Wk9 Motor Control & Action Flashcards
What is the neuromuscular junction?
where the neuron connects to the muscles
What are two descending motor pathways?
Dorsolateral tracts and ventromedial tracts
Which descending motor pathways is ipsilateral (1) vs contralateral (1)?
ventromedial; Dorsolateral
Which dorsolateral tracts are indirect (1) and direct (1)?
Corticorubrospinal; Corticospinal
Where do direct & indirect dorsolateral tracts decussate?
indirect = after red nucleus (first) direct = medullary pyramids
Where do nerves for facial motor actions come from?
Corticorubrospinal tracts (indirect)
What would happen to motor pathways for a cortical lesion vs a lower brainstem lesion?
Some functions may be intact depending for lower level lesions (before nuclei)
What do dorsolateral tracts control?
Distal limb muscles: independent movement activities (reaching)
Which ventromedial tracts are indirect (1) and direct (1)?
Cortico-brainstem-spinal; Ventromedial corticospinal
what do ventromedial tracts control?
Posture, whole-body movements
Which movement tracts pass through the vestibular nucleus?
Cortico-brainstem-spinal ventromedial tracts. This is to coordinate movement such as walking/posture
What is cerebellar ataxia?
Unsteady, wide-based gait
What functions is the cerebellum involved in?
Fine-tuning and learning motor movements; also important in environment navigation
What is intentional tremor?
Result of cerebellum damage; tremor at the end range of action closer to end-goal
What does the basal ganglia do?
Modulate movement;
What cognitive functions does the basal ganglia assist with?
habitual responses & implicit learning
Why are there direct and indirect pathways from the basal ganglia to thalamus?
Selection of actions; inhibition of actions
What are problems with basal ganglia pathways in Parkinson’s? (In terms of D receptors) what are the implications for the condition?
The balance of excitatory and inhibitory connections is thrown off; Movements can be insufficient, excessive, poorly controlled
What are positive symptoms of Parkinson’s? 3
Resting tremor Rigidity or akinesia Cognitive dysfunction, dementia, depression
What is cogwheel rigidity?
passive movement is not smooth
What types of Parkinson’s symptoms might manifest before tremors, and why?
Weightloss and lack of energy; loss of motor movement/control
Why do Parkinson’s patients experience a lot of falls?
Struggle to make corrective postural movements
What are negative symptoms of Parkinson’s? 4
progressive slowing or freezing during movement Reduced range/scale of movement (micrographia) Hypophonia (dull voice without inflection) Mask-like unemotional expression
How could Parkinson’s lead to feelings of isolation and loneliness?
Theory of embodied affect (we understand people because we can express it ourselves)
side effects of L-Dopa: What are on-off cycles? What are long term usage effects?
Individuals show particular behaviours on and off medications. Eventual drudge failure
What are symptoms of Huntington’s disease? 4
Psychiatric/affective Restlessness Poor dexterity Chorea (fragmented movements resembling voluntary actions)
Can stress play a role in motor disorders?
Yes can increase symptoms
What are 3 characteristics of Tourette’s?
Intermittent tics Normal motor Tics Normal cognition
What neuropathology is implicated in Tourette’s?
imbalance of GABAergic activity in basal ganglia
What is hemiplegia?
Weakness in a body part due to damage in primary motor cortex
How is the primary motor cortex organised?
Homonculus
What happens in the secondary motor cortex? What are its inputs?
Programming of specific patterns of movement; input from association cortex
what is processed from inputs into association cortex? 3
Integrates knolwedge (position) of objects Knowledge of body part position Directs attention
What deficits occur from damage to association cortex input?
Ataxia
Where does sensorimotor association cortex output to? 3
Dorsolateral association cortex Secondary motor cortex frontal eye fields
What deficit occurS from damage to outputs of sensorimotor association cortex?
Apraxia
What is the dorsolateral prefrontal area involved in?
Making a decision to perform action (not processing of target object or action itself)
What is ataxia? Where is it more intense?
inability to use visual information to guide movement. More severe in periphery of visual field.
How is ataxia shown in the lab?
Patient has deficit pointing to light array in front of them: reduced range.
What is apraxia?
Inability to make skilled movement
What is intrinsic spatial coding and why do we need it?
Knowing what body parts are doing; vision can be obscured but we still need to know what limbs are doing.
How do we know the superior parietal lobe is critical for sensorimotor integration and internal representation? (Case study)
Wolpert’s patient PJ had a cyst encroaching on the SPL. She couldn’t maintain representations and percieve right arm and leg to drift when unseen.
What are affordances?
actions elicited by certain objects - can be appropriate and inappropriate (requiring inhibition)
What are the basic components of a motor control system? (Wolpert, 2000)
States: - predicted, desired, or estimated actual Predictor which translates movement to perception (efference copies) competing affordances
Where do efference copies reside?
In association cortex
What does the estimated actual state tell us?
Whether the action is on the right track to achieve its predicted state.
How does the motor control model explain alien hand syndrome?
desired state doesn’t influence model, so irrelevant affordances are not suppressed by the intended actions. (No efference copy)
Could we be the only ones with mirror neurons?
lower level primates can also imitate
What is the ideomotor principle? Who didn’t like it?
Forming a mental representation of an action activates the same parts of the brain which perform it. Cattel & Horn moved psychology towards psychometric testing.
What are 4 things we initially thought about mirror neurones (found from monkeys)?
They respond to: 1. Sight of goal-directed actions 2. Goal being achieved, even out of sight 3. Sound of action (multimodal) 4. Action performed by agent, not a tool
What do we know now about mirror neurons?
Can be action (not just physical) goal. Context and experience matters. Non-human models can elicit activation. Individual differences matter.
How do ballet dancers help separate motor familiarity in action observation (mirror neurons), and show the effect of experience?
Males will only have motor-familiarity with male moves. Not just visual familiarity. The motor experience is key and must be meaningful through context/experience.
How can we respond to robotic stimuli with mirror neurons? What does this show?
If we have experience with the stimuli then activation occurs. People may be able to integrate with robotic agents.
