Lecture 7: Motor Cortex and Voluntary Movement Flashcards
(48 cards)
What are two areas of the brain that affect the descending systems (UMN)
- basal ganglia
- cerebellum
What are the descending systems (UMN)? what are their fxns?
- motor cortex: planning, initiating and directing voluntary movements
- Brainstem centers: basic movements and postural control
What are the two pathways that UMN can take? Indirect or direct?
- Interneruons (indirect)-> reflex coordination
- Motor neuron pools(direct)-> LMN
What does LMN lead to?
skeletal muscles
What are two important areas of the brain for motor?
- Primary motor cortex
- premotor cortex
(next to each other)
what is in gray matter and white matter?
- gray: cell bodies
- white: axons
What are the 2 cells in the primary motor cortex
- Betz cells
- Non-Betz pyramidal neurons (smaller)
Where is lower extremity and trunk located on brain? upper extremeity and face?
- Lower (and trunk): medial
- Upper (and face): lateral
What is the topographic map for?
- Patterns of facial weakness and their importance for localizing neurological injury
For somatotopic organization, what is medial? lateral?
- Medial: Ankle control
- Lateral: Face, mouth, mastication control areas.
What areas are larger in the somatopic organization? why?
Face and fingers representations are larger. There is a greater degree of cortical control of these regions of the body.
The motor cortex controls the spinal cord through both _ and _ pathways
direct and indirect
What does the majority of the corticospinal axons do in the lateral corticospinal tract? What about the minority?
- About 90% of the corticospinal axons cross at the pyramidal decussation and travel in the lateral Corticospinal tract
- About 10% remain in an ipsilateral ventral corticospinal tract and project bilaterally to medial motor neurons serving axial muscles
IN CAUDAL MEDULLA
explain the difference of lateral and ventral corticospinal tract when they hit the spinal cord
- Lateral (90%): only inn. neurons on the same side of the spinal cord
- Ventral (10%): sends bilaterally to both sides of the spinal cord
Explain the Corticobulbar tract
Motor cortex down to middle medulla
- Corticobulbar will synapse to reticular formation
- Then the reticulospinal tract will go down to spinal cord
Subcortical motor projections to the spinal cord come from?
- Reticular formation
- Vestibular nuclei (medial and lateral) (NOT MOTOR CORTEX)
- “Red” nucleus (Rubrospinal pathway is well known in non-human primates – preliminary evidence in human beings).
What are the feedforward and feedback mechanism of postural control
- Feedforward for “anticipated” postural instability
- Feedback for unanticipated postural instability
Explain the babinski sign and what is it used for? When cannot we not use this?
- Normally when we use a pointed tool up the bottom of the foot, then the toes would curl in (flexion)
- With babinski sign, the toes will fan out and have a externsor plantar response
- The Babinski sign can indicate an upper motor neuron lesion constituting damage to the corticospinal tract.
- Normal in infants until 12-24 months so we cannot use this test
The somatotopic organization of the motor cortex is “ _ ”
plastic
Representations and neuron properties can be altered with:
- Pathological or traumatic changes -> diease, lose hand, etc
- Normal experience (e.g., motor-skill learning)
- Therapy
explain the somatoptoic reorganization with experience
A rat was trained to a wheel spin task with distal forarm and lever press task with proximal forelimb to get an reward. Measure map of the brain and it showed that the brain remapped itself to be better at the tasks
- Wheel spin task requires use of distal forelimb ->Increased space in cortex devoted to distal forelimb after training
- Lever task requires use of proximal forelimb ->increased space devoted in cortex to proximal forelimb after training
explain the training induced plasticity of apical spine dnesity in individual C8-projecting cortical motor neurons
There is a untrained, active control and skilled grasp (complex)
- Skilled has more dendrites and higher density so they can do the task better. More dendrites= better neuron fxn
- Training and continued experiences can also lead to increased dendritic density of cortical motor neurons. In theory, this could lead to increased efficacy when conducting specific movements.
Explain the robot based hand motor therapy after stroke
Therapy may also lead to somatotopic re-organization in the brain leading to increased efficacy when conducting specific movements.
- HOWEVER, studies indicate that therapy induced reorganization occurs during finely detailed training (i.e. robot grasp therapy) and not with brute movement training (i.e. supination therapy).
explain the study with increased sensorimotor cortex activation with therapy, but not with non-practiced supination tasks
can lead to somotoplasticity but needs to be fine detail thearpy
