Module 2: Upper Motor Neurons Flashcards
what is the M1
primary motor area
what is PMA
premotor area
what is SMA
supplementary motor area
where are upper motor neurons located
on the dorsal/lateral as well as the medial surface of the brain
what parts of the body does the corticospinal tract innervate
upper extremities, trunk, lower extremities
what does the corticobulbar tract innervate
face
what are the three major motor cortical areas
primary motor, premotor, supplementary motor cortex
where do the 1b afferents synapse?
onto inhibitory interneurons that synapse on the same alpha motor neuron that is contracting
1b afferents function
inhibit ‘over-contraction’
what happens when the AMPA receptor is open
the channel undergoes rapid desensitization, stopping the current
where does the corticospinal tract come from
direct output from the primary motor cortex
how to determine which cortical motor neurons to include in decoding upper motor neuron activity
neurons that reliably fire prior to the movement are likely participating in the movemtn
step one of decoding upper neuron activity that controls the direction of arm movements
determine which cortical motor neurons to include: those that control muscle activity for a given movement
step 2a of decoding upper neuron activity that controls the direction of arm movement
record activity of a single neuron prior to arm movement in 8 directions
what is the use of a raster plot
showing a long string of linear data on a trial-by-trial basis
step 2b of decoding upper neuron activity that controls the direction of arm movement
plot a directional tuning curve that depicts all of the raster plots as a curve
how can you identify the neuron’s ‘preferred’ direction of movement?
the direction prior to which it fires the most
step 3a of decoding upper neuron activity that controls the direction of arm movement
represent that neuron’s firing level prior to each of the 8 directions as a vector; the angle of the vector is the preferred direction of movement
step 3b of decoding upper neuron activity that controls the direction of arm movement
do step 3a for all of the neurons you recorded
Imagine the arm is controlled by just two neurons. One neuron prefers firing prior to movement in the 0 degree direction. The other prefers firing prior to movement in the 90 degree direction. If they both fire equally, which way will the arm move?
45 degrees
how is the population vector calculated
the contributions of cells that fire during movement in a particular direction are added vectorially to produce a population vector; the direction of the vector indicates direction
mirror neurons
cortical neurons that exhibit both motor and sensory properties
when do mirror neurons fire
- prior to a movement (premotor)
- when the animal sees another being perform the same movement (sensory)
- when a subject hears the sound normally associated with that movement
what are mirror neurons well-situated for
- mimicry
- empathy
- interpreting intent of another’s action
plasticity in neuroscience
means changeable
synaptic plasticity
synapses get stronger or weaker
anatomical plasticity
changes in the structure of neural connections
behavioral plasticity
learning
three medial descending tracts involved in head position, balance, and posture
tectospinal, reticulospinal, vestibulospinal
where does the reticulospinal tract project from/to
from the reticular formation to local circuit neurons that coordinate axial and proximal limb muscles
what is the reticulospinal tract controlled by
other motor centers in cortex or brainstem
what is the reticulospinal tract important for
stabilizing posture dring ongoing movements
mesencephalic and rostral pontine reticular formation function
modulates forebrain activity
caudal pontine and medullary reticular formation function
premotor coordination of lower somatic and visceral motor neuronal pools
what kind of mechanism does postural control entail
feedforward mechanisms
how are the connections between upper and lower motor neurons organized
somatotopically
true or false: there is little evidence for anticipatory control
false
true or false: the upper motor neuron system neurons are segmentally organized
true
true or false: upper motor neurons exhibit a medial to lateral organization
true
true or false: there is plasticity in the organization of the upper motor neuron systems
true
what pathway is the red nucleus involved in
lateral pathways
where does the motor cortex project to (upper motor neurons)
red nucleus, reticular nucleus, superior collliculus and vestibular nuclei
what pathway is the reticular nuclei involved in
ventromedial pathways
what pathway is the superior colliculus and vestibular nuclei involved in
ventromedial pathways
