control of visual feedback (goal directed actions) Flashcards
what is exteroception
sensory info that tells us about the state of out body in relation to the world around us
- most dominant source is visual
what is the effect of vision on accuracy of reaching mvmts
improves precision
- average endpoints are the same with and without vision
- dispersion is greater without visual feedback
what are the 3 main ways to occlude vision
visual occlusion goggles (charged crystals that turn opaque when a current passes through them)
double jumps
cursor jumps
what is the double jump paradigm
target is displaced unexpectedly left or right during the reach
must react to the visual disturbance and generate rapid corrective responses to complete trial
what is the cursor jump paradigm
same set up as double jump
measuring the time latency of muscle (EMG) and kinematic responses following the cursor jump provides info about how quickly visual info can be used to guide and correct ongoing motor actions
what are the 3 conditions of the cursor jump pertubations
normal - cursor follows true hand path
task relevant - cursor shifted for remainder of trial
task irrelevant - cursor temp shifted but returns to normal by end of trial
what are the 3 conditions of the cursor trajectories
normal - cursor follows true hand position
task relevant - participants must make the correction
task irrelevant - don’t require corrective responses
what are the 3 conditions of the hand trajectories
normal - relatively smooth and straight movements
task relevant - generate corrective responses to reach the target successfully, shift opposite from the direction of the perturbation
task irrelevant - participants don’t correct (relatively smooth and straight movements)
when does the brain correct for perturbations
when they affect the outcome of the task (ignores deviations that don’t impact performance)
- only slight learning effect shown in the task irrelevant condition (learning that they don’t need to correct)
what is caused by damage to the dorsal stream
optic ataxia
what is the result of parietal damage
slower corrective responses
reduction in accuracy of visuomotor corrrections (miss the new target location)
^^optic ataxia
what is the result of frontal damage
fully complete the mvmt to the first target before continuing corrective mvmt to the 2nd target
(not correcting on the fly - fully stop at target 1)
- requires re planning of motor actions from dorsal pre motor cortex (that is damaged in frontal lobe)
is visual or proprioceptive system faster
proprioception
how long does each step in visual processing take
visual stimulus processed in retina = 15-35 ms
processed in LGN within 30-50 ms
transmitted to V1 within 60-100ms
emerge within 100ms in M1
when do EMG responses to a visual stimulus typically emerge
> 100 ms (some rapid responses can be detected using percutaneous EMG)
