L7 Motor Cortex and Voluntary Movements Flashcards
What percentage of the corticospinal axons cross at the pyramidal decussation and travel in the lateral Corticospinal tract?
About 90%
What percentage remain in an ipsilateral ventral corticospinal tract and project bilaterally to medial motor neurons serving axial muscles
About 10%
What structures are the subcortical motor projections to the spinal cord from?
- Reticular formation
- Vestibular nuclei (medial and lateral)
- “Red” nucleus (Rubrospinal pathway is well known in non-human primates – preliminary
evidence in human beings).
What is the purpose of the feedforward mechanism of postural control?
for anticipated postural instability
(essentially keeps you from falling the examples was the calfs bracing for the biceps to contract)
What is the purpose of the feedback mechanism of postural control?
for unanticipated postural instability
Which somatotropic region of the primary motor cortex is assoc. w ankle control?
Medial
Which somatotropic region of the primary motor cortex is assoc. w face, mouth, mastication control?
lateral
Why are the face and finger representation of the haemophilus larger than the other areas?
Bc there is a greater degree of control to these areas
T/F somatotopic organization of moto cortex is not plastic
False
(The brain can be retrained to have more refined control at other body parts depending on how those body parts are exposed to movement)
What three thing can alter neron properties?
- Pathology or trauma
- Normal experience (e.g., motor-skill learning)
- Therapy
What does the primary motor cortex control?
simple features of movement
What encodes Direction of Movement?
- Neurons in motor cortex have a “preferred direction”
What guides movement?
Internal models and are learned with practice
In the theory of “optimal” feedback control, what adjusts sensory feedback?
an efferent “copy” of the motor command
Damage to which motor area is assoc. w complex motor dysfunctions?
premotor area
T/F outputs of the primary motor cortex and premotor areas overlap in the spinal cord.
True, However, inputs to the two cortical regions have differences, and
When are the premotor and posterior parietal cortical areas active?
during mental rehearsal of a movement
Similar same patterns of activity occur during such planning and during the actual movement. Example: reaching for and grasping an object.
What info. does reaching require?
- visual information abt target location proprioceptive info about the limb being used
What is the relationship b/n peak velocity of a movement and the distance of the target?
Peak velocity of a movement to a target is proportional to target distance
(meaning the longer the distance the faster the speed)
What determines grasping of an object?
mostly shape of the target object
(That is, the “kinematics of grasping … depend on the object itself and not on its location.” )
What are the steps of grasping?
- Hand preshapes as it moves toward target object
- Grip size first increases and then decreases as object approached
- Precision grip requires more cortical circuitry (briaon power)
What regulates reaching and grasping?
parallel parietal cortex premotor pathways
reaching and grasping are goal-directed movements that require what?
transformation of sensory information about the environment into signals that control muscles.
Where are mirror neurons primarily located?
ventral premotor area
T/F mirror neurons discharge only when the monkey does the action
Fasle,
they also discharge when the monkey observes another primate (monkey or human) making the same movement.
Studies of motor control include the following protocol: Stand and upon command pull an object toward you by flexing your arms. In this experiment, “upper” motor neurons are most likely to do which of the following?
a. Only activate arm muscles (e.g., biceps)
b. First activate arm muscles (e.g., biceps) followed by leg muscles (e.g., gastrocnemius)
c. First activate leg muscles (e.g., gastrocnemius) followed by arm muscles (e.g., biceps)
d. Activate arm (e.g., biceps) and leg muscles (e.g., gastrocnemius) at the same time
C
Explain the results of robot-based motor hand therapy
Your are able to train the brain post stroke to repeat movement. Those who used this therapy experienced a better recovery of motor neuron function than those who didn’t.
This only targeted very small movements not in simple movements like supination
What does the babinski sign indicate?
an upper motor neuron injury
Who would you not use the babinski sign test on?
Babies under the age of 2
this is because they have not yet developed enough of their neuronal system to give a conclusive response to the foot stimulus.
