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Neuroplasticity (Factors affecting neuroplasticity (lesion size, age, sex,…
Neuroplasticity
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Principles
- Experience-dependent changes interact: metaplasticity
- Plasticity is related to intensity or frequency of experiences
- Similar behavioral changes can correlate with different plastic changes eg. when learning one task, synapses in one brain part could increase and in the other part they could decrease
- Plasticity is age-dependent: if older age, learning new motor tasks becomes more difficult
- Two general types of plasticity derive from experience: experience-expectant (during development), experience-dependent (use-dependent)
- Plastic changes are time-dependent
- Plasticity can be analyzed at many levels: behavior (people can adapt to a visually rearranged world), cortical maps (topographic representations of external world, experience modifies sensory maps), physiology (LTP, kindling), synaptic organization, mitotic activity (new neurons produced in injured cortex), molecular structure
- Plasticity is related to an experience's relevance to us
- Plasticity is common to all nervous systems (even non mammals)
Phantom Limb
sensation that an amputated limb is still attached but majority of the sensations is painful (continuous or intermittent) --> clenching spasm
Mechanism? still unclear
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Neuromatrix: the experience of the body is created by a wide network of interconnecting neural structures
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Treatment
Antidepressants, spinal cord stimulation, accupuncture, hypnosis --> lack of evidence, lack of effectiveness
Mirror Box/ Mirror Visual Feedback: effectiveness is related to ability of the patient to internalize the reflection of the limb as their own limb
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other neurological syndromes e.g. hemiparesis following stroke, focal dystopias, dyspraxia maybe could also benefit
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neural mechanism: mirror neurons, interactions between different modalities eg. vision & motor commands
modality-specific referral from face to phantom limb (topographically face is next to arm representation)
Remapping hypothesis: sensations emerge as a consequence of the changes in topography following deafferentiation
- effects are based partly on unmasking of preexisting connections rather than sprouting
over time, the phantom limb becomes frozen/paralyzed (perhaps because of a continuous absence of visual and proprioceptive confirmation that the command have been obeyed)
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Adaptive aspects
people don't actually recover lost behaviors but they develop new way of functioning to compensate --> the problem of "three-legged cat"
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Maladaptive aspects
Focal hand dystomia: loss of motor control of one or more digits because of increased muscle tone eg. musical training caused the mapped representations of the digits to fuse
experience-dependent plasticity situations eg. drugs --> alterations in dendritic length & spine density
development of pathological pain, pathological response to sickness, epilepsy, dementia
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