Neural System - Postnatal

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Introduction

The human nervous system continues to develop postnatally mostly in glial (white matter) proliferation and in neurons (grey matter) making new connections and remodelling.

In humans, postnatal neurogenesis occurs only in specialised niches within the; rostral sub ventricular zone of lateral ventricles, hippocampal dentate gyrus (subgranular zone), within white matter tracts and external granular layer of the cerebellum.


WHO motor development milestones
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| Neonatal Development | original page

Some Recent Findings

  • The temporal pattern of postnatal neurogenesis found in the neocortex of the Göttingen mini pig brain[1] "The Göttingen minipig (G-mini) is increasingly used as a non-primate model for human neurological diseases. We applied design-based stereology on five groups of G-minis aged 1 day, 14 days, 30 days, 100 days, and 2 years or older to estimate the pattern of postnatal neuron number development in the neocortex. Two time periods for the postnatal increase of neocortical neuron number were observed from the time of birth to day 14 (P=0.013) and from day 30 to day 100 (P<0.001). No significant change in neuron number was found from day 14to 30 (P=0.58) and day 100 onward (P=0.39). The average estimated total number of neurons in the neocortex was 236, 274, 264, 338, and 353 million, respectively. Since neurogenesis and neuronal migration in the human neocortex are generally accepted to be complete before term, the application of G-mini as human disease models may be inappropriate before day 100. However, G-mini may serve as a valuable model for the studies of ongoing neurogenesis in the living brain."

Cortex Development

Recent NIH research has looked at the postnatal development of the cortex in children (Cortex Matures Faster in Youth with Highest IQ)

"The researchers found that the relationship between cortex thickness and IQ varied with age, particularly in the prefrontal cortex, seat of abstract reasoning, planning, and other "executive" functions. .... While the cortex was thinning in all groups by the teen years, the superior group showed the highest rates of change."

Postnatal cortex development trajectory.jpg

The developmental trajectory in cortex thickness differs as the brain matures in different IQ groups. Thickness of the area at the top/front/center, highlighted in MRI brain maps at left, peaks relatively late, at age 12 (blue arrow), in youth with superior intelligence, perhaps reflecting an extended critical period for development of high-level cognitive circuits. (Image and text source: NIMH Child Psychiatry Branch)

Human Tract Development

Human brain white matter tracts.png

MRI diffusion tensor imaging (DTI) provides information on white matter microstructure, including fractional anisotropy (FA).[2]

Neurological Assessment

There are many different neurological assessment tests that have been designed over the years using a number of motor and intelligence (comprehension) skill tests. Some of these assessment tests are applicable to specific early neurological development ages. PD Larsen and SS Stensaas from the Utah School of Medicine have also made a series of movies demonstrating normal postnatal neurological development assessment.

Neonatal

  • Test of Infant Motor Performance (TIMP) can be used in very early development (from 32 weeks post-conceptional age to 4 months post-term). Involves observation of 28 items and elicitation of 31 items measures behaviours of functional relevance.
  • Einstein Neonatal Neurobehavioral Assessment Scale
  • Neurobehavioral Assessment of the Preterm Infant
  • Bayley Scales of Infant Development (BSID) a postnatal (from 1 to 42 months) neurological assessment scale used in screening and diagnosis of development using 178 item mental scale and the 111 item motor scale, the original BSID was revised in 1993 to version 2 (BSID-II).
  • Peabody Developmental Motor Scale II (PDMS-2) tests a child’s motor competence relative to his or her peers. Involves a series of evaluations: reflexes (8 items), stationary/nonlocomotor (30 items), locomotion (89 items), object manipulation (24 items), grasping (26 items) and visual-motor integration (72 items).

Infant

  • Alberta Infant Motor Scale (AIMS) birth to 18 months. Identify infants with motor delay (discrimination) and evaluates motor development over time.
  • Battelle Developmental Inventory Screening Test (BDIST) for children 6 months to 8 years old.
  • Brief Assessment of Motor Function (BAMF) is a series of 10-point ordinal scales developed for rapid description of gross motor, fine motor, and oral motor performance.
  • Fagan Test of Infant Intelligence (FTII)
  • Comprehensive Developmental Inventory for Infants and Toddlers (CDIIT) a developmental test designed in Taiwan.
  • Denver-II (CDIIT) a historic test redesigned as a version 2, for 3 and 72 months of age. It has been suggested that the test may require additional revision for better accuracy.
  • Bruininks-Oseretsky Test of Motor Proficiency (1978) ages 4.5 to 14.5 years.
  • Early Language Milestone Scale-2, Early Intervention Developmental Profile (EIDP), Gross Motor Function Measure (GMFM)

There are also a range of task based tests: Means-End Problem-Solving Task, Operant Discrimination Learning, Mobile/Train Conjugate Reinforcement Tasks, The Transparent Barrier Detour Task, The A-not-B Task

Postnatal Neural Examination

The links below are to a set of postnatal Neural Exam Movies by Paul D. Larsen, M.D., University of Nebraska Medical Center.

Additional postnatal movies are available on the Neural Exam Movies page.

Newborn Normal

Newborn-normal-behaviour.jpg Newborn n 03.jpg Newborn n 17.jpg Newborn n 20.jpg Newborn n 27.jpg
behaviour tone positions reflexes head

Newborn Abnormal

Newborn ab 01.jpg Newborn ab 03.jpg Newborn ab 17.jpg Newborn ab 20.jpg Newborn ab 27.jpg
behaviour tone positions reflexes head

Autism

Autism (autism spectrum disorder, ASD) is a behaviourally defined brain disorder in children. Features include: impoverished verbal and non-verbal communication skills, reduced social interactions (bias their attention towards objects rather than the surrounding social situation), behavioural impairments in attention engagement/disengagement, poor emotional discrimination and facial recognition, and fail to response to their own names. There exist many different and unproven claims as to the origins of autism.

Developmentally associated with neural maturation changes in cortical thickness and organization, and particularly affecting pyramidal neurons. A rat model shows structural and behavioural features of autism as a result of altering the trajectory of early postnatal cortical development.[3]


Additional Images

Magnetic Resonance Imaging of Neural Growth

Human brain and ventricular development imaged by MRI[4]

There are a growing number of magnetic resonance imaging (MRI) studies of brain development.

3 months to 30 years - Changes in cerebral grey and white matter volume from infancy to adulthood[5]

  • images of 158 normal subjects from infancy to young adulthood were studied (age range 3 months-30 years, 71 males, 87 females).
  • volume measures of whole brain, grey matter (GM) and white matter (GM) and gender-specific development
  • The resulting growth curve parameter estimates lead to the following observations: total brain volume is demonstrated to undergo an initial rapid spurt. The total GM volume peaks during childhood and decreases thereafter, whereas total WM volume increases up to young adulthood.
  • Relative to brain size, GM decreases and WM increases markedly over this age range in a non-linear manner, resulting in an increasing WM-to-GM ratio over much of the observed age range.
  • Significant gender differences brain volume and total white and grey matter volume are larger in males than in females, with a time-dependent difference over the age range studied. Over part of the observed age range females tend to have more GM volume relative to brain size and lower WM-to-GM ratio than males.

8 to 30 years - Subcortical brain development[6]

  • Brain development during late childhood and adolescence is characterized by decreases in gray matter (GM) and increases in white matter (WM) and ventricular volume.
  • developmental trajectories of 16 neuroanatomical volumes in the same sample of children, adolescents, and young adults (n = 171; range, 8-30 years).
  • The results revealed substantial heterogeneity in developmental trajectories. GM decreased nonlinearly in the cerebral cortex and linearly in the caudate, putamen, pallidum, accumbens, and cerebellar GM, whereas the amygdala and hippocampus showed slight, nonlinear increases in GM volume. WM increased nonlinearly in both the cerebrum and cerebellum, with an earlier maturation in cerebellar WM.
  • Differences between structures within the same regions: among the basal ganglia, the caudate showed a weaker relationship with age than the putamen and pallidum, and in the cerebellum, differences were found between GM and WM development.

Birth to 2 years - Human brain development[7]

  • Ninety-eight children received structural MRI scans: 84 children at 2-4 weeks, 35 at 1 year and 26 at 2 years of age.
  • total brain volume increased 101% in the first year, with a 15% increase in the second.
  • majority of hemispheric growth was accounted for by gray matter, which increased 149% in the first year
  • hemispheric white matter volume increased by only 11%.
  • Cerebellum volume increased 240% in the first year.
  • Lateral ventricle volume increased 280% in the first year, with a small decrease in the second.
  • caudate increased 19% and the hippocampus 13% from age 1 to age 2.
  • Cerebellum volume also increased substantially in the first year of life.



Links: Magnetic Resonance Imaging

References

  1. <pubmed>21878372</pubmed>PMID 21878372
  2. Imperati D, Colcombe S, Kelly C, Di Martino A, Zhou J, et al. (2011) Differential Development of Human Brain White Matter Tracts. PLoS ONE 6(8): e23437. doi:10.1371/journal.pone.0023437 PloS One
  3. Chomiak T, Karnik V, Block E, Hu B. Altering the trajectory of early postnatal cortical development can lead to structural and behavioural features of autism. BMC Neurosci. 2010 Aug 19;11:102. PMID: 20723245| BMC Neurosci.
  4. <pubmed>20108226</pubmed>
  5. <pubmed>20600789</pubmed>
  6. <pubmed>19776264</pubmed>
  7. <pubmed>19020011</pubmed>

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Cite this page: Hill, M.A. (2019, December 10) Embryology Neural System - Postnatal. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Neural_System_-_Postnatal

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© Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G