final exam Flashcards
rubrospinal tract (start, end, function)
- red nucleus (midbrain)
- contralateral cervical spinal cord (upper limbs only)
- flexor muscles of the arms
- induces flexion and inhibits extension.
tectospinal tract (start, end, function)
- superior (visual) and inferior (auditory) colliculi - contralateral cervical spinal cord (neck muscles only)
- orient toward visual and auditory stimuli in the environment.
extrapyramidal tracts ______ through the pyramids of the medulla and are resonsible for ___________ control
- do NOT pass through the pyramids of the medulla
- responsible for involuntary control
pyramidal tracts pass through the __________ and are responsible for ____________
- pyramids of the medulla
- voluntary muscle control
medial (pontine) reticulospinal tract (start, end, function)
- reticular formation in pons
- interneurons of S.C
- extension of legs for postural support
cortical spinal tract (start, end, function)
- cortex (upper motor neurons)
- medulla/spinal cord
- lateral cortical spinal tract: distal muscles (contralateral hands and feet)
- anterior cortical spinal tract: proximal muscles (ipsilateral trunk, neck, shoulders)
cortical bulbar tract (start, end, function)
- cortex
- cranial nerve nuclei in the medulla and pons
- bilateral control over muscles of the upper head and face
- contralateral control over muscles of the lower face, mouth, and neck
list the two pyramidal tracts
- cortical spinal
- cortical bulbar
list the four extrapyramidal tracts
- tectospinal
- rubrospinal
- vestibulospinal (lateral, medial)
- reticulospinal (lateral, medial)
lateral (medullary) reticulospinal tract (start, end, function)
- reticular formation in medulla
- interneurons of S.C
- flexion
- inhibit the effect of medial R.S.T
lateral vestibulospinal tract (start, end, function)
- lateral vestibular nuclei
- all levels of S.C
- Biased toward extension – controls muscle tone in neck, trunk, shoulder and leg muscles involved in keeping body upright (relative to gravity).
medial vestibulospinal tract (start, end, function)
- medial vestibular nuclei
- upper cervical levels
- biased toward extension in neck and shoulders
lesion method
- if brain area X is involved in performance, then damage to X will cause movement impairment
- what happens to the body (movement impairment) can reveal action of brain area X
decorticate rigidity
pyramidal tracts are interrupted but extrapyramidal tracts are left intact
- input from the cortex (where pyramidal tracts originate) is disrupted
- damage ABOVE midbrain
decorticate rigidity: posture 1)
- loss of inhibitory input from cortex to red nucleus
- Increased activity in rubrospinal tract – increases activity in flexor muscles of upper limbs.
- Flexor activity in rubrospinal tract > extensor activity in vestibulospinal, and reticulospinal tracts
- Posture -> Arms and hands in a flexed position
decorticate rigidity: posture 2)
- disruption of the lateral corticospinal tract of spinal motor neurons to extensors
- vestibulospinal and lateral reticulospinal input: extension > flexion
- Hips extended and internally rotated, feet plantar-flexed
what tract is active when the arms and hands are flexed in decorticate rigidity?
- rubrospinal tract = activie (does flexion)
- this activity is more powerful than vestibulospinal and reticulospinal tracts (extension)
what is the reason for the extension and internal rotation of the hips, and the plantar flexion of the hips in decorticate rigidity?
- lateral corticospinal tract (pyramidal) is disrupted
- vestibulospinal and lateral reticulospinal tracts are more active (cause extension)
decerebrate rigidity
BOTH pyramidal AND extrapyramidal tracts are disrupted
- worse than decorticate (damage BELOW midbrain/red nucleus)
Activation method
If brain area X is involved in performance, then a movement task will increase the activity of X
Activation method: 4 examples
- ELECTROPHYSIOLOGICAL RECORDINGS: in animals can see spatial (where) and temporal (when) activity in brain
- FMRI: can show flow of blood via oxygen in brain, best spatial info (clearest picture), poor temporal (delayed timing)
- ELECTROENCEPHALOGRAPHY: electrodes on the head, good temporal, bad spatial
- OBSERVING DANCE: activation level is influenced by our own motor experiences
stimulation method
stimulate brain area X by applying a (low-voltage) electrical signal and observing the resulting movement
what is prehension?
reaching + grasping
3 steps of prehension
- LOCATE target with vision/dorsal stream (parietal cortex sends location info to PMC and M1)
- REACH: moving hand distance and direction
- GRASP: shaping fingers and generating grip force
ventral stream
- “v” for vision (vision for recognition)
- primary visual cortex (V1) to inferior temporal cortex
- processes visual info: perception and recognition of objects, faces, senses
dorsal stream
- “d” for DOING (vision for actions)
- primary visual cortex (V1) and PMC
- process visual info/ targets of action: location, shape, size
- merges visual and proprioceptive info
patient DF
- lesions in ventral stream (“V” for vision recognition)
- couldn’t recognize objects, faces, scenes
- Visual Form Agnosia: inability to use vision to
determine shape - Visual: recognize touch, hearing, but not vision
- Form: sees free-floating patches, can’t recognize shape
- Agnosia: problem with perception, not with memory (not amnesia)
Patient RV
- lesions in dorsal stream (“d” for doing)
- Optic Ataxia
- optic: visual disorder (can use hearing and touch to reach for objects)
- ataxia: movement disorder (can recognize objects)
hand-path kinematics
- Velocity profile has a typical “bell” shape (Start, accelerate, peak velocity, decelerate, stop)
- Time to peak velocity (TPV)/first half of movement = ballistic stage (projectile) that depends entirely on the motor command
- Time after peak velocity (TAPV)/second half of movement = Sensory feedback used to update and improve movement
- outcome of reaching (certain direction over a specific distance)
GRIP size vs type vs force
size: distance between thumb and index finger
type: power or pinch (determined by goal, size, weight)
force: strength of force needed to lift (determined by weight and surface properties/friction)
PMC (premotor) and M1 (primary motor cortex) codes for _______ in reaching
direction
- Georgopoulos study
M1 (primary motor cortex) codes for _________ in reaching
distance (force)
- Evarts study
grasp/ grip control
using object size/weight information to determine grip size, type, force
parietal cortex involvement in control loop
codes visual feedback and makes the sensory comparison (btw prediction and feedback)
parietal cortex codes ______ for action
target location for action
(movement planning)
parietal cortex codes_______ for sensory comparison
visual feedback
structures of basal ganglia
Corpus striatum:
- striatum: caudate nucleus, nucleus accumbens, putamen (3)
- lentiform: putamen, globus pallidus internal, globus pallidus external (3)
– subthalamic nucleus
– substantia nigra: pars compacta, pars reticulata
4 coritco-cortical circuits of basal ganglia
skeletomotor: control of voluntary movements, balance, gait
oculomotor: eye movement control
limbic: emotional control and motivation
prefrontal: planning, persistence, memory, spatial ability
pathway of input TO the basal ganglia
cortex to the striatum
pathways of output OUT of the basal ganglia
globus pallidus internal (GPi) to…
- cortex (via thalamus)
- spinal cord (via medulla: balance & gait)
- cerebellum (via pons: balance & gait)
What is Parkinson’s disease?
a progressive degenerative disorder of both movement and stillness
- degeneration of the substantia nigra ~ lack of neurotransmitter dopamine (pars compacta)
Negative signs of Parkinson’s disease
- DIRECT ROUTE: interference with cortical excitation
- loss of movement
- akinesia (lack of movement, facial masking)
- bradykinesia (slowness)
- poor balance (postural instability)
Positive signs of Parkinson’s
++ INDIRECT ROUTE: interference with cortical inhibition
+ presence of unwanted movements
+ resting tremor (uncontrollable, repetitive movements of extremities at rest)
+ rigidity (muscle stiffness associated with involuntary co-contraction around joints)
control theory loop
how we use sensory information to start movements (generate motor actions) or update them (from error signals/feedback)
high GPi output = ______ motor cortex excitability
decrease
(GPi inhibits cortex more)
low GPi output = ________ motor cortex excitability
increase
(GPi inhibits cortex less)
global pallidus internal
inhibits cortex to prevent and stop movement
4 ways the cerebellum participates in movement control
- acts in advance of sensory feedback
- motor timing
- relies on model of body (height, weight, bone mass) to coordinate movements
- adaptation + learning
how does the cerebellum control motor timing
- M1 and cerebellar neurons linked
- cerebellar firing happens before muscle contractions
- triphasic EMG: reflects normal timing of muscle activation
what do triphasic EMGs show us about the cerebellum controlling motor timing?
triphasic EMG: reflects normal timing of muscle activation
- the TEMG is disrupted after cerebellar damage
- hypermetria (overshoot target)
- oscillations at movement end
how does the cerebellum store info about your body?
- stores model of limb structure and mass for proper motor commands
- tools that add weight to limb, the cerebellum embodies it (Katniss)
- when the cerebellum is disrupted, no more compensation
- coordination disorders: harder to do multijoint than single-joint movement
cerebellar ataxia
- Jerky, ungraceful, inaccurate movements
– poor balance and gait
– Poor learning - lack of coordination
- dysmetria: over or undershoot target
- action/intention tremor
- disdiadochokinesis: inability to perform alternating movements
- gait ataxia and poor balance: steps irregularly timed and placed
- nystagmus: repetitive beating movements of the eyes
- hypotonia: low muscle tone
- poor proprioception
the role of adaptation in cerebellar motor control
- normal cerebellum: make errors, fix errors, return to baseline
- damaged cerebellum: cannot adapt for errors
posture
ability to control the body’s position in space to maintain orientation and stability
postural orientation
maintain relationship btw segments of body and body and environment
postural stability
(aka balance) ability to keep center of mass within the base of support
base of support
area defined by body’s contact with the support surface
center of mass
point in 3D space that is at the center of the total body mass
- usually around L2
Center of gravity
the vertical projection downward from the center of mass
Center of pressure
center of distribution of total forces applied to the support surface
quiet stance postural control
- goal is to maintain upright body alignment
stability limits
amount of sway body can experience without changing its base of support
3 main reactive postural adjustments
- ankle strategy
- hip strategy
- stepping strategy
how is the ankle strategy different from the hip strategy as reactive postural adjustments?
- ANKLE: responds to small perturbations on firm surface. Distal muscles are activated first, where the body sways at the ankles
- HIP: responds to larger and faster perturbations with a narrow BOS. Proximal muscles activated first, large rapid motions at hip (no swaying)
locomotion
rhythmic, alternating activity of opposing limbs of the body that requires progression, postural stability, and adaptation
