Neuroplasticity Flashcards
What is Neuroplasticity?
ability of neurons to change FUNCTION, CHEMICAL PROFILE, or STRUCTURE
3 mechanisms of neuroplasticity
- habituation - simplest form
- Experience-dependent plasticity - aka use/activity dependent
- Recovery following injury
- peripheral vs. CNS
Habituation
- what is it
- due to (3)
- how can it be long-term?
- techniques
it is a decrease in response to repeated, benign stimulus
- due to decreased synaptic activity between sensory & interneuron (dec NT’s, dec Ca, change in receptor sensitivity)
Effects are resolved or diminished after period when stimulus is not applied UNLESS prolonged repetition leading to more permanent structural changes
Techniques to increase habituation: tactile defensiveness, vestibular disorder
Experience-dependent plasticity
- what is it
- due to (3)
- mechanisms (2)
persistent, long lasting changes in strength of synaptic connections between neurons - involves memory & learning
(ie. learning to play an instrument)
Due to: synthesis of new proteins, growth of new synaptic connections, modification of existing connections
Mechanisms
- Longterm potentiation (LTP): increased chance of neurons firing together
- Long-term depression (LTD): less likely to fire, less receptors, less NT’s being released
- receptors engulfed & inactivated
Astrocytes & Experience-dependent plasticity
- what is their role
contribute by modulating NT release & receptor expression at post synaptic membrane
- absorb NT’s
Gliotransmitters are the modulators released by astrocytes
Memory classification
- working
- STM
- LTM (2 categores)
working memory - right @ that moment
STM
LTM: 2 types are neuroanatomically separate
- Declarative = hippocampus/mediotemporal lobe
- semantic = facts
- episodic = events - Non-declarative = diffuse through BG, cerebellum, S1, M1
- procedural = motor skills
Axonal Recovery in PNS
- what happens during damage
- regeneration (will happen if 3 things happen)
Distal segment undergoes Wallerian degeneration & cell body undergoes central chromatolysis
- glial cells clean up debris
Regeneration via sprouting:
- production of NGF by Schwann cells
- Effective cleaning by glial
- Formation of bands of Bungner to guide growth
1mm/day or 1in/month
Regeneration is increased by exercise!
Maladaptive changes w/ sprouting (2)
Sykinesis: co-contraction of muscles
Altered sensation: cross talk between pain & touch neurons
CNS Axonal Injury
- what happens
- why does regeneration not occur (2)
Majority of damage occurs hours/days after initial injury due to cascade of events
- axonal retraction ball: forms when proximal axon retracts
- eventually leads to wallerian degeneration of distal axon and central chromatolysis of cell body
Axonal regeneration does NOT occur due to:
- development of glial scars
- limited expression or absence of NGF (may actually release Nogo)
Promising treatments for CNS axonal regrowth (2)
drugs that can block the development of Nogo
OR
stem cells that form new neurons and new connections
Synaptic changes following axonal injury in the CNS that aid in re-connecting(4)
- once edema resolves can recover synaptic effectiveness
- denervation hypersensitivity: increased receptors on surface after death of PRE-syn neuron
- synaptic hypereffectiveness: increase in release of NT’s
- Unmasking of silent synapses: receptors migrate making the synapse active
Reorganization of Cerebral cortex
- genetic make-up impacts this why? 1 bad reason
cortical representation areas can be remapped by modifying sensory input, experience, learning & brain injury
Impact of genetic make-up:
- brain-derived neurotrophic factor (BDNF) gene displayed DECREASED motor map reorg. and reduced learning of motor task
- poorer recovery in those w/ BDNF
Neurogenesis
- neural stem cells
- where are they located
neural stem cells are undifferentiated precursors to both glial cells and neurons
found in:
- subgranular zone of hippocampus
- subventricular zone of lateral ventricle wall
Factors that influence recovery of neuronal functioning (2)
- Intensity of rehab - must be intense, but not too soon
- Type of rehab - task specific training induces more normal pattern of brain activation & better functional reorganization of brain
Early rehab results in improved functional recovery & reduced comorbid effects of sedentary behavior
Is brain reorganization and plasticity still capable of happening in someone w/ a chronic stroke?
YES
