Title: BV4 / Modul 3 / Cortical control of movement

Q: Due to what are we able to perform skilled movements
A: Cerebral cortex - movement
respresent the fundamental aspect of kognition

Q: What is the location of the motor cortex in the hierarchy?
A: The motor cortex is located on the top level in the hierarchy of neuronal structures in motor movements

Q: From where does the motor cortex receive feedback?
A: - The motor cortex receives feedback from the basal ganglia - signals motivational aspects of volentary movements
- The cerebellum, signals about proprioception or the coordination, "how did this planned movement turn out?"

Q: How does the motor cortex generally control everything?
A: They way the motor cortex controls all these things is through descending pathways

Q: How did Brodmann subdivide the cortex?
A: Subdivision of the cortex based on the microanatomy of cell types and their micororganisation

Q: How many brodmann areas are there?
A: 52

Q: WHich brodmann areas are we talking about whne talking about the motor cortex?
A: 4 & 6, these are areas infrom the central sulcus

Q: What do we have in bordmann area 4?
A: Area 4 is on the precentral gyrus and there we have the primary motor cortex (M1)

Q: What do we have in bordmann area 6?
A: This is infront fo brodmann area 4 and here we have the premotor cortex

Q: What types of cortical areas do we have when talking about motor functions?
A: We have primary and associative areas

Q: Where is the primary motor cortex located?
A: In the anterior wall of central sulcus (BA4)

Q: WHat is the primary motor cortex important for?
A: - Voluntary movements
- Skill learning, in particular skilled hand/finger movements

Q: From where do we need feedback to the primary motor cortex?
A: In the primary motor cortex we need feedback from other areas and that is where the premotor coretx comes in, adn aslo the supplemental motor areas

Q: What can the premotor cortex be divided into?
A: The premotorcoretx can be divided into a ventral and a dorsal premotor cortex

Q: What is PMD?
A: Dorsal premotor cortex

Q: WHat is PMV?
A: Ventral premotor cortex

Q: What is SMA?
A: Supplementary motor areas

Q: WHere is the PMD located?
A: Dorsolateral surface of precentral gyrus (BA6)

Q: WHat is the PMD important for?
A: - Visou-motor integration
- Selection of movements based on sensory cues

Q: Where is the PMV located?
A: Ventrolateral precentral gyrus (BA6)

Q: What can we find in the PMV?
A: In the ventral u find an area called Broca's area - is important for construction of speech

Q: WHich class of neurons can be found in the PMV?
A: "Mirror neurons"

Q: How do mirror neurons work?
A: Mirror neurons fire during performance of an act and during observation of someone else performing the same act

Q: Where is the SMA located?
A: Medial surface of precentral gyrus (BA6)

Q: What is the SMA important for?
A: - Inernally generated movements, learning and performance of movement sequences
- Bimanual coordination

Q: What can be said about the things the SMA is important for?
A: These are things that occur in the background in our minds, subcontious in a way - this is important when we decide on a motor plan

Q: How do the cortical motor areas control movement?
A: These cortical motor areas control movements through a set of descending pathways - when the axons of the upper motor neurons arise from the cell bodies in the higher centres and then descends to influence the local circuits in the brainstem or in the spinal cord

Q: WHat does the corticobulbar tract consist of?
A: The corticobulbar tract consists of neurons that control the musculature from the neck and up

Q: WHat is special about the corticobulbar tract (its motor neurons)?
A: Whats special about this pathways is that the motor neurons are innervating other motor circuits and sesnory nuclei in the brainstem but not further down

Q: What does the corticobular tract innervate?
A: In fact, the corticobulbar tract innervates the cranial nerves which are important for the musculature in the face etc.

Q: Where are the upper motor neurons of the corticobulbar tract located and where do their axons go?
A: The upper motor neurons have their somas in the cortex and then they descends through capsula interna goes down to the midbrain and it goes in the cerebral peduncle (crus cerebri) to the pons

Q: WHich nuclei does the corticobulbar tract innervate?
A: The corticobulbar tract innervates the trigeminal motor nucleus and the facial motor nucleus for instance

Q: What does the corticobulbar tract innervate, in general?
A: - Motor and snesory nuclei in the brainstem
- Cranial nerves

Q: What does the corticospinal tract consist of?
A: The corticospinal tract consists of upper motor neurons that are located in the cortex but their axons end up somewhere in the spinal cord

Q: WHat can the corticospinal tract be subdivided into?
A: - Ventral corticospinal tract
- Lateral corticospinal tract

Q: What does the ventral corticospinal tract refer to?
A: The ventral corticospinal tract refers to neurons that send their axons on the ventral side of the spinal cord

Q: What are the upper motor neurons of the ventral corticospinal tract involved in?
A: - Postural control
- Trunk movements

Q: WHat happens to the axons of the upper motor neurons of the ventral corticospinal tract in the medulla?
A: They remain uncrossed in the medulla but when they reach their termination in the spinal cord there is bilateral termination, so it can control muscles on both sides of the body

Q: Where are the axons of the ventral corticospinal tract sent?
A: In the ventral white matter of the upper spinal cord

Q: WHy is it called the lateral corticospinal tract?
A: Becuase
their axons travel in the lateral white matter (side) of the entire spinal cord

Q: Where do teh axons of the lateral corticospinal tract travel?
A: In the lateral white matter of the entire spinal cord

Q: What are the axons of the lateral corticospinal tract important for?
A: - Skilled, fine movements

Q: Where do the axons of the lateral corticospinal tract cross?
A: Almost all of these axons (90%) crosses in the medulla at the level/region of the pyramidal decussation

Q: Why is it called the pyramid in the medulla?
A: Called pyramidal bc on the sides of the medulla there are like 2 bumps that look like pyramids - thats how they got their name

Q: What does it imply that almost all the axons of the lateral corticospinal tract cross over in the medulla?
A: This means that at the caudal end of the medulla almost all the fibers present in the corticospinal tract crosses over to the spinal cord - so u have contralateral control of movement from the neck down

Q: Which muscles does the ventral corticospinal tract mainly control?
A: - Trunk muscles
- Proximal limb muscles

Q: Which muscles does the lateral corticospinal tract mainly control?
A: The lateral upper motor neurons controll afta-motor neurons that innervate the forearms, hands, etc. (distal muscles)

Q: What do we have in the spinal cord across the segments?
A: Here we have somatotropic organisation which referrs to there being an organisation of these axons based on which musculature they will control

Q: How are the axons that arrange what arranged somatotropically in the spinal cord?
A: - Medial axons control proximal muscles
- Lateral axons control distal msucles

Q: What defines the primary motor cortex?
A: Agranular cortex

Q: What is the agranular cortex in M1?
A: Very few granular cells in layer IV (4)

Q: What does layer 4 look like in the visual cortex?
A: In the visual cortex there is a reabundant layer 4 which recieves a lot of sensory information through the thalamus so these are a thalamocortical projections

Q: What happens with the thalamocortical projections in M1, where there is no layer 4?
A: In the M1, since it lacks layer 4, thalamocortical projections happen through other layers, namely layer 2 and 3

Q: Which cell is the largest neuron found in any species?
A: Pyramidal cells

Q: What is present in layer 5 in M1?
A: Large pyramidal cells (up to 100 micrometers in diametre)

Q: Which layer represents the output layer of the M1?
A: Layer V (5)

Q: Which projections in the M1 make up the corticospinal tract?
A: Large pyramidal cells in layer V, which represents the output layer -  so
these are the projections that make up, for instance, the corticospinal tract

Q: Which type of pyramidal cells are found in teh M1?
A: These neurons referred to as Betz cells, are distcinct from other pyramidal cells but account for a very big functional portion of the corticospinal tract, in particular the axons that then activte lower motor neurons that activate muscles in distal extremities

Q: What do the Betz-cells account for?
A: They account for a very big functional portion of the corticospinal tract, in particular the axons that then activate lower motor neurons that activate muscles in distal extremities

Q: How big a part of the axons of the corticospinal tract do teh Btez-cells make up for?
A: The
betz cells only account for about 5% of the axons of the corticospinal tract,
they only represent a small number but have a very big functional role when it
comes to the control of lower motor neurons

Q: Whne do the Betz-cells have a big functional role?
A: They have a big functional role when it comes to the control of lower motor neuorns

Q: What does the M1 have connections with?
A: Extensive direct connections with motor neurons and interenurons in the spinal cord and brainstem

Q: What can in conclusion be said about the layers inthe cortex of the M1?
A: Lacking layer 4 (normally we talk about the 6 layer cortex) M1 doesn't have layer 4 and the output neurons/upper motor neurons - some of these are the betz cells and they are located in layer 5

Q: What type of stimulation in the M1 evokes movements?
A: Low current stimulations evokes movements

Q: How can we determine if a muscle fiberis innervated by a single cortical motor neuron?
A: With spike triggered averageing recordings they measure if there is an innervation of  specific motor neuorns with  specific muscles - we can record single spinkes from individual cortial neuorns, atm the neournal activity of activity of the muscle fibers - we can determine if this muscle fiber is innevated by this single cortical motor neuron

Q: What can we dowith the technique used to determine if one muscle fiber is innervated by one neuron?
A: With this technique we can define a muscle field of this upper neurons, this has generated a topographic representation of the body based on which muscles/where they are located and which motor neurons that innervate that motor part

Q: What can be said about topography in M1?
A: There is a topographic representation of the body (homonculus)

Q: How big a part of the axons in the corticospinal tract arise from the PMA?
A: The axons that directly project through the corticospinal and corticobulbar pathways, both these, 30% of the corticospinal tract consists of axons that aries from the PMA, but their strength with motor neurons in the spinal cord is much weaker

Q: Which features (types of movements/part of the motor plan) does the PMA and the SMA deal with?
A: Whereas the M1 deals with movements within armslenght, like i grab my cup, or whether i thought of going to open a door/walk through it that woudl be features that more engare the PMA and the SMA - movements of going towards the door and then pushing the handle enganges the M1, while the plan to go there engages the PMA and SMA

Q: What happens if we stimulate neurons in the PMA or SMA?
A: If we stimulate neurons in the PMA or SMA we elicit very complex behavious, it engages muscle groups in all the extremities and whereas u can engage in a specific movement, these are very complex

Q: What are the PMA and SMA important for?
A: - The PMA and the SMA are important for selection of movements that are appropriate/based on context and the goal of the action

Q: What does microstimulation of teh PMA and SMA evoke?
A: Microstimulation evokes complex behaviours

Q: What does the activity of the neurons in the dorsal premotor cortex (PMD) look like when monkeys are supposted to press a pad based on either external cue or memorized sequence?
A: The activity in the PMD we see that there is a dominance in the activity when the moneky performs the task with visonary triggered cues

Q: What does the activity of the neurons in the supplementary motor area (SMA) look like when monkeys are supposted to press a pad based on either external cue or memorized sequence?
A: If
we record units in the SMA - dominant activity when the moneky performs the
task with a memory sequence, compared to visual cues

Q: What does the activity of the neurons in the primary motor cortex (M1) look like when monkeys are supposted to press a pad based on either external cue or memorized sequence?
A: The neurons in the M1 doesn't care about which trigged task the monkies are performing (doesnt care if its external cue-induced or memory-induced) - just basically performing the task

Q: Which types of tasks is the PMD involved in?
A: The PMD that is involved in visually guided taskts

Q: Which types of tasks is the SMA involved in?
A: The SMA is involved in internally guided tasks (memory sequence)

Q: What conslusion can we draw about the SMA and the movements it's involved in?
A: We can draw the conclusion that the SMA is activated during internally generated movements

Q: What do units signal in the SMA?
A: Here we have units that signal movement sequences, both ordinal (spatial) and temporal aspects

Q: What else are units involved in in the SMA?
A: In this area there are units involved in motor imagery, trying to predict a movement before it has happened

Q: Which potential do many of the neurons in the SMA have?
A: Many of the motor neurons in the SMA have something referrered to as readyness potential

Q: What is meant by the motor neurons in the SMA having a readiness potential?
A: Before
a self-generated movement is occuring there is a slow rise in potential that is
more than 500 ms and up to a second before the execution of this movement
occcurs

Q: What are the units in the PMD involved in?
A: The units in the PMD are involved in the visual cue, this area is important in the selection of behavior based on external cues (choice reaction time tasks)

Q: What is the PMD area important for?
A: Important in the selection of behavior based on external cues (choice reaction time tasks)

Q: Which type of tasks have the PMD been shown to be involved in?
A: It has been shown to be involved in choice reaction time tasks

Q: Which type of integration have the PMD been proven to be especially important in?
A: Visuo-motor integration, such as:
- Reaching
- Targeting of movements in space
- Spatial structure of sequences

Q: What are examples of the visuo-motor integration of the PMD?
A: - Reaching
- Targeting of movements in space
- Spatial structure of sequences

Q: What does a PMD lesion impair?
A: PMD lesion impairs movement selection based on visual cues

Q: WHich area doe sthe PMV contain?
A: Broca's area (BA44, BA45, BA6) - important for the construction of speech

Q: What is Broca's area important for?
A: Construction of speech

Q: What was first found in teh PMV?
A: It's the first region where mirror neurons were found

Q: What are mirror neurons?
A: Neurons that fire during performance of an act during observation of someone else performing the same act

Q: How does the experiment of a monkey watching food being put on a tray investigate/show the function of the mirror neurons in teh PMV?
A: The activity goes up in the motor neurons as the human puts the food on the tray and also when then monkey is grabbing the food on the tray , as well as when the moneky is grabbing the food, doing the same action ,putting food on tray and eating it
- The neurons are not egaged if the food is put on the tray with pliers
-  They are also activated if the monkey cannot see the hand, the same neurons are still activated

Q: Where else can mirror neurons be found?
A: Mirror neurons have also been found in other motor areas and in the inferior parietal cortex ("Mirror system")

Q: What is the advantage/function of the mirror system?
A: - Understanding other's intention?
- Prediction?
- Imitation learning?
Still controversial!

Q: What is the primary motor cortex involved in (M1)?
A: - Voluntary movements
- Skill learning, in particular skilled hand/finger movements

Q: What is the dorsal premotor cortex involved in (PMD)?
A: - Visuo-motor integration
- Selection of movements based on sensory cues

Q: What is the ventral premotor cortex involved in (PMV)?
A: Key region in the mirror system

Q: What is the supplementary motor area involved in (SMA)?
A: - Internally generated movements
- Sequences (memory based?)
- Bimanual coordination

Q: What is the conclusion of the cortical control of movement?
A: Cortical motor areas interact in larger, distributed networks of brain regions that control behavior

Q: What are ex. of structures connected to the fact that; cortical motor areas interact in larger, distributed networks of brain regions that control behavior?
A: - Prefrontal cortex
- Sensory regions
- Subcortical regions (basal ganglia, cerebllum
- etc.

Q: Whan does the units of the SMA increase their activity?
A: - The unit increases their activity in antipication of a movement, there is an internally generated sequence of movements that is generated before the actual sequence of movements - readiness potential

Q: To where does the motorcortical areas have reciprokal connections and what is it important for?
A: The motorcortical areas have reciprokal connections with prefrontal cortex, which is important for cognitive function, also we need sensory integration