Lecture four - Central control of movement

Question 1

What is the difference between the cerebral cortex and the cerebrum?

Answer 1

The cerebral cortex is the outer layer of the cerebrum. It is the outer layer of grey matter. It is primarily involved in consciousness.
The cerebrum is diivided into two halves - the left and right hemisphere. The two halves are connected the corpus collosum.

Question 2

Is it true the cerebelllum contains 80% of the brains neurons?

Answer 2

Yes.

Question 3

What are the sulci and gyri of the brain?

Answer 3

The grooves and ridges of the cerebelal cortex respectively.

Question 4

What are the areas of the brain known to be involved in motor control?

Answer 4

Posterior Parietal Cortex.
Primary Motor Cortex.
The supplementary motor cortex.
The premotor cortex.
The prefrontal cortex.

Question 5

How were the areas of the brain responsible for motor control discovered?

Answer 5

Through animal experiemtns, such as zapping primate brains when animals were anethetised and seeing what movement was generated.

Question 6

The Primary Motor Cortex has a somatotopic organisation. What does this mean?

Answer 6

Each area of the M1 corresponds to a different body area.

Question 7

What determines how big an area for a body part is?

Answer 7

How fine the movement type is. Hands have a relatively large area of the M1. So does the tongue.

Question 8

Do messages from our different body parts go to the M1?

Answer 8

No. Stimulation of these areas lead to movement of the associated body part, but messages from these body parts go elsewhere.

Question 9

What is the difference between upper and lower motor neurons?

Answer 9

Upper motor neurons are located in the cerebrum, cerebellum, or brainstem.

Lower motor neurons are located in the spinal chord.

Question 10

What are the two descending motor tracts?

Answer 10

These descending motor tracts are now information from the brain about movement travel to their target areas, such as limbs. They travel down the white matter of the spinal chord.
1. Pyramidal or lateral tracts - these run down the lateral groves in the spinal chord and carry information about voluntary movement.
2. Medial or ventromedial tracts - these travel down the medial groves of the spinal cord and carry information about involuntary movement, such as balance.

Question 11

What descending motor tract does not enter the spinal chord?

Answer 11

The corticobulbar tract. This tract sends information about movement to face, neck, tongue etc.

Question 12

What are the three lateral descending motor tracts discussed in the lecture?

Answer 12

1. CORTICOSPINAL TRACT
2. RUBROSPINAL TRACT
3. CORTICOBULBAR TRACT

Question 13

Where does the CORTICOSPINAL tract originate, what does it control, and is there crossover (i.e. is the movement controlled contralaterally)?

Answer 13

The corticospinal tract originates in the M1 (primary motor cortex).
It sends messages for movement of the distal parts of the limbs, such as fingers.
There is crossover. This occurs at the MEDULLA (in the brain stem). When the tract enters the spinal chord, it enters on the side opposite to the side of the M1 it originated in, i.e. the left M1 controls the right side fine motor movement.

Question 14

What does the RUBROSPINAL TRACT control?
Where does it originate?
Is there crossover?

Answer 14

The rubrospinal tract controls arms, forearms and independent movement.
It orginates in the RED NUCLEUS in the mid-brain, BUT it receives information from M1.
There is crossover at the midbrain and so information from the right red nucleus informs movement of the left side of the body.

Question 15

What does the CORTICOBULBAR TRACT control?
Where does it originate?
Is there crossover?

Answer 15

The corticobulbar tract controls face, neck, tongue and external eye movents.
It originates in the M1.
There is crossover (50% crossover).
The corticobulbar tract does not enter the spinal chord.

Question 16

What is the significance of M1 for the corticospinal tract, the rubrospinal tract and the corticobulbar tract?

Answer 16

The corticospinal and corticobulbar tract both originate in the M1. The rubrospinal tract originates in the midbrain, but receives information from the M1.

Question 17

What does the VENTROCORTICOSPINAL TRACT control?
Where does it originate?
Is there any crossover?

Answer 17

The ventrocorticospinal tract is part of the corticospinal tract (makes up about 10%) of this tract.
It controls upper legs and trunk.
It originates in M1.
There is no crossover. That is, it is ipsilaterally controlled.

Question 18

What does the TECTOSPINAL TRACT control?
Where does it originate?
Is there crossover?

Answer 18

The tectospinal tract controls the coordination of head and trunk movements with the eyes. It is involved in orientating the head toward auditory and visual stimuli. It works in combination with visual and auditory systems.
It originates in the brain stem (superior colliculi), which are in the brain stem.
Movement is controlled ipsilaterally. There is no cross over. This means it informes movement on the same side that it originates from.

Question 19

What does the VESTIBULOSPINAL TRACT control?
Where does it originate?
Is there crossover?

Answer 19

The vestibulospinal tract controls postural movements.
It originates in the brainstem (vestibular nucleus in the medulla).
There is no crossover. Messages are sent ipsilaterally.

Question 20

What does the RETICULOSPINAL TRACT control?
Where does it originate?
Is there any crossover?

Answer 20

The reticulospinal tract controls postural movements.
It originates in the pons and medulla.
There is no crossover. Messages are sent ipsilaterally.

Question 21

The motor cortex has association areas that send messages informing the motor cortex how and well to move/send messages about movement.
One of these areas is the posterior parietal cortex.

What does this area do?

Answer 21

It gives us information about where we are in our environment. It does this by receiving and coordinating information from the vestibular, auditory, visual, and somatosensory systems.
It coordinates this information to give us an understanding of where parts of our body are in relation to other parts of our body as well as to the environment.

Particularly important in movements such as reaching, grasping, and object manipulation.

Question 22

The Prefrontal cortex is another association area of the motor cortex.
What does it do?

Answer 22

The prefrontal cortex is important for planning movement. Stores and processes information from the posterior parietal cortex and decides appropriate action from there.
Plays a key role in managing impulsive behaviours, concentration, and organization.

Question 23

What happens to movements when there is damage to the prefrontal cortex?

Answer 23

Movements can become disorganised and impulsive or inappropriate.

Question 24

When you are at a crossing and you see the green man and automatically start crossing the road, what area of the brain processes this info and sends it to primary motor cortex to insight movement?

Answer 24

The premotor cortex.

Question 25

How can damage to the premotor cortex manifest?

Answer 25

An inability to process arbitrary information, such as when driving and you see a red light putting on the brake.

Question 26

The premotor cortex is an association area of the motor cortex.
What information does this area process and pass onto the primary motor cortex to inform movement?

Answer 26

Receives both arbitrary and non-arbitrary information (that is info that directly relates to or learned association of a movement and arbitrary stimuli respectively).

Non-arbitrary info: the premotor cortex receives information from the posterior parietal cortex about where something is in the environment or visual/audiotry info related to the movement, as well as info about planned movement from the prefrontal cortex.

Arbitrary info: learned associations between arbitrary stimuli and movements, such as to press the break when you see a red light while driving.

Question 27

What is the supplementary motor cortex?

Answer 27

The supplementary motor cortex is important for programming complex sequences of movement, such as serving a tennis ball, or learning to play a piano song by heart.
It is also important in mentally rehearsing complex sequences of movements.
AND bilateral movement coordination.

Question 28

What part of the brain inhibits you from instinctively grabbing a knife that you drop?

Answer 28

The pre-supplementary motor cortex. This area plays key role in regulating instinctual behaviour. If the instinctual behaviour, such as catching something you’ve dropped, is going to harm you, such as knife might, then the preSMC will prevent the instinctual behaviour.

Question 29

How can damage to the preSMC manifest?

Answer 29

An inability to perform a sequence of complex actions, such as serving a tennis ball or riding a bike or a playing the piano.

Question 30

What does the Primary Motor cortex do?

Answer 30

The primary motor cortex is involved in executing movement.

Question 31

What are the association areas of the Motor cortex?

NB: For studying look at lecture slides for visuals.

Answer 31

The Posterior Parietal cortex.
The Prefrontal cortex.

Question 32

What are the three areas of the Motor cortex?

Answer 32

The primary motor cortex.
The premotor cortex.
THe supplementary motor cortex.

Question 33

Based on the experiments discussed in the lecture that looked at voluntary movement, how long before we make a movement are we aware that we are going to make the movement?
How long before we make a movement does the primary motor cortex become active?

Answer 33

About 200 ms.

About 500 ms.

This suggests that our brain is already in the process of engaging in making a movement, before we becomew consciously aware that we are going to make the movement.

Question 34

What is the role of the Basal Ganglia in movement?

Answer 34

The Basla ganglia regulates movement via a series of feedback loops that either lead to the excitation or inhibition of the motor cortex. These feedback loops influence the thalamus which in turn either excites or inhibits the motor cortex.
There are three loops we discussed:
1. Direct, which is excites the motor cortex.
2. Indirect, which inhibits the motor cortex.
3. Hyperdirect, which rapidly inhibits the preSupplementary motor cortex. This route is very fast acting as it needs to inform the preSMC, which is responsible for inhiniting relexsive movement that may be harmful, e.g. catching a knife that fell of a bench.

Question 35

Have the Basal ganglia been linked to Autism?

Answer 35

Yes. abnormal Basal ganglia structure has been found in those with autism.
Damage to the basal ganglia can cause severe motor deficits, which may explain some of the motor deficits seen in those with autism.

Question 36

Has the ‘pull to sit’ test for babies been found to be a predictor for autism?

Answer 36

There has been some evidence that suggests that if an infant exhibits a lag in being able to support their head and neck when being pulled to sit up from lying down, then they are more likely to be diagnosed with autism.
The rate at which infants gained their head and neck control was predictive of when the development of their speech and social skills.

Question 37

What part of the brain has been linked to our ability to compare our intended movement with our actual movement for future learning?

Answer 37

The cerebellum.

Question 38

Is the cerebellum important for postural control and balance and composition of movement?
What happens if there is damage to the cerebellum?

Answer 38

Yes.
If there is damage to the cerebellum then movement may become disjointed, aim may be difficult and posture and balance may be difficult.

Question 39

What is the role of the THALAMUS in movement?

Answer 39

The thalamus is relay station of sensory and movement information from the body to the cortex (including the motor cortex), except for smell.