Voluntary Motion (Karius)

Question 1

What cortical areas are responsible for voluntary motion?

Answer 1

Primary, supplementary and pre-motor cortices

Also prefrontal and parietal cortex also contribute

Question 2

Briefly, how does visual input get processed and how does this help voluntary motion?

Answer 2

Axons on the dorsal visual pathway go from the occipital cortex to parietal/frontal cortex. Visual input from these axons are used by the parietal/frontal cortex to plan and do movements

Question 3

Explain the mechanism of “reaching” (or knowing where an object is relative to you)

Answer 3

Input from the visual cortex > parietal cortex on the v6a, PEc, MIP and VIP > rough map of space around you is created > F4 in premotor cortex > creates a more detailed map of the space around you

Question 4

Properties of F4 neurons

Answer 4

Are excited by proximity, the closer the object is the more they fire

Question 5

How does the superior parietal cortex help?

Answer 5

Receives visual info about where your arm is in space > send to F2 in premotor cortex > F2 constructs related map (relationship of your arm to body and things around you)

Question 6

Explain the mechanism of grasping:

Answer 6

Anterior intraparietal area and PFG have visual, motor and visuomotor neurons that respond to seeing and grasping object > F5 in premotor cortex > F5 will fire with goal of action, not the motor act itself

Question 7

F5 neurons

Answer 7

Are active when goal is achieved (grasping and drinking tea) even if the grip is different

Question 8

Summarize the role of the premotor cortex in control of voluntary motion:

Answer 8

Receives sensory info required for movement (from F4 and F5)
Dorsal portion applies the rules that determine when it is appropriate to move
Identifies the intent of motion and what motion to produce

Question 9

Summarize the role of the supplementary motor cortex in control of voluntary motion:

Answer 9

Organizing motor sequences, acquiring the motor skills and executive control (e.g. deciding to switch action/strategy to complete action

Question 10

Divisions of the supplementary motor cortex:

Answer 10

2 divisions. The Supplementary motor area (SMA) = postural control
Pre-supplementary area (pre SMA) = planning the action required to make the action occur

Question 11

Describe how the primary motor cortex plays a role in the activation of motor neurons

Answer 11

PMC is arranged in columns. Stimulation of a given column will produce a specific movement

Question 12

General motion vs fine motion in the primary motor cortex

Answer 12

General motion - if this area is stimulated at the PMC, this may produce contraction of a group of muscles
Fine motion - if this area is stimulated at the PMC, this may produce contraction of a single muscle

Question 13

What do layers 4 and 5 of the PMC column do?

Answer 13

4 - receives sensory input

5 - does the action (serves as the output for the corticospinal pathway)

Question 14

Properties of the columns:
What is found in each column?What do neighboring columns do?
What types of columns are present?

Answer 14

Two sets of neurons present. 1 to start motion and 1 to maintain the motion as long as necessary
Neighboring columns control related motion not neighboring muscles
On/off for agonist and on/off for antagonist muscle

Question 15

What is the role of the cerebellum in voluntary motion?

Answer 15

Sequence of complex actions, correct fore/direction, balance/eye movements, learning of complex actions

Question 16

Spinocerebellum functions

Answer 16

Central: posture

Either side of the vermis: force and direction

Question 17

Vestibulocerebellum functions

Answer 17

Balance/eye movements and future movements

Question 18

Where do outputs from the cerebellum originate from?

Answer 18

Dentate, fastigial and interpositus nuclei

Question 19

Draw the schematic for inputs/outputs through each part of the cerebellum:

Answer 19

Ok

Question 20

General concepts about the Basal ganglia:

Answer 20

Default action is inhibitory, the entire pathway is loaded with GABA. It has two controls that basically allow or suppress motion (via Dopamine)

Question 21

Major actions of the basal ganglia:

Answer 21

Planning and programming movement

Initiation of movement

Question 22

Briefly, describe the direct pathway of basal ganglia:

Answer 22

Striatum receives input > GABA release> SNPR and GPI > GABA release > VL and VA of thalamus > EAA to cortex

Question 23

When activated the direct pathway does what?

Answer 23

Allows motion

Question 24

Briefly, describe the indirect pathway of Basal ganglia:

Answer 24

Striatum > release GABA > GPE > release GABA > subthalamic nucleus > release EAA > Subsantia Nigra and GPI > release GABA > VA and VL of thalamus > EAA to cortex

Question 25

When activated, the indirect pathway does what?

Answer 25

Inhibit motion

Question 26

Draw the direct and indirect pathways of basal ganglia circuit to allow motion

Answer 26

Ok

Question 27

Draw what happens at the basal ganglia circuit to inhibit motion

What pathways lead to the activation of the indirect pathway?

Answer 27

Ok

Corticostriate pathway and the Interstriatal cholinergic pathway

Question 28

Huntington’s chorea is physiologically due to ….

Answer 28

Inability to turn on the indirect pathway. Striatum neurons are not producing desired amounts of GABA

Question 29

What are the major functions of the prefrontal cortex?

Answer 29

Planning complex motor actions

Carrying out thought processes

Question 30

How does the prefrontal cortex work to coordinate complex movements?

Answer 30

It interacts with the parieto-temporal-occipital association area, frontal association area, supplementary motor cortex, premotor cortex and cerebrocerebellum (basically everybody)

*if the motion is less complex, need less players

Question 31

Prefrontal cortex and initiation of motion:

Answer 31

Interacts with frontal, premotor, SMC and basal ganglia will determine if the motion will occur. Basal ganglia has the final say.

Question 32

Once motion is planned, sequenced and approved, what happens?

Answer 32

Columns associated with the motion are activated in the PMC > Action potentials travels down the axons and activate the alpha motor neurons that innervate the required muscles

Question 33

What is an obstacle to voluntary motion?

Answer 33

Muscle spindle of the antagonist. It opposes the stretching of the antagonist (because the agonist is contracting) and try to stop it.

Question 34

How does the brain overcome the opposition by the muscle spindle?

Answer 34

Cortex inhibits the alpha and gamma motor neurons in the antagonist to decrease the sensitivity of the muscle spindle to the stretching. This way, the antagonist is relaxed and the agonist is allowed to contract

Question 35

When motion is started, what happens?

Answer 35

Spinocerebellum is called upon to make sure the motion is correct