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The development of a foetus and infant's brain
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Word document about the development of the brain - specifically the very early stages of development
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DevelopmentKey Words:
o Neurogenesis = forming new cells.
o Synaptogenesis = formation of synapses between neurons.
o Exuberant synaptogenesis = an explosion of synapse formation during early brain
development.
o Synaptic pruning = the brain eliminates extra synapses; extensions recede and
synapses are removed.
o Zygote = first stage of development – fertilisation and embryogenesis to 2 weeks.
o Embryo = second stage of development – aka organogenesis, 2-8 weeks.
o Foetus = third stage of development – 9 weeks to birth.
o Neurale plate = external layer of that embryotic disk that gives rise to the neural
tube.
o Neural tube = the structure that will eventually become the brain and spinal cord.
o Spina bifida = a spinal cord anomaly when the back end of the neural tube has failed
to close completely.
o Anencephaly = a failure to develop a forebrain resulting from the front end of the
neural tube failing to close.
o Neurotrophic factors = a chemical compound that acts to support growth and
differentiation in developing neurons and keeps certain neurons alive in adulthood.
o Radial glial cells = a path making cell that a migrating neuron follows to its
appropriate destination.
o Filipod = a process at the end of a developing axon that samples the intercellular
environment.
o Cell adhesion molecule (CAM) = provides a surface for growth cones to adhere to.
o Trophic molecules = serve to attract or repel a growth cone.
o Apoptosis = a genetically programmed cell death.
o Growth spurts = sporadic periods of sudden growth that lasts for a finite amount of
time.
o Amblyopia = a condition in which vision in one eye is reduced as a result of disuse.
o Sensitive period = a development window during which an event will have a long-
lasting influence on the brain.
o Mental retardation = impaired cognitive functioning due to abnormal brain
development – usually reflected by reduced dendritic growth.
o Neonates = a new born infant, less than 4 weeks old.
o Neuroconstructivism = a theory that gene-to-gene interaction, gene to environment
interaction and ontogeny play a crucial role in how the brain sculpts itself and
becomes specialised over time.
o Ontogenesis = the development of an individual organism or anatomical or
behavioural feature from the earliest stage to maturity.
, Key Theories:
Neural dwarfism hypothesis: cell death and synaptic pruning are the outcome of
competition among neurons for connections and metabolic resources in a neural
environment.
Chemo affinity hypothesis: prenatally axons and dendrites are mainly drawn towards
a signalling chemical that indicated its correct pathway.
Key Studies:
Flechsig (1920): cortex myelination begins just after birth and until at least 18 years
old.
- certain regions myelinate earlier than others e.g., frontal lobe is the last area to
mature (and is the first to start deteriorating with age).
Overman et al., (1992): object recognition vs object discrimination – 12-month-olds
learned discriminations rapidly but required training and maturation before learning
the delayed non-matching to sample task (DNMS).
- adults learned both tasks rapidly
- dissociation abilities in infants matched reports in young monkeys
= support for a neurocognitive maturational model.
Farroni et al., (2005): newborns preference for face relevant stimuli – newborns
didn’t show a preference for an upright face related image unless it had darker areas
around the eyes and mouth
= consistent with a sensitivity to the shadowed areas of the face with natural
illumination and/or detection of eye contact.
Campos et al., (2018): neuroconstructivism suggests that mental disorders are the
outcome of a developmental trajectory.
Notes:
Neurobiology of development:
4 weeks after conception =
- neural plate forms the neural tube
- neural tube differentiates into forebrain, midbrain, hindbrain and spinal cord
- forebrain develops into the cerebral cortex
- midbrain develops into the neural relay station
- hindbrain controls physiological processes
- spinal cord is the pathway to the rest of the body
4-8 weeks =
- face becomes human looking
- 2 distinct hemispheres in the cerebral cortex emerge
8-26 weeks = cerebral cortex grows to cover the midbrain
28-40 weeks =
- cortex expands and becomes folded and bumpy
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