Tutorial deck

Question 1

What is prosopagnosia?

Answer 1

• Prosopagnosia- failure to recognise faces

Question 2

What is developmental prosopagnosia?

Answer 2

• Developmental prosopagnosia- individuals who either have CP or have sustained brain damage before birth or in early childhood resulting in prosopagnosia

Question 3

What is acquired prosopagnosia?

Answer 3

• Acquired prosopagnosia- provided unique window into the psychological and neural substrate of face processing

Question 4

What is congenital prosopagnosia?

Answer 4

• Congenital prosopagnosia (CP)- impairment in face processing that is apparent from birth in the absence of any brain damage, and occurs in the presence of intact sensory and intellectual fuctions

Question 5

What is evidence of the properties of congenital prosopagnosia (its mechanism and proof that such people have difficulty recognising faces)

Answer 5

• Decreased reaction time in face matching tasks
• Impaired at discriminating between common objects and between novel objects, especially when the discrimination is at the individual level, even when the pair to be discriminated is visible to the subject for an unlimited duration
• Many CP individuals are also not adversely affected by inversion of faces and can also show the inversion superiority effect
o Less affected than normal people by inversion effect (inversion effect is when there is worse recognition for inverse faces than normal faces)
• BOLD-behavioural response in the fusiform gyrus is the same in CP people as normal people (fMRI)
• CP compensatory mechanisms
o CP subjects use prefrontal cortex more than normal people (fMRI), suggesting a working memory task and hence recruitment of compensatory mechanisms under taxing perceptual conditions by the CP subjects
• CP subjects have a smaller right anterior fusiform region and a larger right mid/posterior-fusiform gyrus
o But no differences observed in the hippocampus or parahippocampal region
o Structural difference could be a cause or a consequence of CP.

Question 6

What are super recognisers?

Answer 6

• Super recognisers are people who are extremely adept at facial recognition

Question 7

What does the existence of superrecognisers and prosopagnosia suggest about face recognition?

Answer 7

• Their existence, as well as that of the prosopagnosia syndrome, suggests that face recognition is on a spectrum

Question 8

What are the advantages and limitations of treating people with deficiencies as a separate clinical groups?

Answer 8

Advantages:

• Less stigma to getting treatment
• Sense of community with others with condition
• More benefits and funding to help
• Easier to study these people as a discrete group

Disadvantages:

• More stigma as not considered “normal”
• Treatment may not be necessary
• Cut-off line: people who are around the cut-off line
• Less motivation to get better if categorised in discrete group

Question 9

What are the advantages and limitations of treating people with deficiencies as part of the normal continuum?

Answer 9

Advantages:

• No stigma as seen more like normal
• Reduces possibility of not needing treatment
• Easier to personalise medicine: treat as a multidimensional problem

Disadvantages:

• Seen as viewing less treatment
• Hard to get special considerations
• Promise of improvement when the quantity may be discrete

Question 10

Describe the procedure of EEG from scratch and the purpose of the steps when applicable

Answer 10

1. Measure size of participants head (widest bit) to know the cap size
2. Measure from nasium (nose) to base of skull
   a. Cz should be halfway between nasium and base of skull
3. Attach the electrodes by matching their numbers to the number on the cap
   a. More electrodes- takes longer to set up and increases the risk of bridging (electrodes record combined signal) but there is more accurate data
4. Put conductive gel to decrease natural resistance of the skull and allow for increased contact between electrodes and the scalp
   a. Gel= salt solution
   b. Use needles to move hair that is under the electrodes and put enough conductive gel under the electrodes
   c. Electrodes have pre-amplifiers: boost signal before sending it to amplifier
   i. These have less environmental electrical noise
5. Measure impedence from each electrode
   a. Red= high impedance
   b. Green= low impedance
6. Need participant to be still with muscles nice and relaxed (including eye movements) as these influence the EEG very strongly
7. Record from electrode
   a. Need neurons firing in concert with each other and arranged in a particular manner
   b. Need numerous additive dipoles to create a bigger signal (such an example is pyramidal cells in the cerebral cortex)
   c. Response specific to activity: e..g response to images of faces vs images of houses

Question 11

What behaviour and symptoms are characteristic of REM sleeping disorders?Give an example of such a disorder

Answer 11

o Acting out dreams is common in dementia diseases
 Rapid eye movement sleep behaviour disorder (RBD)
• Caused by degeneration within the brainstem- disables the mechanisms responsible for immobilizing muscles during REM sleep
• Connected to other neurodegenerative diseases
 Can be hallmark of Parkinson’s
 Clonazepam restored normal dreams and stopped RBD disorder
o Parasomnia- mixed states of sleep and wakefulness
 Releases basic instincts in an inappropriate way during sleep
o Aspects of the brain being damaged/parts of the brain that are awake when they should be asleep
o Can often remember what they are dreaming about

Question 12

What behaviour and symptoms are characteristic of REM sleeping disorders?Give an example of such a disorder

Answer 12

• Non-REM parasomnia-
o Sleepwalk
 More common in children
o Genetic predisposition
o People prone to sleepwalking sleepwalk at times of stress
o Physiological and psychological factors
o Don’t always remember their episodes

Question 13

How old is transcranial magnetic stimulation?

Answer 13

• Transcranial magnetic stimulation

o Been around for 30-45 years

Question 14

What are the physics involved in TMS and how old are they?

Answer 14

o Physics involved in TMS has been known for 200 years (Farraday)
 Electromagnetic induction
• Electrical current will induce a magnetic field
• Showed that changing magnetic field will induce an electrical current

Question 15

What is the biology involved in TMS and how old is it?

Answer 15

o Biology back in 250 years (Galvani)

 Muscle/nervous tissue will create electrical currents and can be activated by electrical currents

Question 16

Who failed to perform elementary TMS and why?

Answer 16

o	Thompson (1910) and Magnusson+ Stevens (1911) tried to use magnetic fields to stimulate the brain
	Failures as magnetic fields generated were too weak and too slow

Question 17

Who was the first person to invent working TMS and when?

Answer 17

o	Barker (1985)- effective stimulation with TMS
	Invented the first usable TMS

Question 18

Describe the procedure of TMS and its design

Answer 18

 2000-3000 amps of current at 2000-3000 volts to generate strong enough magnetic field
 Device has capacitors that stores up charge which is then released
 Current passes through heavily insulated coil and ring
• As electrical current passes around coil, generates a magnetic field strong enough to pass through bone/scalp into the brain
• Machines deliver current as short pulse (50-100 us long) in order to induce changing magnetic field
o Electrical current is passed through the coil-> coil generates a very brief magnetic field-> onset and offset in magnetic field induces electrical field in brain tissue-> depolarises neuronal membrane

Question 19

How invasive is TMS?

Answer 19

 TMS is minimally invasive

Question 20

What are the uses of TMS? Give examples

Answer 20

 Can be used for mapping of brain
• Fairly focal interference
o TMS to motor cortex induces muscle contractions
o TMS to visual cortex induces phosphenes

Question 21

What are the limitations of TMS?

Answer 21

 Generally limited to surface of brain
• Decays with square of distance from surface of coil
-TMS can induce epileptic seizures

Question 22

In TMS, what coils can be used? Why?

Answer 22

o Size of coil affects size of magnetic field
 Figure 8 coil- magnetic fields summate in the middle
• Focal- limits area of stimulation
 Big ring coil- broader magnetic field and deeper in the brain
• But also stimulates everything above target deep in brain

Question 23

Describe the four stimulation protocols of TMS

Answer 23

 Online single pulses (spTMS)
 Paired pulses (3 ms vs 10 ms vs 200 ms)
 Online repetitive trains (rTMS)
 Offline rTMS

Question 24

What are online single pulses for in TMS?

Answer 24

• Localised interference

Question 25

What are paired pulses for in TMS?

Answer 25

• 3 ms before main pulse-First weaker pulse can preferentially stimulate GABAergic inhibitory interneurons- can see effects of inhibition on certain pathways
• 10 ms before main pulse- first pulse can sensitize effects of second pulse
• 200 ms before main pulse- first pulse can diminish impact of second pulse
• Depends on timing
o Study excitatory vs inhibitory pathways interactions

Question 26

What are online repetitive trains for in TMS?

Answer 26

• 4-5 pulses in a row that extends out effect: more time to study task
• Effect of stimulation is no longer than the pulse itself

Question 27

What are offline rTMS for in TMS?

Answer 27

• Repeated stimulation over extended amount of time
o Has effects that outlast duration of stimulation itself
• Low frequency rTMS
• Theta burst
o Trains of pulses in a particular pattern (theta frequency pattern)

Question 28

Where and what method of TMS is the safest?

Answer 28

• Have set safety controls
o Regulate frequency of stimulation and brain location of stimulation
 Paired and single pulses of TMS are safest

Question 29

What are the questions in the TMS safety screening?

Answer 29

• Safety screening-TMS can induce epileptic seizures
o Do you suffer from epilepsy?
o Do you have any first degree relatives who suffer from epilepsy?
o Have you ever been diagnosed with hydrocephalus or increased intracranial pressure?
o Have you ever suffered a serious head injury or a stroke?
o Do you suffer from migraines or severe and frequent headaches?
o Are you taking any drugs for a neurological or psychiatric condition?
o Do you have a pacemaker?
o Do you have metal clips or any other metal in your head other than dental fillings?
o Do you have a heart condition?
o Is there a chance you might be pregnant?
o Have you ever had a fainting spell or syncope?
 Not excluded on this category

Question 30

Describe Kanwisher (1997)’s study, what was found and why it is such a cited study

Answer 30

• Kanwisher 1997
o Compared brain activation for faces to a range of other categories (objects, houses, body parts, scrambled objects)
 Looked for region of brain responding preferentially to faces
o A small region in ventral temporal cortex consistently showed high activation for faces
o Cited so much because early paper that looked for modalities in the brain
 Perspective that we should be looking for little modules in the brain that do specialised function
 Precursor to widespread approach of localising brain regions
o fMRI experiment

Question 31

Describe Haxby’s 2001 study, what was found and the impact of the study in the field. Describe limitations of the study

Answer 31

o Used patterns of activation to predict the category of picture subjects were viewing
o Took activation patterns of even runs (cross-validation) and made pattern template
 Computes correlation for patterns between runs
 Similarity of patterns measured using correlation between voxel response patterns
o Did not look at specialised regions- look at activations around specialised regions
o Birth of decoding approach
 Try to patterns of activation in brain and predict what a person is looking at
o About pattern of activation amongst multiple regions that tells us what the brain is looking at
 If removed major area postulated to be responsible for particular object, could still infer what object the person was looking at
o fMRI experiment
o Challenge to assumption of modularity
o Thought patterns of activation more important than modules
o Used machine learning
o However, limitation:
 If the entire pattern of activity across IT cortex determines what we’re going to see, idea falls down with downstream perspective
• The distributed pattern of activation could just be due to downstream communication to other brain parts

Question 32

Compare Kanwisher’s 1997 study and Haxby’s 2001 study

Answer 32

o Their approaches are not mutually exclusive
o However, their two perspectives cannot be resolved due to the process of selection of controlled stimulus
 Modular and distributed are not easily detangled
Kanwisher-
-Modular
—Modules responsible for specific functions
-Activation
-Finds area that responds strongest to stimulus, which is what she labels as the function
Haxby-
-Distributed representations
—Patterns of activation that determine what the brain is seeing
-Information

Question 33

Describe the approach of representational geometry (kriegeskorte 2013)

• How brain activity is measured
• What the information can be used for
• What categories are the most prominently separated

Answer 33

• Representational geometry (Kriegeskorte 2013)
o Information based approach
 Measure brain activity using recordings (e.g. fMRI, EEG)
• Compute correlation distance between stimuli in activation patterns (like Haxby)
 Measure brain using behaviour
• Collect behavioural ratings for stimuli
• Compute distance between ratings
 Also, can construct computational models
 The collective set of distances (from brain, behaviour or models) define representational geometry
 Compare geometry between brain representations, behaviour and models
 Correlation tells you how far things are in representational space
• Can make similarity matrices
 Brain cares a lot about separation of animate vs inanimate object
• We have to react to animate objects more dynamically than inanimate objects

Question 34

Describe Maguire et al.’s 2000 study on taxi drivers and what it found

Answer 34

• Found that taxi drivers in right posterior hippocampus showed slightly thicker/more volume but found that taxi drivers had a smaller right anterior hippocampus compared to controls
o Posterior hippocampus-affected by intense training
• Volume of right posterior hippocampus increases as the time the participant spent as a taxi driver increases
• Volume of right anterior hippocampus decreases as the time the participant spent as a taxi driver decreases

Question 35

How did Maguire et al. 2000 control for experimental bias?

Answer 35

• To control for experimenter bias in the MRI data, used blind observers to do the pixel counting (verify that the results had real effects)

Question 36

Describe the process of measuring cortical thickness with MRI?

Answer 36

• MRI-cortical thickness
o Original structural image
o Image with skull removed
o Determine borders of cortical gray matter
o Measure thickness of cortical gray thickness

Question 37

Describe the two measures of Gieed and Rapoport’s 2010 study and the point of the study

Answer 37

•	Diffusion Tensor Imaging (DTI)
•	MRI-cortical thickness and volume 
o	Grey matter
o	White matter
•	Development trajectories

Question 38

What is the development trajectory of white matter and how did Giedd and Rapoport 2010 visualise this? What influences white matter during development and can these changes always be seen?

Answer 38

o White matter increases as a function of age
 Visualised by DTI
 Connections between brain areas are being fortified at different times- its not just a matter of simple growth
• Sequence of events could affect higher order cognition and connections
o Deficits can either be reflected or not reflected (if they are reformed) in adults
 By studying patient groups as adults and ignoring developmental trajectory in children, could miss some part of the story

Question 39

What is the development trajectory of grey matter and why?

Answer 39

o Grey matter increases until the age of around 10 and then decreases as a function of age (U shape trajectory)
 Associated with higher order cognition
 Increase may be due to synaptic formation, decrease may be due to synaptic pruning

Question 40

What is the difference between synaptic formation and synaptic pruning?

Answer 40

• Synaptic formation-> potential connections that could be used for a specific function
• Synaptic pruning-> for memory and knowledge. Prunes the irrelevant neurons
o The extra formations are noise

Question 41

What is the subplate in the brain and what is it used for? What is its developmental role?

Answer 41

• Crucial structure for vision
• Special group of cells that are present in development that just disappear from the brain in adults
o Crucial for setting up connections in vision and preparing the brain to see and perceive, but once their job is done they’re gone
• Special category of cells that disappear after trajectory

Question 42

What is the development trajectory of total cerebral volume?

Answer 42

o Total cerebral volume
 Hit a peak at adolescence (girls- 10, boys- 14)
 U shaped trajectory
 However, size of brain doesn’t really determine intelligence

Question 43

What is developmentally needed to make a good brain?

Answer 43

o If you want to make a good brain, need perfect sequence of changes/activity throughout development

Question 44

Describe the developmental changes of child onset schizophrenia and why it is important to look at this developmentally

Answer 44

o E.g. child onset schizophrenia
 Schizophrenia affects cortical thickness
 First stages- affect some parts of the brain, but over time, damage changes and spreads all over the brain
 Cannot look at a single timepoint at a trajectory-> could miss a lot of important conclusions