final Flashcards
forward model
simulates behavior of the body in response to motor commands and captures causal relationship b/t action and consequence
-“predictor”
inverse model
simulates behavior of the motor apparatus and estimates motor commands required to achieve a desired state in advance of the movement and based on current state and corollary discharge
“controller”
describe internal model as part of a mechanism for internal feedback loops
- forward dynamic model provides a constant closed loop feedback system for online adjustment
- together with the inverse model
predictive and anticipatory control in terms of forward model
- predictor (forward model) uses the efference copy to predict the sensory feedback, which allows for anticipatory control of things like grip control
- eg ketchup
- prediction happens due to sensory delay which would be reactive control
sensory confirmation and cancellation in terms of forward model
- sensory signals from the environment during movement are compared to the predicted signals that the forward model predictor predicts from the efference copy
- if they match, the signal is interpreted as reafferent
- if they do not match, it is interpreted as exafferent information
- eg why external stimulation is more intense than self-produce
- but anything that disrupts this comparison (rotation of robot, delay of stimulus) can create a mismatch again in signals
- eg self produced force matching is inaccurate b/c you cancel out some of the feedback and have to create more force to feel it on your finger
internal forward model and action agency
- ability to distinguish an action as self-produced based on comparison of afference to efference copy
- eg schizophrenia patients have symptoms where they are not the agent of their own control
- could be due to a. generating inadequate internal predictions or b. impaired comparison of predicted and actual
reafference principle/internal model at the single neuron level
recorded from vestibular afferents in monkeys
- no difference b/t active and passive movements
- vestibular signal not attenuated on the single neuron level during active movement
- when recording from vestibular nuclei, there was a attenuation of the signal for head movements
vestibular signals during head movements
-active: vestibular signal is attenuated
passive head movement: codes for movement
-simultaneous passive and active movements: proprioception and vestibular afferent signal compared to reafference in vestibular nuclei
-active movement if vestibular attenuation, passive if no attenuation
how is an internal model updated for learning?
- brain learns to expect unexpected signals
- monkeys introduced to unexpected signal (causes error of attribution) over learning trials supressed the vestibular signal more and more
- internal model is reclaibrated
- after effect shown when unexpected signal removed
explain how the CNS determines whether a muscle is actively engaged in balance
it does if the efference copy of the motor command is congruent w/ the sensory signals
- is a balance response when congruent
a. active balancing vs. b. passive balancing where robot does for you - subject doesn’t know they aren’t actually balancing, so this is unconsciously controlled
- when it’s passive movement, the signals are incongruent w/motor response (because of robot) so there’s no balance response
division 1 of visual streams
1st: what vs. where
what=inferior temporal, where=post. parietal
-distinction is based on stimulus features
-both based on conscious perception
-how the stimulus is processed is important
division 2 of visual streams
- what vs. how
- ventral (inferior temporal)=what, dorsal (post. parietal)=how
- visual processing for online control of action
- separate systems to serve visual perception and action
eg of same info different visual system
- use info about shape and size to know it’s a remote
- also to know how to pick it up and how to shape the hand to grasp it
- what vs. how
blindsight
“seeing” what you can’t see
- evidence in monkeys w/visual cortex lesion
- they could still avoid objects and grasp objects and moving objects
- ie this is mediated through subcortical pathways
dorsal vs. ventral streams
both streams go through the visual cortex, ventral goes to inferior occipitotemporal cortex and dorsal to post. parietal
- ventral responsible for object recognition (textures, orientation, etc.)-conscious
- dorsal responsible for spatial recognition (depth perception, location, on-line actions)
evidence for what/how division
patient DF-visual agnosia w/ventral stream damage
- unable to recognize size and orientation of objects
- but preserved dorsal stream
posting: can’t accurately orient card for slot but can put it in the mail slot - can’t estimate size of objects by matching hand size but can go out and grab the object
Patient RV
- damage to dorsal stream (PPC)
- interrupted visuomotor processing for visually guided actions
- optic ataxia-can’t reach for obects accurately
- can recognize objects, can describe orientation of slot
- cannot draw well b/c uses visual info , can’t put card in slot
- grip aperture perception accurate, not accurate when picking up object
how are illusions used in visual systems studying
- illusion fools perception but not grip aperture
- allows for distinguishing b/t memory based and real time control of actions
how are patients w/optic ataxia still able to accurately perform grasping movements?
evidence for real-time vs. memory based control: patients w/optic ataxia (dorsal stream damage) who are still able to perform accurate grasping movements based on memory and internal predictive model
hand eye coordination during movement
- eye movement then initiation of reaching
- proprioceptive and visual information used to calculate appropriate motor output and efference copy
- error computed against efference copy to correct movement
double step paradigm
target moved, then jumps again during eye movement
-takes advantage of saccadic supression to dissociate perception and action
saccadic supression
reduction in sensitivity to visual inflow during eye movements
- affects only CONSCIOUS perception of target location
- limb movements to correct error show correction (guided to dorsal visual stream)
volitional vs. automatic control
- volitional relies on perceptual visual info
- automatic uses visuomotor info largely unavailable to conscious perception
- reaching vs. anti reaching movements
parietal lobe and online control of reaching movements
lesion and TMS leads to impairments in online corrections to mvmt jump
visual masking
=hiding a prime from conscious perception by displaying it briefly then replacing with mask
- mask overrides previously stored sensory stimuli
- prime produces compatibility effect on RT
address specific control
executive exerts control over each individual variable
univocal control
assumes one-to-one correspondence over motor command to output
-same command=same output in different circumstances
bernstein’s challenges
degrees of freedom
-too many variables to control (even more considering muscles and motor units)
-address specific control of MU’s would be 1000s of DOF
context conditioned variability
-role of muscle changes based on limb position, body position, etc-univocal control not possible
solution to DOF problem
-functional constraints an motor units and muscle groups
evidence
-longer RT w/bimanual movements (would be the same if controlled independently)
-during bimanual assymetric task, movements to close objects resemble the long ones (slower and synchronized velocity than expected) b/c limbs are functionally constrained
-both flight paths of limbs affected by obstruction in one’s path
coordinative structure
=functional linkage of mm that act of a single unit to minimize DOF for CNS during response programming
-synchronation can interfere w/tasks that require different actions for each limb
self organization
system that shows organized behavior/patterns of behavior where nothing is dictating it
dynamical dystems
=system w/mutually interacting components and some kind of spatial or temporal definition that changes over time
-tends toward equilibrium or attractor states
attractor state
state the system will move toward b/c of inherent stability
-system returns to this after perturbation through negative feedback loop
spring as example of attractor states
restoring force opposes the stretch/compression of the spring and moves it back to attractor state
-damping force opposes velocity and moves in opposite direction to displacement (essentially friction)
von holsts rules of coordination
- only a few patterns easily performed and are distinguised by stability
- stable patterns are maintained until critical limiting condition is reached, then transition occurs
- tend toward increasing stability
magnet effect and maintenance tendency
magnet effect (entrainment dynamics)-one part of system tends toward other to synchronize maintenance tendancy-each part of system has a preferred rhythm that the magnet effect pulls it out of
importance of transitions
- studied as functional adaptations based on their stability, metabolic cost, and interference
- preferred (more stable) patterns will have lower metabolic cost
- patterns are self-organizing: spinal cat can change pattern
- lower metabolic cost of running/walking preferred
phase transition paradigm and pattern transitions
- in phase and out of phase are inherently stable and can be maintained at lower frequencies
- as frequency increases, it becomes a limiting condition for antiphase and transition to more stable in phase happens
egocentric principle
holds for tasks involving same limb (homologous muscles)
-stability of pattern in in phase depends on symmetric activation of homologous muscles
allocentric principle
holds for tasks involving different limbs/people
-same direction of mvmt is more stable
HKB Model
models intrinsic dynamics of motor coordination
- maps stability of the state as a function of relative phase
- mathematical model predicts attractor states
- stability is analogous to potential energy, current state’s relative position is to attractor states
- z=frequency of oscillation
evidence from HKB model
-constant error and variation decrease as relative phase approaches an attractor state
HKB model predictions and coordination
- HKB model predicts behavior will move toward one attractor state
- some are stronger
- spontaneous transition in ONE direction (hysteresis)
- as parameters of the system change, the strength of the atrractor determines ability to stay in that pattern
- staying in weaker attractor will lead to coordination breaking down and moving toward stronger attractor
- critical fluctuations=variability increases as you approach a transition b/c attractor is weaker
- critical slowing down: how long it takes to get back to a pattern depends on stability of pattern (longer for antiphase)
intention and dynamics landscape
- intention is a specific influence on a pattern
- intrinsic pattern can be further stabalized by intention
- you can attract dynamics toward the pattern you want to perform
- -*coordination dynamics reflect intention interacting w/underlying intrinsic pattern
interaction b/t intention and intrinsic dynamics
- if intention is supported by intrinsic dynamics, the pattern will be helped along
- others will be harder to accomplish
- intending to stay in antiphase as frequency increases–>breakdown of pattern back to inphase or phase wander
- ie intention and ability to carry out intention is very influenced by underlying intrinsic dynamics
learning and coordination dynamics
learning=developing new attractor state to learn new pattern of movement
- requires modification of underlying landscape
- error plot changes and new attractor state error starts high and reduces
scanning coordination landscape
establishes a person’s intrinsic patterns
- most people have seagull effect of in phase and antiphase attractor states
- some people would have more
contingent negative variation
- slow wave during foreperiod
- snesory motor association and expectancy (anticiptation)
- early orienting wave, late expectancy motor prep related wave
- amplitude decreases w/long foreperiod
readiness potential
-slow shift in cortical potential preceding a self initiated voluntary movement
associated with volitional preparation of movement
-earlyRP, late RP, and motor potential
LRP
- detects when on side is more active
- portion of RP on one specific side
- onset=response selection and polarity indicates activation of correct/incorrect hand
LRP fractioning
- pre-motoric processes occur b/t stim onset and LRP onset (stim identification and response selection)
- motoric processes occur b/t LRP onset and EMG onset-final motor preparation/end of response selection
