ch 5b

Question 1

Name the 5 nuclei that the basal ganglia consist of

Answer 1

• Striatum: caudate nucleus and
  putamen
• Globus pallidus
• Substantia nigra
• Subthalamic nuclei

Question 2

Name 4 neural circuits that involve basal ganglia

Answer 2

1. Motor loop
2. Oculomotor loop
3. Prefrontal loop
4. Limbic loop

Question 3

Motor loop

Answer 3

related to movement
–> linked to primary motor cortex and premotor cortex

Question 4

Oculomotor loop

Answer 4

related to eye movements
–> linked to frontal eye fields

Question 5

Prefrontal loop

Answer 5

related to decision making
–> linked to dorsolateral prefrontal cortex

Question 6

Limbic loop

Answer 6

related to emotions

Question 7

How do the basal ganglia contribute to movement?

Answer 7

• Motor learning: selecting actions based on cost/reward
  –> which limb trajectory is more cost efficient?, rewards favoured, motor planning w/ PPC and PM
• Initiation of movement
• Movement vigor: controlling muscle force, speed/size of movement

Question 8

Brainstem

Answer 8

-modulates action of spinal motor circuits
- Medial and Lateral brainstem pathways

Question 9

Medial brainstem pathways

Answer 9

the basic postural control system controlling predominantly axial and proximal limb muscles
* Axial muscles = core/trunk muscles
* Proximal limb muscles = closer to the body (e.g., shoulder muscles)
* Includes: vestibulospinal, reticulospinal, and tectospinal tracts

Question 10

Lateral brainstem pathways

Answer 10

goal-directed limb movements and control muscles of the limbs
* Includes: rubrospinal tract

Question 11

Major descending brainstem pathways
-origin in the brain
-function

Answer 11

1. Reticulospinal pathway (reticular formation)
   -maintains posture and muscle tone
2. Vestibulospinal pathway (vestibular nuclei)
   -posture, balance, location of head and body in space
3. Tectospinal pathway (superior colliculus)
   -coordinates head and eye movements
4. Rubrospinal pathway (red nucleus)
   -excite motor neurons innervating proximal upper limb flexors

Question 12

Area in the brainstem that controls the initiation of walking

Answer 12

Mesencephalic locomotor region (MesLR)

Question 13

3 functional zones of the cerebellum

Answer 13

1. Vestibulocerebellum
2. Spinocerebellum
3. Cerebrocerebellum

Question 14

functions of cerebellum related to movement

Answer 14

-smooth movements
-acts as a comparator (compares actual vs. expected sensory feedback)
-coordinates muscle groups by shaping commands
-gait patterns
-eye movement regulation: helps VO reflex work
-learning a new skill

Question 15

Cerebellar related disorders:
Dysmetria

Answer 15

problem w/ limb trajectory or placement of a body part during active movement
–> reach up to touch dot, bring arm down to touch nose; might poke themselves in the face etc.

Question 16

Cerebellar related disorders:
Dysdiadochokinesis

Answer 16

abnormalities w/ rapid alternating movements

Question 17

Cerebellar related disorders:
Gait axia

Answer 17

coordination problem
-walk as if drunk

Question 18

PPC

Answer 18

posterior parietal cortex

Question 19

PMC

Answer 19

premotor cortex

Question 20

SMA

Answer 20

supplementary motor area

Question 21

PPC divisions/sub-regions (and their specific functions and inputs)

Answer 21

-Parietal Eye Field (PEF)= neurons respond to visual and auditory stimuli; gaze shift planning of eye movements
-Parietal Arm Fields (PAF)= vis. and som. input; guiding arm movements (planning reach)
-Parietal Grasp Field (PGF)= grasping actions; planning forearm orientation and finger movements based on vis. info
-Parietal Face Field (PFF)= vis. and tactile input (from face); planning facial expressions
-Parietal Foot Region (PFR)= planning foot/lower limb movements

Question 22

PPC Functions

Answer 22

1. Planning control of movement (recieves sensory info)
2. Sensorimotor integration
3. Spacial maps (where are you in space) and spatial working memory

Question 23

How to know if a region of the brain is involved in motor planning?

Answer 23

look for changes in brain activity during the foreperiod prior to movement

Question 24

SMA functions

Answer 24

-selection of movement sequences from memory “INTERNAL CUES”/memory
-bimanual movements (e.g playing piano)
-possible role in learning sequences (e.g. playing the piano)

Question 25

Premotor Cortex functions

Answer 25

-selection of movement to EXTERNAL CUES --> works w/ basal ganglia and DLPFC -planning reaching movements based on target location -planning grasping movements based on object details -decision making

Question 26

Primary motor cortex (M1): Functions

Answer 26

1. Neurons in M1 connect to alpha motor neurons in spinal cord to activate muscles 2. Adapts movements to new conditions 3. Neurons are related to muscle force 4. Direction of movement is determined by the net action of M1 neurons 5. Influenced by cortical and subcortical inputs (exact contribution of M1 is still debated)

Question 27

How is activity in individual neurons of M1 related to muscle force? (Experiment w PTN/pyramidal tract neuron and monkeys) Main results=?

Answer 27

A PTN (pyramidal tract neuron) = a motor cortex neuron -Money wrist flexor movement: Load, No load, and Extensor load groups -movement is the same, but increased force: increase in PTN and muscle frequency -This shows that PTN is related to muscle force

Question 28

Do motor cortex cells have a preferred direction?

Answer 28

YES! activity is increased when moving to the preferred direction

Question 29

Cortical motor commands descend in two tracts: (2 fibres)

Answer 29

1. Corticobulbar fibres control the motor nuclei in the brainstem 2. Corticospinal fibres control the spinal motor neurons that innervate the trunk and limb muscles

Question 30

corticobulbar fibres are involved in controlling which muscles?

Answer 30

facial muscles

Question 31

Corticospinal fibres control which muscles/movements?

Answer 31

control voluntary movement of the distal limb muscles

Question 32

6 locations that corticospinal fibres can be found?

Answer 32

1. M1 (30%) 2. Premotor and SMA (29%) 3. Pareital cortex: 4. somatosensory cortex and 5. PPC 6. Cingulate gyrus

Question 33

Walking is an interaction between these 3 factors

Answer 33

1. Spinal cord circuitry 2. Sensory feedback (from muscle spindles, GTOs, cutaneous receptors) 3. Descending commands:

Question 34

How does stretching your hip flexors trigger swing phase of walking?

Answer 34

muscle spindles detect change in length and send info to the CPG/central pattern generator circuitry (via the 1a afferents) which activates flexor/extensor motor neurons which causes the hip flexor muscles to swing the legs forward

Question 35

How does the extensor load information help maintain stance phase of walking?

Answer 35

nervous system must maintain extensor leg muscle activity during stance phase to stop the body from collapsing under the force of gravity -uses feedback from the GTOs in extensor muscles -1b afferents signal weight-bearing load to spinal cord circuitry

Question 36

Extensor load info: stance phase Describe experiment (cat, treadmill extensor and flexor muscle activity, 1b afferents stimulated in extensor muscle)

Answer 36

-1b afferents stimulated in extensor muscle= prolonged extensor muscle activity and delayed flexor muscle activity -RESULT= cat's hindleg is dragged since the spinal cord thinks it has to maintain stance phase

Question 37

Normally, the decrease in loading of the leg would correspond to decreased 1b activity, indicating that

Answer 37

it is "safe" to swing the leg because it is no longer holding the animal's weight

Question 38

Primary motor cortex neurons contribute to changes in gait -when do they increase their activity?

Answer 38

-increase their activity just prior to and during a step over an obstacle

Question 39

Posterior parietal cortex (PPC) neurons are related to motor planning of

Answer 39

gait modifiations

Question 40

How are PPC neurons related to step-advanced neurons (function: example of cat stepping over object)

Answer 40

-step-advanced neurons may encode the relationship (or gap closure) between the obstacle and the cat that allows the animal to change paw position to properly step over the object -the other PPC neurons may encode the same thing (in 'working memory') to facilitate trial limb movements over the obstacle

Question 41

Neurons responsible for the execution of the step over an obstacle

Answer 41

Primary motor cortex neurons

Question 42

Voluntary movements: the brain must do what to activate muscles

Answer 42

brain must integrate sensory info, form a motor plan, and coordinate networks of neurons to develop motor commands to activate muscles (Sensorimotor integration)

Question 43

Sensory systems and receptors encode input in different egocentric-based coordinate reference frames (3)

Answer 43

Vision= eye or retina-centered Vestibular= head-centered Somatosensory= body-part-centered (ex. head, hand, foot)

Question 44

Think of sensorimotor integration as

Answer 44

putting signals into common "language"

Question 45

Sensorimotor integration is largely performed by neurons in the

Answer 45

PPC, Premotor cortex, and SMAs

Question 46

Sensorimotor integration (example of reaching to a doorknob)

Answer 46

-hand and target position can each be defined with respect to different reference frames (eye-, hand-, or shoulder-/body- centered) -brain must compute difference between the position of hand (H) and target (T); which= difference vector (M) -this shapes the reaching movement to doorknob