PSYC 2410 Lecture Notes - Lecture 9: Mirror Neuron, Primary Motor Cortex, Premotor Cortex
31 May 2018
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SENSORIMOTOR SYSTEM
• Principles of sensorimotor function
o Hierarchically organized
▪ President
• Association cortex
▪ Lower levels
• Motor neurons
• Muscles
o Sensory input for motor output
▪ Help with
• Picking things up
• Adjusting to unanticipated forces
• Maintaining constant force
▪ Exception
• Ballistic movements
o Learning changes nature and locus of control
▪ Initially
• Actions under conscious control
▪ With practice
• Actions become integrated sequences
o Do’t eed coscious regulatio
o General model
▪ Association cortex
• Posterior parietal cortex
o Input
▪ Visual
▪ Auditory
▪ Somatosensory
o Output
▪ Secondary motor cortex
o Function
▪ Provide info on where body parts are
▪ Voluntary response initiation
o Damage
▪ Apraxia
• Caused by damage to
o Left parietal hemisphere
• Result
o Unable to perform movements on
command
o Bilateral symptoms
▪ Contralateral neglect
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• Caused by damage to
o Right parietal hemisphere
• Result
o Attend to right side of body or items
in environment only
o Can unconsciously perceive objects
on the left
• Dorsolateral prefrontal association cortex
o Input
▪ Posterior parietal cortex
o Output
▪ Secondary motor cortex
▪ Primary cortex
▪ Frontal eye field
o Function
▪ Assess external stimuli
▪ Voluntary response initiation
▪ Secondary motor cortex
• 8 areas
o premotor cortex
▪ 2
• dorsal
• ventral
▪ function
• encode spatial relations
• program movements
o supplemental motor areas
▪ 2
• pre SMA
• SMA
o cingulate motor areas
▪ 3
• input
o association cortex
• output
o primary motor cortex
o secondary motor cortex
o brainstem
• mirror neurons
o fire when an individual
▪ makes goal directed movements
▪ observes someone doing goal directed movements
o social cognition
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▪ knowledge of others in terms of
• perception
• ideas
• intentions
▪ Primary motor cortex
• Location
o Precentral gyrus of frontal lobe
• Organization
o Somatotopically
▪ According to a map of the body
• Commonly referred to as motor
homunculus
o Representation
▪ Diffuse
▪ Disproportionate
• Function
o Code for preferred direction of movement
• Damage
o Contralateral asterognosia
▪ Reduce speed and force of contralateral
movements
▪ Increase difficulty in moving one part independent
of others
▪ Brain stem motor nuclei
• Subcortical sensorimotor structures
o Characteristics
▪ Do’t trasit sigals to spial cord
o Examples
▪ Cerebellum
• Function
o Correct deviations
o Sequences of movements
• Input
o Primary motor cortex
o Secondary motor cortex
o Brainstem motor nuclei
o Somatosensory system
o Vestibular system
• Damage
o Loss of ability to
▪ Precisely control movement
▪ Adjust motor output
▪ Maintain steady posture
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Document Summary
Initially: actions under conscious control, with practice, actions become integrated sequences, do(cid:374)"t (cid:374)eed co(cid:374)scious regulatio(cid:374, general model, association cortex, posterior parietal cortex. Increase difficulty in moving one part independent of others: brain stem motor nuclei, subcortical sensorimotor structures, characteristics, do(cid:374)"t tra(cid:374)s(cid:373)it sig(cid:374)als to spi(cid:374)al cord, examples, cerebellum, function, correct deviations, sequences of movements. In tendons: connected in series, sensitive to muscle tension, muscle spindles. Intrafusal motor neurons: maintain spindle, tension, responsiveness, connected in parallel, sensitive to muscle length, reflexes, types, stretch, example, patellar reflex, function, make adjustments in muscle tension, occurs in response to, external forces, how. Intrafusal motor neuron adjust length of intrafusal fibers: withdrawal, occurs in response to, painful stimulus, how, sensory neurons synapse on interneurons on flexors. Ie renshaw cell: renshaw cell synapses on cell body of motor neuron that activated it, motor neurons take an enforced rest after firing, complex, walking.
