not circulating, but it thinks there is. Body thinks youre spinning.
-Sit the person up, back in the condition you were in. Dont look at anything spinning
because the vestibular ocular reflex, adds to the sensation. If you take your foot, put it flat on the ground, helps your perception of gravity
Optokinetic Nystagmus:
if you trick one of the ears into thinking that its rotating, activate your ocular reflex, makes your eye move.
They put cold water in the semi-circular canal, cools down, ampula moves, eyes move
ear and ocular systems hardwired into each other
● Proprioception:
perception mediated by kinesthetic and vestibular receptors
What physical effect does IcyHot® have on the skin?
It causes multiple chemical reactions that stimulate thermoreceptors.
The high-resolution part of the eye that is used for detailed vision is called the
fovea
In the fovea, single cones pass information to single ganglion cells via _______ cells
midget bipolar
The vertical pathway in the retina consists of each of the following except
amacrine
If somebody has 20/100 vision, what does this mean?
They see at 20 feet what a person with normal vision sees at 100 feet
Spatial frequency refers to the
number of cycles of a grating per unit of visual angle
Topographical mapping is the
orderly mapping of the world in the LGN and the visual cortex
Hubel and Wiesel uncovered some important properties of the _______ of neurons in the striate cortex.
receptive
Which of the following color pairs is furthest apart in wavelength?
b,r
What kind of cells in LGN compute chromatic differences, such as (L-M) and (M-L)?
cone opponent
Mixing paints to create new colors is an example of _______ color mixing, while shining lights to create new colors is an example of _______ color mixing.
subtractive; additive
When adding colors, blue and yellow create white under ______ color mixing but create green under ______ color mixing.
additive; subtractive
According to the opponent color theory, the perception of color is based on the output of _______ cones, each of them an opponency between _______ colors.
According to the opponent color theory, the perception of color is based on the output of _______ cones, each of them an opponency between _______ colors.
Which of the following areas is not part of extrastriate cortex?
v1
Which of the following is not a monocular cue?
Binocular disparity
_______ is the psychological aspect of sound related to perceived intensity or magnitude.
loudness
A complex tone is a sound wave consisting of
more than one sinusoidal component of different frequencies.
Which of the following best fits the description of being ‘the retina of the ear’ ?
organ of corti
One of the roles of the ossicles is to
amplify sound
The _______ is the difference in time between a sound arriving at one ear versus the other and it helps us localize sound.
interaural time difference
The _______ are relay stations in the brain stem where inputs from both ears contribute to the detection of interaural time differences.
medial superior olives
Which of the following methods of sound localization between the two ears is used most often for tones of higher frequencies?
Interaural level differences
Which of the following does NOT contribute to a directional transfer function?
pinna
ear cannal
torso
head
Correct Response
——malleus
Which of the following terms describes the perception of the position and movement of our limbs in space?
Kinesthesis
Which of the following is not a type of mechanoreceptor?
Retinal ganglion cells
The A-delta and C fibers are types of
nociceptors
The _______ pathway is the route from the spinal cord to the brain that carries signals from skin, muscles, tendons, and joints.
dorsal column–medial lemniscal
The olfactory epithelium contains each of the following cells except
turbinates
Which of the following structures is sometimes called the “retina of the nose”?
Olfactory epithelium
_______ is the total inability to smell, most often resulting from sinus illness or head trauma.
anosia
Sometimes odorants can stimulate the somatosensory system through polymodal nociceptors. These sensations are mediated by the
trigeminal nerve.
The _______ is the blueberry-sized extension of the brain, just above the nose, where olfactory information is first processed
olfactory bulb
__________ sensation is the sensation of an odor that is perceived when chewing and swallowing force an odorant emitted by the mouth up behind the palate into the nose.
retronasal olfactory
_________ are structures that give the tongue its bumpy appearance.
Papillae
_______ are slender projections on the tips of some taste bud cells that extend into the taste pore.
microvilli
