Summaries: the best articles about neurodevelopment and pediatric neuropsychology

Summaries of the best scientific articles about Neurodevelopment and Pediatric Neuropsychology

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Article summary with Malleability, plasticity, and individuality: How children learn and develop in context by Cantor a.o. - 2018 - Exclusive
Article summary with Annual Research Review: DNA methylation as a mediator in the association between risk exposure and child and adolescent psychopathology by Barker a.o. - 2018 - Exclusive
Article summary with Hormonal changes associated with intra-uterine growth restriction: Impact on the developing brain and future neurodevelopment by Baud & Berkane - 2019 - Exclusive
Article summary with Genetic control of postnatal human brain growth by Van Dyck & Morrow - 2017 - Exclusive
Article summary with Early nutrition influences developmental myelination and cognition in infants and young children by Deoni a.o. - 2018 - Exclusive
Article summary with Developmental origins of the human hypothalamic-pituitary-adrenal axis by Howland a.o. - 2017 - Exclusive
Article summary with Concern for others in the first year of life: Theory, evidence, and avenues for research by Davidov a.o. - 2013 - Exclusive
Article summary with Development of visual-spatial attention by Johnson - 2019 - Exclusive
Article summary with Making sense of the world: Infant learning from a predictive processing perspective by Köster a.o. - 2020 - Exclusive
Article summary with The mechanisms and moderators of “Fade-Out”: Towards understanding why the skills of early childhood program participants converge over time with the skills of other children by Abenavoli - 2019 - Exclusive

Article summary with The mechanisms and moderators of “Fade-Out”: Towards understanding why the skills of early childhood program participants converge over time with the skills of other children by Abenavoli - 2019 - Exclusive

Article summary with The mechanisms and moderators of “Fade-Out”: Towards understanding why the skills of early childhood program participants converge over time with the skills of other children by Abenavoli - 2019

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Article summary with Linking language and cognition in infancy by Perszyk & Waxman - 2018 - Exclusive
Article summary with The role of the motor system in action understanding and communication: Evidence from human infants and non-primates by Salo a.o. - 2018 - Exclusive
Article summary with A systematic review of targeted social and emotional learning interventions in early childhood education and care settings by Blewitt a.o. - 2019 - Exclusive
Article summary with Temperamental vulnerability to emotion dysregulation and risk for mental and physical health challenges by Calkins & Dollar - 2019 - Exclusive
Article summary with A systematic review of reviews of the outcome of noninstitutional child maltreatment by Carr a.o. - 2020 - Exclusive
Article summary with Understanding the development of face and emotion processing under a predictive processing framework by Pereira a.o. - 2019 - Exclusive
Article summary with Neural substrates of early executive function development by Fiske & Holmboe - 2019 - Exclusive
Article summary with The neurodevelopment of autism from infancy through toddlerhood by Girault & Piven - 2020 - Exclusive
Article summary with Executive function in the first three years of life: precursors, predictors and patterns by Hendry a.o. - 2016 - Exclusive
Article summary with Early life stress and brain function: Activity and connectivity associated with processing emotion and reward by Herzberg & Gunnar - 2020 - Exclusive
Article summary with Environmental toxicology: Sensitive periods of development and neurodevelopmental disorders by Heyer & Meredith - 2017 - Exclusive
Article summary with Associations between screen-based media use and brain white matter integrity in preschool-aged children by Hutton a.o. - 2019

Article summary with Associations between screen-based media use and brain white matter integrity in preschool-aged children by Hutton a.o. - 2019

Childhood is becoming more and more digitized. Though still not clear, there may be developmental and health risks with excessive screen-based media use. These risks include language delay, impaired executive function, poor sleep, impaired general cognition, decreased parent-child engagement, and possibly neurobiological risks. 

How can increased screen-based media use affect children’s development?

Childhood is becoming more and more digitized. Though still not clear, there may be developmental and health risks with excessive screen-based media use. These risks include language delay, impaired executive function, poor sleep, impaired general cognition, decreased parent-child engagement, and possibly neurobiological risks. 

What is diffusion tensor imaging?

Diffusion tensor imaging (DTI) is a technology to quantify white matter integrity in the brain and its various factors. Parameters of DTI include fractional anisotropy (FA) and radial diffusivity (RD), scalar values associated with microstructural organization, and myelination of white matter tracts. 

What are the structural neurobiological correlates of screen-based media use in preschool-aged children?

A cross-sectional study revealed the following results:

  • Fractional anisotropy is associated with organization of white matter in parallel bundles, whereas radial diffusivity is inversely associated with degree of myelination of such bundles, as well as axonal packing and other microstructural processes. 
  • Increased screen time was associated with lower fractional anisotropy and higher radial diffusivity of the arcuate fasciculus, and also with lower EVT-2 and CTOPP-2 scores. 

What can be concluded based upon these correlations?

Increased use of screen-based media was associated with lower microstructual integrity of brain white matter tracts that support language, executive functions, and emergent literacy skills. Screen use was also associated with lower scores on corresponding behavioral measures.

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Article summary with Autism as an adaptive common variant pathway for human brain development by Johnson - 2017 - Exclusive
Article summary with Neural histology and neurogenesis of the human fetal and infant brain by Kostovic a.o. - 2019

Article summary with Neural histology and neurogenesis of the human fetal and infant brain by Kostovic a.o. - 2019

What general principles are essential for understanding the developmental dynamics of fetal and baby brain?

  • Developmental events occur in specific architectonic compartments, such as embryonic and fetal zones. 
  • The compartments are transient, but can be visualized in historical sections and MR images.
  • To be able to understand the development of functional connectivity, the nature and timing of development of basic connectivity elements and their molecular properties need to be analyzed. 

What are important events in brain development in the early fetal period (eight to fifteen postconceptional weeks)?

  • There are processes of proliferation, migration, and cell aggregation. 
  • All embryonic brain divisions and their major subdivisions are clearly visible on coronal sections at the end of the embryonic period.
  • The formation of the cortical plate is an important cytoarchitectonic event. After its formation, the cerebral wall of the lateral neocortex consists of the marginal zone, the cortical plate, the presubplate, the intermediate zone, the subventricular zone, and the ventricular zone. 
  • According to the radial unit hypothesis, the cortical neurons are generated in proliferative units of the ventricular zone, migrate along radial glial guides and settle in vertical ontogenetic columns within the cortical plate. 
  • With regards to the growth of early afferents to the human cerebral cortex, thalamocortical fibers pass through the cerebral stalk, cross the diencephalo-telencephalic and subpallio-pallial border and fan out within the intermediate zone on their way to the cortical anlage. Basal forebrain fibers reach the neocortical cerebral wall through the external capsule. Corticospinal and corticopontine pathways are located medial to thalamic radiation and are partily intermingled with it. 
  • The first synapses in the neocortical anlage appear. 
  • There is a trilaminar pattern of organization consisting of the cortical plate, the intermediate zone, and periventricular proliferative zone. 
  • Changes in cell aggregation (cytoarchitectonics), proliferation and migration, neuronal and dendritic differentiation, and axonal growth.

What are important events in brain development in the midfetal period (fifteen to twenty three postconceptional weeks)?

  • Four histogenetic-neurogenetic events are most important during this period: neuronal aggregation and cytoarchitectural development, axonal outgrowth and ingrowth, dendritic differentiation, and molecular specification.
  • The formation of synapses continues in the subplate and marginal zone. 
  • Molecular specification of cerebral cortex can be divided in two processes, namely the areal specification and the specification of subsets of cortical neurons. 
  • Major protection and commissural pathways are still growing (think of corticostriatal, corticospinal, thalamocortical, corticopontine, and corpus callosum).
  • Associative pathways are not well developed, except for associative fibers connecting frontal cortex with cingulate neocortical portion of the limbic lobe.
  • The presence of synapses in the subplate and the dense distribution of synapses in the marginal zone indicate circuitry development.

What are important events in brain development in the late fetal period (twenty four to thirty four postconceptional weeks)?

  • Three histogenic and neurogenetic processes are most important during the beginning of the late fetal period: ingrowth of axons, synaptogenesis, and dendritic differentiation of pyramidal neurons.
  • Rapid development of primary sulci and gyri. The central, precentral, and postcentral sulcus delineate the developing precentral and postcentral gyrus. Superior and inferior temporal sulcus appear in the temporal lobe. Superior and inferior frontal sulci mark the position of future superior, medial, and inferior frontal gyrus in the frontal lobe.
  • On the medial hemispheric surface, there is deepening of the parieto-occipital and calcarine fissure and the appearance of the cingulate sulcus.
  • Gradual decrease in the intensity of neuronal proliferation in ventricular and subventricular zone.
  • At the end of the late fetal period secondary sulci develop rapidly, there is an increase in the volume of the cerebral wall, and there is a decline in proliferative zones.
  • During the end of the late fetal period, the most intensive histogenetic events are neuronal aggregation, cytoarchitectonic changes in laminar pattern, axonal ingrowth and outgrowth, dendritic differentiation, and synaptogenesis in the cortical plate.

What are important events in brain development in the neonatal period?

  • The main event is the formation of tertiary gyri.
  • There are advances in neuronal aggregation and cytoarchitecture, with parallel establishment of tangential and radial patterns. There is gradual resolution of layer IV in the premotor cortex and the disappearance of this layer in the motor cortex, resolution of the voluminous subplate and its transformation into a characteristic thin band at the interface between layer VI and the gyral white matter, and an increase in size of pyramidal cell bodies.
  • There is growth of short corticocortical fibers.
  • Dendritic differentiation.
  • Synaptogenesis.
  • Myelination and increase in compactness of axonal pathways.
  • Cell death and axonal pruning.
  • The proliferation and migration of neurons have ceased, while the proliferation of astrocytes and oligodendrocytes is continuing.

What are important events in brain development in early infancy?

There is a rapid and massive increase in the total brain volume during the first year. The elaboration of cortical gyrification continues. Some histogenetic processes rapidly increase in intensity (such as synaptogenesis and dendritic differentiation), while others follow a steady pace (such as cytoarchitectonig development, neurochemical maturation, and myelination). There is a decline in the growth of axonal pathways.

What are important events in brain development in late infancy?

The cerebral hemispheres continue to grow. The most intense histogenetic and neurogenetic events during this period are morphological differentiation of neurons and dendrites, synaptogenesis, myelination, and changes in cortical cytoarchitectonics.

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Article summary with Premature birth and developmental programming: Mechanisms of resilience and vulnerability by Lammertink a.o. - 2021 - Exclusive
Article summary with The relationships between screen use and health indicators among infants, toddlers, and preschoolers: A meta-analysis and systematic review by Li a.o. - 2020 - Exclusive
Article summary with Promoting self-regulation in young children: The role of parenting interventions by Morawska a.o. - 2019 - Exclusive
Article summary with Walk like me, talk like me. The connection between mirror neurons and autism spectrum disorder by Saffin & Tohid - 2020 - Exclusive
Article summary with Effects of parenting interventions for at-risk parents with infants: a systematic review and meta-analyses by Rayce a.o. - 2017 - Exclusive
Article summary with Self-regulation in preschool and early elementary classrooms: Why it is important and how to promote it by Savina - 2021 - Exclusive
Article summary with Institutionalisation and deinstitutionalisation of children 1: a systematic and integrative review of evidence regarding effects on development by Van IJzendoorn e.a. - 2020 - Exclusive

Article summary with Institutionalisation and deinstitutionalisation of children 1: a systematic and integrative review of evidence regarding effects on development by Van IJzendoorn e.a. - 2020 - Exclusive

Article summary with Institutionalisation and deinstitutionalisation of children 1: a systematic and integrative review of evidence regarding effects on development by Van IJzendoorn e.a. - 2020

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Article summary with Annual Research Review: Umbrella synthesis of meta-analyses on child maltreatment antecedents and interventions: differential susceptibility perspective on risk and resilience by Van IJzendoorn a.o. - 2020 - Exclusive

Article summary with Annual Research Review: Umbrella synthesis of meta-analyses on child maltreatment antecedents and interventions: differential susceptibility perspective on risk and resilience by Van IJzendoorn a.o. - 2020 - Exclusive

Article summary with Annual Research Review: Umbrella synthesis of meta-analyses on child maltreatment antecedents and interventions: differential susceptibility perspective on risk and resilience by Van IJzendoorn a.o. - 2020

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Article summary with Towards an integrated account of the development of self-regulation from a neurocognitive perspective: A framework for current and future longitudinal multi-modal investigations by Vink a.o. - 2020

Article summary with Towards an integrated account of the development of self-regulation from a neurocognitive perspective: A framework for current and future longitudinal multi-modal investigations by Vink a.o. - 2020

Poor self-regulation in childhood has been linked to various problems later in life. An integrated account in which longitudinal data on brain, behavior, and environment are all taken into consideration should help to understand causal relationships in terms of specific, well-defined mechanisms and develop interventions for when development goes wrong. An integrated account could help understand how effects of early problems can be prevented or minimized.

What is self-regulation?

Self-regulation refers to the ability to monitor and modulate our emotions, behavior, and cognition to allow us to achieve our goals and adapt to changing circumstances. Self-regulation develops in interaction with the environment in complex ways that result in positive or negative developmental cascades. Low levels of self-regulation early on in life can impede self-regulation development later in life. Unlike some other factors that may cause adverse outcomes, self-regulation may be quite malleable and be a good target for intervention.

What is the difference between effortful control and strategic control?

Effortful control refers to lower-level self-regulation. It involves the use of relatively simple executive functions, such as response inhibition or attention. It focuses on responding to the immediate situation. It can refer to both a trait and a type of process. Strategic control refers to the use of higher-order executive functions to achieve more sophisticated forms of self-regulation, such as planning. Different levels of self-regulation arise at different developmental periods.

How does self-regulation develop?

Self-regulation develops in interaction with a maturing brain. The emergence of brain networks and the quality of their connections, among other developments, dictate the possibilities and limits for self-regulation abilities. In turn, self-regulation abilities, learning, and adapting to new experiences affect subsequent brain development. Brain development is not a linear process. Maturation occurs in distinct developmental periods which can be distinguished by the onset or end of specific neural processes. Neuroimaging measures may improve our understanding of how self-regulation develops.

What is effortful control and how does it develop?

Effortful control refers to the top-down control over bottom-up processes for purposes of self-regulation. The low-level executive functions that are fundamental to early life self-regulation begin to emerge in the first year of life. In early stages of development, self-regulation involves only effortful control and associated low-level executive functions. In later stages of development, age-appropriate self-regulation can involve different and more complex cognitive processes. The development of more complex self-regulation is parallel by the development of the orienting-attention network that enables children to orient to stimuli and to shift attention from one stimulus to another, and subsequently the executive attention network.

How do higher-level executive functions develop in relation to brain maturation?

High-level executive functions build on the integration of the low-level executive functions that have developed in infancy. Brain development early in life can be characterized by volume expansion, neuron growth, and synapse formation. Then, during childhood, gray matter volume starts to shrink. Myelination of white matter nerve fibers and synaptic pruning combine to form brain networks that support the shift from low-level to high-level executive functions.

How does strategic control develop in relation to brain maturation?

Strategic control requires goal-directed coordination of previously acquired low- and high-level executive functions. It is a level of self-regulation that emerges during adolescence due to the effective integration and coordination of executive functions. It co-occurs with the improvement of the quality of connections between cortical and subcortical regions, facilitated by the increase in myelination of white-matter tracts connecting these regions, allowing for faster and more precise neural signaling.

Why whilst fine-tuning effortful control are there so many indicators of reduced self-regulation capacity in adolescence?

Adolescence is associated with behaviors such as increased risk taking, heightened sensitivity to social cues, and impulsivity. These indicators of reduced self-regulation capacity appear to be related to a developmental, transient imbalance between frontal lobe control and subcortical reward processing. There are regional differences in maturation speed across the brain, with the frontal cortex developing the slowest.

Why is there no integrated developmental account of self-regulation?

  • Self-regulation is conceptualized, labeled, and measured in many different ways, hindering the integration of data from different groups and studies.
  • There is a lack of integration of developmental measures of self-regulation with repeated neuroimaging studies.
  • There is a lack of integration across different developmental periods.

What is the benefit of an integrated developmental account of self-regulation?

Poor self-regulation in childhood has been linked to various problems later in life. An integrated account in which longitudinal data on brain, behavior, and environment are all taken into consideration should help to understand causal relationships in terms of specific, well-defined mechanisms and develop interventions for when development goes wrong. An integrated account could help understand how effects of early problems can be prevented or minimized.

What is the role of the Consortium on Individual Development (CID) in developing an integrated developmental account of self-regulation?

The CID combines a series of integrated large-scale, multi-modal, longitudinal studies and uses the same instrument in all cohorts, addresses a range of essential factors in the development of self-regulation, and allows for the analysis of the same concept measured in a comparable way. It researches different cohorts and taps into different environmental factors and brain and behavioral measures throughout childhood and adolescence, with repeated neuroimaging measurements.

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Article summary with Graph theoretical modeling of baby brain networks by Zhao a.o. - 2019

Article summary with Graph theoretical modeling of baby brain networks by Zhao a.o. - 2019

In graph theoretical modeling, a network is composed of a certain number of nodes that are connected by weighted or un-weighted edges. A graph can be classified as a director or undirected type, depending on the existence or absence of directional information associated with the edges. In human brain development studies, the macro-scale network is often used. It is a model that can record the inter-regional connections in the whole brain in vivo through neuroimaging data. Network modes in this model are usually defined by brain partitions that are previously assigned, and the edges are determined by the structural or functional interactions between the separate brain regions.

What is the graph theoretical modeling framework?

In graph theoretical modeling, a network is composed of a certain number of nodes that are connected by weighted or un-weighted edges. A graph can be classified as a director or undirected type, depending on the existence or absence of directional information associated with the edges. In human brain development studies, the macro-scale network is often used. It is a model that can record the inter-regional connections in the whole brain in vivo through neuroimaging data. Network modes in this model are usually defined by brain partitions that are previously assigned, and the edges are determined by the structural or functional interactions between the separate brain regions.

How are network nodes defined?

Acquiring network nodes relies on neuroimaging. In EEG, fNIRS, and MEG studies, nodes are determined by using their derived cortical locations of electrodes, detectors, or sensors. In MRI studies, a parcellation scheme or atlas is needed to divide the brain into different regions of interest which are defined based on anatomical or functional information or on a random algorithm. Different parcellations capture different patterns of structural or functional pathways. The number of nodes significantly influences the absolute value of topological attributes.

How are network edges defined?

Brain regions are structurally connected through a large number of fiber bundles that provide biological pathways for information transfer. Through dMRI-based tractography, these fiber tracts can be reconstructed and then used to define edges of the structural connectivity network. The number of reconstructed streamlines or averaged informative diffusion indexes of the connection can be used as the edge weight.

What is network thresholding?

Before obtaining the brain network, a thresholding step is usually performed to define the edges to be used in the subsequent graph theoretical analysis, though some studies use the raw weighted network without thresholding. There are different ways of doing this:

  • Setting an absolute cut-off value to select edges with greater weights in an individual network. Excluding weak edges may reduce the effects of weak covariance or spurious connections that could be caused by imaging noise, cumulative tractography errors, or head motions.
  • In proportional thresholding a fixed number of the strongest connections are retained in each subject. It equals the network density across individuals to minimize its influence on network topological properties, though it may ignore potentially valuable connections.

What are global and nodal aspects?

The topology of a brain network can be characterized in terms of its global and nodal aspects. The global attributes measure the architecture of the whole network graph. The nodal attributes measure topological features of a single node.

What is meant with the segregation of a network?

The segregation of a network refers to the ability of local information processing that is responsible for specialized functions. The clustering coefficient and modularity are two attributes that provide a quantitative measurement of the segregation capacity of brain network.

What is the clustering coefficient of a node and of a network?

The clustering coefficient of a node refers to the tendency to which the neighboring nodes of a node are interconnected. It reflects the density of local clusters. The clustering coefficient of a network refers to the average nodal clustering coefficients across all nodes in the network.

What is meant with the integration of a network?

Network integration refers to the ability of parallel communication with distributed nodes which can be quantitatively measured by the characteristic path length or global efficiency. The characteristic path length of a network can be calculated by averaging the shortest path lengths between each pair of nodes in the network. A path represents a route of edges that connect one node with others. Its length is defined as the sum of the number or weights of the edges. The global efficiency of a network is the inverse of the average values of the shortest path length between any two nodes. A high degree of network integration is seen in a network that has high global efficiency and the low shortest path length has high global information transfer efficiency.

What is a small-world network?

A small-world network possesses a shorter characteristic path length than a regular network and a higher clustering coefficient than a random network, to guarantee high capacity for local and global information transfer networks. It is an optimized topology that balanced between a regular and a random network. A regular network has a high clustering coefficient and long characteristic path length. A random network has a low clustering coefficient and a short characteristic path length.

What is nodal degree?

Nodal degree is the most direct nodal metric, referring to the number of edges linking to a node. High degree nodes function as hubs in information transmission. The degree distribution of a network indicated the proportion of nodes that have a certain degree, which can be an indication of the resilience of the network. Rich-club organization refers to highly connected hubs, indicating that the hub nodes tend to be more densely interconnected with each other than by random chance would be expected.

Which types of network edges are distinguished?

The network edges can be classified into three types:

  • Rich-club connections which link between rich-club nodes.
  • Feeder connections which link between peripheral and core nodes.
  • Local connections which link between non-rich-club nodes.

How does the prenatal brain network develop?

The prenatal structural network already shows broadly adult-like topological structures. The network is already highly efficient at local and global information transfers, possessing the specialized local communities for segregation and the high-cost backbones for integration. Increased normalized clustering coefficient, stable normalized shortest path length, and increasing small-worldness with development indicate that the shaping of the network seems to lean toward segregation enforcement during the prenatal stage. Short-range connections develop fast, hub regions expand into the inferior frontal cortex and insula regions and develop fast on their nodal connectivity and nodal betweenness centrality.

How does the postnatal brain network develop?

Structural segregation appears to be decreasing while structural integration is increasing, as can be seen by decreased modularity and characteristic path length and increased number of inter-module connectors and global efficiency. During early postnatal life there is dynamic regional reshaping in the structural network, as expressed by upgrades in network robustness and the left anterior cingulate gyrus and left superior occipital gyrus which become hubs. Neonatal functional brain networks maintain highly efficient small-world and modularity structure. The dorsal attention network and default mode network mature at one year of life, whereas the salience network and bilateral frontoparietal network are still developing at that time.

What is the topological development of the baby brain network?

With regards to the structural network, the hypothesis is that the structural network is well-established at the time of birth, with many local connections within modules and several major distant connections between modules. With development, the network becomes more segregated with enhancement of local clusters during prenatal development. Then it becomes more integrated with increasing inter-module connections during postnatal development. With regards to the functional network, the hypothesis is that it is still immature and incomplete at birth. With development, the network shows enhanced segregation during prenatal development. Then the emergence and increase of long connections intensify the integrated ability of networks.

How does preterm growth affect the development of the brain network?

Preterm growth is the most common type of early atypical growth. It involves the sudden interruption of typical development processes as a result of complex genetic and environmental processes. The abnormal brain topology is characterized by disruptions in cortical-subcortical connectivity and short-distance cortico-cortical connections, as well as reduced edge strengths in widespread tracts, increased clustering coefficient, and increased nodal clustering coefficients located at the lateral parietal, ventral, and lateral frontal cortices. The changes in brain network caused by preterm birth continue into later life.

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Developmental Neuropsychology: ADHD

Developmental Neuropsychology: ADHD

Examining a pilot study of methylphenidate, interstimulus interval, and reaction time performance of children with attention deficit/hyperactivity disorder

Attention deficit/hyperactivity disorder (ADHD) is one of the most common found disorders in children. Characterized by inattention and hyperactivity, ADHD is primarily an inherited disorder. Treatment usually involves methylphenidate (MPH), which works by regulating the dopamine system. This often results in a decrease in impulsivity, hyperactivity, and inattention. Despite this, children on MPH still experience deficits in cognitive faculties. Other studies have shown that children with ADHD perform differently depending on the length of a stimulus they are exposed to. If the stimulus is a short interstimulus interval (ISI), the children experience a more positive performance in comparison to a long ISI. A short ISI has been shown to improve memory recognition, vigilance, motor timing, and more. It is thought that both MPH and a short ISI act upon the dopamine levels in the brain. It is proposed that having both of these working at the same time may over-activate the system and lead to detrimental effects. The goal of this study was to measure the isolated and combined effect of MPH and ISI on mean response times and errors of commission.

Procedure

For this study the sample consisted of 13 children (10 boys; 3 girls) diagnosed with ADHD. During the time of the study, MPH was gradually introduced for a two week period, either adjusting to a higher or lower dosage. After the children had been on MPH for 4 weeks, they were tested twice, once after the administration of MPH, and once after a placebo. The task which the participants engaged in was a computer based reaction time test known as Go/No-Go test. This involved pressing a button when the letter Q appeared onscreen and press nothing when the letter O appeared. If the participant responded to the letter O, this was recorded as an error of commission.

Looking at results

The results from the study indicate:

  1. Children respond faster on MPH than not on MPH

  2. Children respond faster in a condition with a short ISI rather than a long ISI

  3. The interaction of ISI and MPH was not significant

  4. Children on MPH made more errors of commission during the condition with a short ISI

  5. Children on the placebo made fewer errors of commission during the condition with a short ISI

For discussion

This study set out to ascertain whether children with ADHD were able to inhibit responses when they are in a state of over-activation. The findings of the study indicate that children perform better with either MPH or in the presence of a short ISI in comparison with a long ISI. When MPH and a short ISI are combined, they have detrimental effects. The stimulus shift hypothesis is supported by this outcome. This outcome calls into question the optimal dosage levels when treating ADHD.

State regulation and motivation in ADHD

Throughout past research, weak motivation has been shown to be a factor involved in ADHD. Two models exist to try and explain this deficit. The response inhibition model hypothesizes that the majority of problems related to ADHD can be explained by impaired response inhibition. The state regulation model, in contrast, associates ADHD with a motivation deficit which then results in negative outcomes for social functioning and cognition. In the more recent years, studies have investigated the effects of incentives, noise, and the rates of the presentation of stimuli.

Presence of incentives

Studies on the effect of incentives on response inhibition have produced mixed results. Some studies have shown that incentives increase response inhibition, others found the opposite. The authors suggest the following as possible reasons for these mixed results:

  1. Variation in the presentation of the rewards

  2. Effort allocation will only take place when arousal deviates from its basic state.

  3. Incentives act as signals; an increase in signals means an increase in motor activation

Noise

In accordance with the state regulation model, noise could activate the arousal system. One study showed that white noise was beneficial for the cognitive performance of children with ADHD, but was detrimental to control groups. The explanation for this result is the under-arousal found in ADHD.

Changing the presentation rate of stimuli

The state regulation model dictates that motor activation is effected by the presentation rate of a stimulus. Research has shown that children presented with a fast stimulus presentation rate perform better than when presented with a slow presentation rate. Very few studies have disputed this.

Top-down or bottom-up

From the studies conducted on reaction time and stimuli presentation rate, we see an interaction between motor activation and its control by effort. The researchers question whether this is due to a bottom up deficit in motor activation which in turn is hard to control by the top down effort mechanism, or actually the motor activation mechanism is functional and it is the effort mechanism which is not sufficiently in control. A suggestion is presented to examine the possibilities: to investigate the combined and individual effects of stimuli presentation rates and incentives on reaction time performance.

Looking at psychophysiological studies, dopamine, metabolic energy, and stimuli presentation rates

The following are findings from research conducted:

  1. Psychophysiological indices, under slow presentation rates of stimuli, support the hypothesis that ADHD is associated with an effort deficit

  2. Response impairments have been associated with either too high or too low levels of dopamine.

  3. Results of fMRI research show that ADHD participants use widespread frontostriatal activity, including the thalamus and the cingulate, when involved in accurate response inhibition

  4. Cortical excitability in adults is optimized by self chosen stimulation

  5. Effort allocation and boredom are negatively correlated

In conclusion

There is a growing accumulation of evidence supporting that cognitive performance of children with ADHD is associated with weak state regulation. The state regulation model is far from perfect. The plausibility of either a top-down or bottom-up deficit must be examined further.

Investigating the dysfunctional modulation of default mode network activity in attention-deficit/hyperactivity disorder

In accordance with the state regulation deficit (SRD) model, individuals with ADHD have difficulty applying mental effort in situations which are suboptimal i.e. when there are either very fast or very slow event rates (ERs). In addition, ADHD has been shown to be associated with a deficit in suppression of the default mode network (DMN) and detriments to performance in tasks requiring effortful engagement. The authors of the study hypothesize that individuals with ADHD would show reduced deactivation in DMN when compared to controls in the tasks. They also predict a failure to modulate DMN activity as a part of ER by the ADHD participants.

Procedure

The sample consisted of 20 adults with ADHD and a control sample of 20 age and gender matched adults. The task to be performed was a simple computer based response task. The task was kept simple to maximize the amount of trials which could be used for the characterization of DMN analysis. During the experiment, fMRI was used to monitor brain activity.

Results and discussion

This study presents evidence for a disparity in the modulation of activity in specific DMN areas by event response in ADHD. Over-activity of DMN was observed only at ER extremes, no group differences were observed at a moderate level. This is in line with the SRD model. Further studies are necessary to test the hypothesis of whether or not individuals with ADHD have problems focusing effort on suppressing DMN interference when in less than ideal or energetically orientated conditions and also to investigate the role of effort allocation impairment on inattention and mind wandering.

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Developmental Neuropsychology: Autism

Developmental Neuropsychology: Autism

Investigating the role of the frontal cortex in autism

Little is known about the underlying neural developmental defects which result in the emergence of autistic behavior during the early years of life. The frontal lobe has been identified as the most likely region to be involved, and yet little is known about it. The frontal lobe plays a key role in higher order language, cognitive, emotional, and social faculties, each one affected by autism. This has provided support for the frontal lobe hypothesis of autism. Through the collection of data from MRI and postmortem anatomical, and also already existing neurofunctional, postmortem, and MRI results from more mature autistic patients, the authors find two suggestions:

  1. In patients with autism, the frontal cortex is poor at interacting with other cortical regions

  2. During early development, the frontal cortex appears to be irregularly over-connected with itself

Examining macroscopic evidence of early frontal maldevelopment

Brain growth of patients with autism is normal at birth, ranging from average to slightly smaller than average. However this is followed by a period of excessive growth which results in an enlarged brain volume at the toddler age. Investigations into which brain regions cause this growth indicate the frontal lobes to be at the site of peak growth. Grey and white matter in the frontal lobes are both disparately deviant in regards to other cortical regions. While several studies have shown that primary sensory cortices in autism function normally, the same cannot be said for the frontal lobes. The deficient functionality found in the frontal lobe is hypothesized as being a factor which disrupts the frontal lobes interaction with other areas of the brain. It is unknown whether autism is to be classified as disorder of overconnectivity, underconnectivity, or a combination of the two.

Examining microscopic evidence of frontal maldevelopment

There remains a lack of knowledge on the microstructural abnormalities that disrupt frontal neural circuit development, facilitate the macroscopic overgrowth of frontal white and grey matter, and facilitate abnormal frontal mediated behavior. Where the link exists between abnormal neuroinflammatory response and initial brain overgrowth in autism is a mystery. It has been suggested that activated glia could be a reflection of a fetal state or development. When it comes to cerebral cortical information processing, a cortical minicolumn is an essential component. Studies have shown that minicolumns and their surrounding neuropil space are unusually small in children with autism throughout the frontal cortex, but not the occipital cortex. One older study found an increased neuron density and reduced neuron size within the frontal cingulate cortex in a number of autistic cases. It is suggested that these glial and neuronal abnormalities are in some way connected.

Drawing a conclusion

This is the first time that studies have shown early developmental abnormalities at the microscopic level and the macroscopic level and the presence of the frontal lobes as the peak of cerebral pathology. The work of abnormal processes (neuroinflammation, migration defects, excess cerebral neurogenesis) cause deformity, which leads to the malfunction of frontal minicolumn micro-circuitry. This in turn leads to reduced connectivity effectiveness between brain regions.

The role of response inhibition and immediate arousal in children with high functioning autism

It has long been the goal of many researchers to investigate the number of impairments that underlie the symptoms which characterize Autism Spectrum Disorder (ASD). Through the use of the executive functioning criteria, studies on ASD have highlighted planning, cognitive flexibility, and working memory to be areas which are weak in individuals with the disorder. The area of response inhibition is what the authors chose to focus on. More specifically, the study aimed to use an immediate arousal task to examine inhibition of responses in children with high functioning autism (HFA), and to look for an association with impulsivity, hyperactivity, or inattention.

Procedure

Participants for the study consisted of 39 children with HFA and a control group of 29 average functioning children. Once written permission was obtained from the parents, questionnaires were sent to the children to ascertain their suitability and possible comorbid disorders. The task consisted of a computer based reaction test. Participants were instructed in condition A to press a response button as quickly as they could upon the appearance of a white cross onscreen. In condition B they were instructed to wait for an acoustic signal before reacting as fast as they could to a white cross onscreen. The speed of the presentation rate was varied. An A-B-B-A style of sequencing of conditions was used.

Results and discussion

The aim of the study was to examine whether or not there existed a response inhibition deficit in children with HFA. The presentation of an auditory signal and a visual stimulus produced an arousal effect which resulted in an increase in error rate and a decrease in reaction time. It was hypothesized that this effect would be strongest in children with HFA. Inhibition errors did increase with the addition of the auditory signal, however this was not unique to the HFA group. The results of this study suggest that children with HFA don’t have a deficit in the inhibition system. This result is in dispute of some studies.

The role of cognitive flexibility in adults with functioning autism

Researchers are agreed that both social inadequacy and a deficit in executive functioning are both large factors which encompass autism. The main aim of this study focuses on investigating cognitive flexibility, more specifically response inhibition, set shifting, and motor presetting in regards to autism. Additionally a priori analysis was conducted by investigating the effects of the stimulus probability on performance. The authors mention the failure of previous studies in this area. Earlier studies failed to mention the patient’s medication status and thus failed to control for it. Additionally, these earlier studies often used experiment groups with varying age ranges. The authors generate four questions:

  1. Is HPA associated with problems presetting the motor system in favor of the most common response type

  2. Is HPA associated with weak set shifting

  3. Is HPA associated with weak response inhibition

  4. Is HPA associated with sensitivity for the given stimulus probability

Procedure

The sample consisted of 23 adults with HFA, and a control group of 32 typically functional individuals. The task consisted of a computer based variant of the Sternberg reaction time paradigm. The task presented participants with a set of letters to be memorized and then another set was displayed. If the participant recognized an item from the memory set in the display set, they gave a ‘yes’ response, otherwise they gave a ‘no’ response. The baseline condition consisted of 50% of the trials requiring a ‘no’ response; the response bias condition consisted of 75% of trials requiring a ‘no’ response. Each condition consisted of 64 trials.

Results and discussion

The aim of this study was to examine elements of cognitive flexibility, mainly set shifting, response inhibition, presetting, and a priori planning in individuals with HFA. Results show that participants with HFA experienced no deficit in response inhibition and the ability to change the response set. Despite this, there was a slow speed of performance found in participants with HFA, in particular those on medication. This slowness in speed may have been a contributing factor to cognitive flexibility deficit found in earlier studies which did not control for it. The study identifies a possible ceiling effect caused by an overall slowness of responses.

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Developmental Neuropsychology: Cognitive control and motivational systems

Developmental Neuropsychology: Cognitive control and motivational systems

Cognitive control and motivational systems in developmental neurobiology

Cognitive control is an executive process which can be vital to the maintenance and monitoring of long term goal oriented behavior. In the past, the development of cognitive control has been explained as a growth from infancy to adulthood. The role of context on cognitive control impacts one’s  behavioral regulation abilities, for example in a stressful context one may experience diminished control.  Recent studies suggest that cognitive control capacity is impacted by specific periods of development whereby one is more susceptible to incentive based modulation.

When examining studies on cognitive control performed in a controlled laboratory settings, we see a relatively stable improvement in cognitive control capacity from infants progressing to adults. However, outside of the laboratory setting, this is often not the case. This is particularly true for adolescence, who experience a reduced capacity for cognitive control when exposure to potentially risky behavior is at its peak. These fluctuations in behavior give evidence of dynamic maturation of the brain mechanisms responsible for motivation and cognitive processes. Two areas of the brain are highlighted for their importance in cognitive and motivational processes: the prefrontal cortex (essential for cognitive control) and the striatum (important for identifying interesting cues in an environment).

Examining the role of motivational modulation of cognitive control across development

Recently, research on the development of adolescences has focused on comparing cognitive capacity in neutral settings as opposed to motivational contexts. This research has implied that there exists a unique influence of motivation on cognition during the adolescent period, and that sensitivity to environmental cues (in particular incentive cues) changes at various points in development.

The behavior of adolescents has been shown to be differentially biased in motivational contexts. Studies have shown that motivational cues of potential reward are especially salient and potentially lead to the engagement in risky behavior and the further weakening of goal-orientated behavior. 

Corticosubcortical control and its developmental neurobiology

This has led to the development of a neurobiological model of motivational and cognitive processes which aims to explain the behavior of adolescents outside of a laboratory context. Working with this model leads to the suggestion linear development of top down prefrontal regions relative to a n-shaped function for the development of bottom-up striatal regions involved in detecting particularly interesting cues in the environment.

The findings of Pasupathy and Miller indicate that the interactions between brain areas (especially within frontostriatal circuitry) is essential in the development of a model of motivational and cognitive control. Further studies have highlighted the important role of signaling inside corticostriatal circuitry for supporting the capacity to employ effective cognitive control. Further evidence for the theory that cognitive maturation occurs in the connectivity of structures rather than in unitary structures was found by examining the interactions between a frontoparietal network and cingulate-lateral prefrontal network. Works by Ernst, Galvan, Luna and Crone have been seminal in response to incentives, striatal responses follow an inverted U function across development. In contexts where a reward or incentive is present, the effect on cognitive control behavior is greater in adolescents than in adults.  

Conclusion

Studies in cognitive and motivational processes are experiencing a bountiful period by focusing on adolescent development. Findings suggest that depending on whether a situation calls for suppression or attention to motivational cues, the cognitive control of adolescents can improve or diminish.

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    Developmental Neuropsychology: Executive function and social cognition in the adolescent brain

    Developmental Neuropsychology: Executive function and social cognition in the adolescent brain

    Executive function and social cognition in the adolescent brain 

    Adolescence is a period of development characterized by intense fluctuations in both physical and hormonal change. Research has been sparse in this area, empirical research on neural and cognitive development is still lacking. For such a period that reflects the growth of cognitive flexibility, self-consciousness and changes in identity, the need for further research is apparent.

    Beginning to experiment on adolescent brains

    Through studies on animals, we have seen that specific sensory regions of the brain go through sensitive periods starting after birth, in which environmental stimulation seems to be crucial fro the normal development of the brain and perceptual capabilities. Experiments suggest that while this is true for animals, it may also be true for humans. During the 1970’s and 1970’s, it was demonstrated that certain brain areas, especially the prefrontal cortex develop far beyond early childhood. Further studies in the decades that followed showed that during the period of puberty and adolescence, the structure of the prefrontal cortex goes through substantial changes. Two important changes highlighted are:

    1. Myelination (increasing the transmission speed of neural information)
    2. Synaptogenesis (regularly used connections are strengthened and seldom used connections are removed)

    Synaptogenesis was first found in 1975 within experiments using cats and was further researched using rhesus monkeys. Synaptic pruning (a period of synaptic destruction) and synaptogenesis in the brain area the prefrontal cortex exist on a differential time line. Proliferation of synapses occurs in the prefrontal cortex during childhood and once again during puberty, however this is followed by a stagnant period and elimination and reorganization of prefrontal synaptic connections following puberty.

    An overall decrease in synaptic density as a result of synaptic pruning in the frontal lobes ensues during adolescence. This process is thought to be essential for refining the effectiveness of neural networks. This is especially true when given the sensitive case of sound recognition development.

    The adolescent brain seen through MRI

    Through the implementation of modern technology, it has become possible to view the brain of living specimens. With the introduction of magnetic resonance imaging, we can non-invasively view the human brain in a detailed three-dimensional visual. This has been instrumental in the furthering of research on the maturation of the frontal cortex of adolescence and onwards into adulthood.

    Linear increases in white matter during adolescence

    Over the past years, researchers have found one consistent outcome across MRI studies: during adolescence and childhood there is a steady increase in white matter located in certain brain regions. One study found a significant between the white and grey matter levels between two age groups. This increase in white matter has been suggested to be the result of developmental changes by some studies. One study found an increase in white matter in the right internal capsule and left arcuate fasciculus. Both regions are associated with speech so it was hypothesized that the increase in white matter was due to speech development.

    Non-linear decreases in grey matter during adolescence

    Grey matter, in contrast to white matter, does not seem to follow a linear pattern. Rather it seems to follow a region specific, non-linear pattern. Research has shown that grey matter follows an inverted-U shape in certain brain regions. Studies suggest that grey matter volume in the frontal lobe reaches its peak during puberty, which is then followed by a stagnation period and a steady decline until though adolescence until early adulthood. MRI research on the decline of grey matter throughout adolescence has two explanations:

    1. Axonal myelination both facilitates an increase in white matter and a decrease in grey matter
    2. The decrease in grey matter is a reflection of the reorganization which occurs during puberty

    Examining the role of gender differences in the development of brain structure

    Research has shown that there exists a significant difference in the amount of grey and white matter found in males and females. This was particularly true in the area known as the inferior frontal gyrus (IFG). Researchers corrected for the possible confound of total cerebral volume but still they found that males had a significantly higher amount of grey matter. Some researchers believe this difference is a result of differential steroid levels, others believe it may be due to greater hemispheric specialization found in males. As of current research, more study is needed to examine variability in frontal cortex anatomy.

    The continuing brain changes after adolescence

    Recent research using MRI suggests that the period at which the brain reaches maturity could be later than the end of adolescence. This change is seen especially in the frontal and parietal cortices following post-mortem cellular examinations of human brains which support an extended period of development. The adolescent brain appears to develop in a dynamic nature when looking at the growth of white and grey matter.

    Examining the development of executive function

    Executive functioning refers to a set of cognitive mechanisms which govern how well we control and coordinate our behavior and cognition. Lesion studies have shown that many of the skills involved in executive functioning are dependent on the frontal lobes. Given that changes occur in the frontal cortex during adolescence, executive functioning might be expected to improve during this period. Behavioral studies have shown that inhibitory control, processing speed, working memory, and decision making continue to develop throughout adolescence.

    Examining the development of social cognition

    Evidence suggests that the prefrontal cortex is associated with many high level cognitive functions, such as self-awareness and theory of the mind. In tandem with this neural development, puberty marks a great period of change for hormonal development. These two factors combined mark a significant change in social cognition. Research concerning the effects of puberty on social cognition capacitates has been limited.

    Looking at perspective taking

    The act of perspective taking refers to putting oneself in another’s shoes and it is an essential component for effective social communication. This act of estimating what another individual is thinking is  related to the first-order theory of mind. It is an area of much theoretical debate. One view surmises that we understand others by simulating their actions and cognitions. In support of this, research has shown that similar brain areas are activated when we perform an action and when we see another perform the same action. This is in line with the function of mirror neurons.  

    The adolescent brain in action seen through fMRI

    With the introduction of fMRI, we have a safe and effective way to examine brain regions.  As an example, through the use of fMRI we were able to examine how response inhibition has developed in addition to examining the structure supporting its development. During studies involving inhibition of a normal response, it was shown that activation of certain brain regions was for the most part the same across age groups.  An exception was a significantly larger volume of activation in the prefrontal of children. In contrast to this, adults showed higher activation in the ventral region of the prefrontal cortex. One suggested reason for this is that children have a heftier dependence on this area than adults.

    The confounds on task performance

    An issue which has been found when conducting fMRI is that of confounding effect of task performance. If there is a difference in the performance between two groups i.e. one outperforms the other, the results are often difficult to interpret.

    Examining the development of social cognition within the brain

    In terms of brain regions, the amygdala is an area which has repeatedly been shown to have a high functioning role in facial recognition and emotional processing. Though research in this area has been investigated with adolescents, still little is known about the continued development of facial recognition. Studies have shown that children may identify neutral faces as being more ambiguous than fearful faces, resulting in an increase in activation in the amygdala.

    Effect on teenagers

    puberty marks a period of synaptic reorganization, and as a result can be more susceptible to experiential input, in particular regarding social cognition and executive functioning. Further studies are needed to examine the further development of brain maturation beyond childhood and the implications this has on cognition. The authors specify questions into which skills undergo perturbation, sensitive periods for improvement and how does the environmental quality impact the changes which occur in the brain.

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    Developmental Neuropsychology: Mild spastic cerebral palsy

    Developmental Neuropsychology: Mild spastic cerebral palsy

    Mild spastic cerebral palsy: An event-related brain potential study of error detection and response adjustment 

    The term cerebral palsy is used to define a number of disorders which affect posture and movement. Cerebral palsy is attributed to damage or abnormal development in the developing brain of fetus’s or infants. Though there are many contributing factors to cerebral palsy, one of particular note are infarcts (tissue death as a result of lack of oxygen) which lead to lesions in white and grey matter tracts. These lesions to white matter tracts are detrimental to executive functioning which has been proven when testing youths with cerebral palsy against a control group without.

    The question posed by this study is whether youths with mild spastic cerebral palsy are aware of their errors when carrying out tasks requiring executive functioning.

    It has often been the findings of neurocognitive research that poor motor preparation precedes error making. Error detection and the adjustments which follow are measured in this case using response-locked error-related negativity. The brain potential for incorrect responses is markedly higher than those following correct responses.

    Method

    Participants consisted of 11 patients, with a mean age of 14 years, diagnosed with mild cerebral palsy and a control group of 12 youths without cerebral palsy, with a mean age of 14, recruited from the same city. Though the intelligent quotient of some of the youths with mild cerebral palsy was within the range of learning disabilities, none were classified as being mentally retarded, as their daily lives were intact.

    A computer based stimulus recognition task and electroencephalograms were used to record brain activity in the study. The task used was comparable to the Sternberg short-term memory paradigm. Participants were presented with 2 letters to be memorized, then were subsequently shown 4 letters, one or none of which were the letters which were memorized. Using two response buttons, participants would indicate either yes or no whether they identified there target letters in the new set. Reaction time was measured starting when the new set appeared until a button was pressed. Total time for the experiment was about 15 minutes.

    Results

    The results of the experiment find that the control group made more correct responses and less error responses than the experiment group. In addition, the patient group reacted slower on average than the control group. Error responses were also shown to be slower than correct responses, which proved true for both groups.  

    Discussion and conclusion

    Given the findings of the study, poor motor preparation appears to be associated with error responses. This is especially salient in the patient group. Error detection was found in both groups and went on to predict better performance. A key point given by the authors is that error monitoring and the adjustment in performance which follows are essential to learning. The research conducted here implies that this process is thankfully present  in the patient group. Additionally, it is proposed that the patient group was more sensitive to their error making than the control group. This suggests that motivation may also be a key to learning in the patient group.

    This leads to the suggestion that the patient group possesses an intact top-down capacity for executive functioning in tandem with a diminished motor action system. This calls for further investigation into the period preceding the execution of an action (i.e. pushing the button) to pinpoint the origin of error making in youths with mild cerebral palsy.

    Limitations

    It must be noted that the study contained a rather small sample size and should be treated as preliminary research.

    Mild spastic cerebral palsy: brain state before error making 

    While the previous article focused on whether youths with mild cerebral palsy were aware of their own error making and what adjustments they made to avoid future error, the following article asks whether error making is preceded by attentional lapses, by poor motor preparation, or both.

    As mentioned in the previous article, the term cerebral palsy is used to define a number of disorders which affect posture and movement. When addressing the subject of quality of life, how well one has a capacity for executive functioning is a relevant question. The term executive functions encompasses a wide range of cognitive faculties including attention control, inhibitory control, and cognitive control. Taken as a whole, executive functioning governs ones capacity to function effectively in life. Recent research indicates that reduced capabilities towards executive functioning has been found in youths with cerebral palsy. This hypothesis is limited, however, for two reasons. Firstly, poor effectiveness by patients with cerebral palsy on executive functioning tasks may be due to their diminished motor system as opposed to deficiencies in cognition. Secondly, weak cognitive skills on cognitive tasks are measured by high error count and slow reaction speed.

    Given the previous research conducted by the authors on event-related potential, they  propose that it is the poor motor preparation preceding a stimulus which is casually associated with error making in individuals with cerebral palsy. In accordance to this, the aim of this study was to measure what happens in the brain preceding errors in both the control and patient groups. To accomplish this, 3 event-related potential elements were recorded:

    • Motor preparation (frontal late contingent negative variation)
    • Attention (parietal P300)
    • Response evaluation (parietal error-preceding positivity)

    Methods

    Participants consisted of 11 patients with cerebral palsy and an average age of 15, and 12 youths with an average age of 14 as a control group. The study design did not differ from that of the previous study. Again, the computer task was administered and responses were recorded as the interval between the new display set and the button press. However the authors were only interested in the 3 successive correct responses preceding an error.

    Results

    Overall, the patient group had fewer sequences of 3 correct trial than the control group (patient group 41 sequences; control group 47). Both accuracy of responses and reaction speed were not found to be of a significant difference between the groups. It was found that contingent negative variation (motor preparation) was weakened for the patient group preceding an error. Attention (P300) levels preceding error making were shown to be low, however this was true for both groups. In the case of response evaluation (error preceding positivity), the groups did not show a difference in their level of performance monitoring preceding an error.

    Discussion and conclusion

    The results of the study show a strong indication that youths with mild cerebral palsy experience  poor motor preparation not only preceding an error, but already one trial before the error occurs.  Given that the control group and patient group did not differ on the amplitude of the parietal P300, the authors conclude that the cognitions responsible for response monitoring were similar in both groups. During the trials the patient group showed high levels of cognition control both preceding and following error making. Despite this however, they still made more errors than the control group. The authors propose that the poor motor preparation could be an indicator of a conflict between motor and cognitive exertion.

    Ultimately, the goal of the study was to find out if error making in the patient group was associated with weak cognitive abilities. Given that the results indicate the source of error as a weakened motor system, they hypothesize that weak cognitive abilities can be dismissed as the source of error.

    Limitations

    As with the previous study, the sample size was small. As such it should be taken as a preliminary study. Additionally, the generalizability is questionable, as it only deals with patients with mild cerebral palsy. Other measures of executive functioning would also be an improvement.

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    Developmental Neuropsychology: Treatments and guidelines for phenylketonuria

    Developmental Neuropsychology: Treatments and guidelines for phenylketonuria

    Revision of treatments and guidelines for phenylketonuria: evidence from neurocognition

    An inborn, inherited, error of metabolism, phenylketonuria (PKU) is a rare, highly treatable disease. In contrast to its relatively treatable nature, when left untreated, PKU can result in seizures, intellectual disability, and further medical issues. The most common method for prevention is the early introduction of a strict diet highlighting the restriction of phenylalanine (Phe). Despite its treatability, patients with PKU show an average 8-10 points lower than normal in addition to underperforming in neuropsychological tests.

    Cognitive impairments have been associated with concurrent blood Phe levels, and even more so with lifetime blood Phe levels. The question being raised by the authors concerns whether or not the recommend Phe level for patients with PKU is too high. Currently, from the age of 0-10, this level varies between 240 and 360 micromolars/L. The drawback is that this range is not the result of studies comparing outcomes at Phe levels <240 micromolar/L, between 240 and 360 micromolar/L, and >360 micromolar/L.

    Current treatment advises an absolute upper target level for Phe levels, not taking into account possible fluctuations of Phe values and the phenylalanine:tyrosine ratio (Phe:Tyr). This feeds into the second area of question the authors pose: what are the effects of lifetime Phe, concurrent Phe, variation in lifetime Phe levels, and lifetime and concurrent Phe:Tyr in predicting cognitive outcome in early and continuously treated children and adolescents with PKU

    Methods

    Participants consisted of 67 patients with PKU with a mean age of 10.8, and a control group of 73 participants with a mean age of 10.9 recruited from friends and families of patients and also local newspaper advertisements. Of the patients with PKU, 27 had pretreatment Phe levels of > 1200, 18 had pretreatment Phe levels between 600-1200, and 18 had pretreatment Phe levels <600, and 12 patients had pretreatment Phe levels <360. To test for concurrent Phe and Tyr levels, a blood sample was taken in the morning following an overnight fast. This was also used to test for lifetime Phe level. Through a series of computer based neuropsychological tests, executive functions inhibitory control and motor control were measured.

    Results and discussion

    Patients with Phe levels >360 differed in 2 of 3 inhibition tasks, motor control, and cognitive flexibility. Controls performed notably more accurately than patients with Phe levels between 240-360. A key finding was that patients with Phe levels <240 performed no different to the control group. Additionally, patients with Phe levels <240 outperformed those with Phe levels between 240-360.

    It was found that Phe variation, lifetime and concurrent Phe, and lifetime and concurrent Phe:Tyr were significantly related to speed and accuracy on numerous cognitive tests and also to each other.

    The two major findings of this study are:

    1. Youths from the age of 6-15 with mean Phe levels of <240 since birth outperformed their peers with Phe levels between 240-360 on cognitive tests measuring motor control, inhibition, and cognitive flexibility.
    2. Phe:Tyr and Phe variation may have predictive value in regards to motor control ad executive functioning.

    The PKU-COBESO study

    As mentioned in previous studies examined, phenylketonuria (PKU) is an inherited metabolic disorder. In the case of someone with the disease, there is a deficiency in the phenylalanine hydroxylase enzyme and as a result, phenylalanine (Phe) cannot be converted into tyrosine (Tyr). This excess of Phe, in combination with a lack of Tyr can lead to shortages of important neurotransmitters such as serotonin and dopamine. Serotonin is linked to cognitive functioning and a lack of it can result in decreased cognitive functioning. Dopamine is associated with the executive functioning primarily in the prefrontal cortex. There is a considerate lack of studies concerning behavioral problems and social skills for those with PKU. The aim of the study presented here is to explain a new Dutch multicenter study, namely the PKU-COBESO study. The primary goal of the PKU-COBESO study is to examine the behavioral problems, social functioning, cognitive functioning, and executive functioning in both continuous and early treatment patients principally in regards to their metabolic control.

    Looking at the procedure for the PKU-COBESO study

    The experiment sample for the study consisted of young adult patients with PKU who had beforehand participated in a neuropsychological study 10-15 years previous, and another group of patients who did not participate in the previous neuropsychological study. In the control group, participants were recruited from either the families and friends of the patients, or from non-family participants.

    The study itself consisted of a neuropsychological assessment, questionnaires, and an analysis of the PKU patients’ metabolic control. The neurological assessment comprised of a combination of either the WISCIII or WAISCIII (depending on the participants age) and the ANT (Amsterdam Neuropsychological Tasks), and numerous paper and pencil tasks. The aim of the neuropsychological component was to measure:

    1. Executive functions

    2. Social cognitive skills

    3. Motor control

    The questionnaires aimed to ascertain:

    1. General demographic information

    2. Executive functioning throughout daily life

    3. Social functioning

    4. Mental health/behavioral problems

    Blood samples were taken from the PKU patients in order to determine concurrent Phe and Tyr levels, and the levels of other metabolic features.

    Examining the findings in the preliminary results

    In the preliminary analysis, results showed that adult PKU patients differed on ‘internalizing problems’, reported more ‘avoidant personality problems’, scored worse on ‘relationships’ and also ‘self care’. Additionally, the concurrent Phe levels of adults with PKU were not significantly related to social skills and behavioral problems. Childhood Phe levels were shown to be significantly related to ‘thinking problems’ and ‘somatic problems’.

    For discussion

    The PKU-COBESO study has two main questions it seeks to answer:

    1. How does leniency of diet in early stages of PKU go on to influence cognitive and behavioral functioning, and the potential for an adult to thrive in life.

    2. To what extent do Phe influenced cognitive problems manifest in the daily living of PKU patients.

    The results of the study should be considered preliminary. Having said that, the results are complimentary to the expected findings and provide evidence for the importance of further study focusing on the mental health and social functioning in early treated PKU.

    Investigating the usefulness of BRIEF in day to day care of patients with phenylketonuria

    The origins, effects, and treatment of PKU have been discussed previously. The following article focuses on the effects PKU has on executive functioning specifically. To ascertain these effects the implementation of the Behavior Rating Inventory of Executive Functioning (BRIEF) is proposed. This is an easily applied standardized questionnaire which can also be employed by non-psychologists. However, the accuracy of the BRIEF has been called in to question. To address this, the authors also use the Amsterdam Neuropsychological Tasks (ANT) measure, which has been used several times in the past to ascertain the neurocognitive functioning of PKU patients of various ages and early and continued treatment. Using the two tests, the authors attempt to investigate whether the BRIEF-A (adult version) is a useful instrument in the screening of patients with PKU during their daily living.

    Procedure

    The sample for this study consisted of 55 Dutch adult patients with PKU. Additionally, this study was a part of the PKU-COBESO mentioned in the previous article. The BRIEF-A test consisted of 75 questions 9 subdomains related to executive functioning, 4 subdomains which determine the Behavioral Regulation Index (BRI). The overall executive functioning in daily life score is denoted as the Global Executive Composite (GEC).

    For the ANT, three tests were used to measure executive functioning: Shifting Attentional Set Visual (SSV), Sustained Attention Dots (SAD), and Feature Identification (FI).

    Looking at results

    Of the 55 patients, 23 scored within the borderline/clinical range of the BRIEF-A. Patients showed problems in the domains of cognitive flexibility and inhibitory control when compared to the healthy population. Subsequently, two groups were formed on the basis of BRIEF-A GEC scores using a cutoff T-score of >= 60 (>1 SD above the mean). No significant differences were found between the groups on the basis of gender, age, and IQ. Additionally, no significant differences were found between the two groups on concurrent and historical Phe concentration levels. There was found to be some agreement between the BRIEF and the ANT indicating that the null hypothesis could not be rejected.

    For discussion

    The fact that patients with PKU still face problems in attention and learning was the driving factor for this investigation into the efficacy of the BRIEF as a tool for monitoring patients. The results show that 42% of patients scored in the borderline/clinical range. Despite this, only 11% of patients showed scores greater than 1 SD. From the results of the ANT, we see that PKU patients had problems with inhibitory control and cognitive flexibility. The BRIEF-A appears to identify executive dysfunction across studies.

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    Samenvattingen: de beste artikelen over biopsychologie en neuropsychologie

    Samenvattingen: de beste artikelen over biopsychologie en neuropsychologie

    Samenvattingen van de beste wetenschappelijke artikelen over Biopsychologie en neuropsychologie

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    Summaries: home page for psychology and behavioral sciences

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    2. Use the check and search pages for summaries and study aids by field of study, subject or faculty
    3. Use and follow your (study) organization
      • by using your own student organization as a starting point, and continuing to follow it, easily discover which study materials are relevant to you
      • this option is only available through partner organizations
    4. Check or follow authors or other WorldSupporters
    5. Use the menu above each page to go to the main theme pages for summaries
      • Theme pages can be found for international studies as well as Dutch studies

    Do you want to share your summaries with JoHo WorldSupporter and its visitors?

    Quicklinks to fields of study for summaries and study assistance

    Main summaries home pages:

    Main study fields:

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