Lecture 6: Motor System Flashcards
Prefrontal Cortex
a large frontal-lobe area anterior to the motor, premotor, and cingulate cortex, including dorsolateral, ventromedial, and orbitofrontal regions that receive projections from the dorsomedial nucleus of the thalamus
plays a key role in controlling functions such as planning and strategizing and in emotional behaviors
Premotor Cortex
frontal lobe areas 6, 8, and 44, lying immediately anterior to the motor cortex
houses a movement repertoire (lexicon) that recognizes others’ movements and selects similar or different actions
also called the supplementary motor cortex
Motor Cortex
area 4 of the frontal cortex
produces muscle movements
Mirror Neurons
cells in the primate premotor cortex that fire when an individual observes a specific action taken by another individual
the core mirror neuron system is transitive, responding to a wide range of actions that might be used to obtain a goal
the distributed mirror neuron system responds to intransitive actions, movements in which a goal is not present
Caudate Putamen
a large cluster of nuclei located beneath the frontal cortex
prominent structure of the basal ganglia
Dyskinesias
any disturbance of movement
Huntington Disease
a hereditary disorder characterized by chorea (ceaseless, involuntary, jerky movements) and progressive dementia, ending in death
Hyperkinetic Symptoms
involuntary excessive movements
symptom of brain damage
Tourette Syndrome
a disorder of the basal ganglia characterized by tics
involuntary vocalizations (including curse words and animal sound)
and odd, involuntary movements of the body, especially of the face and head
Hypokinetic Symptoms
difficulty in making movements
symptom of brain damage
Parkinson Disease
a disorder of the motor system that is correlated with a loss of dopamine in the brain and characterized by tremors, muscular rigidity, involuntary movements (akathesia), and changes in emotion and memory
Globus Pallidus (GPi)
the area of the basal ganglia involved in mediating motor activity
the inhibitory and excitatory pathways to the motor cortex converge in the GPi, which acts as a volume control to determine the strength or weakness of motor activity
Flocculus
a small lobe projecting from the ventral surface of the cerebellum that receives projections from the vestibular and so takes part in controlling balance
Corticobulbar Tracts
descending tracts from the neocortex to the lower brainstem that innervate facial motor neurons
Corticospinal Tracts
descending tracts from the neocortex originating in layer V of the cerebral cortex and ending in the spinal cord
also called pyramidal tracts
Lateral Corticospinal Tract
a pathway in the lateral spinal cord that carries information instructing movement
crosses over to the opposite side of the brainstem at the pyramidal protrusion
Anterior Corticospinal Tract
a pathway that carries instructions from the cortex to the spinal cord for the movement of the trunk
does not cross over to the opposite side of the brainstem at the pyramidal protrusion
Extensor Muscle
a muscle that acts to straighten a limb
Flexor Muscle
a muscle that acts to bend a limb at a joint
What are the functions of the motor system during hand movement?
- visual information required to locate target
- frontal-lobe motor areas plan the reach and command the movement
- spinal cord carries information to hand
- motor neurons carry message to muscles of the hand and forearm
- sensory receptors on the fingers send message to sensory cortex saying that the cup has been grasped
- spinal cord carries sensory information to brain
- basal ganglia judge grasp forces, and cerebellum corrects movement errors
- sensory cortex receives the message that the cup has been grasped
How is the cerebellum involved in the motor system in hand movement?
gets copy of signals
communicates to higher order systems for correction
What is the pathway used to plan motor actions?
- posterior cortex provides sensory information to the frontal cortex
- prefrontal cortex plans movement
- premotor cortex organizes
- motor cortex produces specific movements
Where does blood flow in the brain when completing a simple task like pushing a button?
blood flow increases in the hand area of S1 and M1 when participants use a finger to push a lever
some somatosensory and some motor activation
posterior parietal doesn’t need to be involved
Where does blood flow in the brain when completing a movement sequence?
blood flow increases in the premotor cortex when participants perform a movement sequence
follow sequence to push buttons; engage pre-motor cortex because novel planning is involve
Where does blood flow in the brain when completing a complex task such as a maze?
blood flow also increases in the prefrontal, temporal, and parietal cortex when participants use a finger to navigate a maze
spatial visual: parietal
eye movement: pre-motor and primary motor, posterior parietal
What was the experiment on monkeys natural movement categories?
electrically stimulated regions in natural bursts; created movement with a purpose
stimulating pre-motor; if there’s already a stored plan, it will send that to primary motor
repertoire of movements (ethological categories)
similar in premotor and M1, but more complex available to premotor
damage to premotor disrupts more complex movement
end goal the same
What was the Edward Evarts experiment on movement coding in M1?
recorded neural activity in wrist region of M1 while monkeys flexed wrist
M1 neurons plan & initiate movement
M1 neurons increase firing to increase force of a movement
motor cortex specifies direction of movement
What was the Apostolos Georgopoulos experiment on movement coding in M1?
recorded neural activity in arm region of M1 while monkey moved lever in different directions
each M1 neuron maximally active to particular direction
activity decreased in proportion of displacement from preferred direction
motor neurons calculate distance and direction of movement
What is a motor program?
plan of action
goal information
neuromuscular control information
open to sensory feedback
coarticulation: when you articulate speech, the consonants are influenced by the vowels that come before, have to articulate them together
What is the timing difference in speech between the two hemispheres?
left hemisphere dominant for language so right side of the mouth starts moving earlier because left hemisphere receives the signal slightly faster
What are the findings regarding the areas of the brain involved in the observing, remembering, and imagining of movement?
increased blood flow to hand region of motor cortex when naming tools
pianists exhibit activation in motor cortex when listening to music
similar brain activation during imagined movement and actual movement (e.g., rolling ball on table)
What is the supplementary motor area (SMA)?
motor planning
state of readiness for action
action initiation
complex movements
motor imagery
What are mirror neurons?
neurons that fire when observing others’ movement (also own)
encode a complete action
can “fill in the blanks” when part of a movement is absent
importance in imitating and understanding others’ actions? (goal-directed)
What are mirror neurons in humans?
mirror neurons generally located in left hemisphere
role in self-action, perception of action, self-awareness, & awareness of intention & actions of others
important for gestures & verbal language (Broca’s area)
What is the anterior cingulate cortex?
attention: switch our attention and select our focus
emotion
novel or cognitive actions
motor modulation: doing one thing, then decide to switch and do something else
What is the function of the anterior cingulate cortex in the motor modulation of a pairing task?
level of activation of AC decreases as they complete the task more
then when pairing is switched, increased involvement of the AC; even more active than when they first learned pairing; need to inhibit the previous tasks
What are the separate channels for reaching and grasping?
visual - info about target you’re seeing
channels of communication can be separate because of different types of actions
reaching: dorsal
grasping: ventral
What is the anterior intra-parietal sulcus?
thumb-finger grasping
higher planning activation
preparatory aperture
What is the cerebellum?
organized ipsilaterally: right lobe, right side of the body; left lobe, left side of the body
vermis (body midline)
What is the flocculus in the cerebellum?
vestibular inputs: semi-circular canals, orientation
spinal cord projections (balance)
What is the intermediate zone in the cerebellum?
movement of limbs
What is the lateral zone in the cerebellum?
movement of appendages
motor planning
multi-joint movement (throwing a dart)
What does the cerebellum play a role in?
timing (not just motor, in the auditory system as well), hand eye coordination
examples: metronome and tapping, comparing pairs of tones, cerebellar damage have a hard time on task
movement accuracy
What are the features of damage to the vermis in the cerebellum?
disrupts balance, posture, walking
monkeys fall ipsilaterally, but may show few symptoms when lying down
does not disrupt reaching or grasping
What are the features of damage to the intermediate zone in the cerebellum?
difficulty in smooth movements - action or intentional tremors
nose test (CASE)
What are the features of damage to the lateral zone in the cerebellum?
ballistic movements and overshooting target
multi-joint movement may be impaired
decomposition of movement
What was the experiment with the cerebellum and motor learning with prism goggles?
neurologically intact: initial throws allow them to get used to it, with the prisms initially the throws will be to the left but then adapt and return to target, then with prisms removed they throw too far to the right then return to normal
cerebellar damage: don’t do well in initial trials, show no compensatory actions with prisms, don’t have initial overshoot once prisms are removed
What are the genetics of Huntington’s disease?
genetic: HTT gene (huntington protein)
mutation (dominant allele) produces abnormal form
normal CAG repeats 10-35 times (HD: 40-120)
mutation produces extremely long form, gets sliced into smaller fragments, binds together, & accumulates (toxic)
destroys cells in caudate putamen (ACh and GABA), cortical regions later
What is Tourette’s syndrome?
genetic and environmental factors
symptom onset between 2-15 years of age
dysfunction in cortical and subcortical regions (basal ganglia, thalamus, and frontal lobe)
basal ganglia: dopamine (issue with dopamine levels in basal ganglia)
thalamus: relay of info, lack of inhibition through pathway
involuntary motor and vocal tics
What are the symptoms of Huntington’s disease?
symptom onset = 30-50 years of age
involuntary and exaggerated movements
chorea (twitching; brief, abrupt, irregular movements)
athetosis (writhing; slow, convoluted movements)
cortical atrophy: results in cognitive deficits (e.g., slowed information processing)
What are the motor tics associated with Tourette’s syndrome?
excessive eye blinking, clearing throat, neck twitch, can be more complex
What are the vocal tics associated with Tourette’s syndrome?
inarticulate & articulate; just a sound
echolalia: repeating back what they hear
coprolalia: blurting out swear words, not as common
What is Parkinson’s disease?
genetic and environmental factors
loss of DA cells in substantia nigra
decreased activation along nigrostriatal pathway
age of onset = about 60 years of age (can be younger)
What are the symptoms of Parkinson’s disease?
tremor at rest (CASE), muscular rigidity, involuntary movement (e.g., akathesia), postural disturbance
difficulty initiating and performing movements (e.g., walking)
akinesia: poverty of movement, trouble initiating
bradykinesia: slow movement (e.g., locomotor)
cognitive impairments with progressive disease
What are treatments for Parkinson’s disease?
L-dopa: gives ingredients to make dopamine
deep brain stimulation: embedding an electrode near pathway into basal ganglia so that the basal ganglia can have normal activation
What is apraxia?
problem with skilled, sequential, purposeful movement
cannot be accounted for by lower level motor problems (i.e., subcortical)
oral (buccofacial) - frontal-lobe lesions
limb: left parietal-temporal lesions
What is ideamotor apraxia?
pantomime and imitation affected, but can have proper object use
What is ideational apraxia?
object confused or use unknown
