KHA258 Lecture Notes - Lecture 6: Primary Motor Cortex, Golgi Tendon Organ, Precentral Gyrus
3 Jul 2018
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Behavioural Neuroscience week 6:
Sensorimotor system:
Three principles of sensorimotor function:
- Hierarchical and parallel organisation
- Opposite direction:
oStart at association areas
Abstract plans
Not specified
Some project all the way down to spinal cord
oMultiple communication areas in the brain; provide information that
helps planning of an action
oThis information then fed off to secondary motor area
Refines more about how this plan will be executed
More detail
Works out where things are in relation to you
Help specify which muscles will be involved
Projections all the way down to spinal cord
oPrimary:
Specify what exact muscles have to relax and contract and
when this has to occur
oThis information passed to brainstem and spinal cord, as well as
brainstem motor nuclei
Manage integration with other sensory information that is
coming in
oAll levels have direct projections to spinal cord
Lots of areas involved in the control
Highlights the parallel processing
oAt each level:
Another feature of nervous system organisation
Each projection gets a feedback about what it has done
Feedback loops
Information goes back to where it came from
- Sensory input guides output:
oControl of movements
oNot a requirement that sensory information is there
oNot paralyzed without it; but use it a lot to guide actions
oVisual, etc.
- Nature and locus of control change with learning
oConscious to automatic
oDifferent systems and different parts of systems control action
depending on whether being guided by sensory input or whether being
guided by memory
Different set of neurons engaged at higher levels
One movement not defined by single structures
First learning: lots of attention and conscious control needed
Big shift in the areas that are involved
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- Major areas of sensorimotor association cortex:
oPosterior parietal association cortex
Not just on lateral portions, drops internally
Multi-modal
oDorsolateral prefrontal association cortex:
Frontal lobes engaged, important for the control of actions
Premotor sensory areas
oSupplementary motor area:
Coordinating movements across body
Simultaneous
oEach composed of several different areas with different functions
oNot uniform in what it does across whole area
oPosterior parietal association cortex:
Spatial information integrated
Related to our own body: body part location
External objects: where objects are located in space in relation
to us
Details about how we might use our body part and
interact with it
Kinesia: can I detect myself moving
Input from:
Primary visual cortex
Primary auditory cortex
Primary somatosensory cortex
Outputs to: sent to prefrontal areas
Dorsolateral prefrontal association cortex
Secondary motor cortex: premotor cortex
Frontal eye field: important in control of eye
movements
oSeparate system
Damage to the posterior parietal cortex:
Apraxia: disorder of voluntary movement
oDefined by no muscle weakness or sensory
deficits
oStrange problem when instructed to perform an
action
oParticularly hard when attempting to mime
action without objects being there
Might be okay if object is actually there
oUsually when damaged to left side of the brain
Involved in planning actions and
executing actions
Damage to this side
Don’t understand the serial order of
functions
Different degrees
Contralateral neglect:
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oDamage to the right posterior parietal cortex
oUnable to respond to stimuli contralateral to the
side of the legion
oUsually seen with large legions of the right
hemisphere
oNeglect one half of space (visual space, personal
space, objects around you)
oComplex: tilting head, vertical line in terms of
vision changes
They still neglect same half however
oNo attention to it, or awareness of what is in the
visual field of neglect
oNormally we have an bias in the space that we
look at
oDorsolateal prefrontal association cortex:
Input from: posterior parietal cortex
Output to
Secondary motor cortex
oPrimary
oFrontal eye field
Evaluates external stimuli and initiates voluntary reactions-
supported by neuronal responses
Effects goal planning
Realization behaviour:
Know the behaviour, interpretive action
But don’t know when to stop when already done action
oOCD: loop between basal ganglia and frontal cortex
oSecondary motor cortex:
Major input: association cortex
Dorsolateral prefrontal cortex
oActive during imagining or planning movements
Output: primary motor cortex
Help making decisions about which aras of the body will make
an action
A number of areas in this cortex:
Supplementary motor areas
oSMA, preSMA (slightly different region),
supplementary eye field (
Premotor aareas:
oDorsal and areas (Brocas area)
Three cingulate motor areas:
oRegions below neocortex
oMidline as well as anterior areas
Mirror neurons:
Active when performing an action or watching another
perform the same action
First identified in monkeys in F5
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Opposite direction: start at association areas. Some project all the way down to spinal cord: multiple communication areas in the brain; provide information that helps planning of an action, this information then fed off to secondary motor area. Refines more about how this plan will be executed. Works out where things are in relation to you. Help specify which muscles will be involved. Projections all the way down to spinal cord: primary: Specify what exact muscles have to relax and contract and when this has to occur: this information passed to brainstem and spinal cord, as well as brainstem motor nuclei. Manage integration with other sensory information that is coming in: all levels have direct projections to spinal cord. Lots of areas involved in the control. Highlights the parallel processing: at each level: Each projection gets a feedback about what it has done. Information goes back to where it came from.
