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Chapter 13

PSYB65-Chapter 13 Notes

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Ted Petit

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Chapter 13
Early Development
x 3 weeks:
o Neural plate forms from the ectoderm of the embryo
o Neural plate: patch of cells that are on the dorsal surface of
the embryo (eventually becoming the nervous system)
o Ectoderm: the outermost of 3 layers of cells in the early
embryo (will form the nervous system and skin)
o In the neural plate are stem cells
Will develop into various types of nervous system cells
x Day 24
o Neural plate turns into a grove then become a neural tube
o Different sections of the tube become various parts of the
nervous system
Interior surface of tube=ventricles and central canal
x Proliferation tcell division resulting in new neurons
x Day 40
o 3 prominent bumps: forebrain, midbrain and hindbrain
x Cells migrate from the interior ventricular zone to their final
location by following certain types of glia
x 2nd month
o Telencephalon undergoes tremendous growth
x The deepest layer of neurons develop first
x Cell differentiation begins as the neurons form axons and
dendrites and is complete at birth
x Craniorachischisis
o Defect of the neural tube
o Results when there is a complete failure of the closure of the
neural tube
o Appears as a groove in top of head and body
o Rare, usually partial closure of the neural tube appears
This results in

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x spina bifida
o spinal cord defect, not fatal but can be
x anencephaly
o fatal failure of rostral part of neural plate to
o characterized by an absence of cerebral
x synaptogenesis
o production of new synapses
o shortly before birth-2 years old, synapse formation begins
rapid growth
reaches its maximal rate during puberty
50% more neurons are produced than needed
x As a result, cell death is normal and actually
o Apoptosis-programmed cell death
o ^ÇvZ}v[ulv]}vo}vv]}v}
incorrect also die
x dendritic branching
o become more complex with time
Postnatal Development
x Plastic change:
o Ability of the CNS to alter itself in response to environmental
o During critical periods, plastic change occurs very easily and
the environment has maximum effect on the central
nervous system. Occurs from specific experiences.
Experience-expectant plastic changes
x CNS changes that are dependent on experience
x Most of the sensory cortex has experience-
expectant critical periods

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o Studies show that if there is not enough
stimulation during critical periods, long-
lasting impairments in sensory modality
Experience-dependent plastic changes
x Experiences that occur during critical periods that
affect brain development
o i.e. musical training in childhood=lasting
changes o size of auditory cortex
o ]v[]o]Ç}o]µÁ]ZPUµÀ]}µ
required for learning
o neurotrophins (chemicals enhancing the survival of
neurons) and neurotransmitters play critical roles in plastic
x white matter volumes increase until about the age of 20
x most of the cortex is not myelinated at birth (occurs shortly after
birth and unevenly)
o myelination corresponded to emergence of behavior
Parietal Lobe Development
x little is known about the development of this lobe
x inconsistent levels of development at birth i.e. some parts are
developed at birth, others take long time to mature
x by age 1, myelination in spinal cord and thalamic centres is
x 2months-2years improvement in visuospatial and
visuosensorimotor skill
x Tactile sensation
o Children under the 6 bad tactile sensation
Difficulty localizing the point of touch on their hand
x Williams Syndrome
o Genetic disorder, parts of chromosome 7 deleted
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