CHILD NEUROPSYCHOLOGY
Literature
MSc Psychology, Leiden University
2020-2021
S.M.J.C. Derksen
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,Chapter 4: Recovery from early brain insult
History 1920s → While early insults were regarded as qualitatively and
quantitatively distinct from those occurring in adulthood, there was
little agreement regarding their potential benefits and vulnerabilities.
More recently → Recovery from early brain insult remains imperfectly
understood.
Brain plasticity Plasticity is considered to be an intrinsic property of the brain,
reflecting its capacity to respond dynamically, through modification to
neural circuitry, in response to the environment and e xperience.
Environmental deprivation and/or brain injury → the influence of
plasticity is less well established and the immature brain may not
always benefit from these plasticity processes.
The brain’s capacity for plasticity might also reflect ‘vulnerability’, with
predetermined developmental processes being derailed, neural
resources depleted and an absence of a developmental ‘blueprint’ to
guide recovery.
Plasticity and Exploration of the consequences of brain insult sustained early in life
early brain has a long history, dating back to the 1800s.
insult
→ Example: Broca (speech functions), Barlow (language)
→ These examples are contradictory to the localizationist views of the
time.
Comprehensive reviews emerged through the 1970s, as both animal-
and child-based research began to accumulate.
→ In this literature, early insults were regarded as qualitatively and
quantitatively distinct from those occurring in adulthood.
Early brain insult = insult sustained from early gestation to
pre-adolescence, a protracted timeline during which brain structures
and/or their related functional correlates show most rapid maturation.
Clinical observations and empirical research suggest wide variability
in outcome from early brain insult consistent with the ‘differential
susceptibility theory’.
Differential susceptibility theory → While children may have a great
capacity for plasticity, they also experience poor recovery.
Two contradictory explanations have emerged:
- Early plasticity → immature brain possesses great flexibility
that facilitates good recovery and outcome;
- Early vulnerability → the developing brain is uniquely
susceptible, with early brain insult leading to incomplete
recovery and poor outcome.
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, Both perspectives focus on: (i) if, and to what degree, the developing
brain and the functions it subsumes can recover; (ii) whether normal
development can be re-established post-insult; and (iii) what
mechanisms and influences might lead to specific outcomes.
A central concern in the debate is …
… whether specific brain functions (e.g., language, memory) are
‘innately specialised’ to specific brain regions, with limited potential for
transfer and reorganisation, leading ultimately to poor outcome...
… or if the developing brain is ‘equipotential’, with minimal functional
localisation early, facilitating healthy brain tissue to take up functions
that were previously the responsibility of damaged areas.
The debate is not only brain-specific, but also includes a range of
dimensions as potential mediators of recovery after early brain insult:
- Environment (social context, parenting style, access to
interventions);
- Child characteristics (sex, age at insult, genetics, pre-morbid
adaptive ability and temperament).
Advances in neurosciences (e.g., TMS, fMRI, tractography, deep
electrodes) provide the necessary tools to consider these factors and
their interactions with developmental processes.
Early plasticity Theoretical perspectives
vs early
vulnerability With an evolving capacity to integrate genetic, imaging and
behavioural findings, there is an opportunity to better map the
principles of brain plasticity.
However, take into account the distinction between two separate,
somewhat independent dimensions: neural a nd functional plasticity.
Neural plasticity → the brain’s response to the environment, refers to
physiological processes at molecular, cellular, neurochemical and
neuroanatomical levels and at the level of brain systems.
Functional plasticity → refers to behavioural change or recovery
occurring in response to environmental or injury-related events.
In normal neural and cognitive development → Parallel processes.
In disruption of genetically predetermined sequence of brain
maturation → neural recovery may not necessarily translate to
functional recovery.
Functional Early views regarding the benefits of plasticity for the immature brain
specialisation were largely informed by work investigating ‘equipotential’ or ‘innately
and specialised’ characteristics of the normally developing brain.
reorganization
Equipotential → in the ‘equipotential’ brain both cerebral hemispheres
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, are capable of mediating a wide range of skills, especially language.
This view is consistent with the early plasticity perspective and
predicts that skills disrupted by early brain insult are subsumed by
other brain regions with no loss of function.
→ Research following children from language-deprived backgrounds
shows that the capacity to acquire language skills is best if
intervention occurs within the preschool period, then declines
markedly to age ten.
Innate specialization → Taking a localizationist approach, an innate
specialisation position considers language to be ‘biologically unique’,
with predetermined cortical regions critical for its acquisition and
representation.
Example: If these pre-specified language areas are damaged,
language impairment is expected.
→ However, recently there has been a lack of direct evidence for this
perspective.
Interactive specialization → offers a compromise, where brain
development is characterised by increasing specialisation, or
fine-tuning of response properties, with these properties specific to
brain regions, and changing as they interact and compete to acquire
their roles.
Neurobehavioral Evidence of recovery of function derives from a variety of research
recovery from methods: animal research and human research.
early brain
insult Animal research
Pioneer in the plasticity debate: Kennard’s animal work of the 1930s
and 1940s. Based on her research with monkeys, the ‘Kennard
principle’ was coined.
Kennard principle → Early lesions lead to better outcomes than
similar lesions in adulthood.
Most animal researchers use focal lesion models, but such lesions
are relatively uncommon in children.
Human research
Human studies, mostly with children with focal unilateral lesions (e.g.,
stroke), seizures and hemispherectomy for treatment of intractable
epilepsy, have generally reported good recovery following early brain
insult.
However, some suggested that there are likely limits to plasticity in
the immature brain.
Functional imaging studies also provide evidence that, following early
brain insult, there is potential for relocation of language skills, or at
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