Neural and Linguistic Development Flashcards
Embryonic Stages
Pre-embryonic
Embryonic
Fetal
Pre-embryonic stage
Conception - 2 weeks Ovum begins cell division Becomes blastocyst Outer layer = placenta Innermass = embryo (ectoderm, endoderm, mesoderm)
Embryonic stage
End of week 2-8
Organs are formed
Fetal stage
8 weeks - birth
Nervous system develops more fully and myelination of neurons begin
Ectoderm
Becomes sensory organs, epidermis, nervous system
Endoderm
Gut, liver, pancreas, respiratory system
Neural tube formation
- longitudinal thickening of ectoderm; neural plate forms on surface of embryo
- neural groove forms - edges of plate start to fold
- Day 22 - folds touch to form neural tube
- cells next to tube separate - remaining ectoderm forms the neural crest
- Day 26 - tube differentites into mantle and marginal layer
Mantle layer
Inner wall of neural tube
Becomes grey matter
Marginal layer
Outer wall of neural tube
Becomes white matter; axons and glial cells
Ventricular system
Derived from the neural canal
Filled with CFS
Timing of Development - first 8 weeks
something goes wrong - results in defectively designed structure system
Teratogenesis
Cogential malformations in embryo/foetus
Earlier teratogenesis
major congenital defects
Later teragonesis
Minor defects, functional malformation
Neural tube defects
Incomplete development of the neural tube
Occurs between 17-30th day after conception (critical period)
Related to folic acid deficiency, genetics, maternal diabetes, SES
Cerebral Palsy
Impairment in voluntary movement
Maldevelopment of brain, prenatal/during birth/shortly after birth brain damage
Pre-term, low birth weight at higher risk
Caused by lack of oxygen, infection, impaired rate of growth during pregnancy/early years of life
Cellular level development
Progressive developmental processes balanced by regressive processes that remodel the NS
Epithelial cells lining the neural tube divide to produce neurons and glia
Progressive processes
Cell proliferation, migration and growth, extention of axons to target cells, formation of synapses, myelination of axons
Stages of Brain Development
- cell birth (neurogenesis gliogenesis)
- cell migration
- cell differentiation
- cell maturation (dendrite and axon growth)
- synaptogenesis (formation of synapses)
- cell death and synaptic pruning
- myelogensis (formation of myelin)
Locke’s Theory of Neurolinguistic Development - Overview
Processes orient child to language
Responsiveness to facial/vocal activity - influenced by genetic factors, early experience, supported by neural pre-adaptions
Each phase occurs in a fixed and overlapping sequence, commitment of neural resources
Phase 1 - Vocal Learning
Strongly oriented to face and voice
Specialisation in social cognition - orients child to communication
Heavy genetic influence
Phase 2 - Utterance Acquisition
Rote learning Use of formulaic phrases; mimic length, stress pattern, intonation Correct forms of irregular syntax Stored in prosodic type memory Right hem. - emotional/social Storage limitations LH not involved
Phase 3 - Analytical and Computational
18-20 months
Stored utterances (critical mass) trigger analytical mechanisms
Structure analysis system - locates recurring elements within/across utterances
Phase 4 - intergrative and elaborative
Analytical and computational ability integrated with acquisitive system = growing lexicon
Increasing lexical capacity - syntactic processing becomes more automatic
= appropriately organised grammatical system and lexicon; used with high degree of difficulty
Pragmatics
Social cognition
Word knowledge
Individual Networks and Wiring
Sequence of development/stabilisation of synapses - functional behaviours
Formation, elimination and stabilisation of synapses depend on experiences
