Motor Control Flashcards
Which area of the brain generally directs movement?
Primary motor cortex
List the different cortexes which are in front of the central sulcus.
Primary motor centre
Supplementary motor cortex
Premotor cortex
Prefrontal cortex
List the different cortexes which are behind the central sulcus.
Primary somatosensory cortex
Posterior parietal cortex
Which numbered area is the primary motor cortex?
Area 4
Which numbered area is the supplementary motor cortex and the premotor cortex?
Area 6
Which cortex is in area S1?
Primary somatosensory cortex
Which areas cover the posterior parietal cortex?
Area 5 and 7
Voluntary movement is controlled by motor control. Motor control is a functional hierarchy with three levels.
What is the function of the high level?
Stratergy
What are the structures involved in the strategy of the higher level?
Association neocortex and basal ganglion
Voluntary movement is controlled by motor control. Motor control is a functional hierarchy with three levels.
What is the function of the middle level?
Tactics
What are the structures involved with the tactics of the middle level?
Motor cortex and cerebellum
Voluntary movement is controlled by motor control. Motor control is a functional hierarchy with three levels.
What is the function of the low level?
Execution
What are the structures involved in the execution of the lower level?
Brainstem and spinal cord
Describe what is meant by strategy carried out by the high level?
The goal and the movement strategy to best achieve the goal
Describe what is meant by tactics carried out by the middle level?
The sequence of spaciotemporal muscle contractions to achieve the goal smoothly and accurately.
Describe what is meant by the execution carried out by the low level?
Activation of motor neurons and interneurons to generate the goal-directed movement
Name the two lateral pathways which connect the brain to the spinal cord.
Corticospinal tract
Rubrospinal tract
What do the two tracts connect?
1. Corticospinal
2. Rubrospinal
- Cortex and spine
- Red nuclei to spine
What do the two types of lateral pathways, corticospinal and rebrospinal, do?
Control voluntary movements of distal muscles under direct cortical control.
What do the ventromedial pathways do?
Control posture and locomotion, under brainstem control.
Name the ventromedial pathways.
Tectospinal
Vestibulospinal tract
Pontine reticulospinal tract
Medullary reticulospinal tract
Which lateral pathway is the longest?
Corticospinal tract
Describe the origin of the corticospinal tract (CST).
2/3 originate in areas 4 and 6 of frontal motor cortex
1/3 is somatosensory
At which point does the CST decussate?
Medulla/spinal cord junction
The rubrospinal tract starts at the red nucleus but where in the brain is this?
Midbrain
What happens if there are lesions to the CST and RST?
Fine movements of arms and hands are lost.
Cannot move shoulders, elbows, wrist and fingers independently.
What would happen if there a lesion to the CST alone and the RST remained unharmed?
Initially, same defects seen (loss of movements of upper limbs) but will reappear after a few months as been taken over by RST
Large pyramidal neurones in the motor cortex project via the CST. What do they do?
Monosynpatically excite pools of agonist interneurons.
Also branch and excite inhibitory interneurons.
What do the excited inhibitory interneurons which have been excited by pyramidal neurones inhibit?
Pools of antagonist motoneurons
What does the vestibulospinal tract, one of the ventromedial pathways, do?
Stabilizes head and neck
What does the tectospinal tract, one of the ventromedial pathways, do?
Ensures the eyes remain stable as the body moves
Where do the pontine and medullary reticulospinal tracts originate?
Brainstem
What do the pontine and medullary reticulospinal tracts do?
Use sensory information about balance, body position and vision
Which other part of the brain is intimately involved in body position, balance and vision?
Cerebellum
Which muscles do the pontine and medullary reticulospinal tracts innervate?
Trunk and antigravity muscles in limbs
What do voluntary movements require input from?
From motor cortex via lateral pathways
What do the upper motor neurons in the cortex and brainstem innervate?
Lower motor neurons in the spinal cord
What do the primary motor cortex and pre-motor areas do?
Plan and control precise voluntary movements
Where is the primary motor cortex (area 4)?
In the precentral gyrus
Where do epileptic seziures usually affect first and then where do they spread to?
Usually affect fingers first, then hand -> arm -> shoulder -> face
In those with epilepsy, Penfield electrical stimulation can be used to tell what about the brain?
Which areas of the brain can be spared surgically and which areas need to be removed
What does a weak stimulation of area 4 cause?
Twitching of contralateral muscles
Does the supplementary motor area innervate distal or proximal motor units?
Innervates distal motor units directly
Does the premotor area innervate distal or proximal motor units?
Connects with reticulospinal neurones to innervate proximal motor units
Microstimulation in specific area of primary motor cortex can cause hand movements such as?
- Coordinated hand and mouth movements
- Movements which bring hands into central space to inspect/manipulate objects
How does the brain get a mental image of where your body is in space?
Generated by somatosensory, proprioceptive and visual inputs to the posterior parietal cortex
Where in the brains are decisions taken?
Prefrontal and parietal cortex
Axons from both the prefrontal and parietal cortexes converge on which area?
Area 6
If carrying out practised movements, which areas of the brain are engaged?
Area 6 and area 4
If you think about carrying out movements but don’t actually move, which area of the brain is engaged?
Area 6
Where are the decision making neurons in the motor cortex?
Area 6
Where are the mirror neurons in the motor cortex?
Area 6
What do mirror neurons do?
Fire when movement is made or imagined, wither be seeing others make the same movement or thinking about the movement
Every neurone has a preferred direction to travel in. However, all the responses of neurons combine to produce what?
A population vector
In which area is there integrated activity of large populations of neurons to perform precise movements?
Area 4
When there is change in body position, messages are sent from the brainstem to the motoneurons in the spinal cord. Which type of message is sent to try and correct postural instability?
Feedback messages
->maybe think the body is giving feedback on how it can improve the situation
Before the motoneurons in the spinal cord correct the postural positioning of the body, what does the brainstem reticula formation nuclei initiate?
Feedforward anticipatory adjustments
->this stabilises the body in preparation
Where does the major subcortical input to area 6 come from?
Ventral lateral nucleus in dorsal thalamus
The corpus striatum is a major component of the basal ganglia. It includes the two principle nuclei called?
Caudate
Putamen
What is the role of the corpus striatum?
Receives input from all over cortex
When does the putamen fire neurons?
Before any limb/trunk movement as are anticipatory
When does the caudate fire neurons?
Before an eye movements as are anticipatory
->basically the putamen and caudate both predict movements and feed forward, the putamen predicts limb/trunk movements and the caudate predicts eye movements.
The motor loop goes from the cortex to the basal ganglia and back to the cortex.
Firstly, the pathway goes from the cortex to the putamen. Is this an excitatory or inhibitory pathway?
Excitatory pathway
The motor loop goes from the cortex to the basal ganglia and back to the cortex.
Is the section of the pathway between the putamen and the globus pallidus inhibitory or excitatory?
Inhibitory
The motor loop goes from the cortex to the basal ganglia and back to the cortex.
Is the part of the pathway between the globus pallidus to the VLo neurons inhibitory or excitatory?
Excitatory
The motor loop goes from the cortex to the basal ganglia and back to the cortex.
The final part of the loop goes from the VLo neurons back to the cortex. Is this part of the pathway inhibitory or excitatory?
Excitatory
Describe what globus pallidus neurones are like at rest.
Spontaneously active
What do the globus pallidus neurones inhibit?
VLos
When we decide we want to move, there is cortical excitation. This excites the putamen which in turn, inhibits the globus pallidus, as previously discussed.
What happens as a result of the globus pallidus being inhibited?
Thee is reduced inhibition of VLo cells.
More activity in VLo cells which in turn boosts supplementary motor area
Cortical input flows by direct and indirect loops through the basal ganglia.
Which type of loop is the direct pathway?
Positive feedback loop
What is the function of the direct and indirect pathway?
Direct= selects specific motor functions
Indirect= supresses other/inappropriate actions
The substancia nigra is usually black. What colour does it appear in patient’s with Parkinson’s?
Pale, lost black colour
In Parkinson’s, you get hypokinesia. What does this mean?
Reduced movements
What are some of the symptoms of Parkinson’s?
Slowness, difficult to make voluntary movements, increased muscle tone, tremors of hand and jaw
What causes Parkinson’s?
Degeneration of neurones in substancia nigra.
Which neurotransmitter normally enhances cortical inputs through direct pathways and supresses the input through indirect pathways?
Dopamine
->therefore, in Parkinson’s there is a depletion of dopamine
What happens to the brain in Huntington’s disease?
Wasting of the brain.
Striatum is reduced dramatically and there is also cortical loss.
Huntington’s is associated with hyperkinesia. What does this mean?
Excessive movement
What are some other associated symptoms of Huntingotn’s?
Dementia
Personality disorders
How would one develop Huntingotn’s?
Rare hereditary
Is Huntington’s treatable?
No, progressive and fatal
What is a symptom which is characteristic of Huntington’s?
Chorea
What is meant by chorea?
Spontaneous, uncontrolled, rapid flicks and major movements with no purpose
What is the cause of Huntington’s (like what actually happens, not that it’s genetic)?
Profound loss of caudate, putamen and globus pallidus.
Which anatomical structure is found in the centre of the cerebellum?
Fourth ventricle
Improvement of motor skills is by repetition and practice. Which part of the brain remembers particular movements?
Cerebellum
What do lesions to the cerebellum cause?
Uncoordinated, inaccurate movements (ataxia)
Give an example of ataxia.
Failure to touch nose with eyes shut
What are Brain Machine Interfaces (BMIs) used for?
Allow patients to voluntarily control prosthetic limbs and walk again following spinal cord injuries
What are brain-brain interfaces and what are they used for?
Use brain signals from one animal to teach another animal a task it has never seen.
