Brain - Dr Matt Roser

Question 1

Define agnosia

Answer 1

Loss of ability to recognise objects, people, sounds, shapes, or smells; that is, the inability to attach appropriate meaning to objective sense data

Question 2

Define aphasia

Answer 2

A general term relating to loss of language ability

Question 3

Define apraxia

Answer 3

A general term for disorders of action

Question 4

Define amnesia

Answer 4

Lack of mnemonic abilities

Question 5

Define ataxia

Answer 5

Poor coordination and unsteadiness due to failure to regulate the body’s posture, and strength and direction of limb movements

Question 6

Visual agnosia is associated with lesions of which two parts of the brain?

Answer 6

Left occipital and temporal lobes

Question 7

What can the existence of selective deficits tell us?

Answer 7

They can tell us something about the way function is organised in the brain.

Question 8

What is the goal of behavioural testing?

Answer 8

The goals are to relate brain anatomy to behaviour and to investigate mental processes.

Question 9

In behavioural testing, what can the tasks tell us about the patients deficits? (2)

Answer 9

• What functions are compromised?
• What functions are spared?

Question 10

What does dissociated mean in the following phrase; “cognitive functions can be dissociated from each other through selective impairment”?

Answer 10

Separated to a certain degree

Question 11

Dissociation studies require what?

Answer 11

A minimum of two groups and two tasks

Question 12

What are the limitations of patient studies?

Answer 12

1. Assumption of modularity
2. Lesions extensive and varied
3. Lesion anatomy inaccurate, connections not considered
4. Individual differences in functional anatomy
5. Poor temporal resolution

Question 13

Define modularity of function (a limit of patient studies)

Answer 13

Assumption that mental processes can occur with a high degree of isolation from other mental processes and when one area is damaged other regions do not adapt their function

Question 14

Define ‘brain plasticity’

Answer 14

Intact regions change their behaviour so it is difficult to infer function of damaged region.

Question 15

Why is ‘lesions extensive and varied’ a limitation of patient studies? (4)

Answer 15

1. Most work done with patients who have large lesions
2. Lesions often damage several function centres, so there are few patients with ‘pure’ deficits
3. Lesion size and location variable, hard to find a group of similar patients. Inferences from single patients are weak.
4. Individual differences in recuperative history.

Question 16

Why is ‘lesion anatomy inaccurate and connections not considered’ a limitation of patient studies? (2)

Answer 16

1. Anatomical scans show reginos that are destroyed, but intact regions may not be functioning
2. Regions may be disconnected from other regions that provide input

Question 17

A memory deficit may arise from a failure of what? (3)

Answer 17

Encoding, retention or recall.

Question 18

There is no experimental control over lesion location, but animal studies using what can provide this?

Answer 18

Animal studies using experimental ablation

Question 19

What are the benefits of patient studies? (4)

Answer 19

1. Shows which areas are necessary for a particular cognitive function (double dissociation)
2. Show cognitive, emotional, social consequences of a deficit
3. Cost and time effective, single case studies are possible
4. Can be done right to limit critism

Question 20

Importance of a control group; looking at patients with Visual field deficits (vfd’s), all patients have lesions in the temporo-parietal junction (tpj). Why do we need a control group to study these patients?

Answer 20

We need a control group with right hemisphere brain damage but without VFD’s. This way we can control for the effect of right hemisphere damage and contrast only across the factor of VFD presence.

Question 21

What does fMRI stand for?

Answer 21

Functional Magnetic Resonance Imaging

Question 22

What does an MRI use to produce an image? (2)

Answer 22

A magnetic field (Bo) and radio energy

Question 23

What is the physics behind MRIs?

Answer 23

• A large magnet aligns nuclei that have a net magnetic moment.
• Nuclei absorb and re-emit radio frequency energy

Question 24

How is an image acquired (fMRI)?

Answer 24

Nuclei spin around the main magnetic field.

RF pulse (oscillating magnetic field) tips M out of alignment with Bo and synchronises the phase of spins.

M gradually returns to alignment and spin loses phase coherence. These changes are detected as the ‘MRI’ signal.

Question 25

How can we map brain changes over time? (2)

Answer 25

• Grey matter volume
• Commisural myelination

Question 26

What does BOLD stand for?

Answer 26

The Blood Oxygen Level Dependent Response (the basis of fMRI)

Question 27

Explain briefly the blood oxygen level dependent response (the basis of fMRI) (4)

Answer 27

1- De/oxyhaemoglobin have different magnetic properties
2- Local field strength is affected by relative levels
3- This affects the local signal in the image
4- Increased signal is obtained from ‘active’ regions

Question 28

What originated with reaction time experiments?

Answer 28

Cognitive subtraction

Question 29

Define assumption of pure insertion

Answer 29

Can insert a component process into a task without disrupting the other components BUT tast difficulty (a confound) may differ between conditions, resulting in changed attention.

Question 30

Modelling the data: A change in the signal is due to what? Therefore, what?

Answer 30

A change in the signal is due to regional hemodynamics.

Activations are distantly related to the underlying neurological events.

Question 31

What has functional brain imaging told us? (4)

Answer 31

1- Identified functional areas
2- Corroborated findings from other methods
3- Allowed the localisation of function from undamaged brains
4- Meta-analyses bring some order to the flood of data, but are these maps from multiple different studies any more useful than the 1957 electrophysiology map?

Question 32

What does functional connectivity analyses do?

Answer 32

Calculates correlations between activations in different areas.

Question 33

What does dynamic causal modelling do?

Answer 33

Explicit models of distributed networks are tested to see which best fits the observed data.

Question 34

What two techniques investigate distributed processing and overcome some of the limitations of lesion studies and earlier fMRI studies?

Answer 34

Functional connectivity analyses.

Dynamic causal modelling.