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Neurophysiology > Motor cortical areas > Flashcards

Motor cortical areas Flashcards

1
Q

Which is lateral vs medial of SMA and PM

A

Premotor cortex is lateral area 6, SMA is medial area 6

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2
Q

How does GABA mediate cortical remapping

A

GABA inhibitory interneurons usually suppress local horizontal projectinos between different motor map areas… inhibiting these neurons allows remapping

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3
Q

How active is M1 in a rat running vs not runnning

A

M1 is less active during movement

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4
Q

What is the result of more direct connectinos from cortex to muscles in humans

A

eg corticospinal tract- increased dexterity, fine motor control

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5
Q

How much of motor control is ipsilateral

A

10%

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6
Q

What did Fritsch and Hitzgi find about M1

A

Stimulating different areas in the brain can cause twitching

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7
Q

What is motor control like in people with higher levels of GABA

A

More discrete finger representatinos, better behaviourally at distinguishing sensation in these fingers

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8
Q

Why are these species differences between mice and humans in M1 activation

A

Mice don’t need M1 for a lot of their movements, as most of their outputs come from other subcortical areas, only dexterous movements require mroe direct M1 connections

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9
Q

Why are these species differences between mice and humans in M1 activation

A

Mice don’t need M1 for a lot of their movements, as most of their outputs come from other subcortical areas, only dexterous movements require more direct M1 connections

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10
Q

How do different stimulatino parameters lead to different behaviour

A

Short stimulation- muscle twitches, joint rotation

Longer stimulation- complex movement eg reaching, likely because whole circuits are activated

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11
Q

M1 cortico-cortical inputs

A

Somatosensory cortex (cutaneous info), SMA and PM, rostral parietal cortex

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12
Q

M1 thalamic inputs

A

Dorsal columns via VPL, cerebellum via VL (proprioceptive info)

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13
Q

M1 pyramidal outputs

A

Pyramidal (corticospinal) tract neurons provide 40% of the fibres in the pyramidal tract
20% are monosynaptc to distal muscle motor neurons

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14
Q

M1 output to other brain areas

A

Corticocortical, putamen and intermediate cerebellum

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15
Q

M1 corticobulbar output

A

Projects to red nucleus, cranial nerve nuclei, brainstem reticular formation

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16
Q

How does M1 code force/muscle load

A

Using rate coding- increased firing forhigher load

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17
Q

What is Brodmann’s area 4

A

M1

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18
Q

What is PM divided into

A

PMd, prePMd, PMv

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19
Q

What form of coding does M1 use to code for movement

A

Populatino coding- the summed activity of selective neurons can be represented as a population vector,, indicating desired motor output

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20
Q

How does M1 code direction

A

M1 neurons are direction selective so act as vectors, allowing the use of a population vector to code movement direction

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21
Q

How do different M1 neurons signal movement differently

A

DIfferent or overlapping neuron populations may simultaneously signal kinematic movements (spatiotemporal info) and kinetic movements (force)- M1 may perform that transformations between the 2 representations

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22
Q

What is motor equivalence

A

The idea that different motor systems can perform the same action eg write with a pen
Suggests purposeful representations are represented abstractly in the brain, rather than as specific sets of muscle contractions

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23
Q

What is kinematic info

A

Position, velocity and acceleration of limbs, from muscle spindles

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24
Q

What is kinetic info

A

Forces generated by our body, Golgi tendons

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25
Q

What is inverse kinematic transformation

A

Determine joint trajectories to achieve eg a certain hand path, depenends on the arm’s kinematic properties eg length

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26
Q

What is inverse dynamic tranformation

A

Deetrmine the joint torques/muscle activity necessary to achieve joint trajectories, depends on the arm’s dynamic properties eg mass

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27
Q

What is an internal model

A

A neural circuit that computes transformations like estimating hand position from kinematic info

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28
Q

What are forward models

A

Represent the causal relatinoshpi between actions and their consequents, so predicts how a motor command will change the motor system’s state

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29
Q

What are inverse models

A

Calculate required motor outputs from sensory inputs that will produce a particular movement necessary for a desired sensory consequence

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30
Q

What is redundancy

A

The ability of motor systems to achieve a task in many different ways, plus the many different descending motor tracts

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31
Q

What are movement schemas

A

Stored neural representations of the simple spatiotemporal elements of a complex movement eg typing

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32
Q

What is feedforward control

A

Generated without regard to consequences or sensory feedback, open-loop, used to guide initial parts of movement

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33
Q

Strengths and weaknesses of feedforward control

A

Useful for rapid movements as there is no sensorimotor loop delay, errors can’t be corrected and will compound, can’t really work in complex systems

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34
Q

What is feedback control

A

Action is monitored-online and sensory signals used to correct errors, closed-loop

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35
Q

Strengths and weaknesses of feedback control

A

Necessary for complex movements, robust to neural noise and evironmental perturburations that can cause errors, delay

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36
Q

How does the brain alter movements commands in new kinematic and kinetic conditions

A

By adjusting internal models to maintain an appropriate relation between motor commands and motor outcome eg as body size changes

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37
Q

In learning dynamic tasks, where inverse models must be updated, which modality seems most important

A

Proprioception

38
Q

How are the muscles of the HAND VS ARM mapped in M1

A

Neurons controlling the muscles of the digits/hand are concentrated around the central zone, but different digits are distributed widely, while neurons controlling more proximal arm muscles are in a horseshoe-shaped ring around the central core

39
Q

What does SMA receive input from

A

Reciprocal cnonectinos with M1 and PM, somatosensory cortex and rostral parietal cortex, prefrontal cortex

40
Q

What does PM receive input from

A

Reciprocal connections with M1, SMA, and progressively more caudal/medial/lateral parts of the parietal cortex, prefrontal cortex

41
Q

What is the pyramidal tract

A

Projects from layer V in precentral (M1, SMA, PM) and parietal motor regions, to subcortical areas and the spinal cord
Many pyramidal tract axons decussate and form the CST

42
Q

How does M1 affect reflex and pattern-generating circuits

A

Many CST axons from M1 and premotor areas terminate on spinal interneurons that are components of these circuits, exerting descending control

43
Q

Result of M1 lesinos in humans

A

Muscle weakness, imprecise and slow movement, discoordinatino of multi-joint movements, paralysis

44
Q

Result of PMd and SMA lesions in humans

A

Impact ability to learn and recall sensorimotor mappings eg visuomotor rotations, temporal movement sequences

45
Q

Result of PMv lesions in humans

A

Prevent ability to use visual info about an object to shape the hand to grasp it

46
Q

What is the timing of M1 firing

A

M1 neurons fire just before (50-150ms) and during movement, suggesting they initiate movement/muscle contraction

47
Q

What is the organisation of M1 neurons

A

Cell bodies and apical dendrites form radially oriented columns
Neurons form orientation columns or columns of prefered body part, and tend to cluster in small groups with similar muscle fields

48
Q

What is the organisation of thalamocortical and corticortical axons in M1

A

The terminal arbors of thalamocortical and corticocortical axons form localised columns/bands

49
Q

How do population codes code continuous movement

A

The pattern of neural activit distributed across eg the arm’s motor map varies continuously in time during complex arm movements, signalling moment-to-moment details of desired movement

50
Q

What is the force-control hypothesis

A

The motor system controls a movement by planning and controlling its causal dynamic forces or muscle activity

51
Q

What is the position-control hypothesis

A

The motor system signals the desired endpoints and equilibrium configurations (posture where external forces=internal forces) of the arm and body

52
Q

How is movement encoded at the periphery by the motor cortex in position-control hypothesis

A

Inverse-kinematic and inverse-dynamic transformatinos occur implicitly at local spinal cord circuits and in the motor periphery

53
Q

How does M1 use local spinal cord circuits and the motor periphery in the position-control hypothesis

A

A descending signal specifies a referent configuration that exploits spinal reflex circuits and tone, changing muscle activity and creating an imbalance between external and internal force, that causes arm movement until equilibrium is restored

54
Q

What do M1 neurons use sensory input from proprioceptors or cutaneous mechanoreceptors for

A

Feedback control of ongoing movements, feed-forward control of intended movements, teaching signal during motor learning

55
Q

How does sensory input to M1 allow feed-forward control

A

Sensory input allows continuous pretuning of the pattern of activity in the motor map and spinal motor apparatus, as a function of the limb’s motor state before movement-> correct motor motor command for the desired movement

56
Q

What is the result of learning on connectinos between neurons in the motor map

A

Learning eg an arm mvoement leads to increased synaptic strength of local horizontal connections between different parts of the arm motor map

57
Q

What does motor learning theory suggest about learning

A

Learning involves feedback-error learning and supervised learning

58
Q

Motor learning theory- what is feedback-error learning

A

Sensory feedback about an erorr guides correction for immediate perturbation, via compensating for expected perturburation

59
Q

Motor learning theory- what is supervised learning

A

Adaption of internal models eg internal inverse model uses error signals to learn the motor command that will produced a desired movement by compensating for the expected perturburation, neurons are retuned

60
Q

Where are the neural circuits constituting internal forward and inverse models

A

M1, PM, cerebellum, superior parietal cortex

61
Q

Is the M1 motor map static?

A

No- it has a dynamic adaptive map that generates the motor commands needed to accomplish desired actions under different conditions

62
Q

What happens in PM during preparation for a movement

A

Many PM cells show directionally tuned activity changes that signal the direction of impending movement

63
Q

What can PM activity encode durnig the planning stage

A

Abstract representatinos of motor output, what the arm must do to produce these movements, higher-order aspects such as an action’s goal or expected reward

64
Q

During a monkey exploration task, when do parietal neuron discharge?

A

During eye, arm or hanf movements- neurons discharge strongly during reaching to grasp, or manipulating an object, but are much less active during general arm movements

65
Q

What is the dorsal stream’s role

A

Extracting sensory info about the world andbody to plan and guide movements- the ‘how’ pathway

66
Q

What is the neural component of space

A

There are many spatial maps each related to a different motor effector, each adapted to its specific needs and created through environmental interaction, some in the parietal cortex and other in the frontal cortex

67
Q

Evidence for there being lots of different motor maps each related to a specific motor effectors

A

Parietal cortex is arranged as a sereis of areas working in parallel, near space is encoded in different areas to those that represent far space, functinoal properties of the spatial neurons vary depending on the body part controlled

68
Q

In monkeys, where are peripersonal space representations located?

A

Inferior parietal cortex and interconnected parts of the PMv

69
Q

What stimuli do neurons in F4 in PMv respond to, suggesting its involved in constructing peripersonal space

A

All neurons respond to somatosensory inputs, especially tactile stimuli on the upper body
Half also respond to visual stimuli, and some to auditory stimunli

70
Q

What about the topography of F4 PMv neurons suggests they’re involved in constructing a peripersonal spatial map

A

The modality-specific receptive fields lie in register, and their visual receptive fields move in response to body movement rather than looking direction, suggesting they’re anchored to specific body parts

71
Q

What do neurons in the F4 PMv discharge in correlation with

A

Movements, mostly of the arm/wrist/neck/face, and towards different body parts or close objects

72
Q

What is the main role of the PM

A

Choosing and planning movements

73
Q

How does the superior parietal lobe create a body schema to guide arm movements

A

Superior parietla lobe neurons integrate info on joint and limb segment position with respect to the body

74
Q

When do neurons of the superior parietal lobe fire, suggesting they’re involved in body schema

A

Many discharge during combined movements of multiple joints, assumption of specific postures, or movements of the limbs and body

75
Q

What do more posterior sectors of the superior parietal cortex do

A

Receive input from V2 and V3, integrate this with copies of outgoing motor commands and proprioceptive info to signal the target of reaching via a forward internal model

76
Q

What do PMd neurons do in reaching movements

A

Reach-related neurons fire to represent the intended direction of reaching, independent of gaze or the arm that will perform it

77
Q

What are affordances

A

When we see an object, our visual system identifies the parts of it that allow for efficient manipulation of it and afford specific opportunities for action

78
Q

What does the inferior parietal cortex do

A

Receives input from the dorsal stream, giving it the visual info to code object affordances
Neurons respond preferentially to objects of specific shapes that each require a specific grip shape, linking an object’s affordances to motor actions

79
Q

What does F5 in PMv receive input from

A

Reciprocally connected with the inferior parietal cortex and secondary somatosensory areas

80
Q

What representations does F5 in PMv contain

A

Overlapping representations of hand and mouth movements

81
Q

What special neurons are in F5 in PMv

A

Canonical neurons- discharge identically when an animal grasps OR sees an object, suggesting they signal how to interact with an object

82
Q

What does F5 in PMv firing correlate with

A

A motor act’s goal, independent of what effector is grasping
Different neurons are selective for grip type, allowing us to link object affordances consistently with appropriate motor actions

83
Q

What does the SMA contain a map of

A

The entirety of contralateral body movements, but the map is not as detailed as in M1

84
Q

How do the stimulus requirements of the SMA differ

A

SMA requires strong stimulus currents, evokes complex actions like postural adjustment or stepping

85
Q

What suggests that SMA is involved in conditional control of vountary behaviour

A

Subthreshhold stimulation can evoke the urge to move, SMC lesions produce problems initiating or suppressing inappropriate movement

86
Q

How is the SMA presumably involved in contextual control of behaviour

A

Involved in selecting and executing/inhibiting actions appropriate on the basis of internal and external cues, situating actions in a movement sequence or social context

87
Q

What is motor imagery

A

When humans are asked to imagine performing a certain motor act, the premotor and parietal cortex become active- signifies preparation to act dissociated from execution

88
Q

What is the direct matching hypothesis

A

Observing the actions of others activates the motor circuits responsible for similar motor actions by the observer (mirror neurons)

89
Q

Where are mirror neurons especially prominent

A

PMv, specifically F5

90
Q

What does the mirror mechanism seem to be important for

A

Uderstanding the actions of other through linking the observed actions of others to our own stored knowledge of the nature/motives/consequences of our own corresponding actions

Neurophysiology (23 decks)

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