Sensation And Perception

Question 1

Four Receptors and Senses

Answer 1

Photoreceptors sense Light

Chemoreceptors sense Chemicals/Molecules

Mechanoreceptors sense Mechanical Forces

Thermoreceptors sense Temperature

Question 2

Empiricism

Answer 2

Knowledge comes from outside the mind.
The environment shapes the brain and our experience of the world.
“Black Slate”/Nurture

Question 3

Rationalism

Answer 3

Certain fundamental principles drive/shape knowledge.
Our brain’s architecture shapes and constrains experience.
“Innate Tendencies”/Nature

Question 4

Sensation to Perception - 3 Steps

Answer 4

1. Sample physical information
2. Integrate and encode it in the brain
3. Interpret and use it

Question 5

Wavelength

Answer 5

Visible light is electromagnetic radiation of 380-760 nanometres.

Wavelengths in order of shortest to longest:

1. Gamma Rays
2. X-rays
3. UV
4. Visible Light
5. Infrared
6. Microwaves
7. Radio waves

Question 6

Photoreceptors

Answer 6

How they work:

When light hits a photopigment molecule, it splits. The split activates the photoreceptor cell and this is the moment of transduction from light wave to neural impulse.

Photoreceptors are at the back of the eye so photopigments can be readily replenished.

Question 7

Types of Photoreceptors: Rods and Cones

Answer 7

Rods. Cones

Response. Slow. Fast

Recovery. Slow. Fast

Acuity. Low. High

Sensitivity High. Low

Location Peripheral Central Retina
Retina.

Types. One Three (L, M, S)

How many. 120 million. 6 million

Function. Peripheral Detailed, central,
and chromatic vision
low-light
achromatic
vision.

Question 8

Three Types of Cones

Answer 8

Short (blue) peak at 440 nanometres.

Medium (green) peak at 540 nanometres.

Long (red) peak at 570 nanometres.

Question 9

Colourblindness

Answer 9

Most commonly lose Large/Medium differentiation (red/green colourblind).

Common in Caucasian males.

X-linked genetic trait.

Less commonly lose Small cones, albinism (no cones) or brain injury.

Question 10

Two Retinal Mechanisms.

Answer 10

Two Retinal Mechanisms for Edge Enhancement:

1. Lateral Inhibition.
2. Centre-surround retinal ganglion cells.

Question 11

Two Types of Retinal Ganglion Cells

Answer 11

Midget Cells
Receive input from cones
Receive input from smaller number of cells.
Project to the parvocellular pathway - high acuity colour pathway to the brain (central vision).

Parasol Cells
Receive input from rods
Project to the magnocellular pathway - low acuity but highly sensitive pathway to the brain (low light, peripheral vision, motion and contrast).

Question 12

Hair Cells in the Inner Ear

Answer 12

Three Functions:

1. Sound Perception (cochlea)
2. Head Motion Perception (semicircular canals)
3. Gravity Perception (inner ear)

Question 13

Sounds

Answer 13

High Amplitude - loud sound
Low Amplitude - soft sound
Low Frequency - low-pitched sound
High Frequency - high pitched sound

Question 14

Cochlear Implants

Answer 14

How they Work:

1. Sounds are picked up by the microphone
2. The signal is coded and turned into electrical pulses
3. The pulses are sent to the coil and transmitted across the skin to the implant
4. The implant sends a pattern of electrical pulses to the electrodes in the cochlea
5. The auditory nerve picks up the electrical pulses and sends them to the brain.

Question 15

Mechanoreceptors in the Cochlea

Answer 15

They provide:

1. Loudness - amplitude of sound wave increases firing rate.
2. Pitch - which part of the cochlea is activated.
3. Timbre - composite frequencies - simultaneous activation of multiple locations on the cochlea.
4. NOT location - this comes from time and volume differences between the two ears.

Question 16

Mechanoreceptors in the Skin

Answer 16

Multiple systems: light touch, firm pressure, vibration, pain and skin stretch.

All types respond to physical deformation.

Receptors shapes are specialised for different types of pressure.

Question 17

Distribution of Touch Receptors

Answer 17

Two Point Discrimination Threshold

1. Touch the skin with one or two points.
2. Gradually move the points closer together. At some point two will feel like one.
3. This distance is the two point discrimination threshold.
4. If two points stimulate two receptors, you will feel two points. If two points stimulate one receptor, you will feel only one.
5. Density of receptors in the skin is highest on the hands and face, lowest on the upper arm, calf etc.

Question 18

Haptic Touch

Answer 18

Exploring objects with your subcutaneous mechanoreceptors:

Vibrations = roughness/texture

Position of fingers around object = shape

Skin Stretch, Tendon Stretch = weight

Question 19

Chemoreceptors

Answer 19

Function like a lock and key. Specific classes of receptors are sensitive to specific molecule types.

Found in:
Tongue (gustation)
Nasal Epithelium (olfaction)
Other locations e.g. lungs, stomach

Question 20

The Tongue (gustation)

Answer 20

Each of the papillae on the tongue contains multiple taste buds.

Each taste bud contains multiple chemoreceptors.

Five known receptor types:
Salty
Sweet
Bitter
Sour
Savoury (umami)

Question 21

Taste Receptors and Tastants

Answer 21

Receptor. Signals

Salty        =    NaCL (electrolytes)
Sour         =    Acid (spoiled/unripe food)
Bitter        =    Toxins, inedible substances 
Sweet       =    Sucrose (calorie-dense foods)
Umami      =    Glutamate (protein-rich food)

Question 22

Taste Preferences

Answer 22

Innate preferences

Exposure to amniotic fluid and breast milk

Exposure to flavours over lifespan

Genetic variability in taste bud numbers

Question 23

Aguesia

Answer 23

Inability to taste.

Temporary loss of taste is common.

Permanent aguesia is rare, usually caused by nerve damage or deformity.

Question 24

Nasal Epithelium

Answer 24

Inhaling brings odorants to the nasal epithelium.

Odorants bind to proteins in the cilia of the receptor cells and activate the cell.

Each cell has only a single receptor type.

Question 25

Axel and Buck - 2004 Nobel Prize

Answer 25

Roughly 100 different odorant receptors, each one coded by a different gene. Genetic codes for olfaction receptors alone comprise 3% of our genes.

Question 26

Can We Localise Smells

Answer 26

Orthonasal vs Retronasal - clear differences in perception/recognition. Left vs Right nostril arrival times. Might be mediated by pain pathways. Scent tracking - better with two nostrils than one.

Question 27

Pheromones

Answer 27

Odorants to communicate and control conspecific behaviour.

Question 28

Anosmia

Answer 28

Loss of sense of smell. Temporary loss due to inflammation/blockage is routine. Permanent loss due to range of causes (congenital, head trauma, disease, ageing). Roughly 1-2% in young, >12% in elderly.

Question 29

Chemoreceptors in the Body

Answer 29

The aortic and carotid arteries contain CO2 and O2 sensitive chemoreceptors that sample blood leaving the heart and communicate with brain areas that control breathing rate. Chemoreceptors in the gastric system cause stomach pain, nausea and vomiting.

Question 30

Thermoreceptors

Answer 30

Four types: 1. Fast Cold 2. Fast Hot 3. Slow Cold 4. Slow Hot Found in: The skin The cornea (to trigger blinking) The brainstem (to regulate core temperature)

Question 31

Sensing Skin Temperature

Answer 31

Unmyelinated C-fibres in the skin: - myelin speeds up neural transmission, so myelinated nerves are slow - adapt quickly A-delta fibres: - fast, extreme heat/cold - no adaptation

Question 32

More than 5 Senses

Answer 32

Photoreceptors - vision Mechanoreceptors - hearing, balance, skin pressure, limb position, internal organ sense Chemoreceptors - taste, smell, blood oxygen level Thermoreceptors - skin, eye and internal body temperature

Question 33

Primary Visual Pathway

Answer 33

Five Key Components: 1. Optic Nerve 2. Optic Chiasm 3. Lateral Geniculate Nucleus (LGN) in the Thalamus 4. Optic Radiations 5. Primary Visual Cortex

Question 34

Lateral Geniculate Nucleus

Answer 34

First way station on the way to the cortex. 2 layers: Parvocellular (P) cells: Receives input primarily from cones/midget cells. Pathway for high-acuity vision and colour. Magnocellular (M) cells: Receives input primarily from rods/parasol cells. Pathway for detecting contrast and motion, low light vision.

Question 35

Visual Deprivation

Answer 35

Classic Case Studies: - SB lost sight at 10 months, regained at 53. - Mike May, lost sight at age 3, regained at 45. Current Research - cataract surgery in rural India. Visual Degeneration - Charles Bonnet Syndrome Sensory Deprivation Environments -hallucination

Question 36

Primary Auditory Pathway

Answer 36

Four Key Components: 1. Superior Olive (pons) 2. Inferior Colliculus (mid brain) 3. Medial Geniculate Nucleus (MGN) in the thalamus 4. Auditory cortex

Question 37

Superior Olive

Answer 37

Receives input from both ears. Critical for detecting interaural time and volume differences. This gives us information about the location of sounds.

Question 38

Inferior Colliculus

Answer 38

Primarily receives auditory input. Also receives somatosensory and visual input. Multisensory integration occurs here. Auditory input is influenced by other modalities before it reaches the cortex.

Question 39

The Medical Geniculate Nucleus

Answer 39

Right next to the lateral geniculate nucleus. Like the LGN, acts as a relay station on the way to the primary auditory cortex.

Question 40

Primary Auditory Cortex

Answer 40

Contains a tonotopic map of all the frequencies and selectivity for location, timing and amplitude. Damage leads to an analogous condition to blindsight: inability to consciously identify certain tones, but guessing is above chance.

Question 41

Primary Somatosensory Pathway

Answer 41

Three Key Components: 1. Dorsal Root Ganglion 2. Ventroposterior Nucleus in the thalamus 3. Somatosensory cortex

Question 42

Dorsal Root Ganglion

Answer 42

Skin receptors are just one part of the nerve cell. The cell body is in the dorsal root Ganglion, next to the spinal cord.

Question 43

VPL of the Thalamus

Answer 43

Functions in touch, body position, pain, temperature, itch, taste, and arousal.

Question 44

Primary Somatosensory Cortex

Answer 44

Damage leads to lowered sensitivity to touch and an inability to identify objects to touch. Damage can also lead to a sense of disownership of body parts.

Question 45

Sensation vs Perception

Answer 45

Perception is based on sensory input But Perception can occur without sensation e.g. hallucinations. Sensation can occur without perception e.g. selective attention.

Question 46

Why is it important to perceive the scene correctly?

Answer 46

Disambiguate the stimulus on the receptors. Recognise hidden objects. Recognise blurred objects. Recognise objects from different viewpoints. Recognise objects across changes in size or scale.

Question 47

Structuralism

Answer 47

``` Wilhelm Wundt (1832-1920) Edward B Titchner (1867-1927) ``` The study of conscious experience by examining its structure or component parts (feelings, sensations). Perceptions are created by combining elements called sensations.

Question 48

Gestalt Approach

Answer 48

``` Max Wertheimer (1880-1943) Kurt Koffka (1886-1941) Wolfgang Koehler (1887-1967) ``` The whole differs from the sum of its parts. The whole is greater than the sum of its parts. Perception is a result of perceptual organisation.

Question 49

Principles of Perceptual Organisation

Answer 49

``` Pragnanz Similarity Good continuation Proximity Common region Uniform correctness Synchrony Common fate Meaningfulness/familiarity ```

Question 50

Recognition by Components

Answer 50

Objects consist of basic shapes/components called geons. We have about 36 geons. The combinations and spatial relationships between the geons in an object determine the object identity.

Question 51

Object Recognition

Answer 51

Object recognition involves: Edge extraction (determining basic low level features of the objects) Determine the components (geons) of the object and how they relate to each other. Match this information to stored representations of the objects. Identify the object based on which representation it best matches.

Question 52

Geons

Answer 52

Geons are: View-invariant: can be identified when viewed from different angles. Non-accidental properties: regularities in the visual image reflect the actual regularities in the world. Discriminable: NAPs can be seen when the object is viewed from different angles. Componential Recovery: can rapidly and correctly identify an object if we can perceive its individual geons.

Question 53

Configural Face Processinf

Answer 53

Thatcher illusion (Thomson, 1980) When inverted the face appears normal. We can’t use configural processinf as easily with inverted faces, so we rely on individual features here. When turned around, we can use configural processing, so the effect is obvious.

Question 54

Composite Face Effect

Answer 54

Participants are presented with faces and must determine if the bottom half matched the top. Accuracy is lower for aligned faces where the two halves are fused compared to misaligned.

Question 55

Face Adaptation

Answer 55

After viewing a face with a particular distortion in one direction for a few moments, we will perceive an opposite distortion when viewing an unmanipulated face.

Question 56

Brain Areas

Answer 56

The area in the brain that seems to be particularly important is the fusiform face area or fusiform gyrus.

Question 57

Prosopagnosia

Answer 57

Face blindness where the ability to recognise faces is impaired. Other aspects of visual processing remain intact. Acquired prosopagnosia: leisons in right occipital, temporal of fusiform brain regions. Developmental prosopagnosia: lifelong deficit that manifests itself in early childhood and cannot be attributed to acquired brain damage.

Question 58

Capgras Syndrome

Answer 58

A disorder in which a person holds a delusion that a friend, spouse or other close family member has been replaced by an identical looking imposter. Joseph Capras 1923.

Question 59

Divided Attention

Answer 59

Paying attention to more than one thing at a time. Kahneman 1973 suggests we have a single pool of attentional resources which can be divided between the tasks we are doing. We can attend to more than one thing at a time most easily when we’re skilled at one of the tasks or the tasks are fairly different from each other.

Question 60

Selective Attention

Answer 60

Focusing on specific items, while filtering out other irrelevant pieces of information. If we were to process everything that is projected onto our retinas, the visual system would be overwhelmed. By moving our eyes, we can bring the fovea of the eye onto the regions of the scene/environment Saccades: small, rapid eye movements. Fixations: pauses in eye movements that indicate where a person is attending, approx 3 fixations per second.

Question 61

How to Measure Attention

Answer 61

What determines how we scan a scene: Stimulus salience Our knowledge about scenes Nature of the observers task Learning from past experience.

Question 62

Attention and Perception

Answer 62

Inattentional Blindness: Failure to notice an unexpected stimulus that is in one’s field of vision when one performs other attention demanding tasks. Attention has an effect on perception. Change Blindness: A large change within a visual scene is undetected by the viewer. Occurs often when there has been a visual disruption such as an eye movement or a brief obscuration of the viewed image or scene.

Question 63

Factors influencing Perception

Answer 63

Anxiety Arousal Task Difficulty Skills

Question 64

Attention and Autism

Answer 64

Eye movements were recorded for autistic and non-autistic individuals while they were watching a movie. Non-autistic observers looked at the eyes of the actors to determine their emotional state and looked in the direction a person pointed and then at the face of the person who should reply. Autistic observers look at socially irrelevant stimuli in these situations

Question 65

Why is Motion Perception Important

Answer 65

Allows us to attend to moving items in the environment. Allows for segmentation of foreground from background. Helps compute the 3D shape of an object. Estimate distance from objects. Estimate heading direction. Collision avoidance. Recognise actions and emotions from others.

Question 66

Apparent Motion

Answer 66

Perception of motion when two static stimuli are played one after the other. Influences on motion detection: The length of the inter-stimulus interval: shorter ISIs suggest quicker motion. The distance between items in the first and second frames: longer distances suggest faster motion.

Question 67

Real vs Apparent Motion

Answer 67

Comparing neurological responses to control (no motion), real motion and apparent motion. Activation patterns in response to apparent motion are similar to those for real motion. Activation follows paths of real and apparent motion connecting the cortical representations of the stimulus location.

Question 68

Vision

Answer 68

As we move, there are changes in the Retinal input. These are analysed to determine movement direction.

Question 69

Proprioception

Answer 69

Detection of where our body parts are in relation to each other and how they are moving. A solely internal system - functions without vision. Tells us: Where things are in relation to each other If the body part is moving with enough effort If changes need to be made to the amount of effort.

Question 70

Vestibular

Answer 70

System for balance - found in the inner layer of the ear. Inputs: Forces produced by body and head movements. Outputs: Eye movements Movement sensations Posture changes.

Question 71

Otoliths Organs

Answer 71

Give information about displacement and acceleration. Crystals/stones on top of the organs. Gelatinous mass containing hair cells. When we move, the crystals lag behind the motion of the mass. This drags on the mass, causing the hair cells within to flex. This leads to an influx of Ca2+, the release of neurotransmitters and a signal to the brain. Linear force in a particular direction is perceived.

Question 72

Semicircular Canal

Answer 72

Three types: anterior, posterior, horizontal. Cell bodies of the hair cells synapse with the vestibular nerve to send signals and indicate movement. When the head moves, the endolymph lags behind the cupula. The cupula is pulled and the hair cells within flex.

Question 73

Dysfunctions of the Vestibular System

Answer 73

Vertigo: dizziness, spinning sensation Nystagmus: involuntary eye movements, blurred vision. Nausea. Alcohol also affects the density of the endolymph.

Question 74

Integration of Systems

Answer 74

Integration of vision and vestibular: Vestibular Ocular Reflex (VOR). Disagreements between visual and proprioceptive information can lead to nausea. Motion sickness: When reading, peripheral visual information indicates movement while you are focusing on a stationary page. Vestibular system indicated motion but no strong visual perception of this which leads to nausea