10. motor control and disorders of action I

What is the main goal of motor control?

To coordinate multiple muscles with precise timing to produce smooth and accurate movements.

What higher-level cognitive functions are involved in motor control?

Planning, timing, sequencing, imagery, and expertise.

Name three applications of understanding motor control.

Learning motor skills, rehabilitation for movement disorders, designing artificial limbs.

What is the role of the primary motor cortex (M1)?

Execution of movement contralaterally; it has a somatotopic organisation.

What happens when there's a stroke affecting M1?

Movement on the opposite side of the body is affected.

Define hemiplegia and hemiparesis.

Hemiplegia = paralysis of one side of the body; Hemiparesis = weakness on one side.

ow are movements coded in M1?

Through population coding—cells have preferred movement directions (vector coding)

What are the two systems within M1?

1. Body-part specific for fine motor control of the foot, hand and mouth

2. Somato-cognitive action network (SCAN) for goal integration and whole body movement

How is M1 connected to other brain regions?

• Input from Supplementary motor, premotor and primary somatosensory

• Output to spinal cord (which controls muscles)

What does the premotor cortex do?

Prepares externally generated actions.

What is the role of the supplementary motor area (SMA)?

Controls internally generated actions like well-learned sequences.

When is SMA more active?

During complex or bimanual coordination tasks

What happens with repetitive TMS over SMA?

SMA only interferes with execution of complex sequences, showing its role in internal movement planning

What changes occur in the brain during motor sequence learning (e.g., 8 key presses)?

• Movements become faster and more accurate, shifting from effortful to automatic.

• Brain activation changes over time:

  • ↓ Dorsolateral prefrontal cortex (less conscious effort)

  • ↑ Supplementary motor area (SMA) (internally generated sequences)

  • ↓ Lateral premotor cortex (less reliance on external cues)

  • ↓ Primary motor cortex (more efficiency)

  • Also involves cerebellum and basal ganglia (for motor learning and control)

What functions are associated with the prefrontal cortex in motor control?

Choosing actions, attention to action, long-term goals, and intention.

What are common symptoms of prefrontal lesions?

• Perseveration - repeat same action when no longer relevant

• Utilisation behaviour – act on irrelevant (or inappropriate) object in environment

• Disinhibition e.g. antisaccade task (unable to inhibit/stop action)

• Frontal apraxia – not able to follow steps in routine tasks (e.g. making tea)

How does the Normal & Shallice model suggest we control our actions?

1. Contention scheduling - automatically selects appropriate schema for common situations

2. Supervisory attentional System (SAS) - takes control in for novel/less automatic (less routine) action

What are two action errors explained by the Norman & Shallice model?

• Perseveration – inability to change schemas when inappropriate.

• Utilisation behaviour – acting automatically on objects due to environmental triggers.

What does the parietal cortex do in motor control?

Links sensory information with motor plans.

What is apraxia?

Inability to perform skilled, purposeful movement despite no physical paralysis.

What is ideomotor apraxia?

Disconnect between idea and execution of movement; can understand and recognise actions but fail to perform or pantomime them.

What is the role of the basal ganglia?

Helps initiate and terminate movements.

What is the role of the cerebellum?

Coordinates smooth, accurate movement, posture, and motor learning.

What symptoms do cerebellar patients show?

Action tremor, dysmetria (overshooting/undershooting), coordination/timing deficits.

What is the random saccade test?

A test where participants must look at randomly appearing targets on a screen.

What does the test reveal in cerebellar patients?

Impaired saccades—slower, less accurate eye movements, often overshooting or undershooting (dysmetria).

What causes Parkinson’s disease?

Death of dopamine-producing cells in the substantia nigra pars compacta.

Define bradykinesia.

Slowness of movement and reduced ability to initiate actions.

What is a resting tremor?

Involuntary rhythmic shaking when the muscle is relaxed.

What is rigidity?

Muscle stiffness that resists movement.

What is a shuffling gait?

Small, dragging steps due to rigidity and bradykinesia.

What motor deficits are common in Parkinson’s?

Problems with internally generated movements, bimanual tasks, and complex sequences.

What cognitive deficits can also occur?

Attention shifting difficulties and increased everyday cognitive errors.