Neuronal plasticity

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Transcript of Neuronal plasticity

  • 1.Neuronal Plasticity
    By
    SyedMujtabaHasnain Nadir Mubarak RazaWagha

2. What is neuronal plasticity?
Plasticity is the quality of being plastic or formative.
Neuronal plasticity refers to the ability of the brain to change and adapt itself as a result of ones experience.
3. Applications of Neuronal Plasticity
Learning new things
Making new memories
Rewiring circuits
4. Types of Long-term Memory
5. The NS is a series of connections
Birth = 100 billion neurons
6 year old has twice as many synapses as an adult
By late adolescence, synapses begin to disappear
http://www.eng.yale.edu/synapses.htm
6. Types of Neuroplasticity
TypeMechanismDuration
1. Enhancement of existing connections
Synapse development Physiological ms-1 to hours
Synapse strengthening Biochemicalhours to days
2. Formation of new connections
Unmasking Physiological minutes to days
Sprouting Structuraldays to months
3. Formation of new cells
Self-replicationstem cellvariable
7. Enhancement of existing connections
Increased use of a synapse in existing pathways e.g. learning a new task
Or alternative pathways following damage
Cortical re-mapping (phantom limb)
8. Synapse development
Increased afferent input
+
New synapses evolve leading to increased excitation
+
+
9. Synapse strengthening
Two point discrimination threshold in pianists index finger
R
L
Ragert et al., 2004
10. Synaptic Strengthening
Facilitation (10-100 ms)
Augmentation (several seconds)
Potentiation (seconds to minutes)
11. Formation of new connections
Unmasking of pre-existing pathways
Sprouting of new pathways
12. Unmasking of silent synapses
Possible reasons why some synapses could be silent
On distal dendrites
Inhibited by dominant pathways
Too little transmitter
Too few receptors
Dont fire with other inputs
13. Unmasking inhibition of subservient pathway by dominant pathway
Parallel pathway; neurons with a comparable role
Subservient pathway
Dominant pathway
+
+
14. Unmasking
Lesion to dominant pathway
Subservient pathway is unmasked
+
+
Activity is continued despite lesion
15. Sprouting
Cell body
AP
Axon
16. Sprouting
INJURY
lesion
Nerve Growth Factor (NGF)
17. Sprouting
INJURY
Neurite induced to sprout by NGF
lesion
NGF
18. Sprouting
Injury results in cell death
Cell is re-innervated from alternative stimulus
Sprouting may be a means of recovery; it may also produce unwanted effects
19. Neurogenesis
Replacing dying or damaged neural cells with new ones
New cells originate from stem cells
Introduced stem cells are stimulated to produce neural cells by nerve growth factors (NGF)
Stem cell
/www.stanford.edu/group/hopes/rltdsci/nplast
20. Cortical Re-Mapping
People born deaf
21. Cortical Re-Mapping
People born deaf
What happens?
22. Cortical Re-Mapping
People born deaf
What happens?

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