3 - Signals and Perception Flashcards
3 definitions of sensation
detection of stimulus’s signal
physical feeling due to body contact with something
different modalities
define transduction
converting sensory signal to electrical one at sensory receptors to be carried to the spinal cord (and brain)
what is sensory transduction
sensory stimuli converted to receptor potentials
what does not enough exposure to sensations do during nervous system development
leads to smaller brain and larger ventricles
perception depends on what two things
previous experience
attention
key chain of perception
sensory signal sensory receptor brain/spinal cord perception perceptual understanding behavioural response
what is sensation-perception
brain interprets a stimulus and perception of this stimulus can change
3 dimensions of sound
pitch/frequency
loudness
timbre
define loudness
degree to which condensations and refractions differ from each other
3 components of the outer ear
pinna concha and meatus/auditory canal
how does the outer ear provide protection
skin cells move outwards acidic earwax is antibacterial/fungal oily outward hairs preventing insects
what about the auditory canal protects the tympanic membrane
shape
depth
rigidity
how are signals close to human speech amplified
closed tube resonator which is a space for sound waves to echo and is open at the anti-node and closed to the tymp mem
4 components of the middle ear
tympanic membrane
ossicles
malleus
stapes
role of the ossicles
bones to join eardrum to cochlea for energy transmission
role of the malleus
a hammer transmitting vibrations through the incus and stapes to the cochlea
what is the cochlea and what does it do
inner ear part filled with fluid and connects receptors
how does the cochlea increase the signal’s amplification
less area from the tymp mem to the cochlea, increasing pressure
where is perilymph and endolymph
perilymph in outer corridor of cochlea
endolymph in Organ of Corti in the cochlea
what 3 things does the Organ of Corti have
tectorial membrane
auditory hair cells on the
basilar membrane
where are the stereocilia and what happens when there are sound waves
endolymph
tectorial and basal membrane move so stereocilia bend towards the tallest hair
what happens after the stereocilia bend
mechanically-gated Na+ channels open, Na+ moves in, depolarisation, Ca2+ channels open, Ca2+ enters, glutamate released by exocytosis
what happens when glutamate is released in the Organ of Corti
binds to AMPA receptors in the auditory nerve, producing an action potential
how is there protection in the inner
tensor tympani and stapedius muscles contract if there’s a loud sound so ossicles lock preventing sound transmission
how are the ears responsible for balance
balance info combined with cochlea info in the vestibulocochlear nerve
how are signals received by the inner ear enhanced
contractile proteins shorten and lengthen to amplify vibrations of the basilar membrane
define light and state its 3 dimensions
wave-particle duality involving hue, saturation, and brightness/intensity
define dioptric apparatus
focusing and refracting light onto the right place
what is accommodarion
changing the lens shape to focus on the near or distant
what is sclera
tough, white opaquer outer coat that extraocular muscles attach to
what are the conjunctiva
mucous membranes lining eyelid and folding back to attach to the eye
cornea is what
transparent layer on outer part which lets light in
pupil is what
opening in iris regulating amount of light let in
lens is what
behind the iris with ciliary muscles attached to the outer edge contracting/relaxing to change lens shape
what is the retina
interior lining of back of the eye with rods and cones photoreceptors
what does light pass through after it goes through the lens
the vitreous humour then retina
what is the fovea
retina’s central region consisting of only cones to mediate sharpness/acuity
what is the optic disk
axons with visual info leaving the optic nerve which produces a blind spot since it has no photoreceptors
describe cones
colour vision as differentiates wavelengths
good acuity
bad in the dark
work w moderate-high light levels
describe rods
light-sensitive so work in dark
poor acuity as greater area
monochromatic
peripheral retina
similarities between roads and cones
synaptic terminals
inner segment
nucleus and other organelles
outer segment with photopigments
what are photopigments
made up of opsin and retinal for transduction
what happens after the light hits and rhodopsin is activated in visual transduction
cGMP levels drop so cation channels close, hyperpolarisation, less nt in synapse with bipolar cells, and photoreceptors altered so bipolar and ganglion cell firing rates change
which cells carry info into the dorsal alteral geniculate nucleus
retinal ganglion cells
what is the geniculostriate pathway
LGN has 2 central magnocellular layers, 4 outer parvocellular layers, and ventral koniocellular neurons
role of the dorsal lateral geniculate nucleus
processing information and projecting it to the primary visual cortex aka striate cortex and maybe superior colliculus
the right hemisphere receives which visual fields
left visual fields of both eyes
keychain of the geniculostriate pathway of the LGN
nasal/temporal retina optic nerve optic chiasma optic tract LG body optic radiations primary visual cortex
hearing pathway keychain starting from spiral ganglion from cochlea through the 8th cranial nerve
to cochlear nuclear complex superior olivary complex inferior colliculus medial geniculate nucleus/thalamus auditory complex secondary auditory cortex
how are pitch and frequency coded
place
temporal/rate
how does place code work
using activated basilar membrane hair cells and stimulated afferent neuron
which coding can only be used for above 3000 hertx
place code
describe how temporal code works
locking the release of nt and firing in afferent neuron in time with the basilar membrane’s pulse frequency
what does temporal code not work for
prolonged sounds as fire less frequently
how is intensity of sounds determined
the overall number of firing neurons and higher firing rate means more intense
how does verticle (height) location coding work
angle sound waves reflect off pinna folds/ridges enhances or attenuates them and intensity differs with location due to reflections
how does horizontal coding (distance) work by using the speech of which sound pressure waves reach the ears
olive neurons detect arrival time differences and they use auditory neuron info which fire when eardrums out of phase to detect sound source
what happens if the source is on one side of the head
one ear drum is pulled and the other is pushed
which stream and cortex determine what the sound source is
anterior auditory cortex and ventral stream in the temporal lobe
which stream and cortex determine where the sond is
posterior auditory cortex and dorsal stream in the parietal lobe
what are the 4 sub-modalities of the striate cortex for vision
colour
motion
retinal disparity
spatial frequency
what are the 3 code types’ wavelengths
red - long
green - medium
blue - short
which are excitatory and inhibitory in the red-green channel
red - exc
green - inhib
which are exc and inhib in the luminance channel
red and green both exc
what does the blue-yellow channel contain and which are exc and inhib
luminance channel - inhib
blue cone - exc
how does opponent processing work
neurons respond to primary colour pairs (rg/by) and each cone has different opsonins to absorb different wavelengths
in opponent processing coding what happens when red-green is coded
transmitted from parvocellular layers to cytochrome oxidase blobs in primary visual cortex
in opponent processing what happens if blue is coded
transmitted from koniocellular LGN layers to cytochrome oxidase blobs in primary visual cortex
how does a simple cell’s neurons work in visual motion
in primary visual cortex and is exc if line is in a certain orientation in the centre and inhibitory if off
how does a complex cell’s neuron work in visual motion
responds to presence of a line segment if in a particular orientation within the receptive field
how does a hypercomplex cells’ neurons work in visual motion
responds to presence of line and has an inhibitory region at the end to detect ends of lines
how does spatial frequency work
neurons in PVS respond to specific spatial frequencies and sine-wave gratings
if frequency is low in a visual field what happens
photo receptor turns off and vice versa to produce and image
why are low spatial frequencies neede
to make out what objects are
define retinal disparity
stimulus produces same image on different parts of retina in each eye through stereopsis to indicate differences in object’s distance
what do the binocular (respond to each eye) neurons in the striate cortex do
contribute to depth perception esp ones responding to the LGN’s magnocellular layer in the periphery
what is the bottom up Bayesian Framework
collects data combined from all modalities
what is the top-down Bayesian Framework
what is expected and combines from all previous knowledge and estimate of the two frameworks is combined and somewhere in the middle
how are the visual fields received
nasal retinal halves cross through optic chiasma to contralateral hemisphere and retinal ganglion cell axons of outer retinal halves stay on ipsilateral hemisphere
where are the cytochrome oxidase blobs in the modules of the PVC
a blob in each module halve with neurons sensitive to colour, low frequencies, and small brightness changes, coming in and out
neurons outside blobs are sensitive to what
all sub-modalities but colour
further away blob is, higher freq it’s sensitive to
how does the PVC create binocular vision
neural circuitry combines inputs of each eye into one module halve
what does V5 receive input from
striate, extrastriate, superior colliculus
how does the visual association cortex work
striate cortex axons project to extrastriate cortex regions which analyse info from region beneath then pass on
how does the dorsal stream work
terminates in posterior parietal lobe and receives magnocellular input which is colour-blind but detects small brightness changes
how does the ventral stream work
terminates in inferior temporal cortex
detects what object in lateral occipital cortex
receives info from parvo/koniocellular
analyses CO blob neuron opp-proc
define colour constancy
object colour stays the same regardless of surrounding environment’s wavelength as visual system compensates if too long/short
how does perception of form work
orientation and spatial frequency sensitive neurons in PVC send info to V2 then VAC in ventral stream
define conductive hearing loss
can’t transmit signal to receptors from outer to middle ear, affecting threshold only
define noise induced hearing loss
threshold and ability to discriminate frequencies affected in both ears due to damaged stereocilia which can be prevented through education but has no treatment
define glue ear
hearing loss due to middle canal filling up with fluid
glue ear risk factors
dummy after 11 months passive smoking genes day-care immune suppression allergies inflame structuring connecting throat to ear
impacts of glue ear
isolation
sleeping disturbance due to pressure
shouting as can’t hear
glue ear treatments
do nothing
insert grommet to drain but can scar tymp mem
define sensorineural loss
retrocochlear (after inner ear) cochlear (inner ear) affects discrimination as signal distorted
gradients of hearing loss
mild - moderate (ha) - severe (lr, bsl, ha) - profound (lr, bsl)
what is genetic colour blindness
being unable to see certain colours depending on the affected cone
what ir protanopia or incomplete achromatopsia
rec cones have the green code opsin so red and green are confused, males more at risk and don’t see fulls spectrum
what is deuteranopia or achromatopsia
green codes have the red cone opsin
what is tritanopia
retinas lack of have faulty blue cones so confuse short wavelengths and can’t discriminate them so have reduced visual acuity
how can gene therapy trwat genetic colour blindness
insert gene for missing cone opsin into the photoreceptors
what is acquired colourblindess
(neurotoxins) affecting all cones in different ratios which is treated by removing toxin exposure or stop taking drugs causing damag
risks for acquired colour blindness
MS
diabetes
ocular diseases
neurotoxin exposure
define cerebral achromatopsia
VAC damage leading to colour vision loss, usually to V8 which is assoc w memories of objects’ colours
what is the pulfrich effect
different amounts of light entering each eye from a moving object producing a false percept as image’s difference unresolved
why does the pulfrich effect occur
photopigments in one eye bleached faster than the other so one image older so two positions for same object
pulfrich effect risk factors
MS
cataracts
optic neuritis
retinal neuritis
pulfrich can be treated how
use glasses with filters so light hits retinas at the same time
