9c. Control of Behaviour. Problems of Impulsivity and Compulsivity Flashcards by tabitha Stafford

Striatum Role in Behaviour

Ventral striatum:
- Selects the goal (high level action)

Dorsal striatum:
- Decisions mediating the exact movement (lower level action)

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Disorders of Behavioural Control

- 2 Types

Impulsivity

- Compulsivity

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Impulsivity

- Actions

Impulsive actions are actions which are:

Poorly conceived
prematurely expressed
Unduly risky
Inappropriate to the situation
Often result in undesirable consequences

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Compulsivity

- Actions

Compulsive actions are actions which:

Persist inappropriately to the situation
Have no obvious relationship to the overall goal
Often result in undesirable consequences

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Disorders of Behavioural Control

- Causes

Impulsive and compulsive behaviours result form a shared lack of appropriate behavioural inhibition

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Disorders of Behavioural Control

- Measurement

Experimental

- Psychometric

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Disorders of Behavioural Control

- Experimental Measurement Advantages

Objective so can be compared with other cohorts

- Parameters can be adapted for species

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Disorders of Behavioural Control

- Experimental Measurement Limitations

Focusses on the tendency to show specific behaviour in a specific context at the time of testing, rather than broader trait-level responses underlying behavioural expression
Resource intensive
Requires direct access to animals
Expensive

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Disorders of Behavioural Control

- Psychometric Measurement Description

Involves using questionnaires to assess animal behaviour

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Disorders of Behavioural Control

- Experimental Measurement Description

Involves investigating a very specific behaviour in a very specific context

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Disorders of Behavioural Control

- Psychometric Measurement Advantages

Rapidly
Inexpensive
Measures behaviour over a wide range of contexts
Readily available to owners to increase sampling size

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Disorders of Behavioural Control

- Psychometric Measurement Disadvantages

May lack biological and convergent validity so may not be reliable

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Disorders of Behavioural Control

- Psychometric Measurement Example

Dop impulsivity assessment scale (DIAS)

Higher score = more impulsive

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Impulsivity

- Description

Disorder of:

Stopping
Waiting
Tolerance of delay

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Impulsivity

- Measuring Stopping Method

Stop Signal Reaction Time Task (SSRT)
- Measures the speed of the inhibition process

Train an animal to carry out an action as quickly as possible when given a ‘go signal’.
Then introduce a ‘stop signal’ where the animal must stop the response that they have initiated.

Moving the ‘stop singal’ closer to the ‘go signal’ makes it more difficult to stop, and more impulsive subjects are less likely to stop in time

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Impulsivity

- Measuring Stopping Results

More impulsive subjects are less likely to stop in time and therefore have longer stop signal reaction times (SSRTs)

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Impulsivity

- Stopping Pathways

Direct

- Indirect

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Impulsivity

- Direct Pathway

Promotes movement

Excited striatum inhibits the internal segment of the globus pallidus to disinhibit the thalamus, increasing its excitation of the motor cortex to increase movement

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Impulsivity

- Indirect Pathway

Inhibits movement

Excited striatum inhibits the external segment of the globus pallidus to disinhibit the sub thalamic nucleus, allowing it to excite the internal globes pallidus and increase thalamic inhibition to decrease excitation of the motor cortex

Impulsivity

- Pathway Control

Both the direct and indirect pathway are controlled by dopamine.

Direct pathway involves D1 receptors

Indirect pathway involves D2 receptors

Impulsivity

- D1 Antagonist

SCH23390
Blocks the direct pathway, shifting the balance in favour of the indirect pathway and behavioural inhibition

Lower impulsivity shown by shorter stop signal reaction times (SSRTs)

Impulsivity

- D2 Antagonist

Sulpiride
Blocks the indirect pathway, shifting the balance in favour of the direct pathway and behavioural activation

Higher impulsivity shown by longer stop signal reaction times (SSRTs)

Impulsivity

- Measuring Waiting Method

5 choice serial reaction time test

Animal presented with 5 nose-poke apertures and have to wait until a light is presented in 1 of the apertures, and will then receive a food reward if they nose poke that aperture.

The intertrial interval (ITI) is varied to measure waiting times

Impulsivity

- Measuring Waiting Results

A subset of rats were found to have a high trait impulsivity as they make more premature responses as the intertrial time interval (ITI) is increased.

However, this group of rats performed normally on the stop signal reaction time tase (SSRT).

PET scans and micro dialysis were used t show that D2/D3 receptors decreased in the ventral striatum

Impulsivity | - Measuring Tolerance of Delay Method

Delayed reinforcement task Animal is present with 2 choices: - Choice 1 results in s small amount of food immediately - Choice 2 results in a larger amount of food given after a delay, which can be increased

Impulsivity | - Measuring Tolerance of Delay Results

As the delay increases, preference for the larger reward decreases. This occurs with smaller delays in more impulsive animals

Impulsivity | - Urinary Metabolites

5-Hydroxyindoleacetic acid (5-HIAA) is the main metabolite of serotonin The more impulsive the animal, the higher its urinary 5-HIAA

Impulsivity | - Correlates

- High dog impulsivity assessment scale (DIAS) score - High stop signal reaction time (SSRT) - Many premature responses as intertrial interval (ITI) increases - High maximum delay on the delayed reinforcement task - Increased urinary 5-hydroxyidoleacetic acid (5-HIAA) - Reduced 5-hydroxyidoleacetic acid (5-HIAA)

Impulsivity | - CSF Composition

High CSF 5-hydroxyindoleaceatic acid correlates to impulsive behaviours - Long risky jumps in wild Vervet monkeys - Aggression in primates - Aggression without warning in dogs

Impulsivity | - Treatment

Drugs that boost serotonin: | - Citalopram is a selective serotonin reuptake inhibitor, increasing synaptic secretion levels

Compulsivity | - 2 Types

- Stereotypies | - Compulsive behaviours

Compulsivity | - Stereotypies Description

Behaviours with no purpose other than performance of the motor pattern Repetitive invariant behaviours with no obvious goal or function

Compulsivity | - Stereotypies Examples

- Pacing around a cage - Hungry chickens develop stereotypical pecking - Hungry, confined pigs develop stereotypical bar biting - Hungry rats who periodically receive s small pellet of food develop excessive and compulsive drinking behaviour despite not being thirst

Compulsivity | - Compulsive Behaviour Description

Behaviours that appear to be related to some kind of goal, or have resulted from a previous goal that is no longer applicable

Compulsivity | - Compulsive Behaviour Examples

- Nest building in rodents | - Acral licking in dogs

Compulsivity | - Treatment

Blocking dopaminergic input to the ventral striatum abolishes stereotypical behaviours Large doses of dopaminergic agonists such as apomorphine, INDUCE stereotypical behaviours. Dopamine antagonists such as haloperidol reduce stereotypical behaviour - Acral licking Clomipramine Serotonin reuptake inhibitors Fluoxetine - Mice compulsive nest building

Compulsivity | - Displacement Behaviour Definition

Irrelevant activities that intrude into a stressful situation and can become compulsive Stereotypies

Compulsivity | - Cause

Striatal dysfunction | - erroneous activation of irrelevant low level motor pattern in the striatum

Crib Biting | - Description

Horses grasp a solid object in their incisors, arch their neck and contract the lower netk muscles to retract the larynx

Crib Biting | - Causes

Stress: - More common in isolated horses Nutrition: - Occurs post-prandially - Cereal feeds Striatal Dysfunction: - PET images show high D1 and D2 receptors densities in the nucleus accumbens, and in the caudate nucleus that controls motivation

Crib Biting | - Function?

- May be to generate more saliva to neutralise an uncomfortable, alkaline caecum. Supported by supplements that reduce caecal pH reducing crib biting incidence

Acral Licking | - Description

Acral lucking dermatitis (ALD) is the most common grooming stereotypy in dogs Repeatedly lick or scratch the carpus, metacarpus and metatarsus causing damage

Acral Licking | - Treatment

Dopamine antagonists such as haloperidol

Compulsivity | - T Maze Method

Rats in a cross-shaped maze were trained to run down one arm to gain a food reward. The rat is placed in the opposite arm of the maze so can either exhibit: - Place learning, moving to the correct arm - Reinforced motor response, moving in the same direction

Compulsivity | - T Maze Results

Day 8 = place learning | Day 16 = reinforced motor response

Compulsivity | - T Maze Lidocaine

Lidocaine injection into the caudate blocked the reinforced motor response

Other Agents involved in Compulsivity

- Serotonergic lesions of the orbitofrontal cortex impairs compulsivity in tasks