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Sensation & Perception - Coggle Diagram
Sensation & Perception
General
Sensation vs perception
- Sensation: detect, physical, receptor cells
- Perception: organise/integrate of sensations, psychological, other cells
Psychophysics
- How changes in physical states relate to changes in mental states
Signal detection theory
- Sensitivity: sensory, precision, depends on sense organs
- Response bias: cognitive, decisions, depends on confidence, motivation, desire to not miss/avoid incorrectly detect
Performance measured by
- Hit rate: high - stimulus + yes
- False alarm: low - no stimulus + yes
- Importance depends on situation
Absolute threshold: intensity - barely detect 50% of time
- Subliminal / subthreshold = below line
- Superthreshold = above line
- Different for diff people at diff times
- e.g. lowest volume detected
Difference threshold: smallest change - detect 50% of time
- JND = just noticeable difference
- Relative, not absolute
- e.g. smallest change in volume detected
Weber-Fechner Law
- Ratio of increment threshold to background is constant
- k = ∆𝐼 / 𝐼
- ∆𝐼 = JND in 𝐼, 𝐼 = baseline
- e.g. if k = 0.2, JND is 20% above baseline intensity
Sensory transduction
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Sensory receptor types
- Simple: free nerve endings exposed to environment -> unspecialised & imprecise (pain/touch/pressure, e.g. hair)
- Encapsulated: coated nerve endings, more sensitive to specific stimuli -> selective (e.g. skin - vibration)
- Specialised: dendrites specialised to detect particular information (vision, hearing, smell, taste, balance, touch/pain, e.g. specialised sensory organs)
Perception
Bottom up organisation
- Gestalt principles - integrative: perceived object > sum of sensory parts
- Object centred / viewpoint invariance: perceive from view of objects
Top down processing
- Requires cognition
Vision
Stimuli
- Photons of electromagnetic energy
- Wavelength = colour
- Amplitude = intensity
Body -> brain
- Light refracted by cornea -> pupil -> refracted by lens -> retina
- Cornea: more optically powerful
- Lens: accommodates (adjusts thickness)
- Rods & cones: photoreceptors in retina
- Cones: 3 types - RGB, densely packed & central -> high res
- Rods: black/white/grey, sensitive to light -> peripheral vision, low light
- Retinal ganglion cells bundled into optic nerve -> thalamus -> visual cortex
- Blind spot where optical nerve leaves retina
- Visual cortex
** Combine inputs to integrate visual information & detect features
** Feature detector neurons: respond to light/dark patterns OR direction of motion -> detect location, orientation, width, motion direction
Sensory disorders
Light improperly focused
- Myopia: short sighted, lens/cornea too strong or eyeball too big
- Hyperopia: far sighted, lens/cornea too weak or eyeball too small
- Presbyopia: far sighted due to aging - lens can't increase thickness as object moves closer
Retinal cells not functioning properly
- Colour blindness: red or green cones deficient/mutated -> cannot distinguish red/green
Visual information
Colour
- Trichromacy theory: relative activity of 3 cones
- Opponent-process theory: relative activity of pairs of neurons - red-green, blue-yellow, black-white
Depth
Monocular cues
Pictorial cues
- Relative position/height (close to horizon = far)
- Relative size
- Absolute vs familiar size
- Linear perspective
- Light/shadow
- Interposition/occlusion
- Aerial perspective, relative clarity
- Linear perspective: parallel lines meet
Physiological
- Accommodation: far objects - muscles relax
Motion
- Parallax: objects closer move faster
Binocular cues
- Convergence: how much eyes need to cross to focus
- Binocular disparity: compare info from 2 eyes
Form - Gestalt
- Figure vs ground
- Similar in shape -> coherent object
- Close together -> coherent object
- Continuity
- Fill gaps -> complete object
Motion
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Illusions
- Beta effect: 'different still images -> circle' moves
- Phi effect: images flickered on/off -> movement between circles
Hearing
Stimuli
- Vibrational energy, pressure waves, usually carried by air
- Amplitude = loudness (dB)
- Frequency = pitch (cycles/sec, Hz)
Body -> brain
Hair cells: mechanoreceptors on surface of inner ear that respond to vibrations
- Outer ear: sound wave focused via pinnae -> ear canal -> ear drum vibrates (tympanic membrane)
- Middle ear: -> ossicles (hammer/anvil/stirrup) amplify vibrations - stirrups send push/pull pulsations
- Inner ear: cochlear receives vibration - shearing movement between basilar (hair cells) & tectorial membranes - 1 per Hz ->
- Sends electrochemical impulse -> auditory nerve -> brainstem -> thalamus -> auditory cortex
- Auditory cortex
** Integrates multiple signals
** Responds to specific tones - a
** Arranged tonotopically - higher pitches = back of brain
Sensory disorders
Mechanical/conductive
- Tympanic membrane doesn't vibrate
(air pressure, ear blockage, perforated eardrum)
- Ossicles don't transmit
(ear inflammation, bone tumour, ossicle fusion)
Sensorineural
- Damage to hair cells (tinnitus), vestibulocochlear nerve, auditory cortex
- Cochlear implant: electrodes along basilar membrane, directly stimulate nerve cells
Aural information
Pitch
- Frequency theory: sound wave frequency -> neural impulse frequency; limited to 100 Hz
- Volley theory: group of hairs cells indicate frequency; up to 4000 Hz
- Place theory: parts of basilar membrane detect different frequencies - base = higher, tip = lower; up to 20k Hz
Location
- Binaural: between 2 ears
** Intensity differences
** Temporal differences
Speech: secondary auditory cortex integrates inputs from primary auditory cortex + thalamus -> complex sounds
Taste & Smell
Stimuli
- Taste: chemicals in saliva; proximal
- Smell: chemicals in airborne molecules, distal
Body -> brain
- Tastebuds: chemoreceptors in tongue
- Taste pores (exposed) -> trigger neural impulse
- Made up of receptor & supporting cells
- For specific chemicals: sweet, salty, sour, bitter, piquancy, umami
- Gustatory cortex
- Olfactory membrane in 2 olfactory bulbs
- Bulb: outer part of 2 olfactory nerves from brain to nose
- Receptors/olfactory nerves in olfactory membrane -> trigger neural impulse
- 100s of receptors, 1000s of odours
- Olfactory cortex
- Gustatory & olfactory cortices
- Adjacent, between temporal & frontal lobes
- Interact with spatial info & memories, emotions
- Strong link to emotions (behavioural adaptation)
Chemoreceptors
- Transduce chemicals into neural impulses
- Lock and key: specific to particular chemicals
- Short response, inefficient, recycled
Information
Location
- Differences in intensity of smell
Touch, Balance, Pain
Stimuli
- Mechanical energy, thermal energy, chemical concentrations
Senses
- Somatosensation (touch)
- Equilibrioception (balance)
- Proprioception (body position)
- Nocioception (pain)
Mechanoreceptors
- Transduce pressure, vibration, stretch & texture
- No specialised organ
Body -> brain
Bypass brain - Reflexes
- Receptors -> spinal cord => automatic muscular response
- e.g. maintain balance, pull hand away, increase force, eye contact while moving
- Low leave, but important & complex
Nocioception
- Nocioreceptors: free nerve endings in skin/body -> transduce mechanical & chemical tissue damage
- Diverse region of spinal cord, subcortical & cortical areas
Gate control theory
- Pain competes with other touch senses
e.g. pressure dulls sense of pain
Changed by
- Context: reduced when distracted, aroused; by endorphins
- Cognitive factors:
-- Placebo effect (feel less pain)
-- Nocebo effect (feel more pain because expect to)
Proprioception
- Proprioceptors: respond to position/movement/strain of body parts
- Muscle spindle: muscle length
- Golgi tendon: tendon tension/strain
- Mechanoreceptors in vestibular system
- Fluid in inner ear: head movement
- Weighted hair cells: orientation
- Vestibular area of thalamus & cortex
Via brain
- Mechanoreceptors & proprioceptors -> spinal cord -> somatosensory cortex -> integrated into body matrix
Perceptual Dysfunctions
Visual agnosias
Apperceptive
- Can't organise into percepts
- No object-centred perspective
e.g. categorise, superimposed/unusual/shadowed perspectives
Associative
- Can't link percepts with knowledge
e.g. draw from memory
- Categorical: identify object function
- Integrative: group objects
- Prosopagnosia: recognise faces
Integrative agnosia
- Apperceptive + associative
Other
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Auditory agnosia: recognise/understand sound, music emotion, language
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