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neural control of human movement > Topic 6: Brain Control of Human Movement > Flashcards

Topic 6: Brain Control of Human Movement Flashcards

1
Q

3 stages of movement control

A
  1. Determines what needs to be done (Prefrontal Cortex): Identifies the goal of the movement and best strategy to accomplish goal
  2. Plans the specific movement (Motor cortex): Specific sequences of muscle activations and patterns required to do the movement
  3. Execute the plan (Spinal Cord): Activation of the motor neurons to do the movement and make minor adjustments
    - Also have input from cerebellum and basal ganglia at stage 2
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2
Q

Prefrontal Cortex

A
  • Highest in the chain of command and the greatest complexity
  • Identifies a goal and determines what needs to be done to accomplish this
  • Highly connected with sensory cortex
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3
Q

Executive Function

A
  • Higher cognitive processes for planning, organizing, and controlling thoughts, speech, and behaviour
  • Involves a wide-range of skills
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4
Q

Executive Functions involvement in movement

A
  1. Goal-directed actions
    - Organizing
    - Planning
    - Directing: send info to next processing system
  2. Attention
    - Multitasking: allocating effectively among tasks performed simultaneously
    - Response inhibition: respond effectively with distractions/irrelevant information
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5
Q

Executive Function and aging

A

EXECUTIVE FUNCTION DECLINES WITH AGE
- Lesions in white matter
- loss of grey matter
- loss of dendritic branching
CHANGES ARE HIGHLY VARIABLE
- Decline can be minimal in health adults
- Influenced by things like lifestyle, education, genetics
AGING RELATED DELINES IN:
- overall processing speed
- problem solving ability (Goal-directed actions)
- Controlling attentional resources (Attention)

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6
Q

Changes in gait parameters with age

A
  • Decrease in gait speed and step length
  • Increase in step time and variability in these parameters
  • Reduced executive function may be an important driver of these changes
  • healthy older adults may have little to no change
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7
Q

Executive Function and Gait

A

GAIT IS A COMPLEX MOTOR TASK THAT USES EXECUTIVE FUNCTION
- not fully managed by CPGs
- EF needed to plan, organize, and direct movements
- Often must also divide attention to other tasks
EF ALLOWS EFFECTIVE DIVISIONS OF ATTENTION BETWEEN GAIT AND OTHER TASKS (multitasking)

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8
Q

Area 6 involvement in the planning of movement

A
  • Creates movement plans and holds them until ready to execute (Active just before movement occurs)
  • Plans must be highly integrated with sensory information
  • Details of coding taking place remains unclear
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9
Q

Premotor area involvement in planning of movement

A

Selection of best motor plans based on current sensory information

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10
Q

Supplementary Motor Area in planning of movement

A
  • More Complex motor sequences often with bilateral connections
  • May be more internally driven (remembering sequences)
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11
Q

Measuring the planning of movement

A

Instruction stimulus
- Red light where movement will need to be
- PMA neuron begins firing
Trigger Stimulus
- Blue light tell it to act
- PMA neuron stops firing soon after the action is made

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12
Q

Mirror Neurons

A

Exist in the PMA
- Respond when movement is imagined or watched
- Each cell has very specific movement preference
May be part of an extensive brain system for understanding actions and intentions of others

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13
Q

Primary motor cortex involvement in movement planning

A
  • Transforms the motor plan into specific movement patterns
  • Motor map masks the deeper complexity
  • Very different from lower motor neurons
  • Complex and overlapping neurons work together to control specific movements
  • Coding related to direction and force of movement
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14
Q

Premotor lesions

A

AREA 6
- Difficulty choosing the correct or appropriate sequence of muscle actions needed to accomplish a goal

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15
Q

Primary motor region lesions

A

AREA 4
- While the appropriate action may be taken, there is difficulty in the execution of the task
- Weakness, lack of coordination, or even complete paralysis

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16
Q

The coding of movement in the Primary Motor Cortex

A
  • Movement direction is encoded by the collective activity of neurons
  • Many neurons are active for every movement
  • activity of each cell represents a single vote
  • direction of movement is based on a tally and averaging of votes
17
Q

Direction vector vs population vector

A

DV: a single cells vector vote
- Each cell has a preferred direction
PV: a tally of all cells vector vote

18
Q

How would you train neural decoding AI algorithm?

A

Data must have inputs
- Brain-computer interface
- Signals from neurons in brain
- EEG and/or fNIRs, implants
Data must have outputs
- Know of the resulting movement related to the record electrical signal
Needs lots of data

19
Q

Flaws with recording only cerebral cortex activity in neural decoding algorithms

A
  • Missing sensory feedback
  • maybe missing out on complete information from loops
  • artificial movements lack smoothness
20
Q

Basal Ganglia

A

Group of Subcortical nuclei which supports the selection and initiation of willed movements, while preventing unwanted movements
- Input received from many areas of the cortex
- Loop with major input into area 6 (premotor)

21
Q

What are the 4 main nuclei in the basal ganglia?

A
  • Striatum (caudate nucleus and putamen)
  • Globus pallidus (internal and external)
  • Subthalamic Nucleus
  • Substantia Nigra
22
Q

Direct pathway of the basal ganglia

A

Helps to select motor plans and facilitates movement
- Striatum receives excitatory input from the cerebral cortex and substantia nigra
- Striatum sends inhibitory signal to Globus pallidus internal
- Causes less inhibition of Globus pallidus internal on thalamus
- Thalamus sends excitatory signal to area 6 facilitating movement

23
Q

The indirect pathway of the basal ganglia

A

Helps suppress competing or inappropriate motor plans - inhibits movement
- Excitatory signals sent from cortex to striatum
- Striatum inhibits the globus pallidus external
- less inhibition from the globus pallidus external leading to excitatory signals from the subthalamic nucleus to the globus pallidus internal
- causes greater inhibition from globus pallidus to thalamus
- thalamus sends inhibitory signals to area 6 to suppress inappropriate movements

24
Q

Parkinson’s Disease as a disease of the direct pathway

A
  • Difficulty stimulating wanted movement
  • Reduced direct pathway release of thalamus inhibition
  • arises from loss of dopaminergic neurons acting on the striatum in the direct pathway
  • Hypokinetic disorder (reduced voluntary moto activity), Bradykinesia (slowness of movement), akinesia (lack of movement)
25
Q

Huntington’s disease as a disorder of the indirect pathway

A
  • Difficulty suppressing unwanted movements
  • Reduced indirect pathway = reduction thalamus inhibition
  • Arises from a loss of striatum neurons acting on the globus pallidus external in the indirect pathway
  • Hyperkinetic (excessive involuntary motor activity), Chorea (spontaneous and uncontrollable movements)
  • Rare genetic disorder
  • Symptoms arise in 30s or 40s
    -Neuron loss will also occur in other areas of the cerebral cortex, leading to: dementia, personality changes, and death about 20 years after diagnosis
26
Q

Cortico-Cerebellar Loop

A

Proper execution of planned, voluntary, multijoint movements
- Necessary to fine tune the sequences of muscle contractions
- Made up of:
1. Cortico-ponto-cerebellar pathway
2. Within the Cerebral cortex
3. Cerebello-thalamo-cortical pathway

27
Q

Cortico-ponto-cerebellar pathway

A
  • sensory and motor cortex axons form massive projection on pons
  • Pontine nuclei relay information to cerebellar cortex
28
Q

Within the cerebellar cortex in the cortico-cerebellar loop

A

Granule Cells
- Most numerus cells in cerebellum
- Excitatory output on purkinje cells
Purkinje Cells
- Largest cells in cerebellum
- receive thousands of synaptic inputs
- inhibitory output to deep cerebellar nuclei
Deep Cerebellar Nuclei
- Excitatory or inhibitory output to thalamus

29
Q

Cerebello-thalamo-cortical pathway

A
  • Deep Cerebellar nuclei relay to thalamus
  • VL relays information back to M1 (area 4) - last chance tuning
30
Q

Cerebellar Lesions

A

Can cause Ataxia: uncoordinated and inaccurate movements
- Dysmetria: Overshoot or undershoot target
- Dyssynergia: decomposition of synergistic multijoint movements

31
Q

What are the two major groups of descending spinal tract pathways

A

Lateral motor pathways
- Commands voluntary movement
Ventromedial motor pathways
- Posture and reflex movements

32
Q

Corticospinal Tract (CST)

A

Primary pathway for voluntary motor control (neck to feet - one of the largest and longest pathways)
-Pyramidal cells arising from the motor cortex (M1, but also premotor and other areas)
- Can be divided into lateral and anterior

33
Q

Lateral CST

A
  • Controls Limbs
  • 90% of CST axons
  • Decussate in medullary pyramids
  • Control proximal/distal muscles
33
Q

Anterior CST

A
  • Controls trunk, neck, shoulders (axial muscles)
  • 10% of CST axons
  • Decussate within spinal cord
34
Q

Rubrospinal Tract

A

Much Smaller than the CST
- Originates at the red nucleus
- Receives input form cortex
- Function greatly reduced in humans

35
Q

Lateral pathways Lesions

A

The effects of experimental corticospinal lesions
- Deficit in motor control of limbs
- Recovery if rubrospinal tracts is intact
- subsequent rubrospinal lesion reverses recovery

36
Q

strokes effecting motor cortex or corticospinal tract

A
  • Paralysis on contralateral side
  • some recovery over time

neural control of human movement (6 decks)

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