Perception Flashcards
1
Q
face pareidolia
A
tendency of visual system to see faces in inanimate objects
2
Q
exteroception
A
information about external environment, involves the somatic nervous system
3
Q
interoception
A
processing central information inside bodies, used to control motor output, involves autonomic nervous system
- afferent (sensory input)
- efferent (motor output)
4
Q
reduced afferent sensory input:
A
continuous input is so important that individuals deprived of external stimulation become severely disoriented, vivid hallucinations and delusion, especially when deprivation is involuntary
5
Q
generalised senses
A
sensory receptors scattered throughout the body, simple anatomical structures located in skin, muscles, joints and internal organs
6
Q
specialised senses
A
sensory receptors localised within specialised organs in the head, complex anatomical structures
7
Q
types of sensory receptors
A
mechanoreceptors - respond to movement and pressure, audition and touch
chemoreceptors - respond to airborne and soluble chemicals, smell and taste
photoreceptors - respond to visible light, vision
nocioceptors - respond to pressure, temperature, chemicals, somatic senses
thermoreceptors - respond to changes in temperature, chemical and mechanical stimuli through somatic senses, autonomic sensory pathways
8
Q
stages of processing information
A
- Sensory receptors are stimulated by the appropriate environmental energy
- Sensory transduction: sensory receptors transduce (convert) physical energy into neural energy
- Sensory coding: resulting neural activity is encoded into patterns of neural activity and transmitted to and further processed in the CNS
- Neural processing in the cortex produces perception
9
Q
absolute threshold
A
smallest amount of energy needed to detect a stimulus, not fixed, most physical intensities will be a mixture of supraliminal (perceived) and subliminal (not perceived) intensities
- the minimum amount of energy that can be detected 50% of the time
10
Q
difference threshold
A
otherwise known as just noticeable difference
- the smallest detectable difference between stimuli
- smallest amount something has to change for a person to notice it 50% of the time
- therefore the more intense the stimulus, the larger the detectable difference must be
- used to show how what we percieve and what is in the physical environment differs
11
Q
Weber’s Law
A
says the just noticeable distance is always a constant fraction of the stimulus intensity
- highlights the difference between physical and perceptual and dimensions, what physical instruments record and what we perceive are two different things
12
Q
dynamic aspects of sensory processing
A
- response properties of our sensory and perceptual systems are not fixed
- the sensitivity of our sensory systems constantly change due to differing levels of stimulation and exposures to new physical environments
13
Q
sensory adaptation
A
- A reduction in sensitivity to a stimulus after constant exposure to it
- It reduces our awareness of a constant stimulus and helps to free out attention and processing resources to other (novel) stimuli in our environment
- Present in all sensory modalities but much reduced in pain
14
Q
rapidly adapting receptors (phasic) are:
A
most sensitive to changes in stimuli
15
Q
slowly adapting receptors (tonic)
A
respond as long as the stimuli is applied
16
Q
chemical senses
A
olfaction and gustation
17
Q
olfaction
A
sensations evoked by airborne chemical compounds (odorants) that are able to stimulate olfactory receptors in the nose
- distance sense - provides information about chemicals suspended in the air around us
- strongly linked to emotional and memory processing
18
Q
odorant (olfaction)
A
a molecule that is capable of stimulating olfactory receptors, require characteristics to stimulate sense of smell
- these include: volatility, hydrophobicity, small molecular weight
19
Q
olfactory transduction
A
odorants enter the nasal cavity via a retronasal passage (nose or mouth)
- through the respiratory epithelium and olfactory epithelium
olfactory epithelium: site of olfactory transduction, converting physical energy to neural energy
- size is proportionate to the ability to smell, bigger epithelium the more sensitive the nose is
- located on roof of nasal cavity, where it traps odorants and connects them to receptors
- amount of olfactory receptors correlates to the sense of smell
respiratory epithelium: filter, humidify and warm the air we breath
20
Q
transduction process for olfaction
A
dendrites of olfactory receptors activate in olfactory epithelium - sensory neurons activate in the olfactory bulb
Signals are sent to:
- The primary olfactory cortex (in cerebral cortex)
- Amygdala and limbic system (involved in emotional reactions to odours)
After primary olfactory cortex, it signals to second olfactory cortex (frontal lobe) and is integrated into other systems
21
Q
Types of Sensory Coding in Olfaction
A
shaped-based coding, population coding, vibrational coding
22
Q
Olfactory Sensitivity
A
- Early findings suggest that humans can discriminate between 100,000 different odours but latest estimates suggest differentiation between 1 trillion
- Detection sensitivity differs across different chemical compounds: some chemicals need lower concentration to be detected than other (lower absolute thresholds/better sensitivity)
Factors affecting sensitivity
- Women have lower thresholds
- Worst sensitivity in smokers and drinkers
- Better in the morning
- After 85, 50% unable to detect most smells
23
Q
Recognition threshold, and olfactory example
A
level at which a stimulus can be recognised, labelled as something
- Generally, olfactory identification is poor, and cannot be determined with great accuracy
24
Q
Porter (2007) - work on the ability to smell
A
humans can scent track, improve with practice, nostrils sample spatially distinct regions
25
pheromones
chemicals released by one animal detected by another that shape the second animal’s behaviour or physiology
- not clear role in humans (alteration of mood, menstrual synchrony)
26
major histocompatibility complex genes (MHC) and odour preference
preference for smells replicate a preference for genes that don't match
- if the genes were to match their children would be less healthy (weaker immune systems), so their odour preference replicates gene compatibility
27
anosmia
inability to smell, most often resulting from various infections in the nasal cavity or head trauma
- rare - congenital
- profound loss of taste as well
- associated with decreased well-being and decrease quality of life
28
specific anosmia
the inability to smell one specific compound amid otherwise normal smell perception
29
gustation
sensations evoked by solutions in the mouth that contact receptors there
- receptors located on tongue and roof of mouth in clusters, in taste buds
- the distribution of receptor types on the tongue is even in humans
30
sensory coding of gustation
- simpler than olfaction
- labelled-line coding: modality specific receptors transfer the information through a line to higher levels of processing
- stimulus --> receptor --> perceived taste
31
taste central pathway
- signals from taste cells travel along various cranial nerves
- these pathways first synapse in the spinal cord and then the thalamus
- finally they terminate in the primary taste cortex and then project to the orbitofrontal cortex
32
taste threshold
minimal concentration of a substance detectable by taste
- people are most sensitive to bitter substances, higher preference for sweet and sour substances
33
genetic variations in bitter taste
Fox (1931) - certain bitter substances taste dramatically different to different people.
Gene for PTC/PROP
- Individuals with two recessive genes are nontasters
- Individuals with one or more of the genes are tasters
34
hypotaster, normal taster, super taster
hypotaster - indifferent or likes bitter, seeks spicy, adventurous eater
normal taster - tolerates bitter and spicy food, moderate
supertaster - avoids bitter and spicy food, picky eaters
35
somatic senses
touch, temperature, pain and proprioception
the components of the CNS and PNS that receive and interpret sensory information from the skin, joints, ligaments and muscles
skin senses - touch, pain, temperature
proprioception -
kinesthesia - the sense of position of our body parts with respect to each other that allows us to perform movement
vestibular sense - provides information about the position of body in space by sensing gravity, movement and acceleration (factors that are critical for maintaining our sense of balance)
36
Sensory Coding of Touch
- mechanoreceptors
Four different types of mechanoreceptors embedded in
- outer layer
- underlying layer of skin
- epidermis
- dermis
Each mechanoreceptor responds to a touch stimulus in a specific area of the skin (the receptive field of the receptor)
- All mechanoreceptors respond to touch but have different anatomy, adaptation rate and receptive field (RF) size
37
slow adapting mechanoreceptors
fire continuously as long as pressure is applied
primary functions
- fine detail (pattern, form perception)
- texture perception
- finger position
those with small RF sizes encode information from a smaller area of the skin than larger RF sizes
38
fast adapting mechanreceptors
fire at onset and offset of stimulation
primarily functions
- flutter
- vibration
- fine texture perception (moving fingers across something)
- stable grasp
39
Measuring Tactile Sensitivity and Acuity (3 ways)
absolute detection threshold --> finding the smallest pressure to be detected
two-pointed discrimination --> minimal distance between two points that can be detected, determining if your being touched by one needle or two needle
grating acuity --> distinguishing the minimal amplitude of grooves that can be discriminated to determine if something is a smooth and grooved surface
40
touch sensation
represented somatotopically in the brain
- Adjacent areas on skin connect to adjacent areas in the brain
- Certain body locations have a disproportionate amount of cortical area because of the increased sensitivity in those areas
41
phantom limb sensations (an example of neural plasticity)
- Feel limb sensations when amputated
- Result of cortical remapping that occurs in response to amputation: cortical regions that represent the lost limb before amputation can become responsive to stimuli from other adjacent cortical regions after the amputation
42
Encoding Temperature (through thermoreceptors)
→ types: warmth fibres, cold fibres
- Thermoreceptors respond when you make contact with an object warmer or colder than your skin
- Stimulating cold and warm fibres togethers produces a hot feeling (instead of the expected lukewarm)
43
Pain Perception
→ free nerve endings, source of information that relates to tissue destruction
→ pain perception is adaptive to a degree as it motivates behaviours to terminate the source of the pain
44
congenital analgesia
unable to feel pain
45
factors that lessen the experience of pain
- expectation, when told what to expect they feel less pain
- shifting attention, attention on stimuli other than the pain-inducing one lessens pain
- content of emotional distraction lessens pain to something else
46
Gate Control Theory (Melzak & Wall)
- theory that the spinal cord contains a neurological "gate" that blocks pain signals or allows them to pass on to the brain
- the gate can open by the activity of pain signals travelling up small nerve fibres
- the gate can close by activity in larger fibres or by information coming from the brain
47
Visual-Vestibular Sensory Integration
brain just using eyes and inner ear to coordinate eyes and head movement
examples of where it goes wrong
- vection - illusory sense of self motion produced when you are not moving
- motion sickness - results when there is a disagreement between the motion and orientation signals provided by the semicircular canals, otolith organs, and vision
48
audition
auditory perception is the ability to identify and localise the sound signals in environment
Sound is the periodic vibration of air molecules, originates from a disturbance of the air by any object, the local religion of air has increased energy caused by the motion of the air molecules
49
physical properties - amplitude
amplitude: determined by how much the sound source displaces the waves from the equilibrium
- Sound amplitude is the difference between the peak and the trough of a sound wave (spatial extent of pressure oscillations)
- measured in decibels
Decibel: the difference between two sounds as the ratio between two sound pressures
- Every increase of 10dB is equal to a 10-fold increase in sound pressure level
- 0dB, absolute threshold of hearing
50
physical properties - frequency
Determined by the rate of displacement caused by the sound source - how fast it reaches its displacement from the equilibrium
- The number of complete waveforms, or cycles, that pass a given point in space every second
- Measured in hertz (1hz is one cycle per second)
- Human range: 20-20,000 hz, infrasound and ultrasound are outside of hearing range
- All animals seem to have much wider hearing than voicing range
- Many animals have wider range of frequencies than is possible for humans
- Humans are most sensitive to sound frequencies between 1000-5000 hz (lowest auditory thresholds to these sounds)
51
physical properties - complexity
Combining multiple sound waves together makes it complex
- Sounds are typically more complex and contain energy at multiple frequencies
- Lowest frequency: fundamental frequency
- Integer multiples of lowest frequency are called harmonics
More complex = more frequencies
- Sounds complexity contributes to the perceptual quality of timbre
- Pitch of complex waves determined by fundamental frequency
52
perceived properties
loudness, pitch and timbre
53
acoustic to neural energy
sound vibrations are collected by outer ear and are funnelled into the ear canals, sound waves are transmitted through the middle to the inner ear which is filled with fluid that is much denser than air
- Outer ear and middle ear function is to amplify the intensity of the sound so that it can adequately stimulate the cochlear fluid
54
Outer ear
- Sound waves funnelled into ear and then resonates and amplifies
55
Two Factors in Sensory Coding for Pitch Perception
1. Which hair cells are stimulated: specific groups of hair cells are sensitive to specific frequency and inturn activate a specific set of auditory nerve fibres
- Preferred frequency is at the lowest point of each tuning curve
- Positioned at different places in the cochlear, information about the particular frequency is coded by the place in the cochlear with the maximal response
- tonotropic organisation
2. How auditory nerve fibres are firing: rate or pattern of firing of nerve impulses to specific auditory frequencies
- use volley principle and frequency matching
56
Problems with Hearing
Hearing loss during conduction, Sensorineural hearing loss, Central auditory processing disorders
57
auditory localisation
the ability to determine where in space a sound originates
1. interaural intensity difference
- For certain directions of the sound source, the head creates acoustic shadow, reducing the sound intensity on one side
2. interaural timing differences
- Sound wave coming from the side will hit the nearer ear first, creating a time lag between the two ears
- Perception of the sounds location depends on the sound that reaches the ear first
3. spectral cues from the filtering properties of the Pinna
- Above, in front and behind when trying to localise a sound, the shape of the ear is used to hear different sounds
58
vision
process of discovering from images what is present in the world and where it is
physical stimulus energy --> receptors --> neurons --> brain --> perceptual experience
59
visible light
portion of the electromagnetic spectrum that can be detected by the human eye (400-700 nm), shorter wavelengths correspond to high frequency and higher energy and vice versa for longer wavelengths
60
Reflectance:
the proportion of the incoming light that is reflected by a surface
Reflect light with a particular reflectance spectrum
- Red - primarily longer wavelength
- Green - middle wavelength
- White, grey, black - reflect all wavelengths equally, white reflect 90%, black 3%
Chromatic (colours) surfaces have selective reflectance properties: absorb some reflect others
Achromatic (black, whites) surfaces reflect all wavelengths equally
61
Input: (vision)
light reaching the eye is the product of illumination and surface reflectance
- Surface reflectance properties do not change with different illumination conditions, but luminance reflected from any surface changes as illumination does
62
shaped based coding
Shaped-based coding: assuming a simple correspondence between molecular shape and perceived smell
- However, it is argued that molecules with similar shapes have different smells, similar smells come from molecules with different shapes
63
population coding
Population Coding: assuming odorants are coded by combinations of olfactory receptors, specific time order of activation of receptors might be important, intensity of odorant might change which receptors are activated
64
vibrational coding
Vibrational Coding: odours associated with different chemicals molecules or compounds are determined not by their shape but by their molecular vibrations
65
Sensory transduction
sensory receptors transduce (convert) physical energy into neural energy
- second stage of sensory processing
66
Sensory coding
resulting neural activity after transduction is encoded into patterns at, transmitted to and further processed in the CNS
- third stage of sensory processing
67
sinusoid
simplest possible wave shape
Tuning fork gives a simple sound waves, with oscillations at only one frequency
68
volatility (to determine if it is odorant)
how easy an odorant will vaporise, or turn into a gas, and then reach receptors
69
hydrophobicity (to determine if it is odorant)
extent to which it is repelled by water
- important as it ensures interaction between odorants and receptors despite the presence of mucus
70
small molecular weight (to determine if it is odorant)
- important because smaller molecules tend to produce more intense smells, except methane and carbon monoxide
71
tonotopic organisation
tuning of different parts of the cochlea to different frequencies
- Organised distribution of receptors to different properties
- important in sensory coding pitch perception, through which hair cells are stimulated in the ear
72
frequency matching theory
- important in sensory coding pitch perception (determining how nerve fibres are firing)
Information about the particular frequency of an incoming sound wave is coded by matching the frequency of neural firing
- Potential problem: no neurons can fire faster than 1000hz
73
Volley principle (population coding)
instead of one neuron, multiple neurons can provide a temporal code for frequency by firing action potentials at distinct points in the period of a sound wave, but not on every period
- important in sensory coding pitch perception, through how nerve fibres are firing
74
The precedence effect
phenomenon where an acoustic signal arriving first at the ears suppresses the ability to hear any other signals, including echoes and reverberation of that signal that arrive up to about 40ms after the initial signal
- provided that the delayed signals are not significantly louder than the initial signal
75
middle ear
- Eardrum vibrations moves the middle ear bones (ossicles) so that they can be processed as sound in the inner ear, waves amplified a second time
- relay station
- Vibrate against membrane between the middle and inner ear
76
inner ear
- vibration of membrane displaces fluid in the cochlea
- Movement of the cochlear fluid stimulates the auditory receptors (hair cells) which transduce mechanical into neural energy
77
Hearing loss during conduction
conduction: transmission of excitation
when transmission can't reach the inner ear
- Fluid, wax, infection: air into ear canal can’t get through etc
- Middle and external ear
78
Sensorineural hearing loss
hearing loss due to damage to the inner ear or nerves stemming from the brain
- Middle ear and inner ear and auditory nerve
- Tumor, trauma, malformations, exposure to loud noise, or familial
79
Central auditory processing disorders
inability to process sound
- Damage to cortical areas ultimately can affect auditory discrimination, Pattern recognition, Sound localisation
80
Function of Hearing
- Detection and identification of signals (knowing something is around)
- Speech perception
- Music perception
- Sound localisation (where the sound is coming from)
81
features of light and why vision is useful
- Light travels quickly, gives an almost immediate quantification of surroundings
- Light travels in straight lines it preserves geometric structure of environment
- Contains information about properties of surfaces in the world
82
Equal loudness curves
to be perceived as equally loud, low and high frequency sounds need to have higher physical intensity compared to the intermediate frequency (3000-5000 hz) sounds
83
tastes correlation to survival values
the tastes someone has may signal different dangers in society
- bitter might signal poison
- sour to detect acidic solutions that might harm the body
84
senses in relation to brain
different senses take up different cortical areas of the brain
85
fundamental frequency
lowest frequency present in a series of sound waves
86
harmonics
integer multiples of the lowest frequencies
87
timbre
Timbre, in relation to complexity, is the sounds distinctive tonal quality determined by the non-fundamental frequencies
- Causes the same note to sound different on different instruments
- Also affected by the change in sound over time
88
retina
where light receptors are located
- photoreceptors transduce electromagnetic energy into neural energy
receptors are split into rods and cones
89
rods
- more sensitive to light than cones
- 120 million
- important at low levels of light
- contribute little to colour vision
90
cones
- 6 million
- important for colour and spatial detail
- see only in daylight
91
rods and cones are unevenly distributed in the retina
- cones are predominantly in the centre
- rods exclusively in the periphery
92
retinal ganglion cells
blind spots in each retina contain no photoreceptors and is a place where the axons of retinal ganglion leave the eye and carry the visual information to higher processing regions in the brain
93
central vs peripheral vision
encoding of fine detail is only represented with the focus of vision
- the periphery has the lowest acuity, the parafovea has moderate acuity and the fovea and has high acuity
94
topographic mapping on the retina
external visual field is mapped onto the retina, preserving the spatial relationships between positions in the visual field and retinal projections
95
primary visual cortex
where most retina output goes to
- majority of axons of retinal ganglion cells terminate in the Lateral Geniculate Nucleus (LGN) in the thalamus and carry information to the primary visual cortex
96
retinotropic mapping
connections between neurons in different parts of the visual system remain spatially specific, so each structure contains a map of the visual field which corresponds to the spatial representation of the visual scene
97
path of retina to primary visual cortex
crosses to the opposite hemisphere of the brain before it reaches LGN and then primary visual cortex
- receives left visual field from right side of brain and vice versa
98
cortical maginifcation of part of the retina
larger region of primary visual cortex devoted to the fovea
- therefore there is uneven interpretation
99
Visual Processing in Primary Visual Cortex
neurons in visual cortex respond to specific features, including
- colour
- direction of movement
- contour
- depth
100
dorsal pathway
"where or how" pathway
- motion perception, moment-to-moment representation of spatial layout
- process information necessary for visual control of skilled actions and navigation
101
ventral pathway
"what" pathway
- colour processing and object recognition
- representation of stable characteristics of objects and there relations
102
akinetopsia
stems from damage to dorsal pathway
- cortical motion blindness (seeing something in low shutter speed)
103
object agnosia
struggling to interpret visual objects
- stems from damage to ventral pathway
104
prosopagnosia
struggling to interpret/process faces
- stems from damage to ventral pathway
105
sensory coding of vision (through colour)
Colour provides salient and useful information in an image, aids in object recognition and segmentation of different regions
- Colours are not a physical colour it is a subjective experience, created by our visual system
106
physical dimensions of vision
wavelength, intensity, spectral purity
107
perceived dimensions of vision
hue, lightness, saturation
108
trichromatic theory
there are three colour channels when perceiving colour
- red
- blue
- green
operating at the receptor level, 1st stage of colour processing
109
opponent-process theory
perception of colour is determined by the outputs of three independent mechanisms, composed of a pair of opponent colours
- red-green
- yellow-blue
- black-white
colour processing occurs at post-receptoral level
110
Colour receptors
three different types of cone, each with different spectral selectivity
- The cones differ in photopigment and as a result differ in their sensitivity to light of different wavelengths
- Cone type named for location of the peak of its sensitivity on the spectrum (short, medium, long)
Activity in any single cone type does not result in a colour experience
- Cone responses - relative activity across cone types can be used for code for experienced colours
111
colour-vision deficiency
people who suffer red-green deficiency is more prevalent in males (genetic deficiency carried on X-chromosome)
112
colour constancy
we are able to perceive surfaces as having the constant colour even if the light they reflect changes (due to changes in light or illumination)
- light reflecting from a surface is as much at influence by how it is illumination as it is by the reflectance of the surface
113
colour assimilation
colour segments look more similar to their immediate surroundings
114
simultaneous colour contrast
colours look different when next to different backgrounds
115
depth cue
information about the third dimension of visual space
116
binocular depth cue
depth cues require information of both eyes
117
monocular depth cue
depth cues available with one eye
118
stereopsis
- Binocular visual field is the proportion of the visual field visible with both eyes
- Two eyes have slightly different views of environment together
- Difference can be utilised to provide information about depth (stereopsis)
- binocular
119
convergence
Degree to which eyes have to converge to nose to look at something close
- binocular
120
occlusion
Relative depth order in which the object that partially obstructs the view of another object is perceived as in front
- monocular
121
elevation
For objects touching ground, those higher in visual field appear further away
- monocular
122
texture gradient
Textures more dense appear further away
- monocular
123
aerial perspective
Objects further away appear fuzzier
- monocular
124
interaural intensity difference
For certain directions of the sound source, the head creates acoustic shadow, reducing the sound intensity on one side
125
interaural timing differences
- Sound wave coming from the side will hit the nearer ear first, creating a time lag between the two ears
- Perception of the sounds location depends on the sound that reaches the ear first
126
spectral cues from the filtering property of the pinna
- Above, in front and behind when trying to localise a sound, the shape of the ear is used to hear different sounds
127
vestibular sense
provides information about the position of body in space by sensing gravity, movement and acceleration (factors that are critical for maintaining our sense of balance)
128
kinesthesia
the sense of position of our body parts with respect to each other that allows us to perform movement
129
bottom up processing
brain processes sensory information and uses clues to understand stimuli
130
top down processing
using what you already know to perceive new sensory information
