Lecture 8: attention

Question 1

What are the three levels of motor control in the motor hierarchy?

Top, middle and bottem

Answer 1

1. Top: Cortical areas (association, premotor, supplementary) plan movements and translate intentions into actions.
2. Middle: Primary motor cortex, brainstem, basal ganglia, and cerebellum convert plans into commands for muscles.
3. Bottom: Spinal motor neurons execute commands by innervating muscles and producing reflexes.

Question 2

Muscle innervation: muscles consists of fibers attached to the skeleton

What are antagonist muscle pairs, and how do they work?

Answer 2

Muscles are paired as flexors and extensors; when one contracts (flexes), the other relaxes (extends), enabling smooth movement.

Question 3

Muscle innervation

How do alpha motor neurons contribute to muscle contraction?

Answer 3

Alpha motor neurons release acetylcholine at the neuromuscular junction, triggering muscle contraction. Firing rate and number of activated fibers determine force.

Question 4

Muscle innervation

Where do alpha motor neurons originate, and how do they exit the spinal cord?

Answer 4

Alpha motor neurons originate in the spinal cord and exit through the ventral root to innervate muscles.

Question 5

Muscle innervation

What role do gamma motor neurons play in muscle function?

Answer 5

Gamma motor neurons adjust muscle spindles, enabling the sensory detection of muscle stretch, which helps maintain posture.

Question 6

Muscle innervation

How does the stretch reflex work, and what is its purpose?

Answer 6

When unexpected stretch occurs, sensory neurons activate alpha motor neurons via spinal interneurons, causing contraction. It ensures postural stability and protection.

Question 7

Central pattern generators

What are central pattern generators, and what do they control?

Answer 7

Networks in the spinal cord that generate rhythmic movements (e.g., walking), independent of brain input, showing that the spinal cord can produce movement patterns.

Question 8

What evidence supports central pattern generators in the spinal cord?

Answer 8

Cats with a transected spinal cord can still walk on a treadmill, indicating rhythmic walking is generated by spinal circuits alone.

Question 9

Brainstem structures

What is the role of the brainstem in motor control?

Answer 9

The brainstem contains cranial nerves and nuclei like the vestibular nuclei and reticular formation, controlling posture, reflexes, and movement speed.

Question 10

Brainstem structures

What are the extrapyramidal tracts, and what do they control?

Answer 10

Extrapyramidal tracts originate in the brainstem (not the motor cortex) and regulate posture, muscle tone, and movement speed.

Question 11

Cerebellum

What is the main role of the cerebellum in motor control?

Answer 11

The cerebellum corrects movement errors through forward models, ensuring smooth, coordinated movements.

Question 12

Cerebellum

What happens when the cerebellum is damaged?

Answer 12

Damage to the cerebellum causes ataxia, characterized by difficulties with balance and coordinated movements.

Question 13

Basal Ganglia

What is the basal ganglia’s primary function in motor control?

Answer 13

The basal ganglia acts as a gatekeeper, selecting and initiating the most appropriate action plan among competing motor plans.

Question 14

Basal Ganglia

What are the consequences of damage to the basal ganglia?

Answer 14

Damage causes motor disorders:

• Parkinson’s disease: Hypokinesia (difficulty starting movements).
• Huntington’s disease: Hyperkinesia (excessive, involuntary movements).

Question 15

Functional neuroanatomy of cortical motor regions

What are the main roles of the primary motor cortex (M1)?

Answer 15

M1 initiates voluntary movements via the corticospinal tract, controlling the contralateral side of the body.

Question 16

Primary motor cortex M1

What is hemiplegia, and how is it caused?

Answer 16

Hemiplegia is paralysis on one side of the body due to a lesion in the primary motor cortex (M1).

Question 17

Primary motor cortex M1

Describe the somatotopic organization of the primary motor cortex.

Answer 17

M1 is coarsely organized so that different regions control different body parts, reflecting their importance and precision of movement.

Question 18

Secondary motor areas: Premotor cortex PM

What is the role of the premotor cortex (PM) in movement?

Answer 18

The premotor cortex plans sensory-guided movements like reaching or grabbing based on spatial awareness.

Connections with parietal cortex

Question 19

Secondary motor areas: Supplementary motor area (SMA)

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

Answer 19

The SMA is involved in goal-based movement planning and memory-guided sequences, such as choosing between objects or playing an instrument.

Connections with medial frontal cortex

Question 20

Two dorsal streams to Premotor cortex (PM)

What are the two dorsal streams connecting the parietal cortex to the premotor cortex?

Answer 20

1. Dorso-dorsal stream: reaching actions. (super parietal lobule)
2. Ventro-dorsal stream: object manipulation and gestures. (Inferior parietal lobule)

Question 21

Dorso-dorsal stream

What is optic ataxia, and what causes it?

Answer 21

Optic ataxia is the inability to reach for objects despite visual recognition, caused by lesions in the dorso-dorsal stream.

Question 22

Ventro-dorsal stream

What is apraxia, and what causes it?

Answer 22

Apraxia is the inability to perform coherent gestures (wave goodbye) or actions (use a comb), caused by lesions in the ventro-dorsal stream.

Question 23

Neural coding in motor regions

What does directional tuning in the primary motor cortex (M1) reveal about movement?

Answer 23

M1 neurons fire for movements in a specific direction (preferred direction), independent of starting or target location.

Question 24

Neural coding in motor regions

What question does neural coding in motor regions aim to answer?

Answer 24

Whether motor regions encode specific muscle activity (e.g., force) or abstract movement properties (e.g., movement direction, target location).

Question 25

Neural coding in motor regions

What is the center-out task, and what does it reveal about M1 coding?

Answer 25

A task where a subject moves a lever toward a specific target. M1 neurons fire based on movement direction, not the muscle activity itself.

Question 26

Neural coding in motor regions

What is directional tuning in M1 neurons?

Answer 26

M1 neurons have a preferred direction, where they fire most strongly for movements in that specific direction, regardless of starting or target location.

Question 27

population coding of movement direction

What is population coding in motor control?

Answer 27

Population coding combines activity from multiple neurons (each with a “vote”) to predict the movement direction.

Question 28

How does population coding predict movement direction in motor regions?

Answer 28

Population vectors are created by combining the activity of many neurons. Each neuron’s “vote” (firing strength) depends on how close the movement is to its preferred direction.

Question 29

Why is population coding of movement direction significant?

Answer 29

Population coding allows the brain to predict movement direction with high accuracy using signals from 30–50 neurons.

Question 30

What was achieved in the case of patient M.N. using a brain-machine interface?

Answer 30

M.N., a paralyzed patient, used imagined movements to generate neural signals. These were decoded into population vectors to control a cursor and interact with devices.

Question 31

What is the affordance competition hypothesis, and how does it relate to motor coding?

Answer 31

Multiple action plans are prepared in parallel, and population coding helps select the movement direction by integrating goals, states, and rewards.

Question 32

What do population vectors represent, and how do they summarize neuronal activity?

Answer 32

Population vectors summarize the combined activity of neurons in M1, where each vector reflects a neuron’s preferred direction and firing rate for a specific movement.

Question 33

How does M1 encode complex movement directions?

Answer 33

M1 neurons do not just activate muscles; they represent abstract movement directions, firing based on the planned movement’s trajectory.

Question 34

How does the premotor cortex prepare multiple action plans in parallel?

Answer 34

During a delay period before a “go” signal, neurons in the premotor cortex prepare trajectories for both possible actions, supporting parallel action preparation.

Question 35

What does the affordance competition hypothesis suggest about motor planning?

Answer 35

The brain prepares multiple potential actions simultaneously, and the final selection depends on goal utility, reward expectations, and sensory input.

Question 36

Action preparation in parietal vs. premotor cortex

How do parietal and premotor cortices differ in planning actions?

Answer 36

The parietal cortex represents actions in eye-centered frames, while the premotor cortex transforms these plans into hand-centered reference frames for execution.

Question 37

Movement intentions in parietal vs. premotor cortex

What happens when the parietal cortex is stimulated?

Answer 37

Stimulation causes a feeling of intention to move without actual movement, highlighting its role in motor intention rather than execution.

Question 38

Movement intentions in parietal vs. premotor cortex

How does stimulation of the premotor cortex differ from parietal cortex stimulation?

Answer 38

Stimulation of the premotor cortex triggers complex, multi-joint movements (e.g., arm rotation) without the subject’s conscious awareness.

Question 39

Supplementary motor areas SMA

What is the role of the Supplementary Motor Area (SMA) in motor control?

Answer 39

The SMA is critical for integrating the use of two hands, assigning movements to each hand to achieve an abstract goal (e.g., opening a drawer and retrieving an object).

Question 40

What happens when the SMA is lesioned?

Answer 40

Lesions to the SMA impair bimanual coordination. Actions requiring both hands to work together are disrupted, but actions performed with one hand remain intact.

Question 41

What is alien hand syndrome, and how is it related to SMA damage?

Answer 41

Alien hand syndrome occurs when one limb produces a meaningful action, but the individual denies responsibility for it. This can happen with SMA lesions

In corpus callosum lesions, the hands may work in opposition to each other, further illustrating competitive processes in action planning between the two hemispheres.

Question 42

Mirror neurons

How do mirror neurons link perception and action?

Answer 42

Mirror neurons fire both when performing an action and when observing someone else perform the same action, linking perception with motor planning.

Question 43

Mirror neurons

What are some unique properties of mirror neurons?

Answer 43

A: Mirror neurons are triggered by seeing, hearing, or expecting an action (e.g., cracking a peanut), even if the action is hidden behind an occluder.

Question 44

Mirror neurons

Where are mirror neurons found in the brain?

Answer 44

Mirror neurons are located in the premotor cortex, parietal cortex, and temporal regions, forming a distributed mirror neuron system.

Question 45

Mirror neurons

What is the proposed role of mirror neurons in understanding others’ actions?

Answer 45

Mirror neurons may help us understand others’ actions and intentions by automatically triggering similar motor plans in our own brains.

Question 46

Mirror neurons

What is apraxia, and how is it related to mirror neuron dysfunction?

Answer 46

Apraxia is the inability to perform meaningful actions, like using tools, which may stem from damage to the ventral premotor cortex where mirror neurons are located.

Question 47

Basal ganglia

What role does the basal ganglia play in movement selection?

Answer 47

The basal ganglia acts as a gatekeeper to resolve competition between multiple prepared actions, selecting the appropriate movement to execute.

Question 48

Basal ganglia

How does the direct pathway in the basal ganglia facilitate movement?

Answer 48

The direct pathway disinhibits the thalamus, allowing it to excite the cortex, which promotes movement initiation.

Question 49

Basal ganglia

How does the indirect pathway in the basal ganglia inhibit movement?

Answer 49

The indirect pathway increases inhibition of the thalamus, reducing excitation to the cortex, which suppresses movement.

Question 50

Basal ganglia

How does Parkinson’s disease affect the basal ganglia pathways?

Answer 50

Loss of dopamine in the direct pathway reduces thalamic disinhibition, leading to hypokinesia (difficulty initiating movements).

Question 51

Basal ganglia

How does Huntington’s disease affect basal ganglia circuits?

Answer 51

Damage to the indirect pathway reduces inhibition of the thalamus, causing hyperkinesia (excessive involuntary movements).

Question 52

Error based learning from forward models.

What is the role of the cerebellum in forward models?

Answer 52

The cerebellum predicts the sensory consequences of movements (forward models) and corrects motor errors in real-time.

Question 53

Error based learning from forward models.

What is the role of efference copy in motor control?

Answer 53

The motor cortex sends an efference copy of the motor command to the cerebellum, which predicts and adjusts for expected sensory feedback.

Question 54

Error based learning from forward models.

What are the consequences of cerebellar lesions?

Answer 54

Cerebellar lesions impair error correction and lead to ataxia, characterized by poor balance, lack of coordination, and overshooting or undershooting movements.

Question 55

How does motor learning shift control from the cortex to the subcortex?

Answer 55

With practice, motor control shifts to subcortical structures like the basal ganglia and cerebellum, reducing reliance on the motor cortex.

Question 56

How do brain changes occur with motor expertise?

Answer 56

Structural changes occur, such as increased gray matter in the intraparietal sulcus and greater connectivity in the corpus callosum for bimanual coordination.

Question 57

What evidence shows the cerebellum’s role in motor learning?

Answer 57

During early learning, the cerebellum and basal ganglia are highly active for error correction, but activity reduces as movements become habitual.