Adapting to Novel Forces Flashcards
adapting reaching movements for novel forces: baseline testing
Measuring baseline movements:
no affects, unperturbed hand paths in the robot are smooth and
relatively straight
adapting reaching movements for novel forces: Applied novel load
The most commonly used force environment is velocity-
dependent and perpendicular to the direction of hand motion
Novel load bumps hand movements to the side, need for correction
adapting reaching movements for novel forces: measure hand path deviations
perpendicular distance decreases as we learn to adapt
Measure initial hand path deviations (movement errors) caused by unexpected exposure to the novel load
The motor system learns to compensate for the effects of the load to plan and perform accurate movements
-learn to do deal with novel loads. Make straight accurate movements after adaptation in final tests
Lessons from this testing
The task is set up to examine how the nervous system uses errors experienced on one trial to update the next movement
Final trials look like baseline trials.
Learning curves show that errors decay with practise. Overtime can calculate proper amount of force
Most of error correction comes in cerebellum
What sensory systems provide feedback to the nervous systems with error feedback
- Visual information: eyes
- Muscle spindles: joint angles, where hand is in space
GTO’s: how much force we are using to counter acts novel load
Others: LLR spinal tract, some joint receptors, Ruffini ending (less prominent)
Neural correlation for adapting, Cerebellum in important for force field adapting
Adapting reaching movements for novel force environments
involves a number of different brain structures
-Mostly in cerebellum
Healthy control:
-Baseline, smooth and accurate movements
-Early adapt, hand paths deviate in direction of applied forces
-Late adapt, participants adapt to make relatively accurate movements
- Catch trials, errors in the opposite direction when forces are removed
Cerebellar patient:
-Baseline, jerky movements
- early adapt, hand paths deviate in direction of applied forces
-late adapt, little adaptation
- Catch trials, little effect deviations
Lesson: don’t learn, less smooth the healthy
Motor adaption
- When we learn to deal with load, now it does affect reaching to other places
Subjects adapted to a novel force field while reaching to one training target
Adaptation is local and specific to practice conditions. It decays as a function of the spatial difference between the practice/training movements and generalization targets
training = direction of movement
-father move away from angle, less applicable angle is
- m1 neuron prefers direction of movement
- Important to practise other conditions/movements
Learning by watching others
Subject watches an overhead view of
someone making reaching movements in a robot
- One watches clockwise (most effective)
-One watches counter clockwise (least effective)
-One sees nothing
Participants observe someone else adapt to a novel (CW or CCW) force field. They then encounter the CW force field themselves
-Learning incorrectly interferes and makes things worse, makes it harder
The simple act of observing someone adapt their movements to a novel force field can speed up or interfere with motor adaptation
We can learn new motor skills and modify existing skills simply by observing others perform a motor task
