Cortical motor areas Flashcards
Where is the motor cortex located?
Immediately rostral to central sulcus
What is the role of the primary motor cortex?
Area critical for execution of voluntary movements
Control of precise, independent movement of the extremities
What is the motor association cortex?
Area involved in planning and preparation for action
Rostral to motor cortex
What are the symptoms of a unilateral mild stroke?
Contralateral hemiparesis (one-sided weakness)
Partial paralysis
What are the symptoms of a unilateral severe stroke?
Contralateral hemiplegia (one-sided paralysis)
Abnormal expression of spinal reflexes
Babinski’s sign
What is affected by an anterior cerebral artery infarction?
Lower limbs
What is affected by a middle cerebral artery infarction?
Upper limbs and face
Middle cerebral artery infarctions that affect the outflow of the motor cortex thought the internal capsule are devastating
What is the corticospinal tract?
Crossed pathway arising mainly from primary motor cortex
Fibres descend through ventral part of brainstem
- Internal capsule in forebrain
- Cerebral peduncle in midbrain
- Pyramid in medulla
What do corticobulbar fibres do?
Branches from cortex terminate in regions that control brainstem motor nuclei
Control cranial nerve motor function
Where do the corticospinal fibres cross the midline?
Motor decussation in low medulla
How do the corticospinal fibres continue in the spinal cord?
As the lateral corticospinal tract in the dorsolateral funiculus of the spinal cord
What is the uncrossed ventral corticospinal tract?
In humans, 10-20% of fibres descend ipsilaterally
Ultimately either cross or provide control for axial muscles
What is the result of lesions to the corticospinal tract?
Permanent deficits most extreme in finger movement and manipulation - loss of dexterity
When do direct cortico-motorneuronal connections develop?
Post-natally at about 9 months
What are the sources of input to the motor cortex?
- Motor association areas
- Cerebellum
- Basal ganglia
- Sensory afferents
How is grip force controlled?
- Motor cortex estimates appropriate force
- Cutaneous sensory afferents detect slippage
- Output of corticospinal neurons corrects for slip by strengthening grip
Feedback control system
What is a long latency stretch reflex?
Proprioceptive information projects to motor cortex
Permits precisely controlled movements
What are the inputs to motor association areas?
- Prefrontal cortex
- Parietal cortex
- Cerebellum
- Basal ganglia
Where do the motor association areas project to?
- Primary motor cortex
- Spinal cord
- Cerebellum
- Basal ganglia
What do the cingulate motor areas control?
Expression of emotions via motor systems
Facial expression
What kind of movement is the lateral premotor cortex important for?
Movements dependent on sensory trigger signal
Interaction with an external object
What kind of movement is the supplementary motor area important for?
Internally-generated movement
Bimanual movement
What are mirror neurons?
Neurons that fire in relation to making a movement as well as observing the same movement being performed by others
What area of the brain is involved in mental rehearsal?
Supplementary motor area
Helps predict the sequence of movements needed to achieve a particular end point and in understanding their consequences, a critical element of feedforward motor control using forward models
