Neuroplasticity Flashcards
What makes something plastic?
- something that has a structure
2. structure can change
Any [long term] change in the nervous system that is not periodic; Duration of more than a few seconds; Combination of both flexibility and stability
Neuroplasticity
Decreased response to a repeated stimulus that doesn’t matter; Involves changes in neurotransmitter release (strength of synaptic connections); Reversible
Habituation
How can habituation be reversed?
- Stop repeating the stimulus
- Change the stimulus
- Sensitizing stimulus
How could you use habituation?
Use of techniques and exercises to decrease the neural response to a stimulus; repeated stimulus to create habituation
More long-lasting, persistent; involves changes in strength of synaptic connections
learning and memory
What are the 3 main types of learning and memory?
- Motor memory
- Verbal memory
- Emotional memory
Procedural memory; the more you do a task, the better you will be
Motor memory
Remembering items that can be spoken or written; repetition can help
Verbal memory
Memory for associations of emotions with specific places, people, etc.
Emotional memory
When starting to learn a task, _______ of the brain involved. With repetition the number of brain regions [increase/decrease]. When the the task is learned _______ of the brain show activity during performance of a task.
Large and diffuse areas; decrease; distinct regions (only regions involved)
Long-term memory requires
- the synthesis of new proteins
2. growth of new synaptic connections
Proposed mechanism to explain long-term memory
Long-term potentiation
Where does long-term potentiation occur?
Hippocampus (pt of temporal low)
The hippocampus is important for processing _________. Bilateral damage to the hippocampus results in an inability to form new ____________.
Verbal memory; verbal memories
Repetitive stimulation of hippocampus will [increase/decrease] the responses to the stimulus. how doe one accomplish this in treatment?
increase;
- single stim - measure response
- repeated stem
- single stem - measure response (larger)
What are the effects of long term potentiation
- Increases in synaptic activity
- Increased effectiveness of neuron firing
- Synapses that are effective become more effective (Neurons that fire together, wire together)
What happens to astrocytes in long-term potentiation?
increase in astrocyte-neuron conctacts
What are the mechanisms of LTP?
- Conversion of ‘silent synapses’ into active synapses
2. Postsynaptic membrane is remodeled to form new dendritic spines and synapses
What happens when the cell body of a neuron is injured?
If severe enough, it will kill the cell (dead neurons are not replace)
What happens when the axon of a neuron is injured?
- Will cause degenerative changes, but will not necessarily kill the neuron
- If axon severed, the two ends will seal; has a proximal section of the axon, which is attached to the cell body, and a distal section, which continues to the presynaptic terminal
What will happen to the distal section of the axon after injury?
- “Wallerian degeneration” - section away from body degenerates
- Glial cells will clean up (schwann cells in PNS)
- Postsynaptic cell will show some degenerative changes (trans-synaptic degeneration, some may die)
What happens to the proximal section of the axon after injury?
Central chromatolysis (dissolution of Nissle substance [rough ER]; cell body may die
Does age at the time of injury matter with neuronal cell injury?
Yes, children recover better; recovery decreases with age
Denervated target is reinnervated by branches of intact axons; occurs in polio
Collateral sprouting
Target and axon both damaged, Target dies, and Injured axon sends out collaterals to new targets; new axons sprout to new targets
Regenerative sprouting
Schwann cells make growth factors that contribute to recovery of peripheral axons; Recovery is better with a crush injury compared to a cutting injury; more prevalent in PNS
Functional regeneration
Factors that exist in PNS that improve recover and facilitate regeneration
Nerve Growth Factor (produced by schwann cells)
What are the factors that contribute to the CNS’s inability to regenerate?
- No Schwann cells producing NGF
- Oligodendrocytes inhibit growth of neurons
- Incomplete cleanup of cellular debris by microglia
What problem can occur during regenerate?
Sprouting may innervate inappropriate targets
- Motor neurons may innervate different muscles (These movements are usually short-lived, and the individual relearns muscle control)
- Can also see confusion of sensory modalities
What changes occur in synapses after injury?
- Local edema and recovery of synaptic effectiveness
- Denervation hypersensitivity
- Synaptic hyper effectiveness
- Unmasking of silent synapses
Why can edema cause a neuron to stop working?
Edema can put pressure on axons or cell bodies and cause the neuron to become inactive (function can return after pressure is relieved)
Occurs when there is damage to presynaptic terminals; The postsynaptic cells lose all or some of their synaptic inputs; Postsynpatic neurons (and muscles) respond by producing more receptors (will respond to NTMs released by other axons)
Denervation hypersensitivity
Occurs when only some of the axon branches of a neuron are damaged; The presynaptic cell body still makes the usual amount of neurotransmitter, so each terminal receives more neurotransmitter, and more neurotransmitter is released at each synapse
Synaptic hypereffectiveness
How does unmasking of silent synapses occur?
- Disinhibition of silent synapses
- Many synapses in the central nervous system appear to be non-functional (silent)
- An injury to pathways in the brain can unmask these synapses and they can become functional
What chemicals are important for changes in silent synapses?
- NMDA receptors
- Ca++ ions
- Neurotrophins (growth factors)
- Substance P
- Nitric oxide
- Changes in subtypes of sodium ion channels
What happens to the area of cortex corresponding to a particular part of our body we used more?
Increases in size
What are complications of neuronal reorganization?
- May see referred sensations after an amputation (phantom limb sensation, phantom pain); Stimuli that are applied to one area of the body are felt to occur in a different part of the body; A touch to the chin may be felt as if it were applied to a missing fifth finger
- Functional reorganization may also be a factor in some chronic pain syndromes, where pain persists after the injury heals
_______ of somatosensory pathways causes the increased release of inhibitory neurotransmitters.
If there is _____ of sensory pathways, the cortex can become more sensitive to weak stimuli.
Overstimulation; understimulation
What can promote axonal growth to increase stimulation?
Reduced activity
Supports survival of sensory neurons, basal forebrain cholinergic neurons, and mesencephalic dopaminergic neurons; May be of use in local treatment of neurodegenerative disorders (Parkinson’s Disease); May be of use in protecting motor neurons in patients with motor neuropathies and ALS
Brain-derived neurotrophic factor (BDNF)
May have a role in treating Alzheimer’s Disease (protects cholinergic neurons in primates), Diabetic neuropathy, and Chemotherapy-induced neuropathies; May promote neuroplasticity
Nerve growth facto (NGF)
Patient is made to use the affected body part; patient has an injury to the CNS; mostly done with patients with strokes, extended to patients with CP
Forced Activity (AKA constraint induced moment therapy)
According to a study conducted by Kozlowski et al, what is the effect of making the animal use the affected area in the sensorimotor cortex right away?
The injury will become more severe; Long-term behavioral deficits (Poor limb placement, Decreased response to sensory stimulation, Defective use of limb for postural support)
According to a study conducted by Nudo et al, what is the the effect of waiting 5 days after a lesion in the sensorimotor cortex before making the animal do activity?
The lesion reduced in size and prevented loss of function in the area adjacent to lesion
In human studies in pts with strokes, pts’ unaffected limbs were restrained and were made to use their affected side 8 hours a day 1-2 times per week. What were its results?
Motor functioning were improved
Why could constraint therapy work?
Pt is affected with learned helplessness
- brain learns a body part doesn’t work
- even if some function returns, pts still won’t use it because they have learned it doesn’t work
“too much of a good thing”; happens when brain cells are killed (ischemia or TBI); large amounts of glutamate is released and excite NMDA receptors, causing a large Ca influx, resulting in the neuronal death
Excitotoxicity
