Final Exam - Motor Control Flashcards
To know every slide and ACE the Final!!
What are the categories of movement?
- Reflexive: Level of spinal cord: knee jerk
- Rhythmic: Walking, chewing, swallowing
- Voluntary: See the box, step over it
What are reflexes?
- Involuntary coordinated patterns of movement
- Consistent, assuming external stimuli are constant
- Can be modulated by descending cortical commands
What are rhythmic movements?
- Chewing, swallowing, walking
2. Patterns contained on brain stem and spinal cord and triggered by external stimuli
What is voluntary movement?
- Goal-directed
- Externally or internally triggered
- Modulated by feedback (corrects already-initiated movement) and feed-forward control (anticipates events: used to control posture and movement, eg. catch a ball)
What is motor psychophysics?
- Brain represents outcome, not individual movements or muscles.
- Reaction time depends on complexity of information processing
- Speed of movement inversely related to accuracy
What is the motor hierarchy of the brain?
- Premotor areas
- Primary Motor cortex: M1, BA 4
- Cerebellum and basal ganglia modulate (projects to planning areas and premotor)
What is the motor hierarchy of the brain stem?
- Medial motor system: proximal musculature (trunk and torso: posture)
- Lateral motor system: distal musculature (arms and legs: more lateral systems)
What is the motor hierarchy of the spinal cord?
- Circuitry for reflexes and rhythmic movement
2. Modulated by higher areas
Explain the spinal control of movement.
- Motor neuron cell bodies clustered in spinal column.
- Neurons that control proximal muscles located medially
- Proprioceptive information transmitted up and down to affect posture
Dorsal horn takes ________.
Information in
Ventral horn takes ________.
Information out
In the brain stem, medial pathways control what and consist of what tracts?
Medial pathways control posture: Vestibulospinal, reticulospinal, tectospinal tracts
In the brain stem, lateral pathways control what and consist of what tracts?
Lateral pathways control goal-directed movement: Rubrospinal and corticospinal (from primary motor cortex: fine detailed motor control movements) tracts
Corticospinal tract axons originate from where?
Corticospinal tract axons originate from BA 4, BA 6 (motor planning areas), and BA 3 (most anterior), 1, 2 (sensory areas)
Where does decussation occur for cortical control of movement?
Decussate at pyramids of medulla to form lateral corticospinal tract (75% of axons)
What % doesn’t decussate and descends _______ as the ________.
25% do not decussate and descend ipsilaterally as the ventral corticospinal tract
What is the lateral corticospinal tract responsible for?
Voluntary motor control (typing)
What is the ventral corticospinal tract responsible for?
Involved, but less important in voluntary movement (has info that remains ipsilateral)
What is a reflex?
- Automatically produced adaptive movement
- Can extend over wide range of muscles
- Can be adapted to achieve particular goal
How are reflexes modulated?
By descending commands
What is an example of how reflexes are adaptive?
When holding onto a cup and kneeling down, perturbation will occur to allow excitation and inhibition of muscles (reflexes) to keep the cup balanced and prevent spillage.
What are muscle spindles for?
Sensor for reflexes
- Detect stretch of muscle fibers
- Increase firing rate when fiber elongates
- Detect change in muscle length and steady state length
- More sensitive when performing unpredictable tasks
What are Golgi Tendon Organs for?
Sensor for reflexes
- Junction between muscle and tendon
- Stretching tendon compresses nerve endings, causing them to fire (information for proprioception)
What do gamma motor neurons do?
Strengthen or relax muscle spindles.
Where are rhythmic stepping movements generated?
In spinal cord
Is sensory input required for locomotion?
Not required, but does modulate stepping movements.
Are supraspinal structures necessary for stepping?
No
Spinal circuits can be activated by what?
Descending commands
What is stepping divided into?
Swing and stance phases
What generates a burst of activity in extensor and flexor muscles?
Isolated spinal cord
Pool of neurons controlling extensor muscles does what to neurons controlling flexor muscles?
Inhibits them
Where are central pattern generators for locomotion found at?
L6 in spinal cord
What are central pattern generators?
Network of neurons capable of generating regular patterns of activity without sensory input (spontaneous bursting activity).
Central pattern generators influence what and is modified by what?
- Walking, summing, respiration
2. Output modified based on sensory input and descending commands.
What does the pattern depend on?
Properties of component neurons and synapses as well as connection between neurons.
Pattern is regulated by?
- Mutual inhibition (one excited = one inhibited)
- Rate of recovery from inhibition
- Mutual excitation (one excited = other excited)
What is the sensory input to locomotion?
- Somatosensory input (tactile from feet)
- Vestibular input (equilibrium)
- Visual input (obstacles)
- Commonly divided into proprioceptors and exteroceptors.
Descending control of walking from visual cortex (pathway).
Visual cortex -> visual signals -> motor cortex -> visual guidance -> spinal locomotor system -> limb movement
Descending control of walking from MLR (pathway).
Mesencephalic locomotor region (MLR) -> Medial reticular formation (MRF) -> activation -> spinal locomotor system -> limb movement
Descending control of walking from limb (pathway).
Afferent signals -> spinocerebellar pathway -> cerebellum -> brain stem nuclei -> adjustment -> spinal locomotor system -> limb movement
Intensity of stimulation to MLR affects what?
Intensity of stimulation to mesencephalic locomotor region affects speed of walking.
- Weak stimulation = walking
- Strong stimulation = galloping
Where does the brain stem pathway for the MLR descend from?
Medullary reticular formation via glutaminergic neurons of reticulospinal tract.
When is the motor cortex more involved?
During difficult, coordinated or visually-guided movements.
Cerebellar impairment results in what?
Ataxia: variations in speed and range of movements: abnormal coupling between limbs.
What does the cerebellum do for cortical and subcortical influence?
Compares actual movements (proprioceptive information) with planned movements (information from CPGs) and makes appropriate corrections.
What is involved in voluntary movement?
- Integration of visual and proprioceptive information.
- Goal-directed
- Can be internally/externally generated.
- Improves with practice and experience.
- Primary motor cortex (M1)
- Premotor areas
What is somatotopic organization?
Layout of the body: mapping out what parts of the body use what: larger representation = more control
Corticospinal neurons innervate what?
Multiple muscles (more designed to control movements)
Premotor areas have direct projections to where?
Spinal cord
Premotor areas control _____.
Complex patterns of behavior.
Lateral premotor areas control what?
Externally-guided movements in response to sensation.
Dorsal premotor area controls what?
Delayed movements and responds to non-spatial movement cues.
Ventral premotor area controls what?
Location of objects to guide motion and conforming hand to shape of target.
Medial premotor areas control what?
Internally-guied movements
SMA controls what?
Supplementary motor area: bimanual movement and plans motor movements of learn sequences.
Pre SMA controls what?
Presupplementary Motor area: Learning sequences of movements
Subcortical input to motor areas follows what loop?
Primary motor cortex/Premotor cortex -> Globus pallidus/Thalamus -> pons -> cerebellum -> thalamus -> motor areas.
How does plasticity in the motor cortex work?
- Motor cortex reorganized based on experience.
- Remove sensory input to M1 and reorganization occurs.
- Train particular motor task and brain area dedicated to that task increases.
What does the corticospinal tract provide?
Direct excitatory connection to motor neurons.
Indirect connections influence _____.
Larger-scale movements across joints.
Corticospinal tract connects to?
Inhibitory interneurons, allowing incorporation of reflex movements.
Sectioning tract blocks ____.
Fine motor control
In experiment, what happens after sectioning of corticospinal fibers?
Monkey is unable to pick up dessert from hole (fine motor control).
Motor planning alters ____ before actual movement.
firing pattern
Population code indicates ___.
direction of movement.
Firing dependent on ____.
Exerted force
Neurons are ____ to joint moved and direction of movement.
specific.
What are 3 inputs to the cerebellum?
- Goals
- Commanded action
- Feedback
Output from cerebellum directed to ___.
- Motor planning and execution regions of cortex
- Brain stem
- Spinal cord
Damage to the cerebellum affects ___.
Spatial and temporal accuracy of movement.
Cerebellum has outer ____ matter and inner ____ matter.
Outer grey matter and inner white matter.
Cerebellum consists of what 4 deep nuclei?
- Fastigial
2 & 3. Interposed (Globus and Emboliform) - Dentate
The cerebellum is connected to the brain stem by what?
Cerebellar peduncles (ways to get information into and out of brain).
Anatomy of cerebellar nuclei from lateral to medial.
Dentate -> Emboliform -> Globus -> Fastigial
Describe the cerebellar lobe: Flocculonodular
- Oldest part of cerebellum
- Input from vestibular nuclei (located in brain stem)
- Balance and eye movements
Describe the cerebellar lobe: Vermis
- Runs down midline of cerebellum.
- Auditory, visual, somatosensory input form head and trunk (medial aspect).
- Posture, locomotion, and gaze direction.
Describe the cerebellar lobe: Intermediate Hemisphere
- Somatosensory input from limbs (proprioceptive information).
- Projects to corticospinal tract and controls distal limb movement.
Describe the cerebellar lobe: Lateral Hemisphere
- Interacts with cortex
2. Motor planning, cognitive tasks (timing)
Vestibular inputs are found in what region of the cerebellum?
Medial (vermis area)
Cerebellar output starting at the lateral hemisphere (cerebrocerebellum)
Lateral hemisphere -> Dentate nucleus -> Motor and Premotor cortices (motor planning)
Cerebellar output starting at the Intermediate hemisphere
Intermediate hemisphere -> Interposed nuclei -> Lateral descending systems (Motor execution)
Cerebellar output starting at the Vermis
Vermis -> Fastigial nuclei -> Medial descending system (motor execution)
Cerebellar output starting at the vestibulocerebellum.
Vestibulocerebellum -> vestibular nuclei (balance and eye movement)
Distal motor control: intermediate projections
Intermediate hemisphere projects to contralateral red nucleus, thalamus, and motor cortex.
Distal motor control influences ____.
Descending corticospinal tract to ipsilateral side.
What is the loop important for learning and where?
- Lateral Hemisphere
2. Premotor - Cerebello - rubrocerebellar (red nucleus)
The lateral hemisphere receives input from ____.
Cerebral cortex
Lesions in the lateral hemisphere disrupts ____.
Planning and lengthens reaction time
What cognitive functions are produced by the lateral hemisphere?
- Timing (100s of milliseconds)
- Language (verbal fluency, word association)
- Problem solving
What are prism goggles used for?
- Used for motor learning. Tests eye-hand coordination in dart-throwing. (normal subjects should adapt to prism in 10-30 throws)
- Patients with cerebellar damage fail to adapt to prisms.
- After taking off goggles, need to readjust again.
Subjects with damage to lateral interposed nucleus fail to ____.
Learn eye blink conditioning. (tone plays, puff of air hits eye, supposed to close eyes)
What are the 3 symptoms of cerebellar damage?
- Hypotonia: decreased resistance to passive limb movement
- Ataxia: abnormal execution of voluntary movement
- Intention tremor: tremor at end of voluntary limb movement
Cerebellar lesions to the vermis and fastigial nuclei does what?
- Disrupted control of trunk muscles during sitting or standing.
- Possibly slurred speech
Cerebellar lesions to the intermediate cerebellum or interposed nuclei does what?
Limb tremor
Cerebellar lesions to the lateral cerebellum does what?
- Delays initiating movement
2. Poor coordination across multiple joints