Cognitive Neuroscience

Question 1

What is cognitive neuroscience?

Answer 1

Bridging discipline between cognitive science and cognitive psychology

Question 2

What is meant by information processing?

Answer 2

Information processing is the change of information in any manner detectable by an observer.

Question 3

What discipline did cognitive neuroscience arise from?

Answer 3

From phrenology (feeling the skull to determine psychological attributes)

It lead to eventual recognition of brain lesions (e.g. Broca’s area)

Then to more current techniques of EEG and CT scans

Question 4

What is top-down processing?

Answer 4

The influence of later stages on the processing of earlier ones (e.g. memory influences on perception)

Question 5

What is parallel processing?

Answer 5

Different information is processes at the same time

Question 6

What is meant by interactivity?

Answer 6

Later stages of processing can begin before earlier stages are complete and that stages of processing are not completely separate

Question 7

Why should we study the brain?

Answer 7

Psychology is the study of mental processes and behaviour

Know that the brain carries out these processes

Question 8

What advantage do we get by learning about mental processes and behaviour at a neural level?

Answer 8

Knowing when and where cognitive processes occur in the brain can help us understand the nature of those processes (and gives us more data to validate our models)

Important for understanding and treating neurological disorders

Question 9

Why is cognitive neuroscience useful in theories of cognition? Give an example

Answer 9

Knowing where and when effects occur in the brain can constrain cognitive theories of those effects

N400 → Electrophysiological signal that occurs when we hear an unexpected word
The top of the y axis shows what electrode it is (Cz - the electrode in the centre of your head)
Time zero is when the new stimuli/the thing being tested is introduced (e..g. In this case the unusual addition of ‘dog’ in a sentence)
Black line semantic violation and orange grammatical violation
N400 - Response 400 ms after stimuli introduced
Widely used to study how and when prediction occurs in language

Question 10

How is cognitive neuroscience used in clinical practice?

Answer 10

Understanding neural basis of behaviour = Understand cognitive disorders & predict effects of brain damage

Can have unusual application - Using EEG or fMRI to evaluate patient’s awareness/consciousness or even communicate with them (e.g. if they’re in a vegetative state, use to see if they can hear)

Question 11

What two ways can we design an experiment that investigates how neural activity and cognitive functions related to one another?

Answer 11

Recording Studies - Can change behaviour and measure the effect on the brain

Inference Studies - Can change the state of the brain and measure the effect of behaviour (e.g. causing temporary lesion in brain and seeing if it has impact on stroop test)

Question 12

How could we investigate the example study of - Is the motor cortex involved in understanding action words like “pick” and “kick”?

Answer 12

Reading action words is correlated with greater activity in the motor cortex
Inference: when people process an action word, they simulate the action and this helps them to understand the word
But how do we know this simulation is really necessary to understand the word?
Could use people with a damage to the motor cortex and see if that impacts recognition
Damage to the motor cortex is associated with impaired action word understanding
Inference: activation of the motor cortex is necessary to understand action words
(If we assume that there are no other differences between our two groups that could have caused this effect)

Question 13

What are the independent/dependent variables and causality in recording studies?

Answer 13

IV = Conditions that manipulate behaviour/cognitive process
DV = Brain activity (Electrophysiology - EEG/MEG, Blood flow through fMRI)
Causality = Correlational technique

Question 14

What are the independent/dependent variables and causality in inference methods?

Answer 14

IV = Lesion or Brain stimulation (conditions manipulating behaviour as a validity check)
DV = Behaviour or cognitive process
Causality = Permits causal interference

Question 15

What are the advantages and disadvantages of interference studies?

Answer 15

Allow stronger inference about necessity of a brain region
Have issues such as plasticity and reorganisation of function

Question 16

What are the advantages of recording studies?

Answer 16

Recording studies allow for greater flexibility in experimental design and are often richer source of data
Sample across multiple brain regions with high spatial resolution
Sample at very high temporal resolution

Question 17

Why is converging evidence important?

Answer 17

Strong theories are supported by converging evidence from multiple techniques
Comparing results from different techniques can reveal the limitations in a theory
Or sometimes reveal room for improvement in applying analytical techniques to recorded data

Question 18

What is temporal resolution?

Answer 18

Accuracy that you can measure when something is occurring
Effects of brain damage are permanent so this has no temporal resolution
Methods with temporal resolution - EEG, MEG, TMS, fMRI

Question 19

What is spatial resolution?

Answer 19

Accuracy with which one can measure where an event is occurring
At the level of a neuron rather than a lesion

Question 20

How can biological measures provide an alternative source of evidence for cognitive theory?

Answer 20

Brain and biological factors must provide constraining factors on the nature and development of the information-processing models of cognitive science

Question 21

What is domain specificity?

Answer 21

Cognitive process (or brain region) is dedicated solely to one particular type of information (e.g. words, faces)

Question 22

What is modularity?

Answer 22

Notion that certain cognitive processes (or regions of the brain) are restricted to the type of information they process

Question 23

What are the different causes of brain damage?

Answer 23

Surgery, Tumour, Stroke, Traumatic brain injury, Neurodegeneration (more general damage - e.g. dementia/Parkinson’s)

Question 24

How do we use data from people with brain damage to develop theories about brain and cognition? (Give a few common examples)

Answer 24

Phineas Gage → Behaviour and planning
Broca → Language (case study of Tan)
HM → Memory
Patient DF → CO poisoning showed dissociation - Impacted vision

Question 25

What is classical neuropsychology?

Answer 25

Mapping brain areas to cognitive functions
Typically performed at a group level
Group studies → Performance of different patients is combined to yield a group average
Good at answering clinical questions

Question 26

What is cognitive neuropsychology?

Answer 26

Determining whether functions dissociate under damage → Evidence for distinct cognitive processes
Often relying heavily on single-case studies
Single-case studies → Data from different patients are not combined
Focus on cognitive processes
Doesn’t require information on where the damage is

Question 27

What is a single dissociation?

Answer 27

A situation in which a patient is impaired on one task but relatively spared on another

Question 28

How would a single dissociation approach the question - Do we use different cognitive/neural systems to process nonwords vs irregular words? (Example)

Answer 28

Patient X has a reading impairment & ability to read irregular words = impaired but nonwords = spared
Inferences
X has damage to a neural system that is important for irregular words but not for non words
Reading irregular words requires a different cognitive/neural system
If both words were impacted both types of reading could rely on the same system and damage to this system would affect irregular words more
Need more than one patient to prove they are separate systems

Question 29

What is a task-resource artifact?

Answer 29

(Shallice, 1988) → If two tasks share the same neural/cognitive resource but one task uses it more, then damaged to this resource will affect one task more than the other

Can be discounted if you have a double dissociation

Question 30

What is task-demand artifact?

Answer 30

Shallice , 1988 –> One task is performed worse than another because the task is performed sub-optimally (but not because some aspect of the task is compromised)

Can be minimised by assessing the patient’s general intellectual functioning, giving clearer instructions, using ecological tests

Question 31

What is double dissociation?

Answer 31

Two single dissociations that may have complementary profile abilities

Question 32

How would double dissociation approach what cognitive systems are responsible for non words vs irregular words?

Answer 32

Compare patient X with patient y
He’s impaired when reading nonwords but reads irregular words normally
Can rule out task demand as an explanation
Damage to different neural systems can selectively impair either irregular word OR nonword reading

Question 33

What is a criticism of double dissociation?

Answer 33

Reliance on double dissociation is flawed as it requires the study of “pure” cases
Shallice (1979) - Contradicts this as “pure” cases is up for debate - processes like memory and writing are independent so studying either in isolation is plausible
Double dissociation is just one of the methods considered by neuroscience

Question 34

What are associations?

Answer 34

A mental connection between concepts, events, or mental states

E.g. We’ve found loads of patients who are as equally good at reading nonwords and irregular words

Question 35

Does an association undermine a dissociation in X and Y?

Answer 35

Not necessarily
- These patients may have damaged another neural system that is
necessary for both types
- They may have damaged two different systems that are close to each other in the brain

Traditional view that dissociations are more informative than associations

They don’t allow you to make either or arguments

Question 36

What is the difference between a single case study (cognitive neuropsychology) and group studies (classical neuropsychology)?

Answer 36

Group studies → Performance of different patients is combined to yield a group average

Single-case studies → Data from different patients are not combined

Question 37

What are the three assumptions in single-case research? Caramazza (1986)

Answer 37

Fractionation assumption → Brain damage can selectively affect different cognitive/neural systems (neural specialisation)

Transparency assumption → Brain lesions can affect existing cognitive systems but do not create new systems (what about neural plasticity?)

Universality assumption → All cognitive systems are basically the identical (what about individual differences in how people perform different cognitive operations?)

Question 38

How did Kosslyn and Van Kleek (1990) criticise the fractionation assumption?

Answer 38

Whether cognitive impairments will be observed (fractionation assumption) depends on the neural architecture

Selective deficits may be more likely if neurons performing an operation are clustered together

Question 39

What are the issues with transparency assumption?

Answer 39

Issue that you need to assume that brain damage removes one component of cognition but does not create a rearranged or different cognitive system - Neural plasticity after brain damage in children - creates new systems
Less likely to be violated in adult cases than child cases

Question 40

What is the criticism of the universality assumption?

Answer 40

Assuming that individuals are representative of population to make generalisations to normal cognition

Question 41

What did Caplan (1988) say about individual differences and single-case studies?

Answer 41

Individual differences are more of a problem for single-case studies relative to other methods because this method gives exaggerated importance to exceptional findings

Question 42

How can variation in cognitive abilities impact inferences in neuropsychology in how we read?

Answer 42

Dissociations between nonwords and irregular words show two different systems
For nonwords, use knowledge of english orthography to map letters directly to sounds
Doesn’t work for irregular words (e.g. yacht) - must rely on some other information about the pronunciation of that specific word (something that has been debated by psychologists for 30 years)

Dual route models of reading

Question 43

What are the dual route models of reading?

Answer 43

Connectionist “triangle” model - To read irregular words correctly, we have to activate their meanings (semantic reading)

Dual-route cascaded model - To read irregular words correctly, we do not have to activate their meanings (use lexical representation instead)

Question 44

What did Woollams et al. (2007) find about irregular reading and semantic knowledge?

Answer 44

100 observations in semantic dementia
Impaired semantic knowledge of word meanings
Poor irregular word reading
Suggests that semantic knowledge is necessary to pronounce irregular words correctly
BUT - what if parents have damage to separate semantic and lexical systems that are close to each other in the brain?

Question 45

What is an example of single-case dissociation between irregular reading and semantic knowledge?

Answer 45

Patient EM (Blazley et al. 2005)
Impaired semantic knowledge
Spared irregular word reading
Suggests semantics is not necessary
Can this clear dissociation, in a single individual, overturn the association seen in 100 patients?

Question 46

How did Woollams et al. dispute the claim that patient EM showed about semantic knowledge and irregular word reading?

Answer 46

Woollams et al. argued occasional single cases did not invalidate their theory
Claimed that although in general semantic knowledge is needed to read irregular words, there were individual differences in how much people rely on the semantic route
Some people are so skilled at reading that they can read irregular words without needing the semantic system
Perhaps Patient EM is one of those people
(By the way, Patient EM worked as a secretary, so might have been used to converting spoken to written words without thinking about their meaning)

Question 47

What did Coltheart et al. say about Woollams trying to discount patient EM?

Answer 47

Coltheart et al.’s counter-argument: this is a post-hoc explanation applied to patients who don’t fit the predictions of the “semantic” model
Not good enough - the theory needs to predict in advance who should show a dissociation and who should show an association
This illustrates a potential problem with single-case studies: lesions may affect different people in different ways, if their cognitive systems were different to begin with

Question 48

Why are single-case studies important?

Answer 48

Single-case neuropsychological studies provide some of the most well-known and influential data in psychology

They can provide revealing insights into cognition, triggering new lines of research

Question 49

What is the issue with dissociation logic in single-case studies?

Answer 49

But the dissociation logic overlooks the possibility of individual differences in cognitive and neural architectures
Conclusions are stronger if supported by other data
More patients who show the same (and the reverse) dissociation
Converging evidence from other techniques

Question 50

What are the arguments in favour of single-case studies?

Answer 50

Caramazza and McCloskey (1988) →Suggest the single case study is the onlt acceptable method in cognitive neuropsychology

Argued that even in a group study, each person should be seen as a single-case and examined that way - Nothing more earned by averaging out - not equivalent

Establishing on a case by case basis whether a patient is impaired on a given task and then determining of lesion location

Question 51

What are some objections to single-case studies?

Answer 51

One cannot create a theory based on observations from a single-case/ possible to generalise theories
Theories in neuropsychology - must account from brain damaged and healthy brains

Question 52

What are the different ways of grouping patients in group studies?

Answer 52

Grouping by syndrome → patients assigned by possessing a cluster of different systems

Grouping by cognitive system → Patients are assigned to a particular group on the basis of possessing one particular symptom (made possible by MRIs etc.)

Grouping by anatomical lesion → Patients are selected on the basis of having a lesion to a particular anatomical region (may have been identified as interesting by previous functional imaging studies) - Patient may have damage elsewhere

Question 53

What is the benefit of grouping by syndrome?

Answer 53

Syndrome based approach is more likely to offer a more coarse level of analysis and appropriate for understanding the neural correlates

Advantage of working forward from a symptom to a lesion location is that is could potentially reveal more that one region as being critically involved

Question 54

What are the caveats and complications of lesion-deficit studies?

Answer 54

Can structural imaging techniques identify lesions correctly
Inferences drawn from lesion-deficit associations can lapse into neo phrenology if not articulated properly
Damasio and Damasio (1989) → Discuss how types of neuropathology are more suited to lesion-deficit analysis than others
Reliable lesion images are best obtained three month after onset when the neuropsychology testing is carried out at a similar time
Diaschisis → A discrete brain lesion can disrupt the functioning of distant brain regions that are structurally intact

Question 55

What is the difference between Transcranial magnetic stimulation (TMS) and Transcranial direct current stimulation (tDCS)?

Answer 55

Transcranial magnetic stimulation (TMS) → Non-invasive stimulation of the brain caused by a rapidly changing electrical current in a coil held over a scalp

More recent method =
Transcranial direct current stimulation (tDCS) → Non-invasive stimulation of the brain caused by the passing of a weak electrical current through it
Can temporarily disrupt cognitive function but can also boost cognitive function which is important for rehabilitation

Question 56

What are the main methods for studying the brain activity of animals?

Answer 56

Single-cell recordings and lesion methods are the main methods used in non-humans

Question 57

What are the methods for producing experimental lesions in animals (Murray & Baxter, 2006)?

Answer 57

Aspiration → Aspirating brain regions using a suction device and applying a strong current at the end of an electrode to seal the wound - Damage both gray matter and underlying white matter

Transection → Cutting of discrete white matter bundles such as the corpus callosum

Neurochemical lesions → Certain toxins are taken up by selective neurotransmitter systems and once inside the cell, create chemical reactions that kill it

Reversible “lesions” → Pharmacological manipulations can sometimes produce reversible functional lesions

Heimer and Robards (1981) → Injection enzyme into axons acts a visible tracer so post mortem, tracer can be visualised, showing which regions project to a given region

Question 58

What are the disadvantages of using animals in research?

Answer 58

Welfare of animals
Researchers must justify the number of animals used & have a careful breeding program to avoid having to catch animals in the wild
Give animals adequate space and social contact

Question 59

What are representations?

Answer 59

Properties of the world that are manifested in cognitive systems (mental representation) and neural systems (neural representation)

Question 60

What is neural representation?

Answer 60

Neurons communicate with each other by
Receiving electrical potentials (excitatory or inhibitory) from other neurons
Once a threshold for excitation is surpassed, an action potential propagates along the axon
This triggers the release of neurotransmitters at the synapses with other neurons

Sometimes happens by the synchronisation of firing

Question 61

How is a mental representation different to a neural representation?

Answer 61

A mental representation is encoded (i.e processes information) into a neural representation – but they are not the same!
Mental representation vs neural representation
Mental representation is unlikely to have a one to one relationship with the response properties of a single-neuron

Question 62

How do you measure neural representations?

Answer 62

Measure by single cell or multi cell recordings

Both might depend on sparse and distributed coding - several neurons might be required to represent a stimulus

Triggering of an action potential is often called firing or spiking
In non-human animals, often measure the firing rates of individual neurons with single-cell recording

In humans, often measure the summed activity of large populations with EEG and MEG (hard to know where it’s coming from)

In humans recordings are possible but very rare and only done when electrodes are implanted for a medical purpose

Question 63

What did Rolls and Deco (2002) find about different types of representation at neural level?

Answer 63

Distinguish between three different types of representation that may be found at the neural level

Local representation → All the information about a stimulus/event is carried in one of the neurons (grandmother cell)

Fully distributed representation → All the information about a stimulus/event is carried in all the neurons of a given population

Sparse distributed representation → A distributed representation in which a small proportion of the neurons carry information about a stimulus/even

Question 64

What are single-cell recordings in animals?

Answer 64

Single-cell recordings or single-unit recordings → Measure the responsiveness of a neuron to a given stimulus (in terms of action potentials per second)

Electrodes are surgically implanted in the brains off experimental animals
Normally rodents or non-human primates

Can monitor firing rates of neurons when the animal perceives different stimuli
Provides information on how and where different classes of stimulus are coded on the brain

Question 65

How are single-cell recordings obtained?

Answer 65

Action potential is directly measured by placing a very small electrode into the neuron (intracellular recording) or outside the membrane (extracellular recording) & counting the number of times the action potential is produced in response to a stimulus
Invasive method

Electrodes implanted during full anaesthesia

Extracellular recordings are the norm in the mammalian brain due to the small size of neurons (occasionally done during brain surgery)

Question 66

Why can’t a single-cell recording be done non-invasively?

Answer 66

Impossible to measure action potential from a single-neuron non-invasively as signal is too weak and the noise from other neurons is too high

Multi-cell recordings may occur - Pick up on activity from nearby neurons → Electrical activity of many individual recorded neurons recorded at one or more electrodes

Special algorithms can then be applied to separate the combined signal into individual contributions for different neurons

Question 67

What did Hubel and Weisel find when mapping the feline visual system?

Answer 67

Single-cell recording in cats = Instrumental in mapping organisation of the visual cortex

Initially discovered by accident:
Hubel and Weisel found that certain neurons in primary visual cortex fired strongly when cat saw a straight line caused by a projector fault
Story is apparently that H&W were using a slide projector to show slides of dot stimuli. A slide got stuck so the dark edge of it was on the screen and that’s when the neuron started firing.

Discover that in primary visual cortex are attuned to a particular orientation to be activated and then complex cells that take information from simple cell to respond from a larger area of the visual field - making the receptive field larger

Question 68

What is selectivity?

Answer 68

Specific neurons respond to particular types of visual stimulus

Question 69

What is hierarchical organisation?

Answer 69

Higher-level neurons respond to increasingly complex stimuli
Measurement of individual’s neuron responses was critical for developing this model

Question 70

What is the grandmother cell hypothesis?

Answer 70

Hubel and Wiesel (1959) - Visual perception is hierarchical

Starts from from basic visual elements (patches of light and dark)

Combine into more complex elements (e.g. shapes)

Grandmother cell → A hypothetical neuron that just responds to one particular stimulus

Question 71

How does the idea of sparse and distributed coding fit into the grandmother cell hypothesis?

Answer 71

Logical continuation of this hierarchical model is that neurons at top of hierarchy only respond to one specific stimulus

Sparse Coding - If you had so many highly specialised cells - what if one got damaged - would you not be able to recognise relatives (code becomes sparse - very selective rather than general)

Distributed coding - Certain cells might code for particular features and when they all fire it relates to a representation (e.g. that you’re looking at your Nan)
Idea has been tested with respect to perception of faces and people

Question 72

What are the advantages of distributed and sparse coding?

Answer 72

The sparseness of coding conserves energy and may enable the brain to have a high memory capacity

Distributed representation may protect against information loss if synapses of neurons are lost

May allow the cognitive system to generalise and categorise (e.g. a novel stimulus that resembles a stored representation would partially activate this representation)

Question 73

What has been found about face-selective neurons in primates? (Support grandmother hypothesis?)

Answer 73

Electrodes implanted in inferotemporal cortex

Spiking represented by auditory clicks
View-invariant, sparse coding neuron (responds to a single identity)

Chang and Tsao (2017) - Showed video of images of multiple people - neurons fire when recognise face that they were asked to study beforehand

Question 74

What did Quiroga et al. (2005) find in a single-cell study among humans? (support for grandmother hypothesis?)

Answer 74

Jennifer Aniston cell → There was a cell that just reacted to the face of Jennifer Aniston

Sydney Opera House → Neuron specifically gets triggered at Sydney Opera House picture or mention

Question 75

What was Bayliss et al. (1985) study that contradicted the idea of a grandmother cell?

Answer 75

Neurons on the temporal cortex of monkeys responded to several different faces (from a set of five) but to slightly different degrees - Contradicts idea of grandmother cell

Question 76

What did Perrett et al. (1992) find? (Contradict grandmother cell?)

Answer 76

Activity of neuron when shown shown four different views of faces = Compared with spontaneous activity where no face is shown

The two stimuli that elicit the strongest response (head down and head forward with eyes down) are not related physically but conceptually

Coding of gaze direction may be involved in interpreting social cues (e.g. eye contact is perceived as a threat)

Question 77

Are there actually grandmother cells?

Answer 77

Studies in primates (and occasionally humans) have found neurons that fire selectively for a small number of faces - quite semantic

But hard to say whether they’re truly specific for a single individual, as the grandmother cell hypothesis predicts

A truly local code, with one neuron for each person you know, seems implausible
Wouldn’t be very robust to damage

But these data suggests a sparse distributed code might be used:
A particular face causes firing across a specific set of neurons

Question 78

What are the different ways that information can be represented in neurons?

Answer 78

Information is represented in neurons by response rates to a given stimulus or event sometimes by the synchronisation of their firing

Question 79

What is electroencephalography? (EEG)

Answer 79

Measurements of electrical signals generated by the brain through electrodes placed on different points on the scalp

Changes in electrical signal = Conducted instantaneously = Good for temporal resolution

Direct neural recording may provide more fine-grained information but is rarely possible in humans

But we can place electrodes on the scalp and record changes in electrical potentials caused by neural firing in the brain

These potentials are tiny – around 2-10 microvolts

They are also a combined response of large numbers of neurons

To generate a measurable response, a very large number of neurons have to fire at the same time

In the case of epilepsy – implanted electrodes around the part of the brain involved in seizures, but problem is that this tissue may be abnormal and thus the neural activity may not be typical for healthy people

Can be impacted by factors such as having a thick skull - shields signals to an extent

Question 80

How does an EEG work? Requirements?

Answer 80

EEG signal originates in the postsynaptic dendritic currents than the axonal currents associated with action potential

Harmless - non-invasive and involves stimulation

Requirements
- Whole population of neurons must be active in synchrony to generate a large enough electrical field
- Population of neurons must be aligned in parallel orientation so that they summate rather than cancel out (already this way in cerebral cortex)

Thalamus is impossible to record due to orientation of the neurons

To gain an EEG measure = compare voltage between two or more different sites

Reference site is chosen (one that is likely to be uninfluenced by the IV)

Activity recorded at each location cannot necessarily be attributed to neural activity near to that region

Electrical activity in one location can be detected at distant locations

Question 81

What are rhythmic oscillations in EEG signal?

Answer 81

EEG signals oscillate at different rates (e.g. alpha waves, gamma waves represent different frequencies)

Oscillations arise as large groups of neurons are in temporal synchrony in firing

Different rates of oscillation characterise different phases of the sleep/wake cycle

Increases in the alpha (so neurons more synchronised in 7 to 14 Hz band) → Linked to increased to attention and the filtering of irrelevant information

Increases in the gamma band have been linked to perceptual integration of parts into wholes (important for object recognition)

Rodriguez et al. 1999 → found that increase gamma synchronisation was linked to face perception

Synchronisation or desynchronization of alpha, gamma are linked to a wide range of cognitive functions - shows synchronisation of brain activity has its own role

Question 82

Does an EEG have good spatial resolution?

Answer 82

EEG has poor spatial resolution - should use fMRI instead
Studies use 32 or 64 electrodes placed in a standard configuration over the participants head
You’d think this would give us good information about where in the brain signals are generated
But in practice, the electrical signal is conducted through the skull, so its source may be distant from the electrode where it is measured
So, EEG is most useful for when (temporal) neural activity occurs than where

Question 83

What do EEG signals have to compete with?

Answer 83

EEG signals have to compete with many sources of noise (as measuring tiny electrical signals)
Random, spontaneous neural firing
Electrical activity from movements of the eye and facial muscles
Interference from nearby electrical equipment
The signal-to-noise ratio from a single experimental event (trial) is poor - deal with this by averaging measurements over a large number of trials

Question 84

What is an event-related potential (ERP)?

Answer 84

The average amount of change in voltage at the scalp that are linked to the timing of particular cognitive events e.g. stimulus and response)

Different types of stimuli tend to produce characteristic ERPs at different points in time

These are generally given names that reflect their polarity and timing (N170, P600, N400 etc.) and sometimes also the location of electrodes on which they are observed (N2pc)

Some peaks are positive and some negative, but this doesn’t tell us anything about their cognitive significance – polarity depends on spatial arrangement of neurons generating the activity

Question 85

What is the method of ERP?

Answer 85

Links the amount of change in voltage at the scale with a particular cognitive events

ERP is similar to other cognitive psychology methods such as reaction time - e.g. can see how many milliseconds it takes to read HOUSE vs HoUsE - takes longer for mixed case (Mayall et al. 1997)

Signal to noise ratio in a single trial of EEG is very low (signal is the electrical response to the event

There are positive and negative peaks - Doesn’t reflect excitation etc but the spatial arrangement of the neurons that give rise to the signal at the time

Dipole → A pair of positive and negative electrical charges separated by a small distance
Dipoles from different neurons and different regions summate and conduct to the skull - create peaks and troughs in the ERP

Question 86

What is the practical issue of EEG/ERP?

Answer 86

Avoiding interference from eye movement
Ask PPT to blink after task or withhold from blinking - Although causes secondary task of trying not to blink

Question 87

How do ERPs track timing?

Answer 87

ERPs are often used to track the time course of cognitive processes involved in a task
Components at different points in time may be influenced by different factors
We can see how this plays out in some basic stages of face processing
Perception – is this a face or not?
Recognition – is this a face I saw before?
Person Identity – who is this person and what do I know about them?

Question 88

How does ERP measure timing in the process of facial recognition?

Answer 88

1. Perceptual coding of the face

Rousselet et al. 2004 –> N170 affected by perceptual changes to the image (larger for human and animal faces, compared with other objects

2. Face recognition (identity processing)

Herzmann et al. (2004) –> N250 is larger for familiar faces than unfamiliar

3. Person recognition (faces and names)

Schweinberger et al. (2002) –> P400 -P600 impacted by faces and names

Question 89

What is associative priming?

Answer 89

Reaction times are faster to a stimulus if it’s preceded by a stimulus that co-occurs with the environment (e.g. context related)

Question 90

What is transcranial magnetic stimulation (TMS)?

Answer 90

TMS is a noninvasive technological breakthrough that involves applying a series of short magnetic pulses to stimulate nerve cells in areas of brain

Stimulation temporarily interferes with ongoing cognitive activity in that region and, therefore, provides information about the necessity of that region for performing the task. This has been termed a “virtual lesion.”

Effect is small - Alter reaction time profiles rather than elicit an overt behaviour
TMS works by virtue of electromagnetic induction

A change in electric current in a wire (simulating coil) generates a magnetic field
Greater the rate of change in electric current, the greater the magnetic field
Induced electric current in the neurons is caused by making them fire

TMS causes neurons underneath stimulation site to be activated
Neurons are internally (task demands themselves) and externally activated (TMS)

Question 91

What are the practical aspects of using TMS?

Answer 91

Three main experiments:
When to deliver the pulses
Where to deliver the pulse
Selection of appropriate control conditions

Timing issues - TMS studies of perceptual processes have often used a single-pulse designs whereas studies of “higher”cognition have often used rTMS

Question 92

Why might TMS be better than organic lesions as a study method ?

Answer 92

No reorganisation/compensation

Determine timing of cognition

Lesion is focal

Lesion can be moved within the same participant

Can study functional integration

Question 93

Why might organic lesions be a better study method than TMS?

Answer 93

Subcortical lesions can be studied

Lesions can be accurately localized with MRI

Changes in behaviour/cognition are more apparent

Question 94

What is Transcranial direct current stimulation (tDCS)?

Answer 94

Non-invasive stimulation of the brain caused by the passing of a weak electrical current through it (more modern version of TMS)

Can temporarily disrupt cognitive function but can also boost cognitive function which is important for rehabilitation

Transcranial direct current stimulation (tDCS) has a poorer temporal and spatial resolution to TMS, but has the advantage of being able to facilitate cognitive function (anodal tDCS).

Question 95

What do all methods of studying the brain have in common?

Answer 95

All these methods converge on how cognitive processes are carried out by the brain (the when and where that each method communicates is contributing to the how)

Question 96

What is mental chronometry?

Answer 96

Mental chronometry → Study of the time course of information processing in the human nervous system (Posner, 1978)

Changes in nature or efficiency of information processing will manifest themselves in the time it takes to complete a task - e.g. Difference in reaction times can tell us information about processing

Question 97

What is an example of mental chronometry and reaction times?

Answer 97

Sternberg (1969) → Additive factor Approach → Developed a general method for dividing reaction times into different stages
E.g. In his study of WM he decided the task could be split into separate stages -
Encoding, comparing, decision, responding
Postulated that each of these stages could be independently influenced by different factors affecting the task
This method - Could take an unknown factor and determine whether it has an interactive effect on stimulus perceptibility

Question 98

What is magnetoencephalography (MEG)?

Answer 98

Non-invasive method for recording magnetic fields generated by the brain and the scalp

Same basic principle of EEG but signals are measured by SQUID sensors that record fluctuations in the magnetic field when neurons communicate (as magnetic field and electric fields are somewhat complementary)

Pros: Same temporal resolution as EEG with better spatial resolution & localisation (but only those more close to the surface)

Cons: Not so widely available and expensive, difficult to install

Question 99

How does MEG compare to EEG/ERP?

Answer 99

MEG vs EEG/ERP

• Signal unaffected by skull vs signal affected by skull
• Poor at detecting deep dipoles vs detects deep and shallow dipoles
• More sensitive to activity at sulci vs sensitive to gyri and sulci activity
• Millisecond temporal resolution for both
• Potentially good spatial resolution vs poor spatial resolution
• Expensive and limited availability vs cheaper and widely available