Neurotransmitters
What are the primary neuromodulators associated with VNS?
Norepinephrine, acetylcholine, serotonin
Which number cranial nerve is the vagus nerve?
10 (X)
What is plasticity?
This principle states that neurons that fire together wire together
Hebbian plasticity for 100 bonus points
What parameters can be adjusted for stimulation?
Amplitude, pulse width, frequency, duration
What conditions have FDA approval for VNS?
Epilepsy, depression, stroke
clinical trials for heart failure, rheumatoid arthritis, SCI, PTSD, ???
What are the three brainstem regions that produce NE, ACh, and 5-HT?
NE - Locus Coeruleus
ACh- Nucleus Basalis
5-HT - Dorsal Raphe Nucleus
What is the first brainstem region innervated by the vagus nerve?
Nucleus tractus solitarus (NTS)
What is maladaptive plasticity?
a dysfunctional reorganization of the nervous system where neural circuits change in harmful ways, hindering recovery or creating new symptom
Delivering VNS during unsuccessful movements makes no change in plasticity
What are the standard parameters of VNS-mediated plasticity?
0.8mA, 30Hz, 100usec, and 0.5sec train
How do we use VNS with rehab?
Short bursts of VNS paired precisely with the best behavior
What receptors are thought of as pro-plasticity and pro-stability?
Adrenergic alpha 2 receptors and adrenergic beta receptors
What are the peripheral targets of the vagus nerve?
Heart, lungs, stomach, intestines, liver, kidney, bladder
What technique do we use to evaluate changes in cortical plasticity in preclinical models?
Intracortical microstimulation
ICMS
motor/auditory/somatosensory mapping for half
What parameters exhibit the inverted U relationship of plasticity?
All of them
What are the specific gold standard assessments for upper limb motor deficits in stroke and SCI?
Graded refined assessment of strength, sensibility, and prehension (GRASSP)
Upper extremity Fugl Meyer (UEFM)
Bonus points for Jebsen Taylor for sci and wolf motor function test for stroke (and Action Research Arm Test)
What neurotransmitter is necessary for motor functions?
Acetylcholine
What are afferent A fibers?
Sensory nerve fibers innervated all over the body and send information to the brain
What is spike-timing-dependent plasticity?
VNS enhances this type of plasticity, where stimulus timing relative to neural firing determines synaptic strengthening or weakening.
What is charge per pulse?
This derived quantity combines amplitude and pulse width and determines total electrical delivery per pulse.
What are the different stimulation-triggering strategies?
closed loop and open loop stimulation
bonus points for explaining the differences and why we use each
What neruotransmitters provide an inhibitory and excitatory function in the nervous system?
Glutamate and GABA
bonus points if you say GABA is excitatory as a baby
How many fascicles, breaks, and merges do rats have in their vagus nerve? What about humans?
1 fascicles, no breaks or merges
2-20, breaks and merges happen on and off every 1mm
What is input specificity?
This plasticity principle explains why only circuits active during VNS pairing are strengthened despite global neuromodulator release.
How could chronic pain conditions affect parameterization?
Chronic pain induces phasic or tonic firing of the LC that activates NE release to some degree. Adding VNS at normal parameters may push NE release to be too high to have plasticity in the normal inverted U region.
What are adverse events of high stimulation intensities of VNS?
Vocal cord paralysis, Cushings Reflex, autonomic dysrefelxia, apnea, peptic ulcers