Task 1 - Voluntary Motor Control

Question 1

What is the CNS consisting of?

Answer 1

Brain (cerebrum, cerebellum and brain stem) + spinal cord

Question 2

What is the function of the cerebellum?

Is it ipsilateral or contralateral?

Answer 2

It is the movement control center. Recieves inout from nerves in the body and motor areas in the cortex

Ipsilateral

Question 3

What are the functions of the brain stem?

Answer 3

1. Relay info to cerebral hemisoheres and cerebellum regulation
2. Control of vital function (eg. breathing)

Question 4

What is the PNS consisting of?

Answer 4

Cranial nerves, spinal nerves and peripheral nerves (= somatic PNS + visceral PNS/autonomus nervous system ANS)

Question 5

The spinal cord is part of the CNS but the spinal nerves are part of the PNS.

What is the fuction of the spincal nerves and how do they work?

Answer 5

Their function is to make communication available between the body and the spinal cord - brain.

They consist of ventral roots sending info. from cord to the body (efferent) and dorsal roots, the other way around (afferent)

Question 6

What does efferent mean?

Answer 6

Efferent - Exiting a structure

Question 7

What does afferent mean?

Answer 7

Afferent - Aproching a structure

Question 8

What does the Somatic PNS consist of?

Answer 8

Nerves in skin, joints, and muscles under voluntary control

Question 9

What does the Visceral PNS/ Autonomous Nervours System ANS consist of?

Answer 9

Neurons in internal organs, blood vesels and glands under unvoluntary control

Question 10

What does substantia mean?

Answer 10

Collected neurons deep within brain

–> less distinct borders than nuclei

Question 11

What does nucleus mean?

Answer 11

Clearly distinguishable mass of neurons

Question 12

What is a ganglion (ganglia)?

Answer 12

Collection of neurons in the PNS

Question 13

Describe the triple-layered flatdisk of the neural tube in the early stage

Answer 13

1. Endoderm - gives rise to internal organs
2. Mesoderm - skeleton and muscles
3. Ectoderm - neural plate that gives rise to CNS

Question 14

What happens to the flatdisk after 20 days?

Answer 14

It starts folding forming a groove. The Nerual Folds are the walls of the groove

Question 15

What is Neurulation?

Answer 15

Process in which neural folds close to form a neural tube

Question 16

The motor control hierarchy has 3 levels (high, medium, and low).
Explain their functions and structures.

Answer 16

1. HIGH –> strategy –> association areas od neocortex, basal ganglia
2. MEDIUM –> tactical decision and issue instructions –> motor cortex, cerebellum
3. LOW –> execution –> brain stem, spinal cord

Question 17

What do the association areas of the neocortex do?

Answer 17

Consider the action if a baseball pitcher preparing to pitch to a batter.
The cerebral neocortex has information- based on vision, audition, somatic sensation, and proprioception- about precisely where the body is in space

Question 18

In the high level of the motor control, different options of strategies are considered (the way of throwing the ball). How does the process work?

Answer 18

The alternatives available are filtered by the Basal Ganglia and back to the cortex until a final decision is made

Question 19

What are Ballistic movements?

Answer 19

Movements that once initiated, cannot be altered anymore because they are too fast for sensory feedback.

Question 20

What is the function of the primary motor area M1 (area 4)?

Answer 20

Send signal to execute a movement (externally guided actions –> catching a ball)

This area has the lowest threshold for the elicitation of movement

Question 21

What is the function of the supplementary motor area SMA (area 6 at the top)?

Answer 21

Planning and directing voluntary movements (internally guided actions –> plan to grab a cup of coffee)

Question 22

How does Ready-Set-Go system work in the SMA?

Answer 22

. Cells in the SMA increase their discharge rates about a second before the execution of a hand or wrist movement

1. Ready - no firing
2. Set - firing
3. Go - Shortly after move is initiated firing stops

Question 23

An important feature of the R-S-G system is that the activity occurs in advance of either hand.
What does this mean?

Answer 23

This indicates that the supplementary motor areas of the two hemispheres are close linked via the corpus callosum

Question 24

What is the Layer V?

From what 2 sources does the Layer V get input from?

Answer 24

It contains pyramidal neurons that project directly to the spinal cord and send axons to many subcortical sites involved in sensori motor processing –< corticospinal tract for voluntary movements

Input from:

• Other ortical areas
• Thalamus

Question 25

Neurons in the M1 have a prefered direction in which they fire. Does this mean that they only fire inthat specific direction?

Answer 25

Nee, Cells fired most vigorously during movement in one direction (to the left - monkey experiment) but also discharged during movements that varied 45 degree from the preferred direction

Question 26

What is the one assumption of the malleable motor map (homunculus)?

Answer 26

The larger the population of neurons representing a type of movement, the finer the possible control. the cortical cells in M1 can switch commitmentfrom participation in one type of movement to another as skills are learned

Question 27

What is the function of the Alpha motor neurons?

Answer 27

They are in the spincal cord and they release acetycholine which then rpoduces contractions of muscles fibers and in the end elicit a movement --> number and frequency of action potentials determine the force a muscle can generate

Question 28

The alpha neurons recieve input from 2 sites. Name them.

Answer 28

1. From mucles spindles (sensory receptors in muscles) - -> e.g. strech relfex: : unexpected stretch - activation of alpha motor neuron - muscle is returned to it’s original place - -> involved in maintainance of posture - doesn't involve cortex 2. From spinal interneurons that receive information by sensory nerves (e.g. skin, joints)) and by motor fibers in subcortical and motor cortical structures - -> for voluntary movement

Question 29

From where does the M1 recieve inüut?

Answer 29

From parietal, premotor, supplementary motor and frontal cortices, basal ganglia and cerebellum

Question 30

The M1 consists of 2 regions. Name them and mention where they terminate.

Answer 30

1. Rostral M1: CST terminate on spinal interneurons | 2. Caudal M1: CST terminate on alpha motor neurons, mostly on the upper limbs

Question 31

What is somatotopic representation and how was that discovered?

Answer 31

It means that different brain regions represent different body parts It was possible to map by transcranial magnetic stimulation TMS

Question 32

What is hemiplegia?

Answer 32

It's the loss of voluntary movements due to a lesion in the M1.

Question 33

How can you treat hemiplegia?

Answer 33

Treatment involves 1) TMS stimulation over lesioned cortex and/or (2) behavioural approach: use constraint-induced movement therapy (= the only limb that can be used is the lesioned one)

Question 34

What are the secondary motor areas?

Answer 34

Premotor cortex and supplementary motor area SMA

Question 35

What do the secondary motor areas connect with? With what purpose?

Answer 35

Premotor cortex: connections with parietal lobe for externally/sensory-guided actions, e.g. catching a ball SMA: connections with medial frontal cortex for internally guided actions, i.e. plans movement based on goals, e.g. plan a movement to take a cup of coffee

Question 36

What is apraxia? What are te 2 main types?

Answer 36

It's the loss of skilled action when SMA is lesioned, i.e. unable to link gestures into meaningful actions, e.g. patient can open/close their fist, but cannot sequence an arm movement to gesture a salute Two types: 1. Ideomotor apraxia: patient has sense of desired action but has execution problems 2. Ideational apraxia: more severe: disrupted knowledge about the intent of an action, e.g. does not comprehend appropriate use of a tool

Question 37

What is the main function of the somatosensory cortex (association motor area)?

Answer 37

To give a representation of body and how it’s situated in space

Question 38

Is there evidence that some cells are involved in planning and not only in the execution of a movement?

Answer 38

Yes, there has been several studies where it was shown that a cell will fire strongly if subsequent movement matches it’s preferred direction and based on this researchers can predict what movement the animal will make before animal starts to move

Question 39

Some cells do not show strong directional tuning; interestingly, many cells that show increased activity during delay show a brief drop in activity just before movement begins. What would then be the alternative view?

Answer 39

That set/clusters of neurons code different features depending on time and context, thus there is no simple mapping from neural activity to behaviour and vice versa.

Question 40

The brain leans and adapts quite fast. What would be evidence for this in the M1?

Answer 40

Researchers measured preferred direction of a neuron (e.g. 90 degrees) --> changed algorithm that output of this neuron was now treated as preference of 130 degrees --> Over couple of days of practise the monkey would adapt to the new decoder and achieve near 100% accuracy

Question 41

Definition of non primary motor areas

Answer 41

All areas in the frontal lobe that can influence motor output at the level of both the primary motor area and the spinal cord.

Question 42

What is the function of the Dorsal Premotor area PMd?

Answer 42

PMd is critical for implementing associations between arbitrary cues and motor responses TMS Study results: After repetitive TMS, subjects could no longer select appropriate motor programs for the lifting of the two different weights based on the arbitrary colours cues that they saw

Question 43

What is the function of the Ventral Premotos area PMv?

Answer 43

PMv contributes significantly to the control of hand movements required for the manipulation of objects. It has a dual role in both execution and observation of object- related hand movements