The document discusses several topics related to neuroplasticity in adults. It describes that synaptogenesis is most active early in life but decreases after age 3. For autism, there is increased early brain growth and larger structures that later normalize. ADHD is linked to decreased early synaptogenesis and thinner prefrontal cortex. Gray matter decreases in childhood through synaptic pruning, accelerated in ADHD. White matter increases through myelination in youth. The brain reaches peak size in the 20s then gradually declines through reduced gray and white matter. Peripheral nerves regenerate through Schwann cells but recovery is incomplete. Apoptosis is activated through caspase pathways when Bcl-2 is blocked. Injured CNS areas form glial sc

1. Neuroplasticity in adults
Domina Petric, MD

2. Synaptogenesis
Synaptogenesis is creation of new
synapses.
Synaptogenesis is most active in the
early postnatal life up to 3 years.
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3. Brain size in autism spectrum disorder
There is an increased synaptogensis in early postnatal life
with brain overgrowth.
There is increase in size of frontal and temporal cortex,
amygdala and cerebellum in comparisson to the normal
brain.
The overgrowth of the brain tends to normalize with the
time, but aberrant connections remain during the adult life.
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4. Brain size in ADHD
There is decrease in rate of
synaptogenesis.
Frontal and temporal cortex is thinner
than in children without ADHD.
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5. Gray matter volume
There is a reduction in gray matter volume
during the childhood and adolescence: loss of
synaptic connections.
Loss of synaptic connections is accelerated in
individuals with ADHD.
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6. White matter volume
There is an increase in white matter
volume during childhood and
adolescence: increase of myelination,
increase of axons diameter and/or
increase in number of axons.
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7. Overall brain size
▪ There is increase in brain size during first decade of life and in second
decade of life there is a plato of the brain size.
▪ In the third decade of life there is a gradual decline in brain size: gray
matter is declining, whilst white matter is expanding.
▪ In the fourth decade of life there is a reduction in both gray matter and
white matter of brain.
▪ Decrase in brain size is due to reduction of myelin (white matter) and
reduction of synapses (gray matter).
▪ Loss of neurons is pathological and it is not attributable to normal brain
aging.
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8. Peripheral nerve injury and regeneration
▪ Injured axon has a significant regenerative capacity.
▪ When there is injury to an axon, there will be degeneration of distal parts
from the injured site.
▪ Macrophages invade the injured region and consume debris.
▪ Schwann cells then will proliferate and will create a chanel through wich
the regenerating axon will hit his proximal target.
▪ Schwann cells are key mediators of regeneration and regrowth of injured
axon.
▪ They release axon growth-promoting signals and neurotrophins that will
activate expression of growth-related genes in neuron body.
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9. Peripheral nerve injury and regeneration
There is never a full
functional recovery of
injured peripheral nerve.
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10. Excitotoxicity
Excitotoxicity is destruction of neurons
due to release of GLUTAMATE.
This can happen during acute injury to
the nervous system.
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11. Apoptosis stimuli
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12. Apoptosis
▪ Apoptosis stimuli interupt the normal function of Bcl-2 signal.
▪ When Bcl-2 is blocked, cytochrome C is released by mitochondria
leading to the activation of CASPASE-9 and CASPASE-3.
Apoptosis is then activated:
▪ chromosome condensation
▪ DNA fragmentation
▪ membrane blebbing
▪ cytoskeletal changes
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13. Penumbra
▪ Penumbra relates to the neurons just peripheral to the injured site in CNS.
▪ These neurons will survive.
▪ Glial cells proliferate in the site of injury and release chemical signals that have
negative effect on the growth and regeneration of survived neurons.
▪ Microglia phagocites the debris.
▪ Oligodendrocytes then proliferate.
▪ Glial cells will form a scar of tissue.
▪ Regeneration of axons that run through the white matter of the brain is difficult
because of negative glial cells effect on growth and regeneration.
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14. Penumbra
Neurons that have axons in gray matter
(horizontal axons) will regenerate
because they are not that much
exposed to suppressive signals of the
neuroglia: adaptive plasticity after
injury.
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15. Adult neurogenesis
Production of new neurons in adult human brain is
limited to a special set of stem cells in the basal
region of the dentate gyrus of the hippocampus.
This is important for learning and creation of new
memories.
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16. Literature
https://www.coursera.org/learn/medical-
neuroscience: Leonard E. White, PhD,
Duke University
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