#14075 - Normal And Abnormal Development - Psychology

Normal and abnormal development

Development and plasticity

Timing is of essence

• Protracted developmental changes: changes from childhood into adulthood continue across cortical areas

• Heterochronous developmental changes

  • Rise and fall of synaptic density differs in timing for visual, auditory and prefrontal cortex

Clinical relevance of developmental timing

Language effects children who suffered brain injury prenatally or within 1^st 6 months of life

• Right hemisphere injuries- great risk for delays in word comprehension – however in adults damage occurs in the left hemisphere

• Left posterior injuries: greater risk for production difficulties whereas in adults injury is in the left inferior prefrontal cortex (more anterior-broca’s)

• Children with early unilateral brain injury- their brain difficulties seem to resolve, regardless of the side of lesions. Results of study

  • Child had smaller mean length of utterance with LHD compared to RHD

  • In Adults people with LHD had much greater decrease in length of utterance compared to child. But with RHD the mean length of utterance was greater

Spatial processing

• Children with early LHD have difficulties with processing and producing both local and global aspects of their visual environment when tested with navon figures (Big M made from lots of little z). In contrast adults with LHD can process the global image but not the local image- can see the M but not the z

• Children with early RHD have difficulties with the global aspects of these tasks only, they can spot the local letters. This is the same with adults

Executive function

• Prenatal insults to the frontal lobe performed more poorly across the board on executive tasks such as Tower of London; Fluency tests

• Children with lesions between 7-9 years did best

• Children with lesions in early childhood and after 10 years of age was task dependent and generally poorer than controls

Summary

• Differences in the effect of lesions in children and adults shows that multiple heterchronous processes are involved in pre and post natal changes in brain structure and function

• Some processes seem too be less vulnerable to early brain damage than to later lesions and recover more effectively overall (E.g expressive language). Spatail processing seems to be severely and permanently affected and outcome is variable for executive functions

• Understanding aediatric brain injury cases require moving away from the adult model as risk and recovery differ in terms of localisation of the risk

Childhood onset developmental disorders

Functionally defined disorders

• Unlike cases of acquired brain damage, these are identified by behavioural characteristics and may be heterogenous in aetiology

• Age of diagnosis and progression may differ

• Examples

  • Attention deficit Hyperactivity disorder (ADHD)

  • Autistic spectrum disorder (ASD)

ADHD

Diagnosis: American Psychiatric Association (DSM-IV)

Criterion A

• Symptoms in 2 categories – inattention + hyperactivity

• Child must exhibit 6 or more in either category

• Symptoms must have persisted for at least 6 months to an extent that is inconsistent for developmental level

Criterion B

• Some inattentive/ hyperactive impulsive symptoms present before age 7 years

Criterion C

• Symptoms are exhibiting in two or more settings

Criterion D

• Must be clear evidence of clinically significant impairment in social or scholastic functioning

Criterion E

• Symptoms don’t occur exclusively during the course of or can’t be accounted for by another disorder

Prevalence

• 3-5% school children suffer from ADHD

Different types of ADHD determined by the balance of inattention and hyperactivity/impulsivity symptoms (however this subdivision was dropped in DSM-V)

• AD/HD inattentive type

• AD/HD combined

• AD/HD hyperactive type

Neurocognitive theories

• Inhibition deficit- inability to override natural/habitual behavioural responses (prepotent response) in order to implement more adaptive goal-orientated behaviour. In people with ADHD there is inhibition of the following:

  • Working memory: acting on events held in memory

  • Self regulation: emotional self control

  • Speech internalisation: description and reflection

  • Reconstitution: analysis of synthesis and behaviour

• No go trials- children with ADHD had greater number of errors compared to controls

  • Found there was lower levels of activity for control related circuits (caudate nucleus/ globus pallidus, parietal lobe/prefrontal cortex0

• Pathophysiology

  • Brain structure

    • Children with ADHD there is a proportionally greater decrease in volume in Left sided prefrontal cortex. The posterior parietal cortex also shows thinning compared to controls

    • Prefrontal-strial-cerebellar and prefrontal striatal-thalamic circuits have been found to differ in ADHD

  • Neurotransmitter pathways

    • Dopamine deficiency is thought to be involved as ADHD pts respond to drugs that increase dopamine levels

    • Noradrenaline also likely to play a role

Alternative theories

• Inhibition deficits characterise many children wil AD/HD but not all

• Working memory difficulties

• Sustained attention

• Motivational difficulties

Autism spectrum disorder

Diagnosis DSM IV

• Social impairment (2+ of)

  • Marked impairment in the use of non-verbal behaviours (eye-contact)

  • Failure to develop age appropriate peer relations

  • Lack of spontaneous sharing of enjoyment, interests, achievements with other people

  • Lack of...