essay plan for externalising disorders

Question 1

criticially discuss the aetiological theories of childhood adhd?

Answer 1

1. reduced behavioural inhibition
   - reduction in ability to delay a motor response which effects 4 main executive functions such as working memory and internalising speech, shown to be reduced in tasks and neurological support
   - supported through stop signal and go-no-go trials
   - limited as these may be too difficult for children, be measuring motivation or switching attention abilities
2. delay aversion hypothesis
   - motivational account where dysfunction with reward processing system so have ability to not be impulsive but want to to avoid delay
   - support from findings of choosing immediate reward when no delay but larger when also no delay, and activation in adverse event processing circuits (amygdala) when inescapable delay apparent and reduced processing in ventral-striatal circuit
   - explains all 3 factors of adhd
3. dual pathway
   - combination of both of these theories to explain the combined type
   - supported through findings of poor performance in aspects related to both these areas and double dissociation (found through brain scans) between them as independently contributing to adhd
   - suggestion of addition of temporal processing as found to have poor performance in this as well

Question 2

paragraph 1?

Answer 2

3 subtypes of adhd:

1. inattentive - difficulty in maintaining attention
2. hyperactive-impulsive - struggle with high activity levels with impulsive element
3. combined subtype - difficulty with attention and activity levels

reduced behavioural inhibition - predominantly targets the second type (hyperactive-impulsive)
- views the core feature underpinning the disorder as reduced ability to delay a motor response, which in turn affects the 4 executive functions of working memory, self-regulation of arousal, internalised speech and reconstitution (behavioural analysis) (Barkley, 1997) so adhd should be associated with impairments in these functions

support

• deficits in school age children with adhd in inhibitory control and working memory (Stevens et al, 2002)
• neurological support as executive functioning involves operation of neural circuits, linking frontal cortex with basal ganglia, parietal cortex and other areas, and children with adhd had structural differences and altered activation in prefrontal cortex (Seidman et al, 2005)
• supported through findings of the go/no-go task that children and adolescents with adhd had a higher probability of commission on the no-go trials (clicked ‘go’ response instead so lack of automatic inhibiting) (Bitsakou et al, 2008). also performed a stop signal task whereby press a key for go but inhibit this if hear an auditory tone, those with adhd had longer stop signal reaction times (poorer controlled inhibition)

against

• doesn’t really cover the hyperactivity element of adhd
• only 35-50% of those with combined type adhd show response inhibition deficits (Nigg et al, 2005)
• neuropsychological tests of executive function are complex as they involve lots of them, so hard to isolate the exact area of dysfunction as often work alongside each other, also the suggestion that in inhibition tasks, poor performance may relate to lack of motivation as hyperactive but being made to sit for periods of time (Johnson et al, 2009)
• suggestion that poor performance and slower stop signal reaction time may be due to problems switching attention to stop signal, questioning the validity of this task as a measure for inhibition (Bekker et al, 2005)
• may be too complex for some children, e.g in one sample, 27% of participants data had to be excluded due to high error rates (Solanto et al, 2001)

Question 3

paragraph 2?

Answer 3

delay aversion hypothesis

• impulsivity stems from attempting to avoid delay despite the ability to be able to, choosing immediate small over larger delayed rewards, so have dysfunctions of reward and motivational style (Sonuga-Barke et al, 1992)
• motivational account as suggests children with adhd aren’t impulsive in that they always choose the immediate reward, but only do this when it leads to a shorter delay

support

• explains inattentiveness and hyperactivity as both are actions to avoid delays when they can’t be averted
• supported by findings that children with adhd opt for the smaller-immediate reward over the larger delayed one in conditions where the delay would actually be reduced, so lower % of choosing higher reward when delay of 30s compared to other controls (Bitsakou et al, 2009), with children significantly lower than adolescents
• found higher activation in amygdala and dorso-lateral PFC were associated with cues indicating indicating an increased delay in those with combined adhd, regions associated with processing of adverse events (van Dessel et al, 2018), supported by hyperactivation in amygdala when delayed reward indicating inescapable delay and hyporesponsiveness in ventral-striatal reward system relating to immediate and delayed rewards (diminished processing of rewards) (Lemiere et al, 2012)

Question 4

paragraph 3?

Answer 4

dual pathway model

• explaining combined type through cognitive and motivational deficits (Sonuga-Barke, 2002)
• suggestion that cortico-ventral striatal loop disturbance leads to impaired reward processing and delay aversion and adhd
• cortico-dorsal striatal loop disturbance leads to inhibitory deficits leading to executive deficits and adhd

support

• findings that performance in tasks measuring both pathways was poor in those with adhd, but double dissociation between them, supporting their independent contribution to adhd (Sonuga-Barke, 2002), further supported through MRI study finding reduced connectivity in these 2 circuits in thsoe with adhd, so reduced connectivity in one causes deficits for that factor and not the other (double dissociation), however head movements may have altered findings, especially due to the hyperactivity element of adhd (Posner et al, 2013)
• volumetric inconsistencies in these circuits in those with adhd (Plessen et al, 2006) and abnormal activity in these systems during certain tasks (Posner et al, 2011)
• third pathway added: deficit of temporal processing, which was found alongisde the other 2 in children and adolescents with adhd (Sonuga-Barke et al, 2010)