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Question 1

define complex/volitional movement

Answer 1

motor output that is planned and refined by the motor cortex, basal ganglia, and cerebellum

Question 2

give an example of a complex/volitional movement

Answer 2

a learned and evolved motion like playing the piano

Question 3

what is the function of the red nucleus? how does this contrast to the reticulospinal and vestibulospinal tracts?

Answer 3

• rubrospinal cells within the red nucleus activate localised synergies, especially in distal limbs and in the face (eg gripping and twisted movements of hands)
• contrasted to the reticulospinal and vestibulospinal tracts that organise widespread postural and locomotory synergies

Question 4

describe the structure of the rubrospinal tract

Answer 4

crosses the midline and ends up in the intermediate zones

Question 5

define synergies

Answer 5

group of muscles contracting together for a specific purpose

Question 6

distinguish between the synergies organised by the reticulospinal and rubrospinal tract

Answer 6

• synergies organised by the reticulospinal tract are very widespread (typically cover half of the body) for generating support postures
• synergies organised by the rubrospinal tract are highly localised

Question 7

where is the motor cortex located?

Answer 7

in the pre-central gyrus

Question 8

describe the organisation of the motor cortex

Answer 8

somatotopic: regions of the body with the greatest number of motor innervations are represented by the largest area in the motor cortex

Question 9

describe the two types of descending pathways from the motor cortex

Answer 9

• most of the corticospinal descending axons that go from the motor cortex to the spinal cord go to the interneurons
• some (20%) have direct corticospinal synapses on motoneurons, mostly to the distal limbs and speech motor nuclei

Question 10

describe the different paths taken from the motor cortex to the targets

Answer 10

• from the motor cortex, axons project to the brainstem, where they cross the midline and end up in the spinal cord. they then travel in the lateral white matter and activate motor neurons either directly (20%) or via the interneurons in the spinal cord.
• a small branch of axons stay on the ipsilateral side, but this varies from person to person

Question 11

what is multiple representation?

Answer 11

• the same singular motor nuclei (muscles) are represented in columns at many loci
• each muscle column is in different adjacent columns
• each cortical locus represents a different synergy; muscles which participate in most synergies have the biggest representaiton

Question 12

is multiple representation variable among different people?

Answer 12

yes; it is based on personal experience (eg pianists/gymnasts have synergies in particular areas)

Question 13

in what situation is multiple representation particularly obvious?

Answer 13

when it comes to languages; the ‘motor map’ is laid out in development at very early stages

Question 14

thumb corticomotoneural cell and thumb ecg

Answer 14

• when you perform a precision grip, this particular neuron up in the motor cortex is very active
• when you perform a power grip, this particular neuron up in the motor cortex is not active
• ie same muscle, but different cortical neurons are active

Question 15

describe a motor field

Answer 15

• one corticospinal axon synapses with a set of motor nuclei, in more than one spinal segment
• the set of synaptic contacts with motor nuclei constitutes the motor field; many synapses are ‘silent’

Question 16

why is the motor field important?

Answer 16

it provides potential for plasticity

Question 17

describe the relation between somatosensory inputs and the motor cortex

Answer 17

• somatosensory input is the only sensory input with direct access to motor cortex
• cutaneous input comes from somatosensory association areas. this is related to postural and motion information
• proprioceptive input comes directly from the thalamus (and from somatic association cortex)

Question 18

what are the premotor areas?

Answer 18

a set of regions projecting into the motor cortex (but also with parallel routes to the motor nuclei)

Question 19

what is the function of the premotor areas?

Answer 19

1. process sensory inputs, especially visual and auditory, for cueing movement phases
2. they select motor cortical synergies into proper sequence for a specific movement, playing a pattern generation role for learned, highly evolved movements

Question 20

give three examples of premotor cortices

Answer 20

• Dorsal visual stream to dorsal half (spatial location)
• ventral visual stream to ventral half (object form to shape hand)
• Broca’s area: premotor zone for sequencing language elements for speech or writing-typing: input from Wernicke’s area

Question 21

describe how sensorimotor cues lead to a visuomotor response

Answer 21

• thousands of environmental cues trigger motor reactions (eg doorknob, push button)
• sensory association areas recognise the cues and forward the signal to the frontal lobe (prefrontal and premotor cortex)
• premotor cortex selects appropriate response synergies in the motor cortex
• visuomotor response: coordinated sets of activities and cues to initiate these synergies (hand is both shaped and oriented to suit the target object)

Question 22

at what stage are the premotor neurons active?

Answer 22

premotor neurons set up the motor cortex; hence, they are often not active during performance. they are typically active during preparatory phase of movement, facilitating appropriate synergies in the motor cortex.

Question 23

describe the preparatory activities of the premotor neurons

Answer 23

• a ‘warning’ cue is delivered before a ‘go’ cue
• if you make the delay longer, your premotor neurons will still maintain their activity

Question 24

where is the supplementary motor area (SMA) located?

Answer 24

on medial wall of hemisphere

Question 25

how is the SMA organised?

Answer 25

it has somatotopic representation of the body, but in less detail than the motor cortex

Question 26

describe the function of the SMA

Answer 26

- controls bilateral coordination of the limbs when different motions are done on each side - processes internal 'volitional' signals that drive movements

Question 27

what is the location and function of the cingulate motor area (CMA)?

Answer 27

- located within the cingulate sulcus - processes emotional and motivational drive to movements