the motor system Flashcards
what is the motor system?
-a system that regulates behaviour in response to the environment
how is it organized?
Cortical motor control:
Posterior/Parietal cortex(sends goal)
Prefrontal cortex(plans)
Premotor cortex( make the sequence)
Motor cortex(execution)
Subcortical motor control:
Basal ganglia
Cerebellum
Brain stem
Spinal cord
what are the functions of the posterior\parietal cortex?(cortical motor control)
- (dorsal stream\sensory)
-Provides visual information about the location of object - postural information about location of hand/arm
-Global response to stimuli: reaching, gesturing
what are the functions of the Prefrontal cortex? (cortical motor control)
-(ventral stream)
-Receives info from the limbic system (memory) and sensory association regions
-Movement planning and decision-making
-Based on previous experiences
what are the functions of the Premotor cortex/dorsolateral cortex and the motor cortex? (cortical motor control)
Premotor cortex/dorsolateral cortex:
-mirror neurons
-Rhythmic movement, motor coordination (walking, skills)
-Organizing specific action sequences (e.g. making coffee)
-Movement lexicon of smaller precise movements (pinser & grasping)
Sequencing of motor actions
-Bimanual coordination
-Coordination of multiple limbs (arm, hand, shoulder)
-Coding of force
-Voluntary internally generated movements:
(Active before a movement is executed)
Motor imagery
Force-matching
Motor cortex:
-Execution of exact precise hand movements
-movement lexicon
what are some characteristics\functions of the primary motor cortex(M1)? (cortical motor control)
- in the topographical organization (homunculus) the hands and face are the biggest areas ( specialized neural resources dedicated to controlling movements of the face and hands)
- it controls the adjustment of force\strenght
-deals with concrete motor commands:
Not individual muscle control, but coordinated movements
Representation of movement categories (movement lexicon, pincer grip, gasping)
Fine motor skills
What symptoms do you expect when the M1 is affected? (cortical motor control)
Strokes or tumours often affect M1:
-Loss of fine motor skills
-Hemiparesis= weakness or partial paralysis that affects one side of the body
a)Contralateral muscle weakness= weakness or paralysis affecting muscles on the side of the body opposite to the side of brain injury
b)Affects multiple body parts
c)Often face and hand (= large areas in motor cortex)
-Hemiplegia=paralysis or severe weakness that affects one entire side of the body
a)Paralysis of the contralateral side
-spasticity=stiffness and involuntary muscle spasms or contractions.
Motor function often improves with practice, especially in the first 3 months after stroke (plasticity)
What symptoms do you expect when the premotor cortex is affected? (cortical motor control)
-Problems with tasks that require bimanual or multi-limb coordination
-Problems with motor sequences (throwing a ball)
Premotor-sensory interactions:
Heavy limbs, simple movements feel effort-full, fatigue
whar are the functions of mirror neurons?(premotor cortex) (cortical motor control)
-Simulate actions of others (action/intention understanding)
-Enable fast responses, anticipation
-Understanding emotional expressions/states
-Important social interaction (Rizzolatti)
Or: just sensory-motor associations (Hickok)
what role does the basal ganglia play? (Subcortical motor control)
1)the basal ganglia and its associated circuits play a crucial role in motor control by regulating the generation, intensity, selection, and inhibition of movements. These processes are finely tuned through interactions with cortical and subcortical structures, as well as dopaminergic modulation from the substantia nigra, ensuring efficient and adaptive motor behaviour.
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-Inhibition and excitation of movements through the direct and indirect pathways(GABA:inhibition, Glutamate - excitatory)
-Selection of appropriate actions and inhibition of inappropriate actions
-Highly innervated by dopamine from substantia nigra
-Cognitive control and flexibility
-Associative learning, approach/avoidance, motivation
Prediction errors!
Respond (GO) to cues predicting rewards
Avoid (NOGO) to cues predicting punishments
what happens when the basal ganglia has low dopamine? what happens when it has high dopamine?(subcortical motor control)
Low dopamine = Break
Indirect pathway > direct pathway
Gpi inhibits thalamus
Brake on movement - “NoGO”(difficulties in initiating and executing voluntary movements, )
High dopamine burst = accelerate
Indirect pathway < direct pathway
Gpi no longer inhibits the thalamus
Brake is released - “GO”
Tonic and phasic dopamine
what is the main function of the cerebellum?(subcortical motor control)
-Acquiring and maintaining motor skills
What symptoms do you expect when the cerebellum is damaged ?(subcortical motor control)
-Gait Ataxia (midline)
balance posture, eye movements, walking=drunk
-A-pendicular ataxia (lateral)
arm, hand and finger movements
Loss of timing – tapping a beat or judging the length of an interval
Problems with combined movements
Problems in movement accuracy, adjustment to errors
e.g. finger – nose testing
-Flocundonodular damage: Delayed eye movements
-you can’t learn by trial and error anymore=No adjustments and after-effects with prism glasses( specific example)
