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Neuro > Motor control - 3 > Flashcards

Motor control - 3 Flashcards

1
Q

Describe directional tuning in primary motor cortex

A

Each neuron has preferred direction but responses of all neurons combine to produce popular vector - commands to perform precise movements are encoded in integrated activity of neurons

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2
Q

What does an actual change in body position cause?

A

Initiates rapid compensatory feedback massages from brainstem vestibular nuclei to spinal motor neurons to correct postural instability

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3
Q

What is the feedforward mechanism which control movement?

A

Before movement begins, the brainstem reticular formation nuclei initiates feedforward anticipatory adjustments to stabilise posture

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4
Q

Where does the loop of information cycle?

A

Cortex to thalamus and basal ganglia to supplementary motor cortex

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5
Q

Where does major subcortical input to area 6 come from?

A

Ventral lateral nucleus in dorsal thalamus (VLo)

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6
Q

Where does input from VLo come from?

A

Basal ganglia

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7
Q

Where are basal ganglia targets of?

A

Frontal, prefrontal and parietal cortex

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8
Q

What are the major components of basal ganglia?

A

Corpus striatum - includes 2 principal nuclei
Caudate and Putamen

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9
Q

What are the caudate and putamen?

A

Are input zone of the basal ganglia

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10
Q

Where does corpus striatum receive inputs from?

A

All over cortex
Corticostriatal pathway - multiple parallel pathways with different functions

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11
Q

What do medium spiny neurons in putamen and caudate receive?

A

Excitatory cortical inputs on dendrites

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12
Q

What do large dendrite trees integrate?

A

Massive somatosensory, premotor and motor cortical inputs

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13
Q

Describe the axons of the basal ganglia

A

Are inhibitory
Contacts 1000s of spiny neurons so integrating influence of 1000 cortical cells
Axons project to globus pallidus and SN pars reticulata

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14
Q

When do putamen and caudate fire?

A

Putamen - before limb/trunk movements
Caudate - before eye movements
Both predict movements

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15
Q

What type of pathway if from cortex to putamen?

A

Excitatory

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16
Q

What type of pathway is between putamen to globus pallidus?

A

Inhibitory

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17
Q

What type of pathway is between globus pallidus to VLo neurons?

A

Inhibitory

18
Q

What type of pathway is between VLo and back to SMA?

A

Excitatory

19
Q

What is the functional consequence of cortical activation of putamen?

A

Excitation

20
Q

At rest, what are the globus pallidus neurons?

A

Spontaneously active and inhibit VLo

21
Q

Explain cortical excitation

A

Excites putamen which inhibits globus pallidus - reduces inhibition of VLo cells - activity in VLo boosts SMA activity

22
Q

What does gating by basal ganglia depend on?

A

Dis-inhibitory arrangement

23
Q

What are the upper motor neurons in SMA like at rest?

A

Not excited as little cortical input

24
Q

What are the upper motor neurons in SMA like when excited?

A

Lots of cortical input into globus pallidus which is inhibited so this dis-inhibits the thalamus
Excites upper motor neurons in SMA

25
Q

What is the function of the direct pathway in cortical input flow?

A

Selects specific motor actions

26
Q

What is the function of the indirect pathway in cortical input flow?

A

Suppresses other/ inappropriate actions

27
Q

Describe the direct pathway of cortical input flow

A

Positive feedback loop
Enhances initiation of movements by SMA
Input from cortex releases inhibition on VLo

28
Q

Describe indirect pathways of cortical input flow

A

Antagonises the direct route
Cortex excites subthalamic nuclei which excites GP internal which inhibits thalamus

29
Q

Describe Parkinson’s disease

A

Hypokinesia - slowness, difficult to make voluntary movements, increased muscle tone (rigidity) and tremors in hand or jaw

30
Q

What is the cause of Parkinson’s disease?

A

Degeneration of neurons in substantia nigra so loss of their dopaminergic excitatory inputs to striatum

31
Q

What is the function of dopamine?

A

Enhances cortical inputs through the direct pathway ad suppress inputs through indirect pathway

32
Q

What does depletion of dopamine cause?

A

Parkinson’s - closes down focussed motor activities that funnel through thalamus to SMA

33
Q

Describe Huntington’s disease

A

Hyperkinesia with dementia and personality disorders
Is hereditary, progressive and rare
Chorea - spontaneous uncontrolled rapid flicks and major movements of no purpose

34
Q

What is the cause of Huntington’s disease?

A

Profound loss of caudate, putamen and globus pallidus
So loss of ongoing inhibition by basal ganglia

35
Q

How many CNS neurons does the cerebellum have?

A

50%

36
Q

What is ataxia?

A

Uncoordinated inaccurate movements
Can be due to lesions to cerebellum

37
Q

What structures are a part of cortico-ponto-cerebellar projection?

A

M1 layer 5, areas 4 and 6 and somatosensory cortex
20 mill axons

38
Q

What connects the cerebellum to cortex?

A

Ventrolateral thalamus

39
Q

What is the function of the cerebellum?

A

Instructs direction, timing and force

40
Q

Describe the motor loop through lateral cerebellum

A

Motor loop of voluntary movement through basal ganglia and VLo undergoes ongoing refinement
Via involvement of feedback loop through pons, cerebellum and thalamus then back to cortex

41
Q

Describe Brain machine interfaces

A

BMI - allow patients to voluntary control prosthetic limbs and walk again after spinal cord injuries
Sensory properties in prosthetics

42
Q

Describe brain brain interfaces

A

BBI - brain signals from one animal to teach another animal a task it has never seen

Neuro (40 decks)

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