3. Motor Cortex
Part 5 of 5
James Knierim, Ph.D.
.
Encoding of Movement by Motor Cortex (continued)
Association Cortex
The fourth level of the motor hierarchy is the association cortex, in particular the prefrontal cortex and the posterior parietal cortex (Figure 3.14). These brain areas are not motor areas in the strict sense. Their activity does not correlate precisely with individual motor acts, and stimulation of these areas does not result in motor output. However, these areas are necessary to ensure that movements are adaptive to the needs of the organism and appropriate to the behavioral context.
Figure 3.14 |
Association cortex. |
- Posterior parietal cortex is involved in ensuring that movements are targeted accurately to objects in external space. This area is involved in processing spatial relationships of objects in the world and in constructing a representation of external space that is independent of the observer’s eye position or body position. Such representations allow a stable percept of the world that is independent of viewer orientation, as well as the representation of desired trajectories in space that are independent of body position. Damage to the posterior parietal cortex can result in a number of apraxias, that is, the inability to make complex, coordinated movements. For example, a patient with constructional apraxia is unable to replicate the configuration of a set of blocks in the proper sequence, even though the patient is able to maneuver each block individually with dexterity.
- Prefrontal cortex is involved in the selection of appropriate actions for a particular behavioral context. It is also involved in the evaluation of the consequences of a particular course of action. Patients with damage to the prefrontal cortex have problems in executive processing. They make inappropriate behavioral decisions, and often cannot anticipate the likely consequences of their actions. They display impulsive behavior, often showing an inability to delay instant gratification for a long-term larger reward.
Test Your Knowledge
- Question 1
- A
- B
- C
- D
- E
Betz cells are most abundant in layer...
A. IV of somatosensory cortex.
B. V of somatosensory cortex.
C. IV of motor cortex.
D. V of motor cortex.
E. III of motor cortex.
Betz cells are most abundant in layer...
A. IV of somatosensory cortex. This answer is INCORRECT. Betz cells are not in somatosensory cortex.
B. V of somatosensory cortex.
C. IV of motor cortex.
D. V of motor cortex.
E. III of motor cortex.
Betz cells are most abundant in layer...
A. IV of somatosensory cortex.
B. V of somatosensory cortex. This answer is INCORRECT. Betz cells are not in somatosensory cortex.
C. IV of motor cortex.
D. V of motor cortex.
E. III of motor cortex.
Betz cells are most abundant in layer...
A. IV of somatosensory cortex.
B. V of somatosensory cortex.
C. IV of motor cortex. This answer is INCORRECT. Betz cells are not in layer IV.
D. V of motor cortex.
E. III of motor cortex.
Betz cells are most abundant in layer...
A. IV of somatosensory cortex.
B. V of somatosensory cortex.
C. IV of motor cortex.
D. V of motor cortex. This answer is CORRECT!
E. III of motor cortex.
Betz cells are most abundant in layer...
A. IV of somatosensory cortex.
B. V of somatosensory cortex.
C. IV of motor cortex.
D. V of motor cortex.
E. III of motor cortex. This answer is INCORRECT. Betz cells are not in layer III.
- Question 2
- A
- B
- C
- D
- E
A corticospinal neuron in primary motor cortex can do all of the following EXCEPT:
A. Project to multiple motor neuron pools in the spinal cord.
B. Participate in the initiation of movement.
C. Code for the amount of force of individual muscles.
D. Code for the direction of movement.
E. Code for the extent of movement.
A corticospinal neuron in primary motor cortex can do all of the following EXCEPT:
A. Project to multiple motor neuron pools in the spinal cord. This answer is INCORRECT. This is a TRUE statement. Many different muscle groups are influenced by the activity of single neurons in the motor cortex.
B. Participate in the initiation of movement.
C. Code for the amount of force of individual muscles.
D. Code for the direction of movement.
E. Code for the extent of movement.
A corticospinal neuron in primary motor cortex can do all of the following EXCEPT:
A. Project to multiple motor neuron pools in the spinal cord.
B. Participate in the initiation of movement. This answer is INCORRECT. This is a TRUE statement.
C. Code for the amount of force of individual muscles.
D. Code for the direction of movement.
E. Code for the extent of movement.
A corticospinal neuron in primary motor cortex can do all of the following EXCEPT:
A. Project to multiple motor neuron pools in the spinal cord.
B. Participate in the initiation of movement.
C. Code for the amount of force of individual muscles. This answer is CORRECT! This is a FALSE statement. Motor cortex neurons code for the force of individual movements, not individual muscles. Lower motor neurons (alpha motor neurons) encode the force of individual muscles.
D. Code for the direction of movement.
E. Code for the extent of movement.
A corticospinal neuron in primary motor cortex can do all of the following EXCEPT:
A. Project to multiple motor neuron pools in the spinal cord.
B. Participate in the initiation of movement.
C. Code for the amount of force of individual muscles.
D. Code for the direction of movement. This answer is INCORRECT. This is a TRUE statement.
E. Code for the extent of movement.
A corticospinal neuron in primary motor cortex can do all of the following EXCEPT:
A. Project to multiple motor neuron pools in the spinal cord.
B. Participate in the initiation of movement.
C. Code for the amount of force of individual muscles.
D. Code for the direction of movement.
E. Code for the extent of movement. This answer is INCORRECT. This is a TRUE statement.
 |
 |
Contact the author(s) at nba_course@uth.tmc.edu
© 2003-present, All Rights Reserved
The University of Texas Health Science Center at Houston
Created through the Multimedia Scriptorium in Academic Technology