midterm 2 Flashcards
what is optic flow
visual processing in the dorsal stream that allows person to detect motion, positioning and timing
describe how optic flow can determine distance, speed, direction
distance is proportional to the angle in the retina of the object’s image
speed is proportional to the rate of change of the angle in the retina
direction is proportional to the direction the angle changes about the middle
what is tau
time to contact is proportional to retinal image size/ rate of change of retinal size
describe open loop control
closed loop but no feedback or comparison.
what is the motor program
set of prestructured commands at the executive level and defines the skilled action
what are degrees of freedom
components of the control system that can be controlled to produce action
what are open loops used for
rapid discrete movements.
predictable and stable environments
to initiate movements
long strings of learned/rehearsed movements
how does movement complexity change reaction time
for a simple reaction time test
the more complex, limbs or time of action the longer the RT
what is deafferentation
cut afferent nerves from an arm. blocks proprioception
How does deafferentation support motor program theory
monkey’s performance does not change even without proprioception and vision of arm. no feedback possible so must be open loop
What is a central pattern generator
controls genetically defined repetitive actions like walking or chewing
how does CPG support motor program theory
one input results in complex repetitive behaviour
how does limb blocking support motor program theory
EMG data shows that muscle still activates for the movement that now cannot take place because it is blocked
what does the clock stopping experiment prove.
that if the clock is stopped 150ms to the target then there will be a failure to inhibit the participant stopping it themselves
explain postural/anticipatory adjustments and how they are motor programs
muscles fire from the feet up to stabilise the body for a lift.
postural support and the lift are one programmed action. too complex and must be considered a motor program
what is a reflex reversible phenomenon
M2. reflex with different responses based on the context.
what are the problems with motor program theory
storage problem, novelty problem
how does general motor program theory address the problems with motor program theory
,motor program only defines a pattern of movement but parameters of the movement can be adjusted to make different movement variations for different demands.
how does GMP fit into the 3 stage IP model
perception and decision are to select a GMP
action is to adjust the parameters of the GMP
what is an invariant feature.
parts of the movement that are the same for the GMP
how does relative timing work in GMP
the movement pattern in GMP will always have the same relative timing even if the total duration of the GMP is changed
what is fitts’ law
finds a linear relationship between movement time and Index of difficulty. (differing amplitude and target width). Logarithmic relationship without index of difficulty
independent: amplitude and width
dependant: movement time
testing on closed loop system
what is the linear speed-accuracy trade off test
independant: MT, amplitude
dependant: endpoint variability
endpoint variability increases with independent increases in amplitude and independent decreases in MT
how does muscle force influence accuracy of the movement
increases with muscle force until 70% then declines. This is due to the fact that near maximal contractions recruit almost all muscle fibres which decreases variability. Under 70 % then a random number of muscle fibres will be recruited and this increases variability