KNPE 261 weeks 5-8 Flashcards
A system is open loop when it
doe snot take feedback into account
efference copy
copy of motor command that allows for the prediction of the action outcome and the sensory consequences
Why cant we tickle ourselves
we predict sensory consequence via efference copy
invariant features GMPs contain
-relative timing
-relative force
-relative sequence of events
parapeters GMPs accept
-overall duration
-overall force
-effector used
How does concept of GMP address storage and novelty problems?
storage: reduce amount of programs by half… general motor program but adjust/specify for certain parameters
Novelty: movement is not truly new, you adapt other programs to complete a “new” movement
relationship between speed and accuracy
- fast movements are less accurate
-accurate movements are slower
Fitts’ Law Experiment details
-tap b/x 2 targets as rapidly as possible maintaining 95% accuracy
Main outpus in fitts law
movement time
variables in fitt’s law
movement amplitude and target width
Fitts Paradigm
Index of difficulty= log (2(amplitude)/width)
when you increase ID, you increase movement time
Fitts Equation
movement time = a + b x ID
a= y int
b= slope
Units of ID
bits of information
if movement amplitude is doubled, what happend to ID
increases by 1 (harder)
if width is doubled what happens to ID
decreases by 1 (easier)
How would you get an ID of 0
no amplitude; the 2 targets are touching
Graphing FItt’s Data
+ve linear data
can you have the same ID with different amplitudes and widths
yes
FItts Law holds for
-children
-lower limb movements
-under magnification
-imagined movements
-percieved movements
fitts law is based on
visual feedback
open loop movements examined by Schmidt et al
-participants performed movements to thin target line
-width did not change but time required to make movement did
goal of open loop movements experiment by schmidt et al
determine “spread” about target as a function of D and T
schmidt formula for open loop movements
effective width = a+b (D/T)
Schmidts Law
as time increases, effective width increases
as speed increases, effective width increases
Breaking Fitts Law violation
when contextual target cues were present
-last target faster when all possibilities were shown; preparing for worst case scenario
where do violations of fitts law occur
all last targets when all posibilities shown
what did glazebrook et al find
fiits movement violations were not planning for worst case scenario but controlling via feedback, efficent movement corrections as seen tat most change happens in the middle not the beginning, indicating corrections not planning
glazebrook et al experiment
-performed movements to target location (first, middle or last in an array)
-measured movement variability across trajectory as an indicator of planning (differences earlier would indicate planning, differences later indicate control)
-differences emerged later meaning violation based on movement correction NOT planning
Do we plan for worst case scenario
no, we adapt efficently
what causes speed-accuracy tradeoffs?
Impulse variability theory
Impulse Vriability theory
-the variability in the duration of a group of contractions is related to the mean duration
-the variability in force produced increases as a function of the force produced
Implulse variability and speed accuracy tradeoffs
variability increases to about 65% but then decreases at higher levels of force output
How do we test impulse variability and speed accuracy tradeoffs
aim to target but add resistance OR tell them to do it in less time to increase force
Schmidt and Sherwood
-applied load
-when load was greater then 60% of participant max, variability decreased
-least variable at fastest
