PSY324 Motion

Hierarchical & Parallel Movement Control

Nervous system produces movement; somatosensory system guides it.

Spinal cord → reflexes
Brainstem → timing/control
Cerebrum → voluntary movement

Neuroprosthetics

Use brain–computer interfaces (BCI) to restore lost functions.

Translate brain activity into movement or speech.

Advances allow communication and control, but limitations remain.

Sequentially Organized Movement

1. Vision locates target

2. Motor cortex plans movement

3. Spinal cord sends command

4. Motor neurons activate muscles

5. Fingers detect touch

6. Spinal cord sends feedback

7. Basal ganglia + cerebellum adjust

8. Sensory cortex perceives grasp

Visual input → motor planning (frontal lobe) → spinal cord → muscles move.

Sensory feedback returns to brain → basal ganglia & cerebellum adjust movement.

Afferent vs Efferent

Afferent → sensory info goes to brain.
Efferent → motor commands go from brain to body.

connections btw the nerves and the spine

posterior root (sensory) - back of our spine

anterior root (motor) - front side

Initiating a Motor Sequence

Motor learning = sequences of actions.

Prefrontal → plans
Premotor → sequences
Primary motor → executes movement

Premotor Control

Premotor cortex organizes movement sequences.

Damage → movements become poorly sequenced/disorganized.

Primary Motor Cortex (M1)

Controls precise, skilled movements (hands, fingers, mouth).

Damage → difficulty shaping/grasping objects.

Hierarchical Movement Control (Evidence)

Prefrontal → plans
Premotor → organizes sequence
Primary motor → executes movement

Movement Control in the Brain

Simple → motor + sensory cortex

Sequence → premotor cortex

Complex → multiple areas (prefrontal, temporal, parietal)

Brainstem: Species-Typical Movement

Brainstem controls basic movements (posture, walking, coordination).

Cerebral palsy → difficulty making voluntary movements, often from early brainstem/brain damage.

Locked-in syndrome → person is awake and aware but almost completely paralyzed, usually able to move only the eyes.

Spinal Cord Injuries

Quadriplegia → paralysis of arms + legs (neck injury).

Paraplegia → paralysis of lower body (lower spine injury).

Reflexes can still occur without brain control.

Motor Cortex and Skilled Movement

Motor cortex plans and initiates movement.

Codes force (stronger firing = more force) and direction (flexor vs extensor).