Neuromaturation of the Human Fetus

Flower, Michael J.

doi:10.1093/jmp/10.3.237

Cited by 43 publications

(12 citation statements)

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“…Many of the anatomical features of human V1 develop prenatally. Neurogenesis begins around embryonic day 33 and is complete by birth, 48 – 50 while the thalamic input to layer 4 in V1, 51 , 52 bipolar, and pyramidal cells with long and thin dendritic spines forms distinct laminar patterns at around 20–30 weeks gestation. 16 , 53 Other aspects of cortical development that begin prenatally continue to mature after birth.…”

Section: Stage 1: the First Year Early Maturation Of Vision And The mentioning

confidence: 99%

The development of human visual cortex and clinical implications

Siu¹,

Murphy²

2018

102

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The primary visual cortex (V1) is the first cortical area that processes visual information. Normal development of V1 depends on binocular vision during the critical period, and age-related losses of vision are linked with neurobiological changes in V1. Animal studies have provided important details about the neurobiological mechanisms in V1 that support normal vision or are changed by visual diseases. There is very little information, however, about those neurobiological mechanisms in human V1. That lack of information has hampered the translation of biologically inspired treatments from preclinical models to effective clinical treatments. We have studied human V1 to characterize the expression of neurobiological mechanisms that regulate visual perception and neuroplasticity. We have identified five stages of development for human V1 that start in infancy and continue across the life span. Here, we describe these stages, compare them with visual and anatomical milestones, and discuss implications for translating treatments for visual disorders that depend on neuroplasticity of V1 function.

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Section: Stage 1: the First Year Early Maturation Of Vision And The mentioning

confidence: 99%

The development of human visual cortex and clinical implications

Siu¹,

Murphy²

2018

102

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“…The connections which allow the flow of tactile information along the somatosensory processing pathway structurally develop and refine across the third trimester and perinatal period. Cortical Layer IV begins to differentiate between 20 and 26 weeks of gestation (Burkhalter et al 1993; Rees et al 2010) with early thalamo-cortical contacts, synaptogenesis and vertical inter-layer connections occurring from 24 to 26 weeks (Flower 1985; Burkhalter et al 1993; Volpe 2009). However, synaptogenesis of thalamo-cortical and cortico-cortical connections is most pronounced from 28 weeks until full-term age, in line with extensive dendritic development (Flower 1985).…”

Section: Introductionmentioning

confidence: 99%

“…Cortical Layer IV begins to differentiate between 20 and 26 weeks of gestation (Burkhalter et al 1993; Rees et al 2010) with early thalamo-cortical contacts, synaptogenesis and vertical inter-layer connections occurring from 24 to 26 weeks (Flower 1985; Burkhalter et al 1993; Volpe 2009). However, synaptogenesis of thalamo-cortical and cortico-cortical connections is most pronounced from 28 weeks until full-term age, in line with extensive dendritic development (Flower 1985). The entry of callosal fibers into the cortex from 33 weeks (Volpe 2009), disappearance of the somatosensory subplate from 36 weeks (Kostovic and Rakic 1990), dense intra-layer horizontal cortical connections by 37 weeks (Burkhalter et al 1993), and a peak in axon growth within the parietal white matter at 38–42 weeks (Haynes et al 2005) suggests that the inter- and intra-hemispheric cortico-cortical circuits necessary for higher-order somatosensory functioning may mature within the late pre-term and perinatal period.…”

Section: Introductionmentioning

confidence: 99%

The Emergence of Hierarchical Somatosensory Processing in Late Prematurity

et al. 2019

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The somatosensory system has a hierarchical organization. Information processing increases in complexity from the contralateral primary sensory cortex to bilateral association cortices and this is represented by a sequence of somatosensory-evoked potentials recorded with scalp electroencephalographies. The mammalian somatosensory system matures over the early postnatal period in a rostro-caudal progression, but little is known about the development of hierarchical information processing in the human infant brain. To investigate the normal human development of the somatosensory hierarchy, we recorded potentials evoked by mechanical stimulation of hands and feet in 34 infants between 34 and 42 weeks corrected gestational age, with median postnatal age of 3 days. We show that the shortest latency potential was evoked for both hands and feet at all ages with a contralateral somatotopic source in the primary somatosensory cortex (SI). However, the longer latency responses, localized in SI and beyond, matured with age. They gradually emerged for the foot and, although always present for the hand, showed a shift from purely contralateral to bilateral hemispheric activation. These results demonstrate the rostro-caudal development of human somatosensory hierarchy and suggest that the development of its higher tiers is complete only just before the time of normal birth.

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“…There is some evidence for a primitive electroencephalogram from 19 to 20 weeks, and sustained electroencephalogram from 22 weeks; these have been obtained from very preterm infantsy 9,12 . Electroen‐cephalic patterns are clearly measurable in older preterm babies and have been well characterised from 28 weeks to term 9 .…”

Section: Does the Fetus Feel Pain?mentioning

confidence: 99%

Fetal pain: implications for research and practice

Glover

Fisk

1999

BJOG

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Pain is a subjective experience. The fetus cannot tell us what it is feeling, and there is no objective method for the direct measurement of pain. To address the question of pain in the fetus, one must use indirect evidence from a variety of sources, and then make an informed guess. This approach is similar to that which we use with animals. We cannot ask animals how they feel, but infer from a variety of indirect approaches including study of their behaviour, anatomy, and physiology. Does the fetus feel pain? ConsciousnessTo feel pain, or suffer discomfort, one needs to be conscious, to be aware. We do not know when, if at all, consciousness starts in the fetus. The biological basis of consciousness is little understood although at least in adult humans, the evidence suggests that it is in some way associated with electrical activity in the cerebral cortex. Crick' has suggested that one is conscious of something when there is electrical activity in specific large neural cortical networks, particularly in layers IV to VI of the cerebral cortex2.Greenfield has emphasised that one should not think of consciousness as an all or none phenomenon, rather that it may come on like a dimmer switch. This concept of evolving consciousness could apply to the developing fetus, in whom experience is most unlikely to be the same as that of an adult. Furthermore, the fetus may not have the same physical basis for conscious experience as the older human. Frogs, for example, do not have a developed cerebral cortex, lacking layers IV to VI. If they are conscious at all, their experience must be associated with activity in a less complex neuronal network, possibly more analogous to the fetal subplate zone3. Anatomical evidenceThe most important evidence is anatomical. For the fetus to feel pain, it is necessary for the requisite nociceptive pathways to be developed. This involves neural connections between peripheral receptors and the spinal cord, upward transmission via the spinal cord to the thalamus, and from there to the outer cerebral layers. The development of the human nervous system is a progressive and ascending process, with the cerebral cortex the last region to develop.Connections from the periphery to the spinal cord are formed early, at about eight weeks; C fibres begin to grow into the human fetal spinal cord at about 10 weeks4. The substantia gelatinosa in the dorsal horn is the spinal cord region of interneurones which is thought to play a major part in the modulation of noxious inputs; by 30 weeks of gestation it has most features of the adult4. The cerebral cortex starts to form at 10 weeks, although at that stage it is isolated from the rest of the brain5. Cortical development involves the structural differentiation and maturation of cortical neurones, fibres, glia and blood vessels, and this starts only at about 17 weeks of gestation with layers VI and V, but continues until long after birth. From 15 weeks, the cortex is underlain by the subplate zone, a layer of neurones below the cortex that is specific to th...

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Neuromaturation of the Human Fetus

Cited by 43 publications

References 0 publications

The development of human visual cortex and clinical implications

The development of human visual cortex and clinical implications

The Emergence of Hierarchical Somatosensory Processing in Late Prematurity

Fetal pain: implications for research and practice

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