Module 3 Lecture 2 Flashcards
How the brain influences the activity of the
spinal cord
the central motor system
The central motor system is arranged as a
hierarchy of control levels with the __________
at the top and the __________ at the bottom
forebrain
spinal cord
Types of Movements
- rhythmic
- reflexes
- voluntary
__________ – “simple” neural circuit resides in
spinal cord or brain stem
Reflexes
_________ - includes a central component that
regulates spinal cord oscillatory circuit
Rhythmic
__________ - requires ‘higher’ levels such as
cortex, basal ganglia, cerebellum
Voluntary
___________: motor systems are organized by levels
Hierarchical control
________________: more than one pathway may be active at the same time
Parallel control
____________: The cerebral neocortex has information—
based on vision, audition, somatic sensation, and
proprioception—about precisely where the body is
in space.
Strategy
Filtered through the ___-________ and back
to the ___________ until a final decision is made,
basal ganglia
cortex
during the ____________ stage, The motor areas of cortex and the cerebellum issue instructions to the spinal cord
tactics
___________ are all involved in Coordination
of muscles:
shoulder,
elbow…
Cervical region
Thoracic and lumbar region
Brain stem
• _____________
– Association area of neocortex
– Basal ganglia
High level (strategy)
_____________
– Motor cortex
– Cerebellum
Middle level (tactics)
____________
– Brain stem
– Spinal cord
Lower level (Execution)
Descending Spinal Tracts
– The ventromedial pathways
– The lateral pathways
_____________
• Involved in the control of posture and are under brain
stem control
– The ventromedial pathways
________________
• Are involved in voluntary movement of the distal
muscles
• Under direct cortical control
– The lateral pathways
__________
– Muscles of the trunk
– To maintain posture
Axial muscles
____________
– Muscles of the shoulders, elbows, thighs, and knees
– Locomotion
• Proximal muscles
_________________
– Muscles of the hands, feet, and digits
– Manipulations of objects
• Distal muscles
The Lateral Pathways
- Corticospinal tract
* Rubrospinal tract
_______________ originates in the
neocortex (about 2/3 of axons originate from
areas 4 and 6 of the frontal lobe-motor
cortex)
Corticospinal tract
the remainder neurons derive from the________________ of the parietal lobe
somatosensory area
__________________:
Parallel the corticospinal tract
Receives input from
frontal cortex
the rubriospinal tract
What is the path of rubriospinal tract
spinal cord -> medulla -> midbrain-> rednucleus
Lesions studies of the lateral pathways from
the work of Lawrence and Kuypers in the 60s
showed that
– Monkeys are unable to do fractional movements
– Voluntary movement were slower and less
accurate
– Monkeys could sit upright and stand with normal
posture
• Lesions of the corticospinal tract alone caused
– Movement deficit as severe as the __________
lateral tract lesion
___________
– The only permanent deficit was some weakness in the
distal flexors and inability to move the fingers
independently
• Recovery
• Lesion of the rubrospinal tract _______
reversed recovery
________________
• Originate in the brain stem and terminate in
the spinal interneurons that control the
proximal and axial muscles
The Ventromedial Pathways
The Ventromedial Pathways (4)
– Vestibulospinal tract
– Tectospinal tract
– Pontine reticulospinal tract
– Medullary reticulospinal tract
The Ventromedial Pathways (4)
– Vestibulospinal tract
– Tectospinal tract
– Pontine reticulospinal tract
– Medullary reticulospinal tract
\_\_\_\_\_\_\_\_\_\_\_\_\_ Use sensory information about balance, body position, and the visual environment to reflexively maintain balance and body posture.
Ventromedial Pathways
______________ control neck and back
muscles and guide head
movement. Stability of the head
is important
Vestibulospinal tract
Control the
posture of the
head and neck
Vestibulospinal tract
The The vestibularspinal tract____________ down
to cervical regions
Bilaterally
projection
vestibular spinal tract Not shown Lumbar region projection that facilitating
extensor motor neurons of the legs
vestibular spinal tract Receives information from
___________________
the inner ear via CN VIII
_____________: Receives direct input from
the retina, visual cortex,
somatosensory cortex
tectospinal tract
Orienting response that directs the
head and eyes to move so that the
appropriate point of space is __________
imaged on the fovea.
The tectospinal tract Control muscles of the
neck, upper trunk and
shoulders
trace the tectospinal tract
spinal cord -> medulla ->superior colliculus
where does the tectospinal tract dessicate
cervical region
The Pontine and the Medullary
Reticulospinal Tract Originates mainly from the
reticular formation
The Pontine and the Medullary
Divided into two parts:
– The medial pontine reticulospinal Tract
– The lateral medullary reticulospinal tract
Pontine RST enhances the antigravity reflexes of the
spinal cord
Medullary RST liberates the antigravity muscles from
_________
reflex control
Making movements depends on
1- knowledge of where the body is in space
2-Where it intends to go
3-Selection of a plan to get there
Neurosurgeon
Mapping regions of the
brain
Electrical stimulation
Weak stimulation
to area 4 would
illicit movement on
the opposite side
Two other areas
in the frontal lobe
(area 6)
PMA connects with reticulospinal tract that innervates
proximal motor units
Area 4: Somatotopy
Area 4 is now often referred to as primary motor cortex or M1
Area 4: Somatotopy
Area 4 is now often referred to as _____________
primary motor cortex or M1
SMA and PMA play a major role in the
planning of movement
– Distal musculature
• Cells in the SMA increase their discharge a
second before ________________
the execution of movement
Some neurons in area 6 respond not only when movements are executed, but also when the same movement is only imagined (mentally rehearsed) • They also fire when the movement is observed • These neurons found in the PMA are called \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
mirror neurons
Area 4 has strong connections with the __________ and is called the ____________
spinal tracts
Motor strip
The Input-Output Organization of M1
Can synapse on spinal interneurons as well as lower motor neuron
Recordings from M1 neurons in behaving
animals have revealed that a burst of activity
occurs immediately before and during a
voluntary movement. This activity appears to encode two aspects of the movement:
force and direction
what are the three major areas of the brain for responsive movement
- cortex
- basal ganglia
- cerebellum
All movement goes through
spinal cord
_________ are groups of axons in the central nervous system
tracts
cortex commands which pathways
lateral pathways
brain stem commands which pathways
ventromedial pathways
postural muscles
what is the most important pathway which originates In cortex to spinal pathway
corticospinal tract
_________ is much smaller and is responsible for distal muscle. Is involved in distal studies
The rubriospinal tract
__________ Earlier microstimulation studies
The Work of Apostolos Georgopoulos
Individual M1 neurons have broad functioning allowing them to fire ___________
from many directions
-Move joystick towards a light whose position varied randomly
-Movement direction was encoded instead by the
_________________
collective activity of a population of neurons
The coding of movement of M1 neurons
The neurons in the M1 have a preferred movement with higher force; however, they still fire at other angles
During the coding of M1 neurons
both are firing. but some at lower frequency
The Coding of Movement in M1 • These studies suggest three important conclusions about how M1 commands voluntary movement: – (1) much of the motor cortex is \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
active for every
movement
The Coding of Movement in M1
• These studies suggest three important
conclusions about how M1 commands
voluntary movement:
– (2) the activity of each cell represents a single
_____________________
“vote” for a particular direction of movement
The Coding of Movement in M1
• These studies suggest three important
conclusions about how M1 commands
voluntary movement:
____________ registered by
each cell in the population
tally (and averaging) of the votes
The parietal lobes are extensively interconnected with regions in the _______________
anterior frontal lobes (prefrontal cortex)
Area 3b is the ________________
– (1) it receives dense inputs from the VP nucleus of
the thalamus
– (2) its neurons are very responsive to
somatosensory stimuli (but not to other sensory
stimuli)
– (3) lesions here impair somatic sensation
– (4) when electrically stimulated, it evokes somatic
sensory experiences.
primary somatic sensory cortex
primary somatic sensory cortex:
it receives dense inputs from the VP nucleus of
the_____________
thalamus
primary somatic sensory cortex:
its neurons are very responsive to
________________(but not to other sensory
stimuli)
somatosensory stimuli
primary somatic sensory cortex
lesions here impair ___________
somatic sensation
primary somatic sensory cortex
when electrically stimulated, it evokes____________
somatic sensory experiences.
Areas 1 and 2 receive dense inputs from area 3b. The
projection from 3b to area 1 sends mainly
texture information, while ________________
the projection
to area 2 emphasizes size and shape.
Area 3a also receives a
dense input from the _______________________
thalamus; is concerned
with the sense of body
position rather than
touch.
PET studies: changes in_____________
– Subjects asked to perform series of finger
movements (areas 5, 7, 6, and 4)
– Subjects asked to think about the movement (area
6)
blood flow
The larger the population of neurons
representing a type of movement, the finer
the possible control.
– Hands movements and the muscles of facial
expression
• Fine movements of other muscles can be
learned with ___________
experience
• In one series of experiments, Donoghue and Sanes used cortical
microstimulation in rats
• They mapped the regions of M1 that normally elicit movements of
the forelimb, facial whiskers, or muscles around the eye.
• Then they cut the motor nerve that supplies the muscles of the
snout and its whiskers
• They found that regions of M1 that had evoked whisker
movements now would elicit either forelimb or eye movements
• The motor map had been reorganized.
• They speculated that similar types of cortical reorganization might
provide a basis for learning fine motor skills
The Malleable Motor Map
They cut the motor nerve that supplies the muscles of the snout and its whiskers and found that regions of M1 that had evoked whisker movements now would elicit
either forelimb or
eye movements
Map represents
motor cortex from a
normal rat
Used cortical microstimulation form M1 cells that normally elicit movements of the forelimb, facial whiskers, and muscles around the eye
____________= a set of rules by which a process
can be carried out
• Often refers to a calculation that will be
performed by a computer
• Starting to be created for neural control of
movement: – Breakthrough studies where paralyzed patients move robotic arm by their own thoughts
Algorithm
In Conclusion
• To initiate a movement, a lot of neurons are
involved chorus of activity to the spinal motor
neurons that generate the ____________
the precise movements
necessary to propel the baseball accurately
Neuronal Correlates of Motor Planning
• Ready
– Depends on activity of the parietal and frontal
lobe (prefrontal cortex)
• Set
– SMA and PMA
– Movement strategies are derived and held for
execution
• Go
– MA1
