Lecture 2 - Motor (Dys)Function Flashcards
What are the 4 cortical motor control cortex ?
- Posterior/Parietal Cortex
- Prefrontal Cortex
- Premotor Cortex
- Motor Cortex
What are the 4 subcortical motor control components ?
- Basal Ganglia
- Cerebellum
- Brain Stem
- Spinal Cord
What’s the Posterior/Parietal Cortex’ main function ?
- Provide visual information about location of object
- Provide postural information about location of arm/hand
- Global response to stimuli : reaching, gesturing
What’s the Prefrontal Cortex’ main function ?
- Receives information from limbic system & sensory association regions
- Movement planning & decision making
- Based on previous experiences
What’s the Premotor Cortex’ main function ?
- Rhythmic movement & motor coordination
- Organizing specific action sequences
- Movement lexicon of smaller precise movements (pincer & grasping)
What’s the Motor Cortex’ main function ?
- Execution of exact precise hand movements
- Movement lexicon
How is organized the Primary Motor Cortex (M1) ?
Topographical organization (homonculus)
(face & hands = biggest areas)
What symptoms do you expect if M1 is damaged ?
- Stroke or tumors
- Loss of fine motor skills
- Hemiparesis
- Hemiplegia
- Spasticity
What symptoms do you expect if the Premotor Cortex is damaged ?
- Problems with tasks that require bimanual or multi-limb coordination
- Problems with motor sequences
- Simple movements feel effort-full, fatigue
In what order does an information travel in the cortical motor system ?
- Posterior Cortex
- Prefrontal Cortex
- Premotor Cortex
- Motor Cortex
In which cortex can we find Mirror Neurons ?
Premotor Cortex
What are the Mirror Neurons’ characteristics ?
- Simulate actions of others
- Understanding of others’ actions & intentions
- Enables fast responses & anticipation
- Understanding of emotional expressions & states
What’s the role of the Basal Ganglia in the motor system ?
Volume control :
- Inhibition & excitation of movements through the direct & indirect pathways
- Selection of appropriate actions & inhibition of inappropriate ones
Which Basal Ganglia’s component is essential for motor control ?
Globus Pallidus (GPi)
To what can lead damage to cells of the Caudate Nucleus ?
Excessive movement :
- Huntington’s Disease
- Tourette’s Syndrome
To what can lead damage to Substantia Nigra ?
- Parkinson’s Disease
- Reduced dopaminergic input (tremors, rigidity, cognitive inflexibility)
What are the symptoms of Dopamine dysregulations ?
- Learning deficits, stimulus-response associations (gambling, drug addiction, impulsivity)
- Motivational symptoms
- Mood disorders
What are the possible treatments for Parkinson’s disease ?
- Physical therapy
- Medication (e.g. L-dopa)
- Deep Brain Stimulation (DBS)
What symptoms do you expect when the Cerebellum is damaged ?
- Gait Ataxia (midline)
- Appendicular Ataxia (lateral)
- Flocundonodular damage
What is the Cerebellum’s main function in motor control ?
Acquiring & maintaining motor skills
What are Gait Ataxia’s symptoms ?
- Problems with balance & posture
- Problems with eye movements
- “Drunk-walking”
What are Appendicular Ataxia’s symptoms ?
- Loss of timing
- Problems with combined movements
- Problems in movement accuracy, adjustement to errors
What are Flocundonodular damage symptoms ?
Delayed eye movements
What’s the Neocortex’ main function in motor control ?
Skilled fine motor movements
What’s the Brain Stem’s main function in motor control ?
- Whole body movement repertoires
- Corticobulbar tract : facial movements
What’s the Spinal Cord’s main function in motor control ?
- Executing the actions
- Cortico-spinal tracts (anterior & lateral)
What are the differences between the 2 corticospinal tracts ?
- Lateral corticospinal tract : moves limbs & digits (crossing fibers)
- Anterior corticospinal tract : moves muscles in the body’s midline (non-crossing fibers)
What are the two pathways in the basal ganglia that modulate movement force ?
Inhibitory pathway & excitatory pathway
What is the role of the inhibitory pathway in the Basal Ganglia ?
Excites the Globus Pallidus (GPi), which in turn inhibits the Thalamus, reducing movement force
What is the role of the excitatory pathway in the Basal Ganglia ?
Inhibits the GPi, which in turn allows the Thalamus to excite the cortex, increasing movement force
How does Parkinson’s disease affect the inhibitory pathway in the Basal Ganglia ?
- Reduced dopamine levels
- Decreases the activity of the inhibitory pathway
- Excessive activity of the GPi : increased inhibition of Thalamus
What role does the Substantia Nigra play in the pathways associated with Parkinson’s disease ?
- Provides dopamine to Basal Ganglia
- Disrupt the balance between inhibitory & excitatory pathways
What is the consequence of reduced inhibitory pathway activity in Parkinson’s disease ?
- Thalamus excessively inhibited
- Decrease input to the Motor Cortex
- Hypokinetic symptoms
What are the two main sources of input to the Basal Ganglia ?
- Neocortex & Limbic System (including Motor Cortex)
- Nigrostriatal Dopamine pathway (from Substantia Nigra)
What’s the difference (in terms of components) between the excitatory & inhibitory pathways of the Basal Ganglia ?
- Inhibitory : Cortex -> Putamen -> GPi -> Thalamus
- Excitatory : Cotex -> Putamen -> GPe -> Subthalamic Nucleus -> GPi
