perception Flashcards
perception includes:
visual perception
audition
touch
pain
world to visual signal in brain
signal of 400-700mm for brain to process and encode
photoreceptors convert light wave energy into neural signal
- light energy –> neural activity
structure and function of the eye
Retina
- image on the retina is flipeed upside down and backwards
- light wave energy into back surface of eye
- shadows and disruptions are not seen
photoreceptor specialised function
first stage of information processing
2 photoreceptor types
Cones
Rods
RODS
work in dim lighting
- sensitive to movement but not fine detail or colour
- in dim lighting no colour, cone photoreceptors can’t work
* found in the periphery
CONES
function and location
work in good lighting and are sensitive to fine detail and colour
* interpret colour detail
* predominately found at the fovea
* at the fovea - 170 thousand receptors per mm^2
Visual acuity
ability to see fine detail
- this is determined by the properies of rods and cones
- no light receptors when blinking
context for vision
C + C
- colour contrast - colours we perceive are influenced by its surrounding
- colour constancy - tendency of a surface to appear the same colour under range of illuminants
* need to discount the illuminant (light) and determine true colour
light sources - bent shape, colours to different, creates shadow
retinal image to recognisable objects
- visual info seen on right of fixation is processed in left of brain
- visual info on left of fixation is processed on right
of brain
primary visual cortex
V1
first stage of cortical (visual processing)
- involved with the coding of lines and edges in visual scene
cortical cell sensitive to orientation
rules for visual cues
4 gestalt principles
linking oriented lines to outline shapes
- organise images into figures of interest and background = figure ground segregation
* similarity
* proximity
* closure
* continuity
Similarity
Proximity
Closure
Continuity
2 cues
depth of vision
- monocular cues
- binocular cues
M
- linear perspective
tendency for lines to converge when parallel
further away = smaller
eg. train tracks
2 interposition/occlusion
cue to relative depth order
one object can obstruct the view of part of another object
3 relative heights
- distant objects are seen as smaller and higher in relation to items that are closer.
Relative to horizon
Closer to horizon - further away
4 clarity
Depth cue based on that light is scattered by the atmosphere
More light is scattered when we look through more atmosphere
More distant objects appear fainter, bluer, and less distinct
5 Relative size
comparison of size between items
- if all equal, assume smaller objects are further than larger ones
-
6 motion parallax
Images close to the observer move faster across the visual field that images farther away
binocular clarity
- each eye has different view
- where we are not looking, the brain sees double (fovea)
Audition
sound, F + A
sound = pressure waves in air, water
- frequency
- amplitude
frequency is
number of sound waves or cycles per second
1 Hz = 1 cycle/second
humans - 20 to 2000Hz
Amplitude
the vertical size of the sound waves
Decibels dB - measure of physical pressure at the eardrum
auditory system function
amplitude and frequency into nerve impluses
- waves to mechanical energy
Outer ear
Pina - directing sound wave in
eardrum - sound waves pressure, eardrum flexes, malleable
- eardrum moves with sound waves, F + A
Middle ear
ossicles - arrangement of bones act like an amplifier
transmit sound wave pressure into mechanical movement
Inner ear
cochlea - full of fluid
- sound wave pressure pushing on cochlea
- mechanical movement of fluid in cochlea bends hair cells
- triggers neuronal signal - sway
Hair cells
cilia (hairs) sway and distort at their base
opens ion channel
- sodium potassium exchange
- action potential and voltage
mechanical action potential
- sound wave pressure
- bones mechanical movement
- fluid ripples and moves hair cells
- language of the brain
2 theories for coding frequency
auditory information
- frequency theory
- place theory
freq theory
brain processes low freq sounds as cochlea fluid moves hair
rate in encoded by how fast hair cell is producing action potentials
freq of fluid, freq of hairs moving, freq of action potentials they produce
place theory
area for high and low freq
sense sound frequency according to the locations of fluid activity in cochlear
cochlear basilar membrane:
- brittle end - resonsate high freq
- narrow, stiff end
- gelatinous end - low freq, more activity, wide, flexible
localising sound
sound - perceived first and loudest by closer ear
- sensitive ability
- vision dominates
Balance
SEMI CIRCULAR CANALS
vestibular system
semi circular canals give assocation with up down left right movement
- fluid movement –> neural signals for brain to interpret movement
visual and vestibular different - nausea
horizonal plane
touch receptors are
embedded in epidermis, underlying
- pressure
- vibration
- hot
- cold
kinesthetic receptors are
mechanoreceptors
- muscles, tendons, joints
- sense of where limbs and movements are
touch and sensitivity
different detectors for sensations
- nerve signals, mapping of these in brain give location
information passes through spinal cord
touch sensations - brains role
- somatotopically (homunculus) in the brain
- adjacent areas on skin connect to adjacent area in brain
Homunculus
representation of regions of body in brain
- more sensitivity - lips, fingers, more nerve endings
- larger areas of brain for this
Pain
subjective experience 2 components
= stimulus + emotional response
adaptive sensation
- functional
- survival
Analgesia
decreasing pain sensation during conscious experience
Endorphins
neurotransmitters associated with pain inhibition
endogenous or exogenous factors:
- naturally released in body
- external factors - morphine
Phantom pain
sensation perceived from a physically amputated limp of body
- brain not aware, attributes signals
positive feedback loop:
- brain sends signals to arm
- kinaesthetic receptors (but none present in the area)
- patient no feedback as no limp
- hand stays clenched
