Enquiry 5 - Cortical Motor Control

Question 1

cortical motor control. What does cortical control mean?

Answer 1

1. the normal regulation of an activity, such as movement of a limb, by the cerebral cortex. 2. control of a prosthesis by signals recorded from the cerebral cortex, which are computer-processed and amplified.

Question 2

label this diagram

Answer 2

Question 3

what is the cerebral cortex?

Answer 3

• main centre for the control of voluntary movement - association areas provide the advanced intellectual functions of humans able to perceive, understand and integrate all the various sensations - provides the transition from perception to action.

Question 4

what is the feedback loop of human sensory-action?

Answer 4

Question 5

what does the motor cortex integrate and control?

Answer 5

• integrates the sensations of the association areas with the control of movement and posture

Question 6

what does the motor cortex consist of?

Answer 6

• a number of processing areas including the primary motor cortex, the supplementary motor cortex and the pre motor cortex.

Question 7

what does the areas of the motor cortex interact with and why?

Answer 7

• interact with sensory areas in the parietal lobe and with the basal ganglia at the cerebellar areas to identify where we want to move, to plan movement and to execute our actions.

Question 8

what does the areas of the motor cortex interact with and why?

Answer 8

• interact with sensory areas in the parietal lobe and with the basal ganglia at the cerebellar areas to identify where we want to move, to plan movement and to execute our actions.

Question 9

where do inputs to the motor areas come from?

Answer 9

• the basal ganglia -cerebellum - sensory areas, including… the periphery (via the thalamus), the primary somatosensory cortex and the sensory association areas in parietal lobe.

Question 10

what contributes to the corticospinal tract?

Answer 10

outputs from the primary motor cortex (MI)

Question 11

what can the corticospinal tract also be called?

Answer 11

the pyramidal tract

Question 12

where do the neurons, involved in the corticospinal tract, come from?

Answer 12

from the: - primary motor cortex so around 50% - pre motor areas including, supplementary motor cortex, dorsal and ventral pre motor cortex and somatosensory cortex.

Question 13

what is activated by stimuli from the MI?

Answer 13

• many muscles re activated by stimuli from MI, however… - stimulations activate SIMPLE movements of SINGLE joints..

Question 14

what is the relationship between the premotor cortex and the primary motor cortex?

Answer 14

• when performing a voluntary movement the instructions are relayed (passed on) to the primary motor cortex by the premotor cortex. - premotor cortex sends signals to the primary cortex to elicit multiple groups of muscles.

Question 15

what is the premotor cortex re responsible for?

Answer 15

• the coordination of learned movements - with repetition, the proper pattern of stimulation becomes stored in the premotor cortex - the movement is the performed smoothly and easily by triggering the pattern - sends signals to the primary cortex to elicit multiple groups of muscles - controls movements that are activated by external stimuli, e.g. a visual cue of a traffic light changing from red to green.

Question 16

what is associative learning?

Answer 16

when stimuli are used to direct the action, specifically associating a given sensory event with a movement to be made.

Question 17

what does the premotor cortex (premotor area) connect to?

Answer 17

• cerebellum - basal ganglia * both transmit signals back to the motor cortex via thalamus

Question 18

motor loops?

Answer 18

around basal ganglia, BG. but dont need to know about this untill second year

Question 19

where does the supplementary motor cortex (SMA) send projections to?

Answer 19

the MI and the spinal cord

Question 20

what does the SMA control?

Answer 20

• controls different aspects of motor planning and motor learning - movements that are initiated internally are controlled by the SMA (controls movements that are initiated by internal stimuli)

Question 21

what does the SMA also contribute to?

Answer 21

to motor programmes involved in learned sequences.

Question 22

what does the learning of sequences (themselves) involve?

Answer 22

the pre supplementary motor area, also referred to the rostral extension of the SMA (which is part of the primate cerebral cortex that contributes to the control of movement).

Question 23

how can our ability to control movement be affected?

Answer 23

remember “we can only control what we sense”. So our control of movement can be affected, (even if we have our movement areas or control of movement intact), if our sensory centres and our sensory processing areas are affected by a lesion as this will have a huge impact on our ability to control movement.

Question 24

what are the roles of sensation?

Answer 24

• planning movement - correcting errors through feedback and feed forward systems - ensuring accuracy

Question 25

what is the somatosensory cortex?

Answer 25

the major processing area for all somatosensory modalities

Question 26

coordinated movement requires information about what? (within the somatosensory cortex?)

Answer 26

about the: - position of the body relative to the environment - position of one body segment relative to another

Question 27

our somatosensory system is incredibly sophisticated, give an example of why?

Answer 27

humans can perceive (recognise) activation of a single tactile (sense of touch) receptor in the hand.

Question 28

where is the primary somatosensory cortex and sensory association area found in the brain?

Answer 28

• in the parietal lobe. - anterior/middle part of cerebral cortex.

Question 29

what is the homunculus?

Answer 29

• made up of the primary motor and primary somatosensory cortex (motor front, somatosensory back). - is a complex map of the body - motor map/homunculus is similar to the sensory map/homunculus as both distorts the representation of the body. in both cases the areas that require the most detailed control e.g. the mouth, throat hand - allowing finely graded movements, are the most highly represented.

Question 30

explain neuroplasticity in terms of neurons

Answer 30

receptive fields of neurons are not fixed in size. brain injury or experience can change their dimensions considerably which is known as neuroplasticity.

Question 31

what is important for motor planning and other cognitive behaviours

Answer 31

association areas of the frontal regions are important

Question 32

higher-level association areas have been hypothesised (assumed) to?

Answer 32

• integrate sensory info - important for motor planning - then select the appropriate motor response from the many possible responses.

Question 33

cerebellum role?

Answer 33

its considered one of 3 important brain areas contributing to coordination of movement in addition to the motor cortex and the basal ganglia. - it doesn’t initiate motor activities but plays important role in planning, mediating, correcting, coordinating and predicting motor activities especially for rapid movements.

Question 34

what are the primary functions of the cerebellum?

Answer 34

It is an automatic processing centre and it has two primary functions: - Adjusting postural muscles. (it coordinates rapid automatic adjustments that maintain balance - these alterations in muscle tone and position are made by modifying the activities of the motor centre in the brain stem.) - Programming and fine-tuning movements controlled at the conscious and subconscious levels, so it refines learned movement patterns. this is fucntion is perforemd indirectly by regulating activity. so vital for control of posture and equilibrium where it works in close relationship with the brain stem.

Question 35

what does the cerebellum control and how?

Answer 35

control voluntary movement by utilising feedback circuits from the periphery and the brain, at both conscious and subconscious levels.

Question 36

what is the basal ganglia?

Answer 36

4 different functional circuits 5 nuclei deep inside brain. so part of a series of parallel loops linking thalamus and cortex - receive input from the (cerebral) cortex and project exclusively back to cortex by the thalamus.

Question 37

role of BG?

Answer 37

• involved in all types of movements - but have a predominant role in provision of internal cues for the smooth running of learned movements - plays an essential role in the selective initiation of most activities of the body - as well as the selective suppression of unwanted movements

Question 38

thalamus role?

Answer 38

• huge role in control of movement - part of the BG motor loops, sending impulses to the motor cortex

Question 39

how is the thalamus involved in sensory information?

Answer 39

• thalamic nuclei deal with the relay of sensory info to the basal nuclei and the cerebral cortex - nuclei of ventral group relay info from basal nuclei of cerebrum and cerebellum to somatic motor areas of cerebral cortex.

Question 40

what makes on the brain stem?

Answer 40

midbrain, pons and medulla oblongata

Question 41

what does the brain stem control?

Answer 41

control the flow of messages between the brain and the body

Question 42

how are the tracts involved in the brainstem?

Answer 42

tracts for motor control that pass through, or originate in the brainstem, include: - the medial pathways (control posture and balance) - lateral pathways (control goal-directed movements)

Question 43

locomotor rhythms and regulation of postural tone is generated by what?

Answer 43

brainstem

Question 44

where does integration of sensory info for posture and balance, and anticipatory postural control happen?

Answer 44

brainstem *picture

Question 45

what does the basal ganglia-cortical-spinal pathways control?

Answer 45

control of voluntary movement (*anything that goes via the cortex is considered involuntary.) - WHY?

Question 46

Basal ganglia (SN)-brainstem-spinal cord pathways - control?

Answer 46

automatic movements, e.g. - Locomotion - Postural tone *these are automatic or involuntary because they by pass the cortex

Question 47

explain the control processes of voluntary movement

Answer 47

*diagram/picture 1. Cortical association areas design and plan movement. Project to basal ganglia for refinement, activation and inhibition 2. (and 3.) Thalamus sends impulses to motor cortex 4. Impulses from motor cortex simultaneously sent to cerebellum, brainstem and spinal cord 5. Alpha motor neurons cause muscle contraction 6. Sensation of movement sent towards CNS. Cerebellum compares movement for alterations 7. Correcting signals sent directly to execution centres 8. Thalamus distributes sensory feedback 9. Interpreted by cortical association areas, memorised and stored

Question 48

what is the clinical relevance of movement control?

Answer 48

• as with any illness, condition affecting the nervous system can cause issues with every step in this process. e.g - stroke/brain injury can affect anywhere where theres blood flow in the brain, any region of this control system - Parkinsons or Huntingtons disease directly affects the basal ganglia - someone with the presentation of cerebellar ataxia there are then issues with the cerebellum