Behavioural studies 23/4

Question 1

What are the two main limitations of animal models?

Answer 1

Modelling higher cognitive functions such as decision making and executive function.

Behaviour and motives for behaviour must be measured indirectly - this can be based on assumptions regarding the psychology of animals, the evolutionary development of animals etc. We cannot simply ask the animal how it feels, or why it behaves as it does.

Question 2

What is an animal model?

Answer 2

A model is a simplified representation used to understand how a system works. It does not recapitulate all features of the disorder, otherwise it is just as complex to study as the human disorder.

Simplified representations bring us closer to the biology of a system.

Question 3

What is the phenotype approach to syndrome modelling in pyschiatric disorders?

Answer 3

The deconstruction of psychiatric disorders.
This brings up closer to the biological underpinnings.

Phenotypes may be behavioural, neurophysiological, biochemical, cognitive, endocrinological, neuroanatomical or neuropsychological - there are many levels of phenotypes at which a disorder may be studied.

Endophenotypes are ‘hidden phenotypes’ i.e. they underlie the visible phenotypes such as symptoms and behaviour. Endophenotypes relate to genetics, and clear ‘potential’ pathways between genes and the endophenotype.

Question 4

4 different types of animal models

Answer 4

• genetic models e.g. modifying a gene
• anatomical models e.g. lesion studies
• environmental manipulation models e.g. drug models, stress models
• behavioural models. These are not truly ‘model’ but they are tasks that are used to get a readout of other models. We don’t really manipulate their behaviour but we ‘readout’ their behaviour.

Question 5

Common model organisms

Answer 5

worms

zebrafish

fruit flies

rodents

non human primates

Even very simple organisms such as fruit flies can undergo behavioural tasks such as sexual behaviour, conditioning to odours etc.

Question 6

What are important features of good animal models?

Answer 6

• variety of phenotypes • able to quantify and compare • experimental tractability (e.g. how easy to experiment on) • control their environment

Question 7

What are the relative advantages and disadvantages of rat/mice models?

Answer 7

Rats are easier to handle - larger, friendlier. They are als more similar to humans than mice.

Mice have been bred to be much more diverse and are therefore easy to manipulate.

Both have an immemoriable association with mankind - they have always shared common environments with us because they lived with us and shared our food etc.

Question 8

What are the two overarching approaches to measuring animal behaviour?

Answer 8

Skinnerism - using operant conditioning and trained behaviour. The animals do not get much opportunity to use their natural behaviours, but the behaviours trained are often much easier to measure (less SNR)

Ethological - using the animals innate response to the environment. The environment is manipulated and the response measured.

Question 9

Define construct validity

Answer 9

how well the model reflects the theoretical assumptions

e.g. anxiety induced by a novel stimulus declines with familiarity

Question 10

Define predicitive validity

Answer 10

how well a manipulation predicts performance in the condition being modelled

e.g. is the anxiety paradigm sensitive to anxiolytic drugs

Question 11

Define face validity

Answer 11

degree of similarity between the responses observed in the model and the disorder it simulates in humans.

E.g. although mice may also show defensive behaviour in response to novel stimuli, the repetoire of behaviour may be very different

Question 12

What are some common examples of animal models for depression?

Answer 12

Chronic (unpredictable) mild stress model. The variables include the type, duration and frequency of stressors. Due to this, reproducibility is poor. Some strains are more susceptible to this paradigm than others

Maternal seperation model. Again, can differ as to when and how long pups are seperated, and whether it is the pup or the mother who is separated. Common paradigm used are: pups (day 2-14) repeatedly separated daily for 3 hr • pups (day 9) separated once for 24 hrs. Pitfalls include reproducibility and strains.

Removal of the olfactory bulb, which is part of the limbic-hypothalamic axis. This results in sensory deprivation and models symtpoms of depression. Good predictive validity (e.g. reversed by chronic antidepressant treatment).

anhedonia ethological paradigm measures preference for sucrose flavoured water

forced swimming and tail suspension are other behavioural paradigms