PSYB65 Chapter 13 Detailed chapter notes

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3 Oct 2011

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Chapter 13: Neural Development and Developmental Disorders
Module 13.1 Neural Development
Postnatal Development
- Extensive growth in cortical areas of the brain
-Plastic change - the ability of the CNS to alter itself in response to the environmental stimuli
Critical periods of plastic change - periods in which the environment can have a maximal effect
on the CNS
Occurs in response to specific experiences (experience expectant / experience - dependent
plasticity phenomena)
-Experience - expectant plastic changes - CNS changes that are dependent on experience(s) during
critical period for specific synapses to develop as they should
-Experience - dependent plastic changes - idiosyncratic experiences that occur during critical periods
that also affect brain development
Eg. Musical training in childhood can have long-lasting changes on size of auditory cortex in
Parietal Lobe Development
- Has inconsistent levels of development at birth - some parts of the parietal lobe are more mature than
- Associated with visual perception and spatial ability - takes longer to develop
- Babies who are 2-3 months of age exhibit large increases in glucose utilization in parietal lobes -
increases remain steady until 2-3 years of age
Presumed corresponds to improvement in visuospatial and visuosensorimotor skill
- Basic tactile sensations mature early, complex tactile discriminations require more time to develop
- Component of the dorsal visual stream (the “where” and “how” pathway) - processing of spatial
information and directing behaviours toward certain points in space
- Williams Syndrome
genetic condition in which some of chromosome 7 has been deleted
relatively spares verbal activity but has significant difficulties with visuospatial ability
smaller brain volumes that is not uniform throughout CNS
relatively spares frontal lobe and temporal lobes, and disproportionate reductions in parietal and
occipital lobes
significant reductions in white matter
Occipital Lobe Development
- Development is incomplete at birth
- Newborns do not have an underdeveloped visual systems - are capable of distinguishing between two-
dimensional and three-dimensional stimuli
Have rudimentary form perception
Becomes very competent with more complex stimuli, such as faces, very quickly
- Competence with visual stimuli may depend on the myelination of the optic tract and requires the optic
radiations to become functionally connected with the sensory organs and with other areas of the brain
At birth - myelination of the optic tract is moderate; optic radiations exhibit minimal amount of
3 months of age - heavy myelination to optic tract and optic radiations
6 weeks of age - infants begin to experience binocular vision
- Development of the visual cortex is critically dependent on the environmental experiences of the
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Critical period for binocular vision: first few months of life; peaks between 1 and 3 years of age
Temporal Lobe Development
- Function has two main types: linguistic ability & hippocampally dependent memory function
- Co-operation and development of frontal and temporal lobe = development of speech production and
Requires the ability to perceive sounds, the ability to comprehend the meaning of sounds, and the
ability to coordinate and mouth and tongue to produce language sounds
Development of linguistic competence involves the development of frontal lobe, temporal lobe,
and the myelination of the connections among the lobes
- Auditory cortex is functional at birth but may not make functional connections with other important
language areas
Wernicke’s and Broca’s area undergo significant dendrite branching and extensive synaptic
remodelling during second year of life
Corpus callosum, anterior commissure, and fornix undergo myelination between ages 1-2
Failure to experience linguistic stimulation at this time will result in permanent deficits in
attaining adult-like linguistic skills
- Ages 2-12: marked changes in dendritic arborisation occur in speech areas in the brain
Environment stimuli can affect language development
There is tremendous variability in the development of speech - the speech that children hear at
home and at school affects the vocabulary and speech patterns that children actually use
- Hippocampus attains adult volumes around 7-10 months of age and shows high levels of glucose
utilization from birth but functionally, hippocampus-dependent memory functions develops over the
course of the first 5-7 years (does not reach adult performance until 5 years old)
Before age 4, recollections tend to be incomplete and cue-dependent
CNS systems for encoding, storing and retrieving memories are not yet functional - most people
experience childhood amnesia for events that occur before the age of 3 or 4
- Autobiographical memories are subserved by a diverse number of areas - cingulated, parietal,
temporal, prefrontal areas
Areas of prefrontal cortex associated with autobiographical memory increase in cortical thickness
until the child is about 4 years of age, which is consistent with the time frame for the emergence
of stable autobiographical memory
Frontal Lobe Development
- Role in language and memory
- Motor and executive functions
- Motor development follows cephalocaudal and proximodistal patterns of development
Head is controlled before the arms and trunk are, but the arms and trunk are controlled before the
legs are (cephalocaudal)
Proximodistal - motor skills develop in the head, trunk, and arms before they develop in the hands
and fingers
Gross motor skills develop before fine-motor skills
Gross motor skills - large muscles involved in walking, balance, or holding up the head
Fine-motor skills - small muscles that are used in the coordination of hands and fingers
Typical motor development relies on postnatal differentiation of neurons, synaptogenesis,
dendritic arborisation, neurotransmission, and myelination
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