212 final Flashcards
cerebral achromatopsia
colour blindness due to brain injury
chromatic colours
selective reflection of light = red, green, blue, etc.
achromatic colours
equal reflection of light (white, black, greys)
spectral colours
in the visible spectrum
nonspectral colours
results of mixing other colours
hues
chromatic colours
saturation
intensity of colour
value
light-dark dimension
trichromatic theory (Young-Helmholtz)
3 principal colours/receptors with different spectral sensitivities
colour matching
matching a reference colour (only requires 3 wavelengths)
microspectrophotometry
determining absorption spectrum by directing a beam of light at a specific receptor
metamerism
different stimuli create the same perceptual experience (colour matching)
monochromatism
no functioning cones = only rods (shades of grey), intensity of light can help differentiate between WLs (number of photons)
- if photons in a wavelength are altered, you can create the same perception
principle of univariance
once isomerization has occurred, the wavelength loses its identity (only the amount of energy is known by the receptor)
photons
small packets of energy in light
dichromatism
ratio of response in two pigments (confuse some spectral colours), diagnose with ishihara plates
protanopia
missing long wavelength pigment, neutral point is 492 nm = blues to yellows
deuteranopia
missing medium wavelength pigment, neutral point is 498 nm = blues to yellows
tritanopia
missing short wavelength pigment, neutral point is 570 nm = blues to reds (without green)
neutral point
wavelength at which colour is so desaturated it is perceived as grey
anomalous trichromatism
wavelengths are mixed at different proportions to match a colour (trouble differentiating wavelengths that are close to each other) - pigments have different absorption spectra
opponent-process theory of colour vision
opponent neurons in the lateral geniculate nucleus create colour vision by causing opposing responses blue-yellow and red-green
phenomenological evidence for opponent-process theory
hue scaling experiments - the four ‘pure’ primary colours which weren’t created by mixing other wavelengths
psychophysical evidence for opponent-process
hue cancellation experiments - yellow could be added until the ‘blue’ perception disappeared
physiological evidence for opponent-process
opponent neurons found in monkeys’ LGN
- circular single opponent (for large areas of colour)
- circular double opponent (for borders and patterns)
- side-by-side opponent (for large areas of colour)
colour constancy
colours appear constant no matter what the illumination is
chromatic adaptation
after prolonged exposure to a wavelength, cones become less sensitive to it = those colours appear less saturated
creates partial colour constancy
partial colour constancy
when one is adapted, the colour perception is less different than unadapted (in a red-lit room, the colours of objects remain constant because LWL cones are adapted and respond less to LWLs)
memory colour
familiarity of objects contributes to colour constancy (appear more saturated) - yellow bananas, red stop signs
illumination
amount of light striking an object’s surface
reflectance
percentage of light being reflected off an object into our eyes
lightness constancy
perception of lightness comes from reflectance, not illumination (as long as the percentage of the total amount of light stays the same, our perception stays the same)
reflectance of black
under 10%
reflectance of grey
10-70%
reflectance of white
80-95%
ratio principle in colour constancy
in even illumination, lightness perception is determined by that object’s reflectance compared to its surrounding objects
illumination edge
borders at which lighting changes/we see shadows
reflectance edge
borders at which the reflectance of two surfaces changes
how to differentiate between illumination vs. reflectance edge
shadows have meaningful shapes and have a penumbra (fuzzy borders)
monochromatic light
light composed of a single wavelength
red
long wavelengths 620-700 nm
green
medium wavelengths 500-575 nm
yellow
medium-long wavelengths 575-590 nm
blue
short wavelengths 450-490 nm
white
long, medium, short WLs equally transmitted/reflected
describe the structure and map of the cochlea
- goes from thick and narrow at the base to thin and wide at the apex
- scala vestibuli on top (oval window) and scala tympani on the bottom (round window)
- tonotopic map: high frequencies encoded at the base, low frequencies at the apex
when do we use place coding and temporal coding for hearing?
- place coding for high frequencies; only works for resolved harmonics close to the fundamental that make a peak in the basilar membrane
- phase-locking for lower frequencies (up to 5,000Hz), the main mechanism for pitch perception
what is the generalization gradient?
in place coding, the tonotopic map means some cells are maximally activated for certain frequencies, but other areas also get activated (just less)
what is the role of outer hair cells and what occurs when they are damaged?
- cochlear amplifiers: they increase the response to certain frequencies by elongating/contracting to make the basilar membrane move = they are responsible for loudness
- a loss of outer hair cells makes us less sensitive (inner hair cells will require a greater intensity sound to respond to their characteristic frequency)
phase-locking/temporal coding
responses of the inner hair cells are synchronized to the sound wave (tip links pulled = ion channels open at the height of the wave, then close at the valley)
what is the purpose of the ossicles?
they amplify the sound for it to accurately transmit from a lower-density environment (air) to a higher-density environment (cochlear fluid) by operating in a lever-like mechanism and transferring the sound to smaller bones = concentration
what is the purpose of the pinnae?
the folds of the pinnae help to localize sounds on the vertical plane (elevation)
what is the purpose of the auditory canal?
to amplify the intensity of the sound by resonance
frequency spectra
represents a complex wave (fundamental + harmonics)
what are equal loudness curves and what do they show?
in the audibility curve - points along the equal loudness curves are perceived as the same level despite having different decibel levels - shows the relationship between frequency and amplitude (lower frequencies need to be more dB to be perceived as the same loudness as higher frequencies)
spectrum of human hearing and sounds we cannot hear
humans can perceive sounds that are 20-20,000Hz, but are most sensitive to sounds in the 2000-4000Hz range
infrasounds are frequencies below the human audibility threshold and ultrasounds are too high
pathway of sound
pinnae - ear canal - tympanic membrane - malleus - incus - stapes - oval window - cochlea (basilar membrane, organ of Corti, hair cells transduce sound) - auditory nerve - cochlear nucleus (crosses over) - superior olivary nucleus - inferior colliculus - medial geniculate nucleus of the thalamus - primary auditory cortex - dorsal (localization) and ventral (identification) streams
presbycucis
age-induced hearing loss from living in an industrialized environment - decreased sensitivity to higher frequencies, common in males
noise-induced hearing loss
degeneration of hair cells, damage to the organ of Corti likely due to leisure noise (gunshots, power tools)
hidden hearing loss
damage to the auditory nerve (hair cells unaffected), difficulty hearing in noisy environments, cannot be diagnosed with an audiogram (which determines thresholds in silence)
binaural cues
use both ears
- interaural level difference (intensity that reaches each ear is different because of the acoustic shadow of the head), only for high frequencies
- interaural time difference (sounds on the azimuth dimension reach both ears at different times), for lower frequencies = dominant binaural cue
spectral cues
use one ear
- pinnae folds help determine location on the elevation plane (for higher frequencies)
Jeffress Neural Coincidence Model
place code; which ITD detectors (coincidence detectors) fire will indicate the ITD
an ITD of 0 as indicated by the centre neutron of the circuit means the sound is from straight ahead
what is the difference between birds and mammals in the Jeffress model?
- birds have narrow ITD tuning curves (high precision, smaller receptive fields) = place code
- mammals have broader tuning curves so place coding doesn’t work - they use broadly tuned neurons in each hemisphere which fire in response to sound from the contralateral side (population code)
precedence effect
short time delay between direct sound and the first echo = the first sound that reaches the ears is perceived to be the source
a longer delay will indicate separate streams
reverberation time and its ideal time
time it takes for a sound to decrease to 1/1000th of its original pressure (decrease in intensity by 60dB)
too long = muddled sounds
too short = dead sounds (difficult to reach high intensity)
ideal time is about 2 seconds
intimacy time and ideal
time between the direct sound and the first reflection
ideal time is about 20ms
bass ratio and ideal
ratio of low to middle frequencies reflected
higher is better (more pronounced low frequencies)
spaciousness factor
fraction of sound received by the listener that is indirect
higher is better
simultaneous grouping principles
sounds which occur together in time
- location (sounds moving continually are one source)
- onset synchrony: start time is different = different sources
- same timbre and pitch = same source
- harmonicity: one series of harmonics = one source
sequential grouping principles
sounds which follow each other in time
- similarity in pitch = same source (auditory stream segregation, scale illusion)
- auditory continuity (sounds staying constant/moving together = one source)
- experience (melody schemas)
ventriloquism effect
visual capture - sounds appear to come from visual input (surround sound)
two flash illusion
auditory capture (two beeps + a single flash = perception of two flashes)
speechreading
mouth movements help us hear what is being said
echolocation
sounds become spatial experiences, visual cortex is activated
Merkel receptors
- slowly adapting fibres (SA1) near the surface of the skin (small receptive fields)
- respond to continuous pressure for fine details and texture perception
Meissner’s corpuscles
- rapidly adapting fibers (RA1) near the surface of the skin (small receptive fields)
- respond to on and off pressure for hand gripping and motion across the skin
Ruffini cylinders
- slowly adapting fibers (SA2) deeper in the skin (large receptive fields)
- respond to continuous pressure for stretching of the skin
Pacinian corpuscles
- rapidly adapting fibers (RA2) deeper in the skin (large receptive fields)
- respond to rapidly alternating on and off pressure for vibrations
proprioception
position of body and limbs in space
nociception
pain due to activation of nociceptors which are responsible for actual or potential tissue damage
skin
heaviest organ in the body, acts as a barrier and protector against viruses, temperature, moisture
composed of the epidermis (outer layer of skin) and the dermis (second layer)
kinesthesis
movement of body and limbs
gate control model of pain perception
gate in the spinal cord can be opened/closed by other signals than nociceptors to determine the strength of the signal to the brain (mechanoreceptors can mitigate pain)
mechanoreceptor pathway inhibits transmission cells in the dorsal horn of the spinal cord and lowers pain
nociceptor pathway excites transmission cells
central control pathway inhibits transmission cells
brain areas associated with pain perception
anterior cingulate cortex and anterior insula for affective component of pain
somatosensory cortex and posterior insula for sensory component
hypothalamus, amygdala, thalamus
duplex theory of texture perception
- spatial cues: stationary hand on a surface gives cues about large elements (bumps and grooves), size, and shape - for coarse textures
- temporal cues: moving fingers across a surface gives fine texture details through vibrations - for fine textures
cortical neuron responses to textures
- different neurons have different responses to the same texture
- the same neuron has different responses to different textures
pathway of touch signals
skin receptors - dorsal root - 31 segments of spinal cord - ventral posterior/ventrolateral nucleus of the thalamus - primary somatosensory cortex (S1) - secondary somatosensory cortex (S2)
two pathways in the spinal cord
- medial lemniscal pathway (ipsilateral) has large fibers for high speed: for proprioception and perceiving touch
- spinothalamic pathway (contralateral) with smaller fibers: for temperature and pain
brain areas for touch and pain
insula for light touch (also social touch associated with pleasure)
anterior cingulate cortex for pain
tactile acuity
capacity to detect details
measuring tactile acuity
two-point threshold: presenting two points to determine how far apart they need to be to be perceived as separate
grating acuity: narrowest spacing of grooves for their orientation to be perceived
evidence for tactile acuity in fingertips
pattern of Merkel receptor firing matches the pattern of grooves (higher density of receptors in fingertips = greater acuity)
surface texture
physical texture created by peaks and valleys
which receptors are associated with textures
coarse textures activate neurons that receive signals from Merkel receptors (SA1 fibers)
fine textures activate neurons that receive signals from Pacinian corpuscles (RA2 fibers)
what is active touch and what does it depend on?
actively exploring an object
depends on functioning of sensory (to detect stimuli), motor (to move hands and fingertips), and cognitive (to think about the object) systems working together
haptic perception
3D object perception by touch
exploratory procedures
uses will depend on goals of object perception (lateral motion, contour, enclosure, pressure - ways of exploring an object)
- texture: lateral motion and contour
- shape: enclosure and contour
neurons in the ventral posterior nucleus of the thalamus
have centre-surround organizations
*for touch
cortical neurons for touch perception
- some have center-surround organization
- specialized neurons for certain stimuli, orientations directions of movement across skin, grasping a specific object
- when we pay attention to a tactile stimulus, the response of cortical neurons increases
- our receptors habituate after being exposed to a tactile stimulus for a long period of time
inflammatory pain
due to damage to tissue or inflammation of joints or tumour cells
neuropathic pain (and examples)
due to damage to the nervous system
ex: carpal tunnel, spinal cord injury, brain damage due to stroke, shingles can lead to neuralgia)
direct pathway model of pain
nociceptors stimulated which send signals to the brain
not the whole picture (phantom limb and severe injuries without pain perception are opposing evidence)
top-down processes influence on pain perception
- expectations (placebo and nocebo effects)
- attention (distracting yourself can alleviate pain)
- positive emotions (music, positive images)
- cognitive regulation (analyzing the pain = detachment)
- social environment (surround by friends and family lowers pain)
physical-social pain overlap hypothesis
- dorsal anterior cingulate cortex is activated by social rejection, dACC and anterior insula (affective component) are activated by the threat of negative social evaluation - share brain mechanisms
- giving people painkillers before experiencing social pain decreases their perception of it - giving meds for physical can alleviate social
relationship between social touch, empathy and pain
social touch decreases pain (synchronizes brain waves and decreases activity in pain brain circuits)
empathy can cause pain (watching someone receives shocks activates ACC and anterior insula)
experience-dependent plasticity in somatosensory maps
maps can change based on how much that area is used or in response to injury (violin players have developed maps for the fingers that pluck the strings, loss of a finger = map adjusts for adjacent fingers to get more real estate)
hand dystonia patients have abnormal organizations of maps (locations for fingers too close together)
