Summary Developmental Neuropsychology
Developmental Neuropsychology: A clinical approach (2nd edition), H1 t/m H12 + articles
Summary book
Chapter 1: What is child neuropsychology and how has it developed over the past
twenty years?
Child neuropsychology, also known as paediatric neuropsychology, is the study of
association between brain and behavior within the context of an immature, but rapidly
developing, brain and the implementation of knowledge gained from that into clinical
practice. The main focus of child neuropsychology is to generate a developmentally informed
knowledge base that facilitates optimal understanding of the impact of early brain injury on
brain development and child function, which in turn can be used as guidance for designing
evidence-based interventions to minimize disability.
Child neuropsychology takes its foundations from adult neuropsychology. Yet, whereas adult
neuropsychology relates to a more static and tightly organized system, child neuropsychology
relates more to a dynamic path that can be characterized by plasticity, vulnerability, and
critical periods. Consequently, adult-based models needed to be adapted to be relevant for
implementation with infants, children, and adolescents.
Nowadays, developmental perspectives have extended our knowledge base significantly,
acknowledging the complex interplay of neurologic, cognitive, socio-emotional, and
environmental factors important to child neuropsychology.
The earliest contributions to child neuropsychology can be traced back to researchers such as
Kennard (1936; 1940) and Teuber (1974), who gave descriptions of plasticity and recovery of
function after childhood brain damage. These researchers documented relatively good
recovery following early brain insult. This is also nicely covered in the Kennard principle: "If
you're going to have brain damage, have it early". This early research offered an important
contribution to the field, because, among others, they acknowledge the unique processes that
may be acting in the developing brain following an injury or insult.
Later research added information about critical periods to the knowledge base, improving our
understanding of the mechanisms at play following early brain insult. A critical period is
defined by Mogford and Bishop (1993) as: "the time window during which external
influences have a significant effect". It was found that early brain insult can have different
effects at different times throughout development and, sometimes, may even be more
destructive than later injury, because some aspects of cognitive development are critically
dependent on the integrity of particular cerebral structures at specific stages of development.
To date, only a handful of studies have attempted to formulate brain-behavior paradigms of a
truly developmental nature. There is basically no theoretical framework that successfully
integrates biological, psychological, and environmental dimensions in a clinical meaningful
way. It has even been argued that there has been little theoretical progress since 2 seminal
models that have been developed in the late 1980s. These models are: (1) Non-verbal learning
disability, developed by Byron Rourke in 1989, and (2) Multidimensional age at insult,
developed by Maureen Dennis (1989).
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,Model 1: Non-verbal learning disability (NVLD)
According to this model, non-verbal learning disability in children is characterized by:
1. Bilateral tactile-perceptual deficits, more marked on the left side of the body
2. Impaired visual recognition and discrimination and visuospatial organizational
deficiencies
3. Bilateral psychomotor coordination problems, more marked on the left side of the
body
4. Difficulties managing novel information
In addition, children with NVLD may also demonstrate intact skills, in particular within the
auditory-verbal domain. These are listed as follows:
1. Simple motor skills
2. Auditory perception
3. Rote learning
4. Selective and sustained attention for auditory-verbal information
5. Basic expressive and receptive language
6. Word reading and spelling
This model offers an important contribution to the field, because it incorporates knowledge
from the neuro dimension with the development of a specific cognitive development:
the psych dimension. A key contribution of this model is the linkage between cognitive
characteristics to an underlying neurologic explanation: the white matter hypothesis. The
underlying assumption of this model is that normal development of white matter is essential
for intact child development.
Model 2: Multidimensional age at insult
This 'heuristic' describes the impact of brain damage on language development. Skill
development can be divided into several levels:
− Emerging: the ability is in the early stages of acquisition, but is not yet functional
− Developing: the ability is partially acquired, but not fully functional
− Established: the ability is fully matured
These developmental skills are integrated with 3 crucial age-related variables:
− Age at time of lesion: determines the nature of the cognitive dysfunction. For example,
early lesions are associated with a disrupted onset and rate of language development,
whereas later lesions are associated with a specific symptom pattern, such as high-
level language dysfunction (e.g., impaired pragmatic skills)
− Age at testing: early brain insults may cause relatively few problems early after the
injury, yet children may "grow onto" deficits with ongoing development, as they fail
to acquire age-expected skills
− Time since insult: there are different performance patterns at different stages of
recovery
Advances in the neurosciences have led to the development of theories that propose a
complex relationship between risk factors. More specifically, it is argued that these risk
factors interact and vary over time, determining functional outcomes after early brain insult.
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,Within this framework, 2 familiar models are:
1. The cognitive reserve model (Dennis and colleagues, 2007): proposes 2 types of
factors:
− Mediating factor: children differ in their reserve capacity, which is composed
by: brain reserve capacity (BRC) and cognitive reserve capacity (CRC)
− Moderating factors: age at the time of brain insult, age at examination, and
time elapsed since brain insult
2. Recovery continuum model (Anderson and colleagues, 2011): proposes that recovery
is best understood by considering a continuum approach, whereby various potential
risk and resilience factors interact to determine long-term outcome
− Injury: severity, nature, complications
− Cognitive skill: simple, complex
− Development: age at injury, age at assessment
− Environment: distal and proximal factors
Another model that is well-established nowadays is the biopsychosocial model. According to
this model, threats are numerous and span multiple domains:
1. The bio dimension: neurodevelopment of the brain
2. The psych dimension: cognitive and socio-emotional development
3. The social dimension: environmental influences: familial (language, cognitive skills,
social behavior, rules) and extrafamilial contexts (academic skills, motoric skills,
identity development)
To more comprehensively study the interacting influences of biology and environment, we
need to build robust cross-discipline collaborations. The combined knowledge, in turn, can be
translated into ' best' practice in the field to enhance optimal outcomes for children, as well as
for the benefit of the community.
Chapter 2: What are the main characteristics of brain development?
Cerebral development is an ongoing process, beginning early in gestation and continuing into
childhood through early adulthood. Brain development can be divided into 2 phases in which
birth is a rough marker for the transition between these 2 qualitatively distinct stages:
1. Prenatal development: is mainly concerned with the structural formation of the
central nervous system (CNS). This stage is thought to be largely determined by
genes. The quickest rate of brain growth occurs during the prenatal stage, when it is
estimated that 250,000 brain cells are formed each minute through continuous rapid
cell division
2. Post-natal development: is mainly characterized by elaboration of the brain, in
particular dendritic aborisation, myelination, and synaptogenesis. While these
processes are still largely determined genetically, they are more susceptible to the
impact of neuronal activity and they are thus more susceptible to environmental and
experimental influences
Brain development is complex with many different developmental mechanisms occurring
both in sequence and simultaneously. In addition, a number of factors can interfere with this
process, potentially causing irreversible changes to these developmental processes and to the
final outcome. Prenatal risk factors include: maternal stress and age, maternal health (e.g.,
history of infection, rubella, AIDS, herpes simplex), nutrition (diet, malnutrition), maternal
drug and alcohol addiction, environmental toxins (e.g., lead, radiation, trauma).
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, Post-natal risk factors include: birth complications, nutrition, environmental toxins (e.g., lead,
radiation, trauma), cerebral infection, environment/experience
Cerebral development is not a simple linear process of development. Instead, there is a range
of developmental processes, with many occurring simultaneously, reflecting differential
developmental timing for various brain regions. These developmental brain processes are:
− Hierarchical progression: first the brainstem and the cerebellum, then the posterior
regions of the forebrain, lastly the anterior regions of the forebrain. The corpus
callosum develops from anterior to posterior
− Additive and regressive events: additive development refers to the
ongoing accumulation of growth processes, for example myelination, shown by the
increasing connectivity of myelinated white matter from birth to 18 years. Regressive
development refers to initial overproduction, followed by selective elimination of
redundant element. For example, excess synapses are overproduced in infancy and
those that do not form functional networks become obsolete connections and are
pruned
− Growth spurts in neurological process: brain maturation is not linear, but is
characterized by a series of growth spurts. An initial growth spurt is recorded between
1.5 and 5 years, a second growth spurt between 5 and 10 years, and a final growth
spurt between 10 and 16 years. These accompany critical periods for development.
However, many questions regarding these periods remain. For example, are there
different critical periods for different neurobehavioral domains? Do some skills have
shorter critical periods than others?
Brain development progresses via the rapid generation of 2 main classes of cells:
1. Neurons: form the basic functional unit of the CNS and are responsible for neural
transmission within the brain. Neurons consists of 4 primary components:
− Cell body: important for the metabolic functions of the neurons. The cell body
holds the RNA and DNA
− Axon: conducting neural impulses away from the cell body. It is progressively
sheathed with myelin throughout childhood
− Dendrites: branch off the cell body and receive impulses from other neurons,
conducting them towards the cell body. Dendrite spines are the locus of the
synapse: they form the location where information is transmitted from one
neuron to another
− Presynaptic terminals: where neurotransmitters are stored and released. They
activate the neurons at the post-synapse
2. Glial cells: play a supportive and nutrient role within the CNS enabling regeneration
of damaged neurons. They produce scar tissue to occupy damaged sites and transport
nutrients from nerve cells. There are different types of glial cells:
− Astrocytes: form the blood-brain barrier. They support the cellular structure of
the brain and contribute to the migration of neurons and cleaning of plug injury
sites
− Oligodendrocytes: are responsible for speeding up the transmission of neural
impulses throughout the nervous system by coating axons with myelin
− Microglia: clean up injury sites, mainly in the grey matter
Prenatal brain dysfunction has different consequences, depending on the timing of the insults.
A brief summary is provided in the table on the next page.
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