Week 1 Phsyics+ intro

Question 1

Epistemological scepticism:

Answer 1

the view that we cannot know anything certain - there is a chance that what we hear and see and taste is not actually what it is. - chuang tzu

Question 2

Plato’s cave

Answer 2

prisoners chained in a cave face a blank wall, watching shadows and hearing sounds created by people passing in front of a fire behind them. They think the sounds are coming from the shadows. The shadows are the prisoners’ reality, but are not accurate representations of the real world - just the fragment of reality that we can normally perceive through our senses.

Question 3

Aristotle

Answer 3

believe perception is taking on form without matter - the sense of organ or the sense itself takes on the perceptible quality.

Question 4

Galileo

Answer 4

“Hence i think that taste odours, colours and so on are no more than mere names as far as the object in which place them is concerned and that they reside only in the consciousness. Jence if the living creature were removed all these qualities would be wiped away and annihilated” he challenged Aristotle in 19660.

Question 5

Dualism

Answer 5

mind-body distinction. Attempts to overcome the question of how matter (brain) can give rise to inner mental life. Originally focused on the role of the soul/mind
Extended substance: material entities (physical) Mental substance: - mind/soul/consciousness (non-physical)

Question 6

Monism

Answer 6

distinguished from dualism (there is no duality).only brain gives rise to perception (from internal and external stimuli).
Whilst part of what we perceive comes through our senses from the object before us, another part always comes from our head.
Notes: most people today would hopefully agree that sensation by definition requires a physical force and that a nervous system is required for perception.
Most would also agree that the brain(without external triggers) can generate some elements for perception. The midbrain problem is still debated mainly in terms of “how” not “if”. Many would agree that physical/biological phenomena give rise to psychological phenomena.

Question 7

Sensation

Answer 7

physical process - receiving stimuli from the environment via the sensory system.

Question 8

Perception

Answer 8

cognitive process - interpreting sensory signals into a conscious experience - interpreting sensory signals is where things get complicated. Transforming them into conscious experience.

Question 9

Recognition

Answer 9

cognitive process -process of identifying and/or categorising our perceptions. - identifying is where things get complicated.

Question 10

Sensation recognition

Answer 10

bottom up processing - taking the elementary building blocks of sensation from the sensation world and using them to building a pattern of electrical signals that are fed into the brain -will only travel in that direction which is why its called bottom up process

Question 11

Perception recognition

Answer 11

taking the electrical signals from the sensory system and building on them integrating them, converting them into higher order signals - bottom up process
There is also a top down process - the higher order levels of the perceptual process can influence what is happening at the lower order levels which is not necessarily directional (one way only). For example, two or three jabs in the arm from the doctor. People normally look away but that doesn’t change the sensory signals coming in, you will still feel the pain sensation (bottom up process).people look away Sensitivity: get measures from proportion
Because they don’t want to attend to that painful stimulus. If you look away it’s not anticipated as much and don’t expect it to happen. Most people find there is a significantly less degree of pain when looking away - this is top down processing higher order elements influencing the lower order levels of perception.

Question 12

Weber’s two concepts:

Weber is Psychophysics

Answer 12

1. The absolute threshold (detection)
   The minimal limit of detection. The minimum stimulus that produces sensation 50% of the time. Keep adding weight and the patient won’t feel it and once they feel it that’s the absolute threshold.
2. The relative threshold (discrimination) The minimal change in stimulus required to elicit a change in sensation 50% of the time. Now called the ‘just noticeable difference’ (JND).

Question 13

Examples of absolute thresholds

Answer 13

1. Vision - a candle burning 20 miles away on a dark night
2. Hearing - a watch ticking 20 feet away
3. Touch - a bees wing dropped on your
   check from 1cm
4. Taste - 1stp of sugar in 2 gallons of
   water
5. Smell - 1 drop of perfume in a 6 room
   building

Question 14

Weber fechner law

Answer 14

The relationship between the stimulation level and the perceived sensation is proportional %based, not consistent

• To detect change in stimulus intensity must increase relative to the current level
• In other words, the larger the stimulus magnitude the greater amount of difference needed to produce a JND
• Webber constant (k): a constant proportion of the initial stimulus value the represents the JND

Question 15

How much needs to be change to notice a difference:

K values

Answer 15

Vision - 1/60 (2%)
Hearing - 1/10 (10%)
Smell - 1⁄4 (25%)
Taste - 1⁄3 (33%)
Touch 1/50 to 1/7 (2-14%) - the reason its a range is because touch covers many things such as pain, pressure, itch, heat

Question 16

Adaption

Answer 16

ekman et al. adaptation to odour presentation
- Perceived magnitude (intensity) decreases over time if stimulus is constantly present.
Adaption is critical for survival

Question 17

Threshold methods

Answer 17

Fechner’s 3 methods
Signal detection theory
Magnitude estimation

Question 18

Fechner’s 3 methods

Answer 18

1. Constant stimuli
   - To determine absolute threshold
   - Stimuli 1,2,3,4 … present multiple
   times, random order
   - To determine JND
   - Is the other weaker/stronger/same
   Detections are set to 50% detection by convention.
2. limits
   Determining absolute threshold
   - Stimuli 1,2,3,4… present ascending/descending order Determining JND
   - Standard vs comparator stimuli a,b,c,d… in ascending value
   - Tell me when comparator goes from weaker/stronger - Now
3. adjustments
   Determining absolute threshold
   - Adjust the stimulus until you can detect it
   Determining JND
   - Standard stimulus provided
   - Adjust the comparator stimulus until it
   matches the standard
   - Magnitude of variance = JND
   Dial it up or down until it matches the standard
   Q: how certain are we that we are just measuring sensitivity to the stimulus? You are depending on the participants’ self report - waiting for a yes i can detect it or no i can not detect it or yes/no there is/isn’t a difference. This is subjective
   Inherently prone to bias - these measures are biassed and need to get around the biasism.

Question 19

Neurons

Answer 19

electrically active, multiple subtypes classified by anatomy, location or function – unique ability to conduct bioelectric signals

Question 20

Glia

Answer 20

electrically passive, involved in support roles, immune response, aiding neuronal transmission, growing awareness of other roles

Question 21

Synapses

Answer 21

Junctions between cells – when the presynaptic cell is excited past threshold, it releases neurotransmitter onto the postsynaptic cell

Question 22

Sensory receptor neurons 3 key features:

Answer 22

• Sense organs always
• Must respond to stimuli from environment
• Convert to electrically stimuli

Question 23

Traditionally 5 senses (“modalities”):

Answer 23

1. Sight (vision)
2. Hearing (audition)
3. Touch (somatosensation)
4. Smell (olfaction)
5. Taste (gustation)
6. Balance (the vestibular sense)?

Question 24

Sensory systems

• Four criteria

Answer 24

1. Specialized to receive particular stimulus – i.e. has specific receptors for specific physical energy/chemical molecules
2. Performs signal transduction (stimulus → neuronal potential)
3. Relays the neural signal to the brain via certain pathway (synapse 1 → synapse 2 → synapse 3 …)
4. Has its own cortical region for processing (sensory cortices + association cortices)

Question 25

Example of sensory system 4 criteria– the olfactory system

Answer 25

1. Specialized to receive particular stimulus
   – olfactory neurons have special receptors that respond to odorants
2. Performs signal transduction (stimulus → neuronal potential)
   - odorants trigger action potentials in olfactory receptor neurons
3. Relays the neural signal to the brain via certain pathway
   - olfactory receptor neurons → olfactory bulb neurons → brain
4. Has its own cortical region for processing (sensory cortices + association cortices)
   - olfactory cortex

Question 26

Muller’s Doctrine of Specific Nerve Energies (1842):

Answer 26

brain distinguishes between different senses by monitoring activity in different sensory nerves
• e.g. anything that activates optic nerve will elicit ‘light’, anything that activates auditory nerve will elicit ‘sound’

Question 27

Specificity Coding

Answer 27

– qualities are represented by activation of specific neurons
Quality X is perceived when only ‘X specific’ neurons fire Quality Y is perceived when only ‘Y specific’ neurons fire
Requires neurons that respond only to a specific environmental stimulus e.g. “Grandmother cells” (Lettvin & Konorski, 1960s)
“Luke Skywalker cells” (De Falco et al., 2016)
These neurons represent associated concepts, not individual items/qualities per se!

Question 28

Population Coding

Answer 28

qualities are represented by the pattern of activity across a group of neurons
Allows the representation of many different stimuli by the firing of a group of neurons

Question 29

Rate coding

Answer 29

qualities are represented by the firing rate of the neuron
Useful for coding stimulus intensity
Useful for coding stimulus duration
rate coding can occur in single neurons or at the population level

Question 30

Computational neuroscience

Answer 30

David Marr - proposed 3 critical levels of analysis:

1. Computational theory – what is the goal of the computation?
2. Representation & algorithm – what represents the input and output? What is the algorithm (formal set of rules) used to convert input to output?
3. Hardware implementation – how can the representation be realised physically?

Question 31

Representation

Answer 31

a key component in computational models of perception
• Perception must involve the formation of representations in the brain – how does the brain construct and use these representations?
• Analog representations: magnitudes in one system map to analogous magnitudes in another system (such as brain)
• Symbolic representations: arbitrary symbols in one system map to states/entities in another system

Question 32

Representation in sensory systems

Answer 32

Each processing stage receives a representation of the sensory stimulus as its input.
• Each representation is transformed to a new representation that is passed on to the next processing stage (and so on).
• The modification that takes place at each processing stage can be considered as a computational operation that transforms one representation into another.