Movement L5

Question 1

whats motor association cortex used for?

location?

Answer 1

planning and prepoaration of movement

rostral to primary motor cortex

Question 2

The motor cortex mediates which kind of movements, e.g. where movements are made to interact with objects in space.

Answer 2

The motor cortex mediates goal directed or voluntary movements, e.g. where movements are made to interact with objects in space.

Question 3

Unilateral mild stroke produces

…

Answer 3

Unilateral mild stroke produces contralateral hemiparesis (one-sided weakness and partial paralysis)

Question 4

severe unilateral stroke will cause….

Answer 4

severe unilateral stroke will cause contralateral hemiplegia (one-sided paralysis).

Question 5

can larger strokes lead to the unmasking of spinal reflexes?

Answer 5

yes

Question 6

stroke site:

anterior cerebral artery infarction affects?

, middle cerebral artery infarction affects ?

Answer 6

anterior cerebral artery infarction affects lower limbs,

middle cerebral artery infarction affects upper limbs and face.

Question 7

Middle cerebral artery infarctions that affect the outflow of the motor cortex thought the _____ ______ are devastating.

Answer 7

Middle cerebral artery infarctions that affect the outflow of the motor cortex thought the internal capsule are devastating.

Question 8

describe how the motor cortex exerts control over descending motor pathways

Answer 8

all mamals:

particularly the reticulospinal and rubrospinal pathways

most mammals:

a distinct corticospinal tract that has a direct effect spinal interneurons which in turn control motoneurons.

Question 9

T or F

In quadrupeds that use the forelimbs for manipulation (cats and rodents) there is a corticospinal tract as well

Answer 9

T

Question 10

The __________ pathway is the most important route through which willed or voluntary movements are mediated in mammals

Answer 10

The corticospinal pathway is the most important route through which willed or voluntary movements are mediated in mammals

Question 11

were doe the corticospinal tract cross the mid line?

Answer 11

Most Corticospinal tract fibres cross the midline in the low medulla (the motor decussation)

Question 12

describe the path of the corticospinal tract fibres

Answer 12

• The fibres descend through the ventral part of the brainstem.
• In the forebrain these fibres lie in the internal capsule
• In the midbrain the fibres form the cerebral peduncle
• In the medulla the old name for the fibres is the pyramid (hence pyramidal tract). In the medulla many cortical output fibres branch to terminate in regions that control brainstem motornuclei.
• cros midline
• continuing into the spinal cord as the lateral corticospinal tract in the dorsolateral funiculus of the spinal cord.

Question 13

Pictre:

Answer 13

Question 14

motor cortex gives rise to which skils?

Answer 14

motor cortex in primates allows the control of precise, independent movement of the extremities (e.g. fingers).

manual dexterity

Question 15

T or F

There is huge species diversity in the corticospinal tract.

Answer 15

T

Question 16

A small stroke may cause a ……

A larger stroke may cause a ……

Answer 16

A small stroke may cause a contralateral hemiparesis (weakness)

A larger stroke may cause a contralateral hemiplegia (paralysis).

Question 17

“Upper motoneuron lesion” to refer to motor cortex lesions that are complicated by ,….

Answer 17

“Upper motoneuron lesion” to refer to motor cortex lesions that are complicated by spasticity

Question 18

compared to “lower motoneuron lesions”, which cause ….

Answer 18

compared to “lower motoneuron lesions”, which cause flaccid paralysis

Question 19

issue with this picture

Answer 19

• lead people to think the motor cortex controls individual muscles.
• but single neurones control groups of muscles
• Different groups of motor cortex neurons thus provide alternative ‘libraries’ of muscle synergies which might be used in different movements

Question 20

give some sources of input to the motor cortex

Answer 20

1. Motor association areas (direct cortico-cortical connections)
2. Cerebellum (via VL thalamus)
3. Basal Ganglia (via VL thalamus)
4. Sensory afferents (via VL thalamus and sensory cortex)

Question 21

describe how the motor cortex uses sensory feedback

Answer 21

both tactile and proprioceptive afferents.

allow correction

eg: reguation of force grip

1. initial estimate
2. cutaneous afferents detect slippage
3. grip strengthened (60ms response time)
4. until slip stops

Negative feedback - slow and reactive.

Question 22

describe motor association areas - where do they get input from?

where do they project to?

Answer 22

inputs from higher cortical association areas (prefrontal and parietal) and from the cerebellum and basal ganglia.

direct projections to primary motor cortex

Question 23

motor associatio areas are involved in?

Answer 23

planning

Question 24

Two regions of motor association cortex were initially recognised in primates:

what are the?

Answer 24

Two regions of motor association cortex were initially recognised in primates:

lateral Premotor Cortex

and Supplementary Motor Area (SMA)

Question 25

describe the Supplementary Motor Area function?

Answer 25

most important in internally generated or self-paced movement (you decide when and how to move) and bimanual movements.

Question 26

d: Lateral premotor cortex

Answer 26

more important for movements that are dependent on a sensory trigger signal, or when sensory information constrains the options (e.g. interacting with an external object – to catch something. You can only catch something if your hands are in the right place at the right time!).

Question 27

major inputs to lateral Premotor Cortex and Supplementary Motor Area (SMA).

Answer 27

Cerebellum provides major input to lateral premotor cortex;

the basal ganglia to the supplementary motor area.

Question 28

Lateral premotor cortex lesions leads to?

Answer 28

Lateral premotor cortex lesions lead to
an inability to appropriately incorporate
sensory information (visual, tactile) into
motor actions, particularly into
grasping.

Question 29

descrbie the visuomotor grasp circuit

Answer 29

the location of objects in egocentric space is represented is an area of the posterior parietal cortex (area AIP - the apex of the ‘where’ visual stream). This projects to lateral premotor cortex, which in turn projects to primary motor cortex.

There is a heavy interconnection between these
areas and the cerebellum.

Lesions in these areas do not prevent attempts at movement, but this movement is often poorly organised in relation to objects in the outside world.

Question 30

humans with lesions in the lateral premotor cortex show what condition?

Answer 30

apraxias

Question 31

where were mirror neurones first described?

Answer 31

Part of the lateral premotor cortex is the site at which ‘mirror neurons’ were first described

Question 32

what are mirror neurones (specifically in the lateral premotor cotex)

Answer 32

useful for imitation

these are neurons that fire in relation to making a grasping movement, but also when seeing another person making the same grasping movement – e.g. they contribute to action, but also 2 action observation. This may be useful in imitation, but much has been made of this beyond motor control (see link to video on Moodle site).

Question 33

role of the SMA?

Answer 33

SMA helps predict the sequence of movements needed to achieve a particular end point and in understanding their consequences. This type of activity is an essential element of feedforward motor control,

SMA important in feeforward control too

Question 34

T or F

The very large amounts of cortex in the motor association areas in man are poorly understood

Answer 34

T

Question 35

there are areas and the medial part of the hemisphere (part of the cingulate cortex) which have motor functions. These areas are thought to be involved in emotionally driven and related movements.

give an esxmaple

Answer 35

An example might be the limbic laugh: voluntary facial paralysis in patients who suffer a primary motor cortex a stroke these them unable to voluntarily smile or laugh (or pretend to laugh), yet they can laugh when told a genuinely funny joke.

Question 36

may types of apraxia?

Answer 36

Several forms of apraxia have been described for example an inability to make gestures or movements when instructed (ideomotor apraxia), inability to link the elements of a sequence of movements correctly (ideational apraxia) or an inability to link physical structures or pictures/shapes in an appropriate way (constructional apraxia).

Question 37

fat

Answer 37

mamba