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PS3032 > Methods for assessing psychological dysfunction > Flashcards

Methods for assessing psychological dysfunction Flashcards

1
Q

What are the criteria for a valid assessment?

A

Validity, Reliability, Sensitivity, Specificity and positive predictive value

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2
Q

What are the two types of validity?

A

Construct validity - measures what it claims to measure

Ecological validity - How assessment data reflects behaviour in a natural, everyday setting

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3
Q

What is reliability? What are the two types?

A

Ability to produce consistentn results on administration
Inter-rater
Test-test

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4
Q

What is sensitivity?

A

Able to correctly identify individuals who have a disease

- fidelity with which the test distinguishes behavioural outcomes

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5
Q

What is a specific test?

A

Can correctly identify patients who do not have the disease

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6
Q

What is positive predictive value?

A

Ability to detect a disease given the results of the test - depends on sensitivity and specificity but also prevalence of disease in the population

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7
Q

What is the Mini-Mental State Examination (MMSE)?

A
  • Questions with a score attached (such as where are we now, naming objects)
  • Some spatial tasks (e.g copying a figure)
  • If score is below 24 indicates mental deterioration
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8
Q

How does the MMSE do in terms of validity?

A

Well

  • Correlation of >0.6 with other cognitive tests
  • Correlation of >0.4 with daily living activities
  • Longitudinal studies show point decrease 2-3 a year
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9
Q

How does the MMSE do in terms of sensitivity and specificity?

A

Not well

  • All controls obtain normal scores
  • However 45% of patients with mild dementia also have a normal score
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10
Q

How are

  1. sensitivity
  2. specificity
  3. positive predicted value calculated?
A
  1. sensitivity = true positive /(true positive + false negative)
  2. Specificity = True negative / (true negative + false positive)
  3. = True positive / (true positives + false positive)
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11
Q

What problems arise when a patient is given a false positive?

A

May result in unnecessary worry and treatment

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12
Q

What problems arise when a patient is given a false negative result?

A
  • Feelings of guilt

- Treatment not administered to stop disease progression

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13
Q

What is Huntignton’s disease?

A
  • Genetic disease caused by autosomal dominant gene

- First symptom is uncontrollable movement which then results in depression and mood disorder followed by memory loss

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14
Q

How is Huntington’s tested for?

A

Genetic screening looks at number of CAG repeats (if over 40 likely to be huntington’s)

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15
Q

What have genetic studies of depression revealed?

A
  • 44 risk variants, with all humans carrying more or less of these genes
  • Genes expressed in frontal and cingulate cortex
  • Likely a constellation of variants along with environmental factors
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16
Q

What are the ethical implications of genetic screens?

A
  • Prenatal screens, should people be able to abort
  • Some family members may not want to know they have a genetic disease
  • Insurance companies
17
Q

What are the 3 main categories of imaging techniques?

A

Anatomical - CT, MR, VLBM, VBM
Functional - fMRI
Molecular - PET

18
Q

What do CT scans produce?

A

Images of tissue density using X-rays

19
Q

What are the advantages and disadvantages of CT scans?

A 
Adv
- Good for detecting cerebral hemorrhage 
- cheaper and widely available 
Disadv
- Low spatial resolution 
- Radiation 
- Not good for lesions
20
Q

Which images are most sensitive to a stroke?

A

Diffusion-weighted images - MRI scans

21
Q

How is diffusion tensor imaging carried out and what does it show?

A

Shows brain structural connectivity

- Looks at directional rate of diffusion in water molecules (asymettrical in fibres)

22
Q

What is voxel-based morphometry?

A
  • Satistical procedure to contrast differences in structural MR scans on a voxel by voxel basis, allows mapping of differences in brain structure between patients and controls over time
23
Q

How are voxel-based morphometries made?

A
  • Take MR images from certain group and smooth indivdual differences to form a template
  • Compare subject to group (normal distribution assumption)
24
Q

What are some of the potential issues with voxel based morphometry?

A
  • Can this account for individual differences?
  • Is there a linear relationship between neuronal loss and intensity of MR image?
  • Is neuronal density normally distributed in healthy populations for all brain regions?
25
Q

What are the advantages of voxel based morphometry?

A
  • Provide criterion for a lesion

- Can account for variables of no interest

26
Q

How does voxel-wise lesion behavior mapping differ from VBM?

A

Similar to VBM however does not assumer linearity between neuronal loss and MR signal activity and uses non-paramteric statistics (does not assume normal distribution)

27
Q

What are the components of VLBM?

A
  • Measurement of a behavioural variable (e.g CoC score in spatial neglect)
  • Delineate the lesion of MR scans
  • Comparison of behaviour of patients with lesion and without leasion
  • output map of voxels with lesions associated with lower behavioural scores
28
Q

What are the disadvantages of VLBM?

A
  • laborious
  • subjective
  • assumption that brain normalization works
  • error in locating cortical area by 1-2 cm due to underlying vascular anatomy
29
Q

What is a ‘BOLD’ signal?

A
  • Blood oxygen level dependent
  • Oxygenated haemoglobin has the same magentic properties as surrounding tissue but deoxygenated does not (measure changes in oxygenated verses deoxyhaemoglobin)
  • Disrupts signal from surrounding tissue
  • This is measured in fMRI
30
Q

Why can fMRI analysis of a stoke be difficult?

A

Heamodynamic flow is often disrupted

31
Q

What are the advantages and disadvantages of Positron Emission Tomography?

A

adv
- Can measure receptors, neurotranmitters and drugs in humans
disadv
- radioactive
- expensive and logistically difficult as tracers are short lived
- difficult interpretation, requires careful design

PS3032 (5 decks)

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