9c. Control of Behaviour. Problems of Impulsivity and Compulsivity Flashcards
Striatum Role in Behaviour
Ventral striatum:
- Selects the goal (high level action)
Dorsal striatum:
- Decisions mediating the exact movement (lower level action)
Disorders of Behavioural Control
- 2 Types
- Impulsivity
- Compulsivity
Impulsivity
- Actions
Impulsive actions are actions which are:
- Poorly conceived
- prematurely expressed
- Unduly risky
- Inappropriate to the situation
- Often result in undesirable consequences
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
Disorders of Behavioural Control
- Causes
Impulsive and compulsive behaviours result form a shared lack of appropriate behavioural inhibition
Disorders of Behavioural Control
- Measurement
- Experimental
- Psychometric
Disorders of Behavioural Control
- Experimental Measurement Advantages
- Objective so can be compared with other cohorts
- Parameters can be adapted for species
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
Disorders of Behavioural Control
- Psychometric Measurement Description
Involves using questionnaires to assess animal behaviour
Disorders of Behavioural Control
- Experimental Measurement Description
Involves investigating a very specific behaviour in a very specific context
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
Disorders of Behavioural Control
- Psychometric Measurement Disadvantages
- May lack biological and convergent validity so may not be reliable
Disorders of Behavioural Control
- Psychometric Measurement Example
Dop impulsivity assessment scale (DIAS)
Higher score = more impulsive
Impulsivity
- Description
Disorder of:
- Stopping
- Waiting
- Tolerance of delay
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
Impulsivity
- Measuring Stopping Results
More impulsive subjects are less likely to stop in time and therefore have longer stop signal reaction times (SSRTs)
Impulsivity
- Stopping Pathways
- Direct
- Indirect
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
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
