Chapter 9: Organization of the Motor System Flashcards
Explain the steps of the nervous system when picking up a cup
- visual information required to locate target
- frontal-lobe motor areas plant the reach and command the movements
- the spinal cord carries the info to the hand
- motor neurons carry message to muscles of hand and forearm
- sensory receptors in the fingers send a message to the sensory cortex saying that the cup has been grasped
- the spinal cord carry sensory info to brain
- basal ganglia judge grasp forces cerebellum corrects movement errors
- the sensory cortex receives the message that the cup has been grasped
What are the major region of the motor system that participate in all movements?
- neocortex (parietal and frontal cortex) for planning and commanding
- brainstem and spinal cord for movements
- motor neurons
- cerebellum (accuracy)
- basal ganglia (force )
What are the four neocortical regions central to our initiating movement?
- parietal cortex
- prefrontal cortex
- premotor cortex
- motor cortex
What does the parietal cortex do for movement
- the parietal cortex receives and integrates sensory information and initiates movements
- vision, touch and hearing
- the parietal cortex sends goals
- it is brodmanns areas 5 and 7
- online and offline movements
What are online movements?
- actions made in direct response to sensory info
- done by parietal cortex
What are offline movements
- actions mediated by perception
- done by the parietal cortex
What role does the prefrontal cortex play in initiating movements
- the prefrontal cortex plans movements
- Brodmanns areas 9,10,11,45,46,47
- prefrontal cortex plans are based on previous experience as well as ongoing sensory input
What is the premotor cortex’s role in initiating movement
- also called the supplementary motor cortex
- BA 6 and 8
- premotor cortex organizes movement sequences
- making whole body movements, rhythmic movements (walking) and coordinated movement (using both hands)
What role does the motor cortex play in initiating movement
- produces elementary movements
- BA 4 or M1
- chewing, bringing food to mouth, picking things up
What does hierarchical control of movements in the brain mean
- as movements become more complex, more regions of the brain are involved
Finger tap example - blood flow increases in the primary motor cortex parietal cortex when participants tap finger
- the premotor cortex becomes involved when the participants perform a movement sequence
- last the prefrontal, temporal and parietal cortex when ps use a finger to navigate a maze
What was Wilder Penfields findings
- brief pulses of electrical stimulation to map the cortices of conscious human patients who were about to undergo neurosurgery
- they found that most movements were mainly triggered by the stimulation of the precentral gyrus (BA4)
- also contained evidence that movement can be produced by stimulating the dorsal part of the premotor cortex (BA6) also called the supplementary motor cortex
What is Penfield’s Motor Homunculus
- homunculus= “little human” spread out across M1
- because the body is symmetrical, each hemisphere contains an almost mirror-image representation of this homunculus
- the secondary homunculus was used to summarize movements obtained from the supplementary cortex (premotor cortex)
Is Penfield’s Homunculus useful today?
- remains useful for understanding the motor cortex’s topographical and functional organization
What are Ethological Movement Categories
- experiment done in conscious monkeys using electrical stimulation, produced movements that the monkey might use everyday
(ethology is the scientific study of animal behaviour under natural conditions) - primary motor cortex: hand in lower space, manipulating in central space, chewing, licking
- premotor cortex: climbing, reaching to grasp, defense, hand to mouth
- prefrontal cortex:
Are our movements learned or robotic
- learned
what are mirror neurons?
- neurons that reflect the movements made by others that we might make under similar circumstances
What does the human core mirror neuron system respond to
- transitive actions ( movements with a goal)
- includes Brocas area (BA 44) which is responsible for speech
Symptoms of some disorders related to the mirror neuron system are?
- the absence of empathy, the ability to see other points of view
- occurs in ASD and may be related to mirror neuron system dysfunction
What is the Basal Ganglia
- a collection of subcortical nuclei in the forebrain
- connects the motor cortex with the midbrain
- connections the sensory regions of the neocortex with the motor cortex
- the caudate putamen is a prominent structure of the basal ganglia , beneath the frontal cortex
What are the 2 main sources the basal ganglia receives input
- the neocortex and limbic cortex (including the motor cortex)
- the Nigrostriatal Dopamine pathway from the substantia nigra
What are the two pathways in the basal ganglia that modulate cortically produced movements
- Direct
- Indirect
- these two pathways converge on the internal part of the globus pallidus (GPi) then go to thalamus
- if activity in the indirect pathway dominates the thalamus shuts down and the cortex cannot produce movement
- if the direct pathway predominates the thalamus can become overactive amplifying movement
What are the two kinds of movement disorder symptoms that can result from damage to the basal ganglia?
- Hyperkinetic Symptoms: damage to the caudate putamen create unwanted choreiform movements
- Hypokinetic Symptoms: of the cells of the basal ganglia are intact but the inputs are damaged the injury results in difficulty making movements
- hyper and hype kinetic symptoms work like a volume dial where damage to the basal ganglia can cause movements to be too strong or weak
What are Hyperkinetic Symptoms and what disorders are they associated with
Hyperkinetic Symptoms: damage to the caudate putamen create unwanted choreiform movements (twitching) called Dyskinesias
ex Huntington disease (genetic disorder) destroys caudate putamen cell and results in involuntary movements
ex tourettes syndrome
What are Hypokinetic Symptoms and what disorders are they associated with
Hypokinetic Symptoms: if the cells of the basal ganglia are intact but the inputs are damaged the injury results in difficulty making movements
ex. parkinsons (voluntary movements)
- caused by the loss of dopamine cells from the substantia nigra and of their input into the basal ganglia via the nigrostriatal pathway
- muscular rigidity and difficulty initiating and performing movements
What is the Basal Ganglia’s role in controlling emotional expression and cognitive function
- Hypokinetic symptoms are frequently associated with blunted emotion
- Hyperkinetic symptoms associated exaggerated emotion
What is the primary role of the Cerebellum in motor learning?
- acquiring and maintaining motor skills
- timing and accuracy (timing movements so they are accurate)
- grasping objects, targets
Cerebellum Anatomoy
- has 2 hemispheres (flocculus
- contains 4x more neurons than the neocortex
- the cerebellum is divided into several regions each specializing in a different aspect of motor control
- midline areas of cerebellum associated with face and trunk of body
- next section out associated with limb, hand, feet and digit movements
Damage to the Cerebellum regarding movement
people with damage to the cerebellum show deficits in
- they do not correct errors
- lack moment - moment motor learning such as throwing a dart and getting closer with practice
How does the Cerebellum correct errors?
- by comparing the intended movement with the produced movement the cerebellum sends an error message to the cortex to improve the accuracy of the subsequent movement
- same for mispronouncing and reading
- after an attempt or a couple we can correct it
Which tracts are involved in correcting movements
- corticospinal tracts (to spinal cord) and spinocerebellar tract (cerebellum)
