Lecture 6 - Intro to Motor Systems Flashcards
Eight steps of sequential organized movement?
- Visual information required to locate target.
- Frontal-lobe motor areas plan to reach and command the movement.
- Spinal cord carries information to hand.
- Motor neurons arry message to muscles.
- Sensory receptors send messages to sensory cortex saying the action has been complete.
- Spinal cord carries sensory information to the brain.
- Basal ganglia judge forces, and cerebellum corrects movement errors.
- Sensory cortex recieves message that the action has been completed.
ie. the mug grasping.
Where does the afferent somatosensory information travel?
From the sensory organs inward via the somatic nervous system.
Efferent motor system?
Movement information travels out of the central nervous system through it.
Connections between the nerves and spine?
[four steps]
- Fibers entering the posterior root bring sensory info from sensory receptors.
- Fibers leaving the anterior root carry motor info to the muscles.
- Collateral branches of sensory neurons may cross to the other side and influence motor neurons there.
- White-matter fiber tracts carry info to and from the brain.
Each spinal segment corresponds to a region of body surface called a?
Dermatone.
Which layer of the neocortex is relatively thick in the sensory cortex but relativly thin in the motor cortex?
Layer IV [afferent].
Which layer is relatively thick in the motor cortex and relatively thin in the sensory cortex?
Layer V [efferent].
What did Lashley argue about motor movement?
Argued that movements must be performed as motor sequences, with the next sequence held in readiness while the ongoing was underway.
Motor sequence?
Movement modules are preprogrammed by the brain and produced as a unit.
3 regions of the frontal lobe that are responsbile for initating motor sequences?
- Prefrontal cortex.
- Premotor cortex.
- Primary motor cortex [M1].
Prefrontal cortex?
- Plans complex behavior [executive function].
- Does not specify the precise movements to be made, but simply makes a decision about which goal to select.
Premotor cortex?
- Produces the appropriate complex movement sequences.
Primary Motor Cortex [M1]?
- Specifies how each movement is to be carried out.
- Specializes in producing focused skilled movements, such as those involving our arms, hands, mouth, etc.
Order of initiating a motor sequence?
[4 cortexes]
- Posterior sensory cortex sends goal.
- Prefrontal cortex plans.
- Premotor cortex sequences.
- Motor cortex executes actions.
Damage to prefrontal cortex results in?
Those with damage often break social and legal rules, as they have faulty decision making abilities.
Damage to premotor cortex results in?
Movement involving many body parts cannot be accomplished.
Damage to the primary motor cortex [M1] results in?
Difficulty performing reaching movements and shaping their finger correctly to perform various hand grasps. Also have difficulty enunciating words and performing many skilled hand, arm, and trunk movements [such as bringing your hand to your mouth to feed yourself].
weakness at best, hemiplegia at worst.
Fill in the blanks:
Indivudal neurons in M1 are ____ to direction of movement, not _____.
Broadly tuned; target location.
Where does the premotor area recieve input from?
The parietal cortex.
Premotor area:
Ventral premotor area contains ____ which respond selectively when viewing an animal perform an action.
Mirror neurons.
Movement control in the brain:
A.) Simple movement?
B.) Movement sequence?
C.) Complex movement?
A.) Blood flow increase in hand area of primary somatosensory and primary motor cortex when partipants use a finger to push a lever.
B.) Blood flow increases in premotor cortex when participants perform a sequence of movements.
C.) When participants use a finger to find a route through a maze, blood flow also increases in prefrontal, temporal, and paritel cortex.
What did Fritsch and Hitzig discover?
That they could electrically stimulate the neocortex of an anesthetized dog to produce movements of the mouth, limbs, and paws on the opposite side of the dogs body.
Which areas of the motor cortex are the largest?
The parts that control the:
- hands.
- fingers.
- lips.
- tongue.
Position point theory?
The theory that the action map represents where a part of the body must be in body-relative space, such that when a part of the cortex is stimulated, the associated part of the body moves to the appropriate spatial position, regardless of its starting position.
How is the M1 organized according to Penfield?
Topographically.
How is the M1 organized according to Graziano?
Organized according to fundamental ethological categories of movement.
Nudo and monkeys?
Without rehabilitation: lost most ability to move hand.
With rehabilitation: retained some ability to move hand.
Corticospinal tract?
The main efferent pathways from the motor cortex to the brainstem and spinal cord.
Layer V, the largest layer of the motor cortex, projecting via corticospinal tracts to the motor neurons of the spinal cord to produce movement.
What are the two main efferent pathways from the motor cortex?
The corticobulbar tracts, which project to the brainstem cranial nuclei to produce movement of head muscles [except the eyes] and the corticospinal tracts, which connect with motor neurons of the spinal cord to control muscles in the rest of the body.
Lateral corticospinal tract vs. ventral corticospinal tract
Lateral is crossed, ventral is uncrossed.
