Neuroscience

Question 1

what did psychologists learn from the case of phinneas gage

Answer 1

damage to frontal lobe lead to major selective changes

showed psychologists specific areas = specific functions

Question 2

why do we study the brain

Answer 2

knowing when + where cognitive processes occur helps us understand them
understanding and treating neurological disorders
create therapies

Question 3

how do we measure language when and where

Answer 3

event related potential info in graph

e.g hear unexpected word 400 ms later get the N400 which helps us understand how prediction works in language.

Question 4

what is the aim of cognitive neuroscience in clinical practice

Answer 4

understand neural basis of behaviour = understanding cognitive disorders and predict effects of damage in brain
basic understanding of neural processes can have unanticipated applications

Question 5

how can vegetative state patients use fmri

Answer 5

they are not thought to be able to respond to their environment, are they conscious? The idea is they cant respond to their environment. But this study asked them to do tasks such as imagining walking around their house, they recorded activated regions of the brain similar to those of healthy objects. They got them to do different tasks as a response for yes or no. showed using fmri can communicate with patients in a vegetative state, not all patients responding this way but some responded reliably. Revolutionary study allowed them to communicate when they couldn’t through physical action. Clinical application that came out of this science.

Question 6

when designing an experiment to investigate neural activity how can we do it

Answer 6

change behaviour and measure effect on brain - stroop test ask them to read the word then to say the colour

change state of the brain and measure the effect on behaviour - make temporary lesion then look at effect on behaviour

Question 7

describe a recording study

Answer 7

manipulate the brain and record whats goin on in the brain. Does it get activated in the same way as when you actually do the action as to when you process the word. Desing exp give people some action words to process in some way and make a decision about it, then compare to some non action words that are similarly sounfing. Go in Fmri scanner and measure brain activation in the brain when process both types, compare the activation in the two conditions, motor cortex activated when presented with action words

Question 8

what are the results from the recording study on action words

Answer 8

reading action words is correlated with greater activity in motor cortex

inference when people process an action word they simulate the action and this helps them understand the word

Question 9

how do we determine if the activation is necessary for the comprehension of the words.  

Answer 9

an interference study
determine if activity is optional or part of the comprehension process. Manipulate the status of the brain compare people with damage to motor cortex to people without damage to the motor cortex as controls. Observe behaviour of patients performing the task, same paradigm same material, might find the results above. Control for alternative explanations, make sure its action words not all words. etc

Question 10

what can we conclude from an interference study

Answer 10

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 no other diff between groups that could have caused it

Question 11

IV, DV causality for recording vs interference methods

Answer 11

Recording:
Iv = behaviour or cog process
DV = brain activity - EEG/MEG blood flow
causality = correlational

Inference:
IV = brain damage lesion or brain stimulation
DV = behaviour or cog process
permits causal interference

Question 12

strength and limitation of interference studies

Answer 12

strengths = allow stronger inference about necessity of a brain region

limitations = plasticity and reorganisation

Question 13

strengths and weaknesses of recording studies

Answer 13

greater flexibility in experimental design often richer source of data

sample across whole brain with high spatial resolution
sample at high temporal resolution

Question 14

is converging evidence from different types of measurement viable

Answer 14

strong theories are supported by converging evidence from multiple techniques
comparing results from diff types can also reveal limitations in the theory
or in the method being used

Question 15

causes of brain damage from selective to diffuse

Answer 15

surgery
brain tumour
stroke
traumatic brain injury 
neurodegeneration

Question 16

describe in more detail the causes of brain damage

Answer 16

surgery - remove specific part of the cortex to prevent seizures.
tumour - grows and damages the tissue around it.
stroke - damages the blood supply to the brain blocked or haemorrhagic stroke where the wall of the blood vessel bursts and leaks so blood doesnt get to the brain and therefore cells die
traumatic brain injury - cu = initial place of impact and contra cu is the site of impact after the brain has moved in the skull.
neurodegeneration = diseases e.g alzheimers slowly damage brain functioning

Question 17

what are the two approaches to neuropsychology

Answer 17

classical - mapping brain areas to cog functions
performed at group level typically
good at answering clinical questions

cognitive neuropsychology = determining whether functions dissociate under damage - evidence for distinct cognitive processes
rely heavily on single case studies
focus on cog processes
doesnt require info about where the damage is

Question 18

difference between reading non words and irregular words

Answer 18

Read non words due to knowledge of alphabet sounds. Irregular don’t follow usual letter sound rules but are real words. Does brain use two diff systems whne reading diff types of words. Look at a dissociation in a single patient to start with.

Question 19

how do we build a single dissociation for non words and irregular words

Answer 19

patient x reading impairment of irregular words, can read non words
inferences - x has damaged a neural system responsible for reading irregular words but not nonwords
reading irregular words requires a different cognitive system to reading non words

Question 20

what is the problem with a single dissociation

Answer 20

what if they are in the same cognitive system but reading irregular words is just harder

Question 21

how to tackle the problem with a single dissociation

Answer 21

do a double dissociation - compare x with y who has impaired non words reading but intact irregular word reading
rule out task demand as an explanation
damage to diff neural systems can selectively impair either irregular word or non word reading

Question 22

does finding patients that are equally bad at non words as they are irregular words does this undermine the double dissociation

Answer 22

not necessarily because these patients may have damaged another neural system that is necessary for both types
or damaged two different systems that are close to each other in the brain

Question 23

what are the assumptions applied to a single case research

Answer 23

fractionation - brain damage can selectively affect different cog/neural systems

transparency - brain lesions can affect existing cognitive systems but do not create new systems

universality - all cognitive systems are basically rhe same

Question 24

what are the issues with the assumptions

Answer 24

fractionation - neural specialisation can occur and is a basic principle in cognitive neuroscience
transparency - existing systems can be reconfigure due to neural plasticity
universality - individual differences in how people perform different cognitive operations

Question 25

how are individual differneces applied to neuroscience

Answer 25

people vary in cog abilities and the strategies they use to solve problems same brain damage can affect people differently

Question 26

what have psychologists interested in the reading domain investigated for years

Answer 26

non words - use knowledge of orthography - rules of english | irregular words this doesnt work - how do we read irregular words is debated

Question 27

what are the two models of reading that have developed from the debate about irregular words

Answer 27

connectionist triangle model | dual route cascaded model

Question 28

describe the connectionist triangle model

Answer 28

to read irregular words correctly we have to activate their meanings for the correct pronunciation meanings are semantic

Question 29

describe the dual route cascaded model

Answer 29

to read irregular words we dont have to activate meaning we use lexical representations instead. this means a mental dictionary remembers that the letter form is pronounced a certain way and is separate from meaning

Question 30

is there evidence against the connectionist model

Answer 30

there is a single dissociation between irregular reading and semantic knowledge -patient EM impaired semantic knowledge spared irregular word reading suggests semantics not necessary but is this enough

Question 31

what is the alternative explanation to the evidence against the connectionist model

Answer 31

woollams et al. argued that occasional single cases did not invalidate theory claimed that although semantic knowledge is needed in irregular words there were ind diff in how much people rely on the semantic route some are skilled at reading dont need semantic system em could be one of them as she was a secretary

Question 32

is there evidence for the connectionist model

Answer 32

woollams et al - discovered strong association between irregular reading and semantic knowledge 100 obs in semantic dementia poor irregular word reading suggests semantics needed but what if patients have damage to separate semantic and lexical systems that are close to each other

Question 33

who criticised woollams explanation for the single dissociation

Answer 33

coltheart et al argued it was a post hoc explanation applied to patients who dont fit the semantic model not good enough - theory needs to predict in advance who will show an association and who will show a dissociation illustrates issue with single case studies \individual diff clouding the view, cant see how exactly the cognitive system has changed.

Question 34

if a patient has a cog deficit and damage in a particular brain area can we infer that region is the only one necessary for the cognitive def

Answer 34

no - two problems with this | specificity of behaviour and specificity of the lesion

Question 35

explain the problem of specificity of the behaviour

Answer 35

rarely a 1:1 mapping between cognitive abilities and brain areas most abilities involve multiple processes supported by a network of brain regions to link damage to a particular cognitive process we need to assess how specific the behavioural deficit is

Question 36

explain the problem of specificity of the lesion

Answer 36

Brain lesions not always very specific can include multiple areas and need to map the brain lesions.

Question 37

are lesions specific or random

Answer 37

neither - Stroke and middle cerebral artery results in interruption of blood supply which supplies a lot of areas in the frontal and temporal lobe, lots of damage in diff areas. Set of areas compromised, referred to as perisylvian cortex as its near the perisylvian fissure. how do we tackle this - Move away from single case to larger groups of patients so can study relationships between them and look at statistical significance between the damage and behaviour.

Question 38

how do we tackle lesions being neither specific nor random

Answer 38

Move away from single case to larger groups of patients so can study relationships between them and look at statistical significance between the damage and behaviour.

Question 39

how do we map lesion symptoms

Answer 39

acquire structural scans of patients - 50 or more, identify areas and then combine them to make the lesions overlap. Automated algorithms can look over the scans and identify the areas of damage. Individual brain lesions over the top of each other on a brain map. can then identify areas of high overlap red = more overlap

Question 40

what area were lesions mapped to study reading

Answer 40

poor irregular word reading correlated with amount of damage to the anterior temporal lobe

Question 41

what does symptom-lesion mapping tell us

Answer 41

important clinical information about what deficits are likely to result from particular areas of damage info on which cog processes are associated with which area - develop brain theories of organisation - also for cognitive level theories in this case association of anterior temporal damage with both irregular word reading and semantics supports the claim that these are related cog processes

Question 42

what are the limits of natural lesions

Answer 42

limited to between subject designs - always compare people with/without lesion to particular area assume behavioural differences are due to the lesion but cant guarantee this people vary before lesion too damage frequently extends across multiple areas of the brain possibility of reorganisation with longstanding conditions

Question 43

what is transcranial magnetic stimulation and what does it do

Answer 43

technique for temporarily disrupting neural activity in healthy ppt allows for small area of cortex to be disrupted through application of a rapidly changing magnetic field. Measure effects of disruption on cogn processes

Question 44

how does transcranial magnetic stimulation work

Answer 44

based on electromagnetic induction alternating current passed through coil and creates a rapidly changing magnetic field which will induce a current in a nearby coil - the brain is the second coil in this system as the magnetic field induces current in underlying brain tissue - neurons communicate less efficiently as the electricity interferes with the natural electricity neurons use

Question 45

how is transcranial magnetic stimulation set up in the lab

Answer 45

Typical lab has coil over head with infrared camera to track location of coil and location of head so the stimulation goes to the correct part of the brain.

Question 46

what can be done with Transcranial magnetic stimulation

Answer 46

Small areas of brain tissue, choose where it is = advantage over the natural lesion. Can decide precisely where in the brain to investigate. Within subject design allows us to deal with individual differences as they have healthy brains can change many different areas. No changes to system due to plasticity after damage either.

Question 47

how does a typical transcranial Magnetic Stimulation study go with the stroop test example

Answer 47

Baseline results from the stroop task prior to stimulation. Give stimulation, 1-10 mins used to give stimulation Then 10-15 mins where function is slightly impaired, which gradually wears off during this time. During this time give them the task again Compare the two performances. After stimulation they tend to get slower or get more things wrong

Question 48

what if transcranial magnetic stimulation has a general effect

Answer 48

worsened performance may have been inferred as lesion being responsible but the stimulation may have a general effect maybe people are distracted or anxious before and perform better after placebo effect may also cause someone to perform worse after

Question 49

how can we use a control condition for removing the overall effects of the magnetic stimulation

Answer 49

control site - stimulate a region we arent interested in AND/OR use an additional task dont think is involved in the region

Question 50

an example of TMS with irregular word reading

Answer 50

Disrupting anterior temporal lobe In Japanese use kanji characters which have meaning on their own or be combined to make another word. Some words pronounced differently and is irregular. In Japanese participants. Reading after temporary lesion, impaired irregular word reading. Want to include control conditions so have a tasl to read different types of regular words before and after which wasn’t affected. Brain stimulation didn’t affect regular word reading. Want to then stimulate an area not typically linked to reading irregular words. After stimulating a different nonrelated area there was no significant difference between the performance on the task. Control conditions show the effects observed are specific to one place in the brain and to one specific task.

Question 51

how are individual differences involved in transcranial magnetic stimulation

Answer 51

studying same brain with/without lesions so ind differences can not explain the effects can select ppt with different characteristics to compare the effects of stimulation on each - woollams stimulated ATL with irregular word reading on people who relied heavily on semantic meaning and those who didnt

Question 52

what are the limits of transcranial magnetic stimulation

Answer 52

stim only penetrates 2-3cm below the skull so deeper brain structures cant be investigated effects on cog function are very small needs careful design to test - even may be impossible to test complex ones, easiest to measure motor effects effects are transient (10-15 mins) cant study long term processing

Question 53

how do neurons communicate with each other

Answer 53

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

Question 54

how do we measure neural representations

Answer 54

triggering of an action potential is often called firing or spiking In animals, we often measure the firing rates of individual neurons with single-cell recording In humans, we often measure the summed activity of large populations of neurons with EEG and MEG

Question 55

how do we carry out single cell recordings

Answer 55

Electrodes are surgically implanted in the brains of experimental animals Typically rodents or non-human primates We can then monitor firing rates of the neurons when the animal perceives different stimuli Provides information on how and where different classes of stimulus are coded in the brain

Question 56

how did single cell recording in cats map their visual system

Answer 56

discovered by Hubel and Weisel who found that certain neurons in primary visual cortex fired strongly when cat saw a straight line caused by a projector fault

Question 57

what did they discover from the mapping of the feline visual system

Answer 57

Selectivity: specific neurons respond to particular types of visual stimulus Hierarchical organisation: Higher-level neurons respond to increasingly complex stimuli Measurement of individual neurons’ responses was critical for developing this model

Question 58

what is the grandmother cell hypothesis

Answer 58

There is one cell to represent your grandmother which fires when you see her. This idea is called sparse coding – through the hierarchy we end up with more and more sparse representations of various types of information. Distributed coding = neural representations are hierarchical but when get to the top they are not sparse and sets of neurons are capable of doing the same thing e.g recognizing grandma

Question 59

is there evidence for the grandmother cells

Answer 59

Studies in primates (and occasionally humans) have found neurons that fire selectively for a small number of faces 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 60

how does EEG electroencephalography work

Answer 60

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

Question 61

what is the issue with using EEG on people with epilepsy

Answer 61

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

Question 62

why does EEG have poor spatial resolution

Answer 62

Studies typically use 32 or 64 electrodes, placed in a standard configuration over the participant’s 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

Question 63

what is a result of EEG poor spatial resolution

Answer 63

Consequently, EEG is most useful for learning about when neural activity occurs, rather than where

Question 64

why is EEG measurements noisy

Answer 64

EEG is measuring tiny electrical signals These signals have to compete with many sources of noise Random, spontaneous neural firing Electrical activity from movements of the eye and facial muscles Interference from nearby electrical equipment This means the signal-to-noise ratio from a single experimental event (trial) is poor

Question 65

how do studies deal with noisy signals

Answer 65

by averaging measurements over a large number of trials

Question 66

what are event related potentials

Answer 66

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 67

how do you use ERP to track timing

Answer 67

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 68

for information on how to read an ERP see lecture 4

Answer 68

see slides 21-23

Question 69

how does magnetoencephalography work (MEG)

Answer 69

Same basic principle of EEG but signals are measured by SQUID sensors that record fluctuations in the magnetic field Pros: Same temporal resolution as EEG with better spatial resolution Cons: Not so widely available and £££

Question 70

what is functional neuroimaging

Answer 70

The media usually refer to it as brain scanning but as psychologists we prefer a more specific term: functional neuroimaging (of which fMRI is the most common form) Thousands of fMRI studies have been published reporting that brain regions are activated or deactivated under particular conditions

Question 71

how is the brain using oxygen and how does this relate to measurement

Answer 71

The brain uses around 20% of the body’s total supply of oxygen, delivered via the blood supply When brain regions are highly active, their metabolic demands increase and the delivery of oxygen to them increases PET and fMRI measure these changes in the blood supply and use them to make inferences about the activity of brain regions They are indirect measures of brain activity (unlike EEG/MEG)

Question 72

what is positron emission tomography (PET)

Answer 72

First technique developed to measure cerebral blood flow Participant is injected with a radioactive tracer which enters the bloodstream and flows to the brain The blood flow in a brain region is calculated by measuring the particles emitted as the tracer decays

Question 73

how does positron emission tomography (PET) work

Answer 73

Cyclotron used to make a substance that is usually normal into a radioactive version of it this is called a radioactive tracer. Inject it and it goes to the part of the brain that is currently active and using energy. Radioactive nucleus emits positrons as they decay which starts very shortly after being injected. It travels out of the nucleus and it bumps into an electron and because they are opposite they annihilate and two photons are emitted which travel in opposite directions at the same speed. The particles will get detected in the scanner and has detectors at 360 degrees around the brain, due to timings of arrival can map where the annihilation occurred and therefore where the activity originated

Question 74

what are the negatives of PET positron emission tomography

Answer 74

Participants exposed to radiation Expensive and complex to use Task has to be performed for at least a minute at a time Rarely used now in cognitive neuroscience, but still has some clinical applications

Question 75

what is magnetic resonance imaging

Answer 75

Uses strong magnetic fields to generate detailed images of soft tissue: structural MRI Can also be used to be measure changes in blood supply, allowing inferences about neural activity: functional MRI

Question 76

how are hydrogen atoms involved in magnetic resonance imaging

Answer 76

protons are a key component of atoms and they're always spinning Fmri always detecting hydrogen different tissues have different amounts of hydrogen atoms. The protons in the hydrogen atoms all spin in random directions Very powerful magnet can align the spin of the protons with the magnet so they are all aligned with the magnet

Question 77

how do we use these hydrogen protons to make an image

Answer 77

When we want to make an image, we send out a radio frequency pulse that knocks the protons out of alignment They then relax back into alignment, emitting a signal that we can measure Different tissues relax at different rates We use this information to build up an image

Question 78

how can fmri also use oxygenated and deoxygenated blood

Answer 78

Haemoglobin carries oxygen in the blood. It can be oxygenated or deoxygenated as it has already given away its oxygen to active neurons, when an area is active more oxygen flows into that area. The iron in the haemoglobin allows it to interact with the magnet in the machine and allows magnetic resonance imaging to get the response called BOLD.

Question 79

describe the BOLD response to a brief event

Answer 79

neural processing increases demand for oxygen peaking 4-6 seconds after the processing once oxygen is consumed BOLD level eventually return to baseline

Question 80

what is the issue with the BOLD response

Answer 80

slow - poorer temporal resolution than EEG

Question 81

an example of setup of an fmri study

Answer 81

Stimuli of faces and different places used. See which parts are more engaged in the two categories. All stimuli in separate blocks or mixed together. Normal to mix them together, don’t want ppt to have expectations but in fmri people use block designs because there is a slow response from the haemodynamic response being slow. Researchers were worried the slow nature would inhibit separation of the responses. To make sure they are paying attention can give a test or can just passively view. These choices determine the depth of processing and is difficult to design an fmri study.in this they are just passively viewing the picutres and see which brain regions more active.

Question 82

example of modelling a BOLD response

Answer 82

Stimuli are blocked so have five images of faces followed by 5 images of places and then it swaps again. Each set of images ilicits response from the brain in the region that processes eother faces or places. The hemodynamic reponse should correlate and can be superimposed one on top of another. Then swap to places and those areas are activated. Can separate in time when expecting to see activity to one condition compared to the others. The events are separate in time allow you to focus on each of the blocks

Question 83

how do we map the results from an experiment

Answer 83

Divide brain into different areas of volume. These are called voxels. In each voxel is one unit of measurement. One signal for each voxel. In this one shown the response fits better with the face response than the places. Can correlate the place and face responses and the voxels in the brain

Question 84

how do fmri studies work

Answer 84

The MR scanner provides data on the BOLD response in each voxel in the brain and how it changes over the course of our experiment Changes in the BOLD response indicate when neural activity has taken place To analyse the results, we create a predicted BOLD response for each of our experimental conditions We then test whether the actual BOLD signal from each voxel matches any of our predictions By repeating this process throughout the brain, we produce an image of which voxels are activated to what degree in each condition

Question 85

explain blocked vs event related designs

Answer 85

If present stimuli in blocks ppt expect stimulus to look a certain way, they perform in a strategic way and allocate different resources to perform the task, the differences between face and place response may be due to the allocation of brain activity strategically rather than the natural response of the brain. Develop a way to do an event related design to avoid this. Never know whats going to be next

Question 86

what is the issue with event related designs

Answer 86

end to have lower statistical power than block designs Spread stimuli in time a little bit allow us to do time series Give time in between for the response to go down before the next one Match up the stimulus with the peaks in the results. Each peak isn’t one stimulus it can be built on top of another making it more noisy. This means the data analysis will be more noisy as well for an event related design

Question 87

the brain is never off and neurons always require oxygen, what does this mean for BOLD responses

Answer 87

you measure the difference between the BOLD response between two conditions, fmri studies use a subtraction design to do this

Question 88

what does subtraction analysis allow us to do

Answer 88

for example Regions where the BOLD response is greater for faces compared with scenes Regions where the BOLD response is greater for scenes than for faces - This does tell us which voxels are active fitting one versus the other. Find that a certain brain area has a higher activity for one task than the other. To answer the last question need more experiments that test different things.

Question 89

why might the brain respond differently to faces vs places

Answer 89

faces - need fine discrimination for similar faces, critical info in the centre of the image, strong emotional/social component places - can identify without processing fine detail, critical info spread across the image, strong spatial component

Question 90

what is the study structure for the faces vs places

Answer 90

shown faces and have to discriminate one face from another. Monitor images and say if it’s the same person appearing twice. Need to discriminate between very similar information, fine info about location of nose etc. places - show two locations don’t need to use fine information to see the differences Pay attention to different parts of the image between the two tasks. These differences between the tasks mean lots of possibilities to explain why the brain might activate differently between the two tasks.

Question 91

what is the positive and weakness of this faces vs places design

Answer 91

strong ecological validity | need more tightly controlled studies to fully understand why they differentially activate the brain

Question 92

in subtraction analysis are the voxels identified for places not used for faces

Answer 92

Not necessarily! It just means they are more involved in processing scenes Can never conclude this part of the brain is only for this or something else, can be engaged for both but just less so than the other or if they are both activating an area fully then subtract that for both of them it = 0 even though they are both activating the area at 100%. this is why it is important to choose a good baseline

Question 93

what baseline would we use if we wanted to identify areas that are used in faces and places

Answer 93

We’ll need another condition that involves neither of these stimuli There’s no absolute baseline because the brain is never off But often researchers use a resting baseline, in which the participant lies in the scanner doing nothing diff because the ppt might be daydreaming and creating noise

Question 94

what is the problem with using a resting baseline and how to solve it

Answer 94

You’d probably start day-dreaming – a complex cognitive activity, involving memory retrieval, visual imagery, planning, language… instead use an active baseline that doesn’t involve the process being studied

Question 95

what is the aim of studies focussing on functional connectivity

Answer 95

identify large distributed brain networks used for complex cognitive abilities

Question 96

how do resting state connectivity studies work

Answer 96

Ppt think about different things, diff parts of brain start engaging and disengaging with each other parts of the brain responsible for this will come in synch with each other, are brain regions and changes over time correlated. Measure similar bold patterns in regions far away they are communicating and potentially sharing info and noise and working in the same network.

Question 97

what is the default mode network

Answer 97

The brain network that’s most active when you’re not really doing anything Strongly active at rest and often deactivates when we start doing a specific task Implicated in spontaneous thought, memory retrieval and attention to our internal world Mind-wandering and lapses in attention have been associated with increased DMN activity

Question 98

how does multivariate fmri work

Answer 98

Brain area, series of voxels become active when shown a stimuli, activated again with different stimuli gives patterns of activation over different voxels. May be diff for one type vs another type of stimulus. Don’t take an average of the activation, take the pattern for each trial and these are given to an algorithm which differentiates the patterns between the two types of stimuli. Then give it a pattern from one of the two types and see if it can correctly say this is related to a place stimuli rather than a face one. If it gets it correct more than 50% of the time then we can say there is some degree of information about identity that is preserved in this region.

Question 99

what can we learn from multivariate fmri and give an example

Answer 99

Allows us to conclude something about the information that is being presented rather than just saying on average this responds more to this than this. Perceptual knowledge of faces stored in this area, can it tell a difference between two familiar identities. Contains nine voxels for this example, record pattern of faces will elicit a pattern, black = not activated white – highly activated. Pattern of voxels for both of the professors. The patterns are similar but different. Certain number of pics used to train the classifier, make a criterion and if it gets an image that produces a level of criterion either high or low decides which person it thinks it is. Then see if the classifier can correctly categorise the new pictures into the categories correctly, if it is correct the patterns should match the correct person.

Question 100

why do we do multivariate fmri

Answer 100

The pattern of activation in this part of the brain is reliably different for these stimuli This brain area “knows” that these stimuli are different in some way It codes information about face identity (perhaps) Multivariate fMRI studies tell us what information it might be coding

Question 101

what are the negatives of multivariate fmri

Answer 101

Classifiers often only achieve 60-70% accuracy Requires a lot of data and processing power (doesn’t work in real-time) Only works when inside a MRI scanner so need one takes 6-7 hours