Motor systems Flashcards
Movement starts with an internal representation (the goal of the intended movement)
And translates it into the appropriate into the appropriate motor commands to achieve the goal
Motor system has hierarchical and parallel organization
Motor cortex -> brainstem -> spinal cord
What works in parallel w motor cortex and brainstem?
Basal ganglia and cerebellum
The abstract aspects of action are
ROSTRAL
Specific action required to achieve abstract goal are
CAUDAL
Frontal lobe
Involved in action
Area 4
M1
Most directly involved in controlling movement
Area 6
Lateral premotor cortex
SMA and pre-SMA
Supplemental motor area
Pre-motor cortex/SMA
Control organization and control of movements
Motor cortex controls ipsilateral or contralateral muscles?
Contralateral
Individual motor neurons fire…
Just before and during movement
Reciprocal connections b/w the parietal lobe and the premotor cortex mediate…
Sensory-motor transformations
Sensory-motor transformations
The computations that enable sensory info to guide interactions w objects in the environment
What network is involved in directing arm movements towards objects
Parietal, dorsal premotor cortex and M1
Peripersonal spatial map
Used to guide goal-directed movements
Many neurons in parietal lobe respond to both tactile and visual stimuli with receptive fields that are spatially in register
These neurons are thought to be involved construction of a peripersonal spatial map
Ventral premotor neurons (vPMC) respond to…
preferred shapes
Mirror neurons
Discovered in premotor cortex.
Respond when monkey reaches for an object AND when he watches the experimenter reaches for the object
They do not respond to the object alone or to non-goal directed movements of the experimenter’s arm
Do primary motor cortex neurons activate contralateral and/or ipsilateral motor neurons?
Contralateral
Do premotor cortex neurons activate contralateral and/or ipsilateral motor neurons?
Can be both!
When do premotor neurons fire?
During movements and during an imposed delay prior to the movement
This suggests they are involved in planning and preparation to move
CUE ——– REACH
When do neurons in primary motor cortex fire?
Before and during voluntary movements of contralateral muscles
Monkey: Cue vs reach
Pre-motor neuron goes nuts for cue AND for reach, yellow and green dot
Mirror neurons respond to …
Purposeful goal directed movements
Understand the intentions of others
Mirror neurons in Autists
Not great
SMA and pre-SMA
pre-SMA: Linking movement to higher order executive functions
Linking together Complex Movement sequences
Activating the movement
Implicated in internally generated movements/Volitional movements
When SMA is damaged…
Alien Limb Syndrome
Alien limb syndrome
A limb just acts on its own but does purposeful movements , e.g take of glasses
OR loss of spontaneous movement
Sequential finger movent
SMA is activated along with hand part of S1 and M1
Single finger flexion
Just S1 and M1
Mental rehearsal of sequential movement
ONLY SMA gets activated
Turn, Push, Pull
SMA neuron is active prior to third movement in the sequence regardless of what the movement is
Readiness Potential (Berietschaftspotential)
EEG signal that is recorded before the medial frontal lobes (SMA) of humans
Around 1 sec before voluntary movements
What region is most directly connected to movement?
M1
How much does M1 contribute to cortical motor output?
1/3 of cortical motor output to brainstem and spinal cord
Remainder comes largely from premotor cortex, SMA and S1
Corticospinal tract
Projections from motor cortex to spinal cord form Corticospinal tract
Projections from motor cortex to the brainstem form the…
Corticobulbar tract
Cerebral peduncle
Formed by internal capsule
Pyramids
Come after cerebral peduncles
Pyramidal decusation
fibers cross over to contralateral side
Midbrain: Corticospinal tract
Corticospinal tract (cerebral penduncles)
At the left bottom and right bottom
Very big
Pons
Corticospinal tract is more in middle
Rostral medulla
Corticospinal tract(cerebral penducles) is at the bottom
Caudal medulla
At the bottom
Corticospinal tract AKA…
Cerebral penducles
Lesioning the pyramids of a monkey…
Monkey will be paralyzed BUT will recover functions EXCEPT it will lose control of individual fingers
This indicated that there are alternative parallel pathways for controls of voluntary movement
Brainstem
Controls stereotyped movements of the head (e.g facial expressions, chewing, gag reflex)
Through descending connections w the spinal cord it contributes to the control of voluntary movements of the body
Anything to do with cranial nerves involved in voluntary movements of the head?
Some corticobulbar projections control these
Medial brainstem pathways
Innervate axial muscles that control posture and balance
Travel down the ventral spinal cord white matter and terminate in ventromedial regions of the cord gray matter
1)Vestibulospinal tract
2)Tectospinal tract
3)Reticulospinal tract
Main lateral pathway
Rubrospinal tract
What in the brainstem is the origin of the rubrospinal tract?
red nucleus of the midbrain
Rubrospinal tract…
Contributes to control of voluntary limb movements
Rubrospinal fibers descend…
In the contralateral dorsolateral column of the spinal cord and terminate in the dorsolateral gray matter
Spinal cord
Descending projections terminate on spinal cord PREMOTOR neurons or directly on ventral horn motor neurons
The direct connections may be especially important for control of individual digits
Central pattern generators
Intrinsic circuitry of the spinal cord
Walking, swimming fish
