Lecture 18: Motor Cortices Flashcards
What three areas of the frontal lobe make up motor cortex?
- Primary Motor Cortex
- Premotor Cortex
- Supplementary Motor Cortex
Purpose of Broca’s Area
Activation of appropriate muscles for speech production
Purpose of Frontal eye fields
Activation of extraocular muscles used in horizontal eye movements
Another name for primary motor cortex
M1
Input/Output of M1
Input: PMC, SMA, Primary somatosensory cortex, posterior parietal areas involved with integrating multpile sensory inputs
Output: PMC, SMA, M1 on other side of brain
Input/Output of PMC
Input: M1, PMC, Posterial parietal cortex, Basal ganglia and cerebellum via VA/VL, prefrontal cortex
Output: M1, SMA
UMNs of corticospinal and corticobulbar pathways
Giant Betz cells in layer 5 of motor cortex
What part of primary motor cortex stimulates legs?
Medial part of contralateral M1
Internal Capsule
Small space where the UMNs from primary motor cortex are condensed between the thalamus and basal ganglia
How are the neurons in the internal capsule arranged?
- It is a sideways V shape looking from above
- Face is at the bend
- Arm, trunk, and limb in posterior branch
Upper motor neuron influences
- Direct cortical stimulation of spinal cord; contralaterally
- Direct cortical stimulation of brainstem bilat. by alpha motor neurons
- Cortex innervates rubrospinal path via corticorubral tract
- Corticotectal tract lets cortex activate tectospinal tract
- Corticoreticular lets cortex modulate reticulospinal
- Interneurons may be involved
What does the corticostriate pathway innervate?
Caudate nucleus and putamen of basal ganglia
What do the corticopontine and corticoolivary tracts innervate?
Important inputs to the cerebellum
Purpose of corticocortical pathways
Cortical areas communicate with each other; connections often go via thalamus.
May receive input from basal ganglia and cerebellum through thalamus.
Functions of primary motor cortex
- Relay motor commands to alpha motor neurons
- Firing rate will increase with increased movement force
- Neurons display left/right direction selectivity
- Neurons fire in correlation with distance moved
- Firing patters encode movement speed
How does the premotor cortex help with movement?
It selects a motor plan appropriate for the situation.
Mirror neurons of premotor complex
Will fire just by watching or hearing an action
True or False: Premotor complex neurons are sensitive to the inferred intentions of a movement.
True
True or False: PMC neurons cannot distinguish between correct and incorrect actions
False
What does the SMA do?
Remembers and programs learned sequences of movements
Muscle memory
Fires while rehearsing in head beforehand
What makes up the association cortex for motor purposes?
- Prefrontal cortex
- Posterior parietal cortex
Role of posterior parietal cortex in movement
- Target objects in space
- Forms a view of the world independent of orientation
- Damage leads to apraxias of complex coordinated movements
Role of prefrontal cortex in regards to movement
Decides what actions to take; executive function
Delay of instant gratification
