Neuroplasticity and Neuromodulation

Question 1

Define neuroplasticity

Answer 1

Continuous alterations of neural pathways and synapses based on experience or injury (we have some control over it, habits affect brain structure, especially in childhood)

New learning drives neuroplasticity. Not repetition of already learned
tasks.

Question 2

Describe, compare and contrast ways that neuroplasticity can be quantified at the genetic, epigenetic, cellular, synaptic, and neural network levels.

Answer 2

Environmental enrichment promotes neural plasticity. Opportunities for learning, exploration, social activity. In contrast to sensory deprivation

Genetic/Epigenetic:
at the level of gene expression and protein levels using DNA microarray, ELISA, Western blot, etc

Cellular:
  Complex environments produce brain changes:
• Growth of dendrites
• Altered synaptic structure
• More synapses
• More glia
• Increased coverage of synapses by 
astrocytes
• More capillaries
• Thicker, heavier cerebral cortex

Synaptic:

Neural Network levels:

Resting State Functional Connectivity..Areas of the brain that are functionally connected to each other show similar low frequency fluctuations of the fMRI BOLD signal when the person is in a
resting state

Question 3

Define Hebbian plasticity

Answer 3

when two neurons fire together, they wire together. Long Term Potentiation (LTP)

Question 4

Describe 6 cellular or synaptic mechanisms underlying Hebbian plasticity

Answer 4

Typically measured in animal models.

 Increased probability that a synaptic vesicle will attach to the cell
membrane and release its neurotransmitter
 Increased number of sites along the cell membrane where
synaptic vesicles can ‘dock’
 Increased number of synaptic vesicles
 Increased sensitivity of receptors on the post synaptic cell
membrane
 Increased number of receptors on the post synaptic cell
membrane
 Growth of additional synapses

Question 5

Describe how cortical representations of muscles can be determined in animal models and humans

Answer 5

In animals, the cortical representation of a movement or a muscle can be determined using intracortical microstimulation. The area of cortex from which microstimulation elicits an electromyographic response is the muscle’s cortical representation.

In humans - transcranial magnetic stimulation (TMS) to accomplish cortical mapping non-
invasively.

Question 6

Explain methods that are being investigated in animals and humans to increase or decrease neural excitability

Answer 6

Electronic interfaces are being developed to influence neuroplasticity and brain connectivity

Applications of Hebbian plasticity in animal models (long term
potentiation, neurons that fire together, wire together).

In a monkey model, paired stimulation methods can increase
connectivity between neurons through LTP.

In a rat model, closed-loop stimulation demonstrates the importance of spike timing. Random firing does not increase connectivity, but specifically timed firing does.

Implantable microelectrodes can allow humans to regain a sense
of touch after spinal cord injury.